Adding upstream version 2.10.22.upstream/2.10.22upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 2494 insertions, 0 deletions

diff --git a/app/display/gimptooltransformgrid.c b/app/display/gimptooltransformgrid.c
new file mode 100644
index 0000000..b186b91
--- /dev/null
+++ b/app/display/gimptooltransformgrid.c
@@ -0,0 +1,2494 @@
+/* GIMP - The GNU Image Manipulation Program
+ * Copyright (C) 1995 Spencer Kimball and Peter Mattis
+ *
+ * gimptooltransformgrid.c
+ * Copyright (C) 2017 Michael Natterer <mitch@gimp.org>
+ *
+ * Based on GimpUnifiedTransformTool
+ * Copyright (C) 2011 Mikael Magnusson <mikachu@src.gnome.org>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include "config.h"
+
+#include <gegl.h>
+#include <gtk/gtk.h>
+
+#include "libgimpbase/gimpbase.h"
+#include "libgimpmath/gimpmath.h"
+
+#include "display-types.h"
+
+#include "core/gimp-transform-utils.h"
+#include "core/gimp-utils.h"
+
+#include "widgets/gimpwidgets-utils.h"
+
+#include "gimpcanvashandle.h"
+#include "gimpcanvastransformguides.h"
+#include "gimpdisplayshell.h"
+#include "gimptooltransformgrid.h"
+
+#include "gimp-intl.h"
+
+
+#define MIN_HANDLE_SIZE 6
+
+
+enum
+{
+  PROP_0,
+  PROP_TRANSFORM,
+  PROP_X1,
+  PROP_Y1,
+  PROP_X2,
+  PROP_Y2,
+  PROP_PIVOT_X,
+  PROP_PIVOT_Y,
+  PROP_GUIDE_TYPE,
+  PROP_N_GUIDES,
+  PROP_CLIP_GUIDES,
+  PROP_SHOW_GUIDES,
+  PROP_INSIDE_FUNCTION,
+  PROP_OUTSIDE_FUNCTION,
+  PROP_USE_CORNER_HANDLES,
+  PROP_USE_PERSPECTIVE_HANDLES,
+  PROP_USE_SIDE_HANDLES,
+  PROP_USE_SHEAR_HANDLES,
+  PROP_USE_CENTER_HANDLE,
+  PROP_USE_PIVOT_HANDLE,
+  PROP_DYNAMIC_HANDLE_SIZE,
+  PROP_CONSTRAIN_MOVE,
+  PROP_CONSTRAIN_SCALE,
+  PROP_CONSTRAIN_ROTATE,
+  PROP_CONSTRAIN_SHEAR,
+  PROP_CONSTRAIN_PERSPECTIVE,
+  PROP_FROMPIVOT_SCALE,
+  PROP_FROMPIVOT_SHEAR,
+  PROP_FROMPIVOT_PERSPECTIVE,
+  PROP_CORNERSNAP,
+  PROP_FIXEDPIVOT
+};
+
+
+struct _GimpToolTransformGridPrivate
+{
+  GimpMatrix3            transform;
+  gdouble                x1, y1;
+  gdouble                x2, y2;
+  gdouble                pivot_x;
+  gdouble                pivot_y;
+  GimpGuidesType         guide_type;
+  gint                   n_guides;
+  gboolean               clip_guides;
+  gboolean               show_guides;
+  GimpTransformFunction  inside_function;
+  GimpTransformFunction  outside_function;
+  gboolean               use_corner_handles;
+  gboolean               use_perspective_handles;
+  gboolean               use_side_handles;
+  gboolean               use_shear_handles;
+  gboolean               use_center_handle;
+  gboolean               use_pivot_handle;
+  gboolean               dynamic_handle_size;
+  gboolean               constrain_move;
+  gboolean               constrain_scale;
+  gboolean               constrain_rotate;
+  gboolean               constrain_shear;
+  gboolean               constrain_perspective;
+  gboolean               frompivot_scale;
+  gboolean               frompivot_shear;
+  gboolean               frompivot_perspective;
+  gboolean               cornersnap;
+  gboolean               fixedpivot;
+
+  gdouble                curx;         /*  current x coord                    */
+  gdouble                cury;         /*  current y coord                    */
+
+  gdouble                button_down;  /*  is the mouse button pressed        */
+  gdouble                mousex;       /*  x coord where mouse was clicked    */
+  gdouble                mousey;       /*  y coord where mouse was clicked    */
+
+  gdouble                cx, cy;       /*  center point (for moving)          */
+
+  /*  transformed handle coords */
+  gdouble                tx1, ty1;
+  gdouble                tx2, ty2;
+  gdouble                tx3, ty3;
+  gdouble                tx4, ty4;
+  gdouble                tcx, tcy;
+  gdouble                tpx, tpy;
+
+  /*  previous transformed handle coords */
+  gdouble                prev_tx1, prev_ty1;
+  gdouble                prev_tx2, prev_ty2;
+  gdouble                prev_tx3, prev_ty3;
+  gdouble                prev_tx4, prev_ty4;
+  gdouble                prev_tcx, prev_tcy;
+  gdouble                prev_tpx, prev_tpy;
+
+  GimpTransformHandle    handle;        /*  current tool activity              */
+
+  GimpCanvasItem        *guides;
+  GimpCanvasItem        *handles[GIMP_N_TRANSFORM_HANDLES];
+  GimpCanvasItem        *center_items[2];
+  GimpCanvasItem        *pivot_items[2];
+};
+
+
+/*  local function prototypes  */
+
+static void     gimp_tool_transform_grid_constructed    (GObject               *object);
+static void     gimp_tool_transform_grid_set_property   (GObject               *object,
+                                                         guint                  property_id,
+                                                         const GValue          *value,
+                                                         GParamSpec            *pspec);
+static void     gimp_tool_transform_grid_get_property   (GObject               *object,
+                                                         guint                  property_id,
+                                                         GValue                *value,
+                                                         GParamSpec            *pspec);
+
+static void     gimp_tool_transform_grid_changed        (GimpToolWidget        *widget);
+static gint     gimp_tool_transform_grid_button_press   (GimpToolWidget        *widget,
+                                                         const GimpCoords      *coords,
+                                                         guint32                time,
+                                                         GdkModifierType        state,
+                                                         GimpButtonPressType    press_type);
+static void     gimp_tool_transform_grid_button_release (GimpToolWidget        *widget,
+                                                         const GimpCoords      *coords,
+                                                         guint32                time,
+                                                         GdkModifierType        state,
+                                                         GimpButtonReleaseType  release_type);
+static void     gimp_tool_transform_grid_motion         (GimpToolWidget        *widget,
+                                                         const GimpCoords      *coords,
+                                                         guint32                time,
+                                                         GdkModifierType        state);
+static GimpHit  gimp_tool_transform_grid_hit            (GimpToolWidget        *widget,
+                                                         const GimpCoords      *coords,
+                                                         GdkModifierType        state,
+                                                         gboolean               proximity);
+static void     gimp_tool_transform_grid_hover          (GimpToolWidget        *widget,
+                                                         const GimpCoords      *coords,
+                                                         GdkModifierType        state,
+                                                         gboolean               proximity);
+static void     gimp_tool_transform_grid_leave_notify   (GimpToolWidget        *widget);
+static void     gimp_tool_transform_grid_hover_modifier (GimpToolWidget        *widget,
+                                                         GdkModifierType        key,
+                                                         gboolean               press,
+                                                         GdkModifierType        state);
+static gboolean gimp_tool_transform_grid_get_cursor     (GimpToolWidget        *widget,
+                                                         const GimpCoords      *coords,
+                                                         GdkModifierType        state,
+                                                         GimpCursorType        *cursor,
+                                                         GimpToolCursorType    *tool_cursor,
+                                                         GimpCursorModifier    *modifier);
+
+static GimpTransformHandle
+                gimp_tool_transform_grid_get_handle_for_coords
+                                                        (GimpToolTransformGrid *grid,
+                                                         const GimpCoords      *coords);
+static void     gimp_tool_transform_grid_update_hilight (GimpToolTransformGrid *grid);
+static void     gimp_tool_transform_grid_update_box     (GimpToolTransformGrid *grid);
+static void     gimp_tool_transform_grid_update_matrix  (GimpToolTransformGrid *grid);
+static void     gimp_tool_transform_grid_calc_handles   (GimpToolTransformGrid *grid,
+                                                         gint                  *handle_w,
+                                                         gint                  *handle_h);
+
+
+G_DEFINE_TYPE_WITH_PRIVATE (GimpToolTransformGrid, gimp_tool_transform_grid,
+                            GIMP_TYPE_TOOL_WIDGET)
+
+#define parent_class gimp_tool_transform_grid_parent_class
+
+
+static void
+gimp_tool_transform_grid_class_init (GimpToolTransformGridClass *klass)
+{
+  GObjectClass        *object_class = G_OBJECT_CLASS (klass);
+  GimpToolWidgetClass *widget_class = GIMP_TOOL_WIDGET_CLASS (klass);
+
+  object_class->constructed     = gimp_tool_transform_grid_constructed;
+  object_class->set_property    = gimp_tool_transform_grid_set_property;
+  object_class->get_property    = gimp_tool_transform_grid_get_property;
+
+  widget_class->changed         = gimp_tool_transform_grid_changed;
+  widget_class->button_press    = gimp_tool_transform_grid_button_press;
+  widget_class->button_release  = gimp_tool_transform_grid_button_release;
+  widget_class->motion          = gimp_tool_transform_grid_motion;
+  widget_class->hit             = gimp_tool_transform_grid_hit;
+  widget_class->hover           = gimp_tool_transform_grid_hover;
+  widget_class->leave_notify    = gimp_tool_transform_grid_leave_notify;
+  widget_class->hover_modifier  = gimp_tool_transform_grid_hover_modifier;
+  widget_class->get_cursor      = gimp_tool_transform_grid_get_cursor;
+  widget_class->update_on_scale = TRUE;
+
+  g_object_class_install_property (object_class, PROP_TRANSFORM,
+                                   gimp_param_spec_matrix3 ("transform",
+                                                            NULL, NULL,
+                                                            NULL,
+                                                            GIMP_PARAM_READWRITE |
+                                                            G_PARAM_CONSTRUCT));
+
+  g_object_class_install_property (object_class, PROP_X1,
+                                   g_param_spec_double ("x1",
+                                                        NULL, NULL,
+                                                        -GIMP_MAX_IMAGE_SIZE,
+                                                        GIMP_MAX_IMAGE_SIZE,
+                                                        0.0,
+                                                        GIMP_PARAM_READWRITE |
+                                                        G_PARAM_CONSTRUCT));
+
+  g_object_class_install_property (object_class, PROP_Y1,
+                                   g_param_spec_double ("y1",
+                                                        NULL, NULL,
+                                                        -GIMP_MAX_IMAGE_SIZE,
+                                                        GIMP_MAX_IMAGE_SIZE,
+                                                        0.0,
+                                                        GIMP_PARAM_READWRITE |
+                                                        G_PARAM_CONSTRUCT));
+
+  g_object_class_install_property (object_class, PROP_X2,
+                                   g_param_spec_double ("x2",
+                                                        NULL, NULL,
+                                                        -GIMP_MAX_IMAGE_SIZE,
+                                                        GIMP_MAX_IMAGE_SIZE,
+                                                        0.0,
+                                                        GIMP_PARAM_READWRITE |
+                                                        G_PARAM_CONSTRUCT));
+
+  g_object_class_install_property (object_class, PROP_Y2,
+                                   g_param_spec_double ("y2",
+                                                        NULL, NULL,
+                                                        -GIMP_MAX_IMAGE_SIZE,
+                                                        GIMP_MAX_IMAGE_SIZE,
+                                                        0.0,
+                                                        GIMP_PARAM_READWRITE |
+                                                        G_PARAM_CONSTRUCT));
+
+  g_object_class_install_property (object_class, PROP_PIVOT_X,
+                                   g_param_spec_double ("pivot-x",
+                                                        NULL, NULL,
+                                                        -GIMP_MAX_IMAGE_SIZE,
+                                                        GIMP_MAX_IMAGE_SIZE,
+                                                        0.0,
+                                                        GIMP_PARAM_READWRITE |
+                                                        G_PARAM_CONSTRUCT));
+
+  g_object_class_install_property (object_class, PROP_PIVOT_Y,
+                                   g_param_spec_double ("pivot-y",
+                                                        NULL, NULL,
+                                                        -GIMP_MAX_IMAGE_SIZE,
+                                                        GIMP_MAX_IMAGE_SIZE,
+                                                        0.0,
+                                                        GIMP_PARAM_READWRITE |
+                                                        G_PARAM_CONSTRUCT));
+
+  g_object_class_install_property (object_class, PROP_GUIDE_TYPE,
+                                   g_param_spec_enum ("guide-type", NULL, NULL,
+                                                      GIMP_TYPE_GUIDES_TYPE,
+                                                      GIMP_GUIDES_NONE,
+                                                      GIMP_PARAM_READWRITE |
+                                                      G_PARAM_CONSTRUCT));
+
+  g_object_class_install_property (object_class, PROP_N_GUIDES,
+                                   g_param_spec_int ("n-guides", NULL, NULL,
+                                                     1, 128, 4,
+                                                     GIMP_PARAM_READWRITE |
+                                                     G_PARAM_CONSTRUCT));
+
+  g_object_class_install_property (object_class, PROP_CLIP_GUIDES,
+                                   g_param_spec_boolean ("clip-guides", NULL, NULL,
+                                                         FALSE,
+                                                         GIMP_PARAM_READWRITE |
+                                                         G_PARAM_CONSTRUCT));
+
+  g_object_class_install_property (object_class, PROP_SHOW_GUIDES,
+                                   g_param_spec_boolean ("show-guides", NULL, NULL,
+                                                         TRUE,
+                                                         GIMP_PARAM_READWRITE |
+                                                         G_PARAM_CONSTRUCT));
+
+  g_object_class_install_property (object_class, PROP_INSIDE_FUNCTION,
+                                   g_param_spec_enum ("inside-function",
+                                                      NULL, NULL,
+                                                      GIMP_TYPE_TRANSFORM_FUNCTION,
+                                                      GIMP_TRANSFORM_FUNCTION_MOVE,
+                                                      GIMP_PARAM_READWRITE |
+                                                      G_PARAM_CONSTRUCT));
+
+  g_object_class_install_property (object_class, PROP_OUTSIDE_FUNCTION,
+                                   g_param_spec_enum ("outside-function",
+                                                      NULL, NULL,
+                                                      GIMP_TYPE_TRANSFORM_FUNCTION,
+                                                      GIMP_TRANSFORM_FUNCTION_ROTATE,
+                                                      GIMP_PARAM_READWRITE |
+                                                      G_PARAM_CONSTRUCT));
+
+  g_object_class_install_property (object_class, PROP_USE_CORNER_HANDLES,
+                                   g_param_spec_boolean ("use-corner-handles",
+                                                         NULL, NULL,
+                                                         FALSE,
+                                                         GIMP_PARAM_READWRITE |
+                                                         G_PARAM_CONSTRUCT));
+
+  g_object_class_install_property (object_class, PROP_USE_PERSPECTIVE_HANDLES,
+                                   g_param_spec_boolean ("use-perspective-handles",
+                                                         NULL, NULL,
+                                                         FALSE,
+                                                         GIMP_PARAM_READWRITE |
+                                                         G_PARAM_CONSTRUCT));
+
+  g_object_class_install_property (object_class, PROP_USE_SIDE_HANDLES,
+                                   g_param_spec_boolean ("use-side-handles",
+                                                         NULL, NULL,
+                                                         FALSE,
+                                                         GIMP_PARAM_READWRITE |
+                                                         G_PARAM_CONSTRUCT));
+
+  g_object_class_install_property (object_class, PROP_USE_SHEAR_HANDLES,
+                                   g_param_spec_boolean ("use-shear-handles",
+                                                         NULL, NULL,
+                                                         FALSE,
+                                                         GIMP_PARAM_READWRITE |
+                                                         G_PARAM_CONSTRUCT));
+
+  g_object_class_install_property (object_class, PROP_USE_CENTER_HANDLE,
+                                   g_param_spec_boolean ("use-center-handle",
+                                                         NULL, NULL,
+                                                         FALSE,
+                                                         GIMP_PARAM_READWRITE |
+                                                         G_PARAM_CONSTRUCT));
+
+  g_object_class_install_property (object_class, PROP_USE_PIVOT_HANDLE,
+                                   g_param_spec_boolean ("use-pivot-handle",
+                                                         NULL, NULL,
+                                                         FALSE,
+                                                         GIMP_PARAM_READWRITE |
+                                                         G_PARAM_CONSTRUCT));
+
+  g_object_class_install_property (object_class, PROP_DYNAMIC_HANDLE_SIZE,
+                                   g_param_spec_boolean ("dynamic-handle-size",
+                                                         NULL, NULL,
+                                                         TRUE,
+                                                         GIMP_PARAM_READWRITE |
+                                                         G_PARAM_CONSTRUCT));
+
+  g_object_class_install_property (object_class, PROP_CONSTRAIN_MOVE,
+                                   g_param_spec_boolean ("constrain-move",
+                                                         NULL, NULL,
+                                                         FALSE,
+                                                         GIMP_PARAM_READWRITE |
+                                                         G_PARAM_CONSTRUCT));
+
+  g_object_class_install_property (object_class, PROP_CONSTRAIN_SCALE,
+                                   g_param_spec_boolean ("constrain-scale",
+                                                         NULL, NULL,
+                                                         FALSE,
+                                                         GIMP_PARAM_READWRITE |
+                                                         G_PARAM_CONSTRUCT));
+
+  g_object_class_install_property (object_class, PROP_CONSTRAIN_ROTATE,
+                                   g_param_spec_boolean ("constrain-rotate",
+                                                         NULL, NULL,
+                                                         FALSE,
+                                                         GIMP_PARAM_READWRITE |
+                                                         G_PARAM_CONSTRUCT));
+
+  g_object_class_install_property (object_class, PROP_CONSTRAIN_SHEAR,
+                                   g_param_spec_boolean ("constrain-shear",
+                                                         NULL, NULL,
+                                                         FALSE,
+                                                         GIMP_PARAM_READWRITE |
+                                                         G_PARAM_CONSTRUCT));
+
+  g_object_class_install_property (object_class, PROP_CONSTRAIN_PERSPECTIVE,
+                                   g_param_spec_boolean ("constrain-perspective",
+                                                         NULL, NULL,
+                                                         FALSE,
+                                                         GIMP_PARAM_READWRITE |
+                                                         G_PARAM_CONSTRUCT));
+
+  g_object_class_install_property (object_class, PROP_FROMPIVOT_SCALE,
+                                   g_param_spec_boolean ("frompivot-scale",
+                                                         NULL, NULL,
+                                                         FALSE,
+                                                         GIMP_PARAM_READWRITE |
+                                                         G_PARAM_CONSTRUCT));
+
+  g_object_class_install_property (object_class, PROP_FROMPIVOT_SHEAR,
+                                   g_param_spec_boolean ("frompivot-shear",
+                                                         NULL, NULL,
+                                                         FALSE,
+                                                         GIMP_PARAM_READWRITE |
+                                                         G_PARAM_CONSTRUCT));
+
+  g_object_class_install_property (object_class, PROP_FROMPIVOT_PERSPECTIVE,
+                                   g_param_spec_boolean ("frompivot-perspective",
+                                                         NULL, NULL,
+                                                         FALSE,
+                                                         GIMP_PARAM_READWRITE |
+                                                         G_PARAM_CONSTRUCT));
+
+  g_object_class_install_property (object_class, PROP_CORNERSNAP,
+                                   g_param_spec_boolean ("cornersnap",
+                                                         NULL, NULL,
+                                                         FALSE,
+                                                         GIMP_PARAM_READWRITE |
+                                                         G_PARAM_CONSTRUCT));
+
+  g_object_class_install_property (object_class, PROP_FIXEDPIVOT,
+                                   g_param_spec_boolean ("fixedpivot",
+                                                         NULL, NULL,
+                                                         FALSE,
+                                                         GIMP_PARAM_READWRITE |
+                                                         G_PARAM_CONSTRUCT));
+}
+
+static void
+gimp_tool_transform_grid_init (GimpToolTransformGrid *grid)
+{
+  grid->private = gimp_tool_transform_grid_get_instance_private (grid);
+}
+
+static void
+gimp_tool_transform_grid_constructed (GObject *object)
+{
+  GimpToolTransformGrid        *grid    = GIMP_TOOL_TRANSFORM_GRID (object);
+  GimpToolWidget               *widget  = GIMP_TOOL_WIDGET (object);
+  GimpToolTransformGridPrivate *private = grid->private;
+  GimpCanvasGroup              *stroke_group;
+  gint                          i;
+
+  G_OBJECT_CLASS (parent_class)->constructed (object);
+
+  private->guides = gimp_tool_widget_add_transform_guides (widget,
+                                                           &private->transform,
+                                                           private->x1,
+                                                           private->y1,
+                                                           private->x2,
+                                                           private->y2,
+                                                           private->guide_type,
+                                                           private->n_guides,
+                                                           private->clip_guides);
+
+  for (i = 0; i < 4; i++)
+    {
+      /*  draw the scale handles  */
+      private->handles[GIMP_TRANSFORM_HANDLE_NW + i] =
+        gimp_tool_widget_add_handle (widget,
+                                     GIMP_HANDLE_SQUARE,
+                                     0, 0, 10, 10,
+                                     GIMP_HANDLE_ANCHOR_CENTER);
+
+      /*  draw the perspective handles  */
+      private->handles[GIMP_TRANSFORM_HANDLE_NW_P + i] =
+        gimp_tool_widget_add_handle (widget,
+                                     GIMP_HANDLE_DIAMOND,
+                                     0, 0, 10, 10,
+                                     GIMP_HANDLE_ANCHOR_CENTER);
+
+      /*  draw the side handles  */
+      private->handles[GIMP_TRANSFORM_HANDLE_N + i] =
+        gimp_tool_widget_add_handle (widget,
+                                     GIMP_HANDLE_SQUARE,
+                                     0, 0, 10, 10,
+                                     GIMP_HANDLE_ANCHOR_CENTER);
+
+      /*  draw the shear handles  */
+      private->handles[GIMP_TRANSFORM_HANDLE_N_S + i] =
+        gimp_tool_widget_add_handle (widget,
+                                     GIMP_HANDLE_FILLED_DIAMOND,
+                                     0, 0, 10, 10,
+                                     GIMP_HANDLE_ANCHOR_CENTER);
+    }
+
+  /*  draw the rotation center axis handle  */
+  stroke_group = gimp_tool_widget_add_stroke_group (widget);
+
+  private->handles[GIMP_TRANSFORM_HANDLE_PIVOT] =
+    GIMP_CANVAS_ITEM (stroke_group);
+
+  gimp_tool_widget_push_group (widget, stroke_group);
+
+  private->pivot_items[0] =
+    gimp_tool_widget_add_handle (widget,
+                                 GIMP_HANDLE_CIRCLE,
+                                 0, 0, 10, 10,
+                                 GIMP_HANDLE_ANCHOR_CENTER);
+  private->pivot_items[1] =
+    gimp_tool_widget_add_handle (widget,
+                                 GIMP_HANDLE_CROSS,
+                                 0, 0, 10, 10,
+                                 GIMP_HANDLE_ANCHOR_CENTER);
+
+  gimp_tool_widget_pop_group (widget);
+
+  /*  draw the center handle  */
+  stroke_group = gimp_tool_widget_add_stroke_group (widget);
+
+  private->handles[GIMP_TRANSFORM_HANDLE_CENTER] =
+    GIMP_CANVAS_ITEM (stroke_group);
+
+  gimp_tool_widget_push_group (widget, stroke_group);
+
+  private->center_items[0] =
+    gimp_tool_widget_add_handle (widget,
+                                 GIMP_HANDLE_SQUARE,
+                                 0, 0, 10, 10,
+                                 GIMP_HANDLE_ANCHOR_CENTER);
+  private->center_items[1] =
+    gimp_tool_widget_add_handle (widget,
+                                 GIMP_HANDLE_CROSS,
+                                 0, 0, 10, 10,
+                                 GIMP_HANDLE_ANCHOR_CENTER);
+
+  gimp_tool_widget_pop_group (widget);
+
+  gimp_tool_transform_grid_changed (widget);
+}
+
+static void
+gimp_tool_transform_grid_set_property (GObject      *object,
+                                       guint         property_id,
+                                       const GValue *value,
+                                       GParamSpec   *pspec)
+{
+  GimpToolTransformGrid        *grid    = GIMP_TOOL_TRANSFORM_GRID (object);
+  GimpToolTransformGridPrivate *private = grid->private;
+  gboolean                      box     = FALSE;
+
+  switch (property_id)
+    {
+    case PROP_TRANSFORM:
+      {
+        GimpMatrix3 *transform = g_value_get_boxed (value);
+
+        if (transform)
+          private->transform = *transform;
+        else
+          gimp_matrix3_identity (&private->transform);
+      }
+      break;
+
+    case PROP_X1:
+      private->x1 = g_value_get_double (value);
+      box = TRUE;
+      break;
+    case PROP_Y1:
+      private->y1 = g_value_get_double (value);
+      box = TRUE;
+      break;
+    case PROP_X2:
+      private->x2 = g_value_get_double (value);
+      box = TRUE;
+      break;
+    case PROP_Y2:
+      private->y2 = g_value_get_double (value);
+      box = TRUE;
+      break;
+
+    case PROP_PIVOT_X:
+      private->pivot_x = g_value_get_double (value);
+      break;
+    case PROP_PIVOT_Y:
+      private->pivot_y = g_value_get_double (value);
+      break;
+
+    case PROP_GUIDE_TYPE:
+      private->guide_type = g_value_get_enum (value);
+      break;
+    case PROP_N_GUIDES:
+      private->n_guides = g_value_get_int (value);
+      break;
+    case PROP_CLIP_GUIDES:
+      private->clip_guides = g_value_get_boolean (value);
+      break;
+    case PROP_SHOW_GUIDES:
+      private->show_guides = g_value_get_boolean (value);
+      break;
+
+    case PROP_INSIDE_FUNCTION:
+      private->inside_function = g_value_get_enum (value);
+      break;
+    case PROP_OUTSIDE_FUNCTION:
+      private->outside_function = g_value_get_enum (value);
+      break;
+
+    case PROP_USE_CORNER_HANDLES:
+      private->use_corner_handles = g_value_get_boolean (value);
+      break;
+    case PROP_USE_PERSPECTIVE_HANDLES:
+      private->use_perspective_handles = g_value_get_boolean (value);
+      break;
+    case PROP_USE_SIDE_HANDLES:
+      private->use_side_handles = g_value_get_boolean (value);
+      break;
+    case PROP_USE_SHEAR_HANDLES:
+      private->use_shear_handles = g_value_get_boolean (value);
+      break;
+    case PROP_USE_CENTER_HANDLE:
+      private->use_center_handle = g_value_get_boolean (value);
+      break;
+    case PROP_USE_PIVOT_HANDLE:
+      private->use_pivot_handle = g_value_get_boolean (value);
+      break;
+
+    case PROP_DYNAMIC_HANDLE_SIZE:
+      private->dynamic_handle_size = g_value_get_boolean (value);
+      break;
+
+    case PROP_CONSTRAIN_MOVE:
+      private->constrain_move = g_value_get_boolean (value);
+      break;
+    case PROP_CONSTRAIN_SCALE:
+      private->constrain_scale = g_value_get_boolean (value);
+      break;
+    case PROP_CONSTRAIN_ROTATE:
+      private->constrain_rotate = g_value_get_boolean (value);
+      break;
+    case PROP_CONSTRAIN_SHEAR:
+      private->constrain_shear = g_value_get_boolean (value);
+      break;
+    case PROP_CONSTRAIN_PERSPECTIVE:
+      private->constrain_perspective = g_value_get_boolean (value);
+      break;
+
+    case PROP_FROMPIVOT_SCALE:
+      private->frompivot_scale = g_value_get_boolean (value);
+      break;
+    case PROP_FROMPIVOT_SHEAR:
+      private->frompivot_shear = g_value_get_boolean (value);
+      break;
+    case PROP_FROMPIVOT_PERSPECTIVE:
+      private->frompivot_perspective = g_value_get_boolean (value);
+      break;
+
+    case PROP_CORNERSNAP:
+      private->cornersnap = g_value_get_boolean (value);
+      break;
+    case PROP_FIXEDPIVOT:
+      private->fixedpivot = g_value_get_boolean (value);
+      break;
+
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, property_id, pspec);
+      break;
+    }
+
+  if (box)
+    {
+      private->cx = (private->x1 + private->x2) / 2.0;
+      private->cy = (private->y1 + private->y2) / 2.0;
+    }
+}
+
+static void
+gimp_tool_transform_grid_get_property (GObject    *object,
+                                       guint       property_id,
+                                       GValue     *value,
+                                       GParamSpec *pspec)
+{
+  GimpToolTransformGrid        *grid    = GIMP_TOOL_TRANSFORM_GRID (object);
+  GimpToolTransformGridPrivate *private = grid->private;
+
+  switch (property_id)
+    {
+    case PROP_TRANSFORM:
+      g_value_set_boxed (value, &private->transform);
+      break;
+
+    case PROP_X1:
+      g_value_set_double (value, private->x1);
+      break;
+    case PROP_Y1:
+      g_value_set_double (value, private->y1);
+      break;
+    case PROP_X2:
+      g_value_set_double (value, private->x2);
+      break;
+    case PROP_Y2:
+      g_value_set_double (value, private->y2);
+      break;
+
+    case PROP_PIVOT_X:
+      g_value_set_double (value, private->pivot_x);
+      break;
+    case PROP_PIVOT_Y:
+      g_value_set_double (value, private->pivot_y);
+      break;
+
+    case PROP_GUIDE_TYPE:
+      g_value_set_enum (value, private->guide_type);
+      break;
+    case PROP_N_GUIDES:
+      g_value_set_int (value, private->n_guides);
+      break;
+    case PROP_CLIP_GUIDES:
+      g_value_set_boolean (value, private->clip_guides);
+      break;
+    case PROP_SHOW_GUIDES:
+      g_value_set_boolean (value, private->show_guides);
+      break;
+
+    case PROP_INSIDE_FUNCTION:
+      g_value_set_enum (value, private->inside_function);
+      break;
+    case PROP_OUTSIDE_FUNCTION:
+      g_value_set_enum (value, private->outside_function);
+      break;
+
+    case PROP_USE_CORNER_HANDLES:
+      g_value_set_boolean (value, private->use_corner_handles);
+      break;
+    case PROP_USE_PERSPECTIVE_HANDLES:
+      g_value_set_boolean (value, private->use_perspective_handles);
+      break;
+    case PROP_USE_SIDE_HANDLES:
+      g_value_set_boolean (value, private->use_side_handles);
+      break;
+    case PROP_USE_SHEAR_HANDLES:
+      g_value_set_boolean (value, private->use_shear_handles);
+      break;
+    case PROP_USE_CENTER_HANDLE:
+      g_value_set_boolean (value, private->use_center_handle);
+      break;
+    case PROP_USE_PIVOT_HANDLE:
+      g_value_set_boolean (value, private->use_pivot_handle);
+      break;
+
+    case PROP_DYNAMIC_HANDLE_SIZE:
+      g_value_set_boolean (value, private->dynamic_handle_size);
+      break;
+
+    case PROP_CONSTRAIN_MOVE:
+      g_value_set_boolean (value, private->constrain_move);
+      break;
+    case PROP_CONSTRAIN_SCALE:
+      g_value_set_boolean (value, private->constrain_scale);
+      break;
+    case PROP_CONSTRAIN_ROTATE:
+      g_value_set_boolean (value, private->constrain_rotate);
+      break;
+    case PROP_CONSTRAIN_SHEAR:
+      g_value_set_boolean (value, private->constrain_shear);
+      break;
+    case PROP_CONSTRAIN_PERSPECTIVE:
+      g_value_set_boolean (value, private->constrain_perspective);
+      break;
+
+    case PROP_FROMPIVOT_SCALE:
+      g_value_set_boolean (value, private->frompivot_scale);
+      break;
+    case PROP_FROMPIVOT_SHEAR:
+      g_value_set_boolean (value, private->frompivot_shear);
+      break;
+    case PROP_FROMPIVOT_PERSPECTIVE:
+      g_value_set_boolean (value, private->frompivot_perspective);
+      break;
+
+    case PROP_CORNERSNAP:
+      g_value_set_boolean (value, private->cornersnap);
+      break;
+    case PROP_FIXEDPIVOT:
+      g_value_set_boolean (value, private->fixedpivot);
+      break;
+
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, property_id, pspec);
+      break;
+    }
+}
+
+static gboolean
+transform_is_convex (GimpVector2 *pos)
+{
+  return gimp_transform_polygon_is_convex (pos[0].x, pos[0].y,
+                                           pos[1].x, pos[1].y,
+                                           pos[2].x, pos[2].y,
+                                           pos[3].x, pos[3].y);
+}
+
+static gboolean
+transform_grid_is_convex (GimpToolTransformGrid *grid)
+{
+  GimpToolTransformGridPrivate *private = grid->private;
+
+  return gimp_transform_polygon_is_convex (private->tx1, private->ty1,
+                                           private->tx2, private->ty2,
+                                           private->tx3, private->ty3,
+                                           private->tx4, private->ty4);
+}
+
+static inline gboolean
+vectorisnull (GimpVector2 v)
+{
+  return ((v.x == 0.0) && (v.y == 0.0));
+}
+
+static inline gdouble
+dotprod (GimpVector2 a,
+         GimpVector2 b)
+{
+  return a.x * b.x + a.y * b.y;
+}
+
+static inline gdouble
+norm (GimpVector2 a)
+{
+  return sqrt (dotprod (a, a));
+}
+
+static inline GimpVector2
+vectorsubtract (GimpVector2 a,
+                GimpVector2 b)
+{
+  GimpVector2 c;
+
+  c.x = a.x - b.x;
+  c.y = a.y - b.y;
+
+  return c;
+}
+
+static inline GimpVector2
+vectoradd (GimpVector2 a,
+           GimpVector2 b)
+{
+  GimpVector2 c;
+
+  c.x = a.x + b.x;
+  c.y = a.y + b.y;
+
+  return c;
+}
+
+static inline GimpVector2
+scalemult (GimpVector2 a,
+           gdouble     b)
+{
+  GimpVector2 c;
+
+  c.x = a.x * b;
+  c.y = a.y * b;
+
+  return c;
+}
+
+static inline GimpVector2
+vectorproject (GimpVector2 a,
+               GimpVector2 b)
+{
+  return scalemult (b, dotprod (a, b) / dotprod (b, b));
+}
+
+/* finds the clockwise angle between the vectors given, 0-2π */
+static inline gdouble
+calcangle (GimpVector2 a,
+           GimpVector2 b)
+{
+  gdouble angle, angle2;
+  gdouble length;
+
+  if (vectorisnull (a) || vectorisnull (b))
+    return 0.0;
+
+  length = norm (a) * norm (b);
+
+  angle = acos (SAFE_CLAMP (dotprod (a, b) / length, -1.0, +1.0));
+  angle2 = b.y;
+  b.y = -b.x;
+  b.x = angle2;
+  angle2 = acos (SAFE_CLAMP (dotprod (a, b) / length, -1.0, +1.0));
+
+  return ((angle2 > G_PI / 2.0) ? angle : 2.0 * G_PI - angle);
+}
+
+static inline GimpVector2
+rotate2d (GimpVector2 p,
+          gdouble     angle)
+{
+  GimpVector2 ret;
+
+  ret.x = cos (angle) * p.x-sin (angle) * p.y;
+  ret.y = sin (angle) * p.x+cos (angle) * p.y;
+
+  return ret;
+}
+
+static inline GimpVector2
+lineintersect (GimpVector2 p1, GimpVector2 p2,
+               GimpVector2 q1, GimpVector2 q2)
+{
+  gdouble     denom, u;
+  GimpVector2 p;
+
+  denom = (q2.y - q1.y) * (p2.x - p1.x) - (q2.x - q1.x) * (p2.y - p1.y);
+  if (denom == 0.0)
+    {
+      p.x = (p1.x + p2.x + q1.x + q2.x) / 4;
+      p.y = (p1.y + p2.y + q1.y + q2.y) / 4;
+    }
+  else
+    {
+      u = (q2.x - q1.x) * (p1.y - q1.y) - (q2.y - q1.y) * (p1.x - q1.x);
+      u /= denom;
+
+      p.x = p1.x + u * (p2.x - p1.x);
+      p.y = p1.y + u * (p2.y - p1.y);
+    }
+
+  return p;
+}
+
+static inline GimpVector2
+get_pivot_delta (GimpToolTransformGrid *grid,
+                 GimpVector2           *oldpos,
+                 GimpVector2           *newpos,
+                 GimpVector2            pivot)
+{
+  GimpToolTransformGridPrivate *private = grid->private;
+  GimpMatrix3                   transform_before;
+  GimpMatrix3                   transform_after;
+  GimpVector2                   delta;
+
+  gimp_matrix3_identity (&transform_before);
+  gimp_matrix3_identity (&transform_after);
+
+  gimp_transform_matrix_perspective (&transform_before,
+                                     private->x1,
+                                     private->y1,
+                                     private->x2 - private->x1,
+                                     private->y2 - private->y1,
+                                     oldpos[0].x, oldpos[0].y,
+                                     oldpos[1].x, oldpos[1].y,
+                                     oldpos[2].x, oldpos[2].y,
+                                     oldpos[3].x, oldpos[3].y);
+  gimp_transform_matrix_perspective (&transform_after,
+                                     private->x1,
+                                     private->y1,
+                                     private->x2 - private->x1,
+                                     private->y2 - private->y1,
+                                     newpos[0].x, newpos[0].y,
+                                     newpos[1].x, newpos[1].y,
+                                     newpos[2].x, newpos[2].y,
+                                     newpos[3].x, newpos[3].y);
+  gimp_matrix3_invert (&transform_before);
+  gimp_matrix3_mult (&transform_after, &transform_before);
+  gimp_matrix3_transform_point (&transform_before,
+                                pivot.x, pivot.y, &delta.x, &delta.y);
+
+  delta = vectorsubtract (delta, pivot);
+
+  return delta;
+}
+
+static gboolean
+point_is_inside_polygon (gint     n,
+                         gdouble *x,
+                         gdouble *y,
+                         gdouble  px,
+                         gdouble  py)
+{
+  gint     i, j;
+  gboolean odd = FALSE;
+
+  for (i = 0, j = n - 1; i < n; j = i++)
+    {
+      if ((y[i] < py && y[j] >= py) ||
+          (y[j] < py && y[i] >= py))
+        {
+          if (x[i] + (py - y[i]) / (y[j] - y[i]) * (x[j] - x[i]) < px)
+            odd = !odd;
+        }
+    }
+
+  return odd;
+}
+
+static gboolean
+point_is_inside_polygon_pos (GimpVector2 *pos,
+                             GimpVector2  point)
+{
+  return point_is_inside_polygon (4,
+                                  (gdouble[4]){ pos[0].x, pos[1].x,
+                                                pos[3].x, pos[2].x },
+                                  (gdouble[4]){ pos[0].y, pos[1].y,
+                                                pos[3].y, pos[2].y },
+                                  point.x, point.y);
+}
+
+static void
+get_handle_geometry (GimpToolTransformGrid *grid,
+                     GimpVector2           *position,
+                     gdouble               *angle)
+{
+  GimpToolTransformGridPrivate *private = grid->private;
+
+  GimpVector2 o[] = { { .x = private->tx1, .y = private->ty1 },
+                      { .x = private->tx2, .y = private->ty2 },
+                      { .x = private->tx3, .y = private->ty3 },
+                      { .x = private->tx4, .y = private->ty4 } };
+  GimpVector2 right = { .x = 1.0, .y = 0.0 };
+  GimpVector2 up    = { .x = 0.0, .y = 1.0 };
+
+  if (position)
+    {
+      position[0] = o[0];
+      position[1] = o[1];
+      position[2] = o[2];
+      position[3] = o[3];
+    }
+
+  angle[0] = calcangle (vectorsubtract (o[1], o[0]), right);
+  angle[1] = calcangle (vectorsubtract (o[3], o[2]), right);
+  angle[2] = calcangle (vectorsubtract (o[3], o[1]), up);
+  angle[3] = calcangle (vectorsubtract (o[2], o[0]), up);
+
+  angle[4] = (angle[0] + angle[3]) / 2.0;
+  angle[5] = (angle[0] + angle[2]) / 2.0;
+  angle[6] = (angle[1] + angle[3]) / 2.0;
+  angle[7] = (angle[1] + angle[2]) / 2.0;
+
+  angle[8] = (angle[0] + angle[1] + angle[2] + angle[3]) / 4.0;
+}
+
+static void
+gimp_tool_transform_grid_changed (GimpToolWidget *widget)
+{
+  GimpToolTransformGrid        *grid    = GIMP_TOOL_TRANSFORM_GRID (widget);
+  GimpToolTransformGridPrivate *private = grid->private;
+  gdouble                       angle[9];
+  GimpVector2                   o[4], t[4];
+  gint                          handle_w;
+  gint                          handle_h;
+  gint                          d, i;
+
+  gimp_tool_transform_grid_update_box (grid);
+
+  gimp_canvas_transform_guides_set (private->guides,
+                                    &private->transform,
+                                    private->x1,
+                                    private->y1,
+                                    private->x2,
+                                    private->y2,
+                                    private->guide_type,
+                                    private->n_guides,
+                                    private->clip_guides);
+  gimp_canvas_item_set_visible (private->guides, private->show_guides);
+
+  get_handle_geometry (grid, o, angle);
+  gimp_tool_transform_grid_calc_handles (grid, &handle_w, &handle_h);
+
+  for (i = 0; i < 4; i++)
+    {
+      GimpCanvasItem *h;
+      gdouble         factor;
+
+      /*  the scale handles  */
+      factor = 1.0;
+      if (private->use_perspective_handles)
+        factor = 1.5;
+
+      h = private->handles[GIMP_TRANSFORM_HANDLE_NW + i];
+      gimp_canvas_item_set_visible (h, private->use_corner_handles);
+
+      if (private->use_corner_handles)
+        {
+          gimp_canvas_handle_set_position (h, o[i].x, o[i].y);
+          gimp_canvas_handle_set_size (h, handle_w * factor, handle_h * factor);
+          gimp_canvas_handle_set_angles (h, angle[i + 4], 0.0);
+        }
+
+      /*  the perspective handles  */
+      factor = 1.0;
+      if (private->use_corner_handles)
+        factor = 0.8;
+
+      h = private->handles[GIMP_TRANSFORM_HANDLE_NW_P + i];
+      gimp_canvas_item_set_visible (h, private->use_perspective_handles);
+
+      if (private->use_perspective_handles)
+        {
+          gimp_canvas_handle_set_position (h, o[i].x, o[i].y);
+          gimp_canvas_handle_set_size (h, handle_w * factor, handle_h * factor);
+          gimp_canvas_handle_set_angles (h, angle[i + 4], 0.0);
+        }
+    }
+
+  /*  draw the side handles  */
+  t[0] = scalemult (vectoradd (o[0], o[1]), 0.5);
+  t[1] = scalemult (vectoradd (o[2], o[3]), 0.5);
+  t[2] = scalemult (vectoradd (o[1], o[3]), 0.5);
+  t[3] = scalemult (vectoradd (o[2], o[0]), 0.5);
+
+  for (i = 0; i < 4; i++)
+    {
+      GimpCanvasItem *h;
+
+      h = private->handles[GIMP_TRANSFORM_HANDLE_N + i];
+      gimp_canvas_item_set_visible (h, private->use_side_handles);
+
+      if (private->use_side_handles)
+        {
+          gimp_canvas_handle_set_position (h, t[i].x, t[i].y);
+          gimp_canvas_handle_set_size (h, handle_w, handle_h);
+          gimp_canvas_handle_set_angles (h, angle[i], 0.0);
+        }
+    }
+
+  /*  draw the shear handles  */
+  t[0] = scalemult (vectoradd (           o[0]      , scalemult (o[1], 3.0)),
+                    0.25);
+  t[1] = scalemult (vectoradd (scalemult (o[2], 3.0),            o[3]      ),
+                    0.25);
+  t[2] = scalemult (vectoradd (           o[1]      , scalemult (o[3], 3.0)),
+                    0.25);
+  t[3] = scalemult (vectoradd (scalemult (o[0], 3.0),            o[2]      ),
+                    0.25);
+
+  for (i = 0; i < 4; i++)
+    {
+      GimpCanvasItem *h;
+
+      h = private->handles[GIMP_TRANSFORM_HANDLE_N_S + i];
+      gimp_canvas_item_set_visible (h, private->use_shear_handles);
+
+      if (private->use_shear_handles)
+        {
+          gimp_canvas_handle_set_position (h, t[i].x, t[i].y);
+          gimp_canvas_handle_set_size (h, handle_w, handle_h);
+          gimp_canvas_handle_set_angles (h, angle[i], 0.0);
+        }
+    }
+
+  d = MIN (handle_w, handle_h);
+  if (private->use_center_handle)
+    d *= 2; /* so you can grab it from under the center handle */
+
+  gimp_canvas_item_set_visible (private->handles[GIMP_TRANSFORM_HANDLE_PIVOT],
+                                private->use_pivot_handle);
+
+  if (private->use_pivot_handle)
+    {
+      gimp_canvas_handle_set_position (private->pivot_items[0],
+                                       private->tpx, private->tpy);
+      gimp_canvas_handle_set_size (private->pivot_items[0], d, d);
+
+      gimp_canvas_handle_set_position (private->pivot_items[1],
+                                       private->tpx, private->tpy);
+      gimp_canvas_handle_set_size (private->pivot_items[1], d, d);
+    }
+
+  d = MIN (handle_w, handle_h);
+
+  gimp_canvas_item_set_visible (private->handles[GIMP_TRANSFORM_HANDLE_CENTER],
+                                private->use_center_handle);
+
+  if (private->use_center_handle)
+    {
+      gimp_canvas_handle_set_position (private->center_items[0],
+                                       private->tcx, private->tcy);
+      gimp_canvas_handle_set_size (private->center_items[0], d, d);
+      gimp_canvas_handle_set_angles (private->center_items[0], angle[8], 0.0);
+
+      gimp_canvas_handle_set_position (private->center_items[1],
+                                       private->tcx, private->tcy);
+      gimp_canvas_handle_set_size (private->center_items[1], d, d);
+      gimp_canvas_handle_set_angles (private->center_items[1], angle[8], 0.0);
+    }
+
+  gimp_tool_transform_grid_update_hilight (grid);
+}
+
+gint
+gimp_tool_transform_grid_button_press (GimpToolWidget      *widget,
+                                       const GimpCoords    *coords,
+                                       guint32              time,
+                                       GdkModifierType      state,
+                                       GimpButtonPressType  press_type)
+{
+  GimpToolTransformGrid        *grid    = GIMP_TOOL_TRANSFORM_GRID (widget);
+  GimpToolTransformGridPrivate *private = grid->private;
+
+  private->button_down = TRUE;
+  private->mousex      = coords->x;
+  private->mousey      = coords->y;
+
+  if (private->handle != GIMP_TRANSFORM_HANDLE_NONE)
+    {
+      if (private->handles[private->handle])
+        {
+          GimpCanvasItem *handle;
+          gdouble         x, y;
+
+          switch (private->handle)
+            {
+            case GIMP_TRANSFORM_HANDLE_CENTER:
+              handle = private->center_items[0];
+              break;
+
+            case GIMP_TRANSFORM_HANDLE_PIVOT:
+              handle = private->pivot_items[0];
+              break;
+
+             default:
+              handle = private->handles[private->handle];
+              break;
+            }
+
+          gimp_canvas_handle_get_position (handle, &x, &y);
+
+          gimp_tool_widget_set_snap_offsets (widget,
+                                             SIGNED_ROUND (x - coords->x),
+                                             SIGNED_ROUND (y - coords->y),
+                                             0, 0);
+        }
+      else
+        {
+          gimp_tool_widget_set_snap_offsets (widget, 0, 0, 0, 0);
+        }
+
+      private->prev_tx1 = private->tx1;
+      private->prev_ty1 = private->ty1;
+      private->prev_tx2 = private->tx2;
+      private->prev_ty2 = private->ty2;
+      private->prev_tx3 = private->tx3;
+      private->prev_ty3 = private->ty3;
+      private->prev_tx4 = private->tx4;
+      private->prev_ty4 = private->ty4;
+      private->prev_tpx = private->tpx;
+      private->prev_tpy = private->tpy;
+      private->prev_tcx = private->tcx;
+      private->prev_tcy = private->tcy;
+
+      return private->handle;
+    }
+
+  gimp_tool_widget_set_snap_offsets (widget, 0, 0, 0, 0);
+
+  return 0;
+}
+
+void
+gimp_tool_transform_grid_button_release (GimpToolWidget        *widget,
+                                         const GimpCoords      *coords,
+                                         guint32                time,
+                                         GdkModifierType        state,
+                                         GimpButtonReleaseType  release_type)
+{
+  GimpToolTransformGrid        *grid    = GIMP_TOOL_TRANSFORM_GRID (widget);
+  GimpToolTransformGridPrivate *private = grid->private;
+
+  private->button_down = FALSE;
+}
+
+void
+gimp_tool_transform_grid_motion (GimpToolWidget   *widget,
+                                 const GimpCoords *coords,
+                                 guint32           time,
+                                 GdkModifierType   state)
+{
+  GimpToolTransformGrid        *grid    = GIMP_TOOL_TRANSFORM_GRID (widget);
+  GimpToolTransformGridPrivate *private = grid->private;
+  gdouble                      *x[4], *y[4];
+  gdouble                      *newpivot_x, *newpivot_y;
+
+  GimpVector2                  oldpos[5], newpos[4];
+  GimpVector2                  cur   = { .x = coords->x,
+                                         .y = coords->y };
+  GimpVector2                  mouse = { .x = private->mousex,
+                                         .y = private->mousey };
+  GimpVector2                  d;
+  GimpVector2                  pivot;
+
+  gboolean                     fixedpivot = private->fixedpivot;
+  GimpTransformHandle          handle     = private->handle;
+  gint                         i;
+
+  private->curx = coords->x;
+  private->cury = coords->y;
+
+  x[0] = &private->tx1;
+  y[0] = &private->ty1;
+  x[1] = &private->tx2;
+  y[1] = &private->ty2;
+  x[2] = &private->tx3;
+  y[2] = &private->ty3;
+  x[3] = &private->tx4;
+  y[3] = &private->ty4;
+
+  newpos[0].x = oldpos[0].x = private->prev_tx1;
+  newpos[0].y = oldpos[0].y = private->prev_ty1;
+  newpos[1].x = oldpos[1].x = private->prev_tx2;
+  newpos[1].y = oldpos[1].y = private->prev_ty2;
+  newpos[2].x = oldpos[2].x = private->prev_tx3;
+  newpos[2].y = oldpos[2].y = private->prev_ty3;
+  newpos[3].x = oldpos[3].x = private->prev_tx4;
+  newpos[3].y = oldpos[3].y = private->prev_ty4;
+
+  /* put center point in this array too */
+  oldpos[4].x = private->prev_tcx;
+  oldpos[4].y = private->prev_tcy;
+
+  d = vectorsubtract (cur, mouse);
+
+  newpivot_x = &private->tpx;
+  newpivot_y = &private->tpy;
+
+  if (private->use_pivot_handle)
+    {
+      pivot.x = private->prev_tpx;
+      pivot.y = private->prev_tpy;
+    }
+  else
+    {
+      /* when the transform grid doesn't use a pivot handle, use the center
+       * point as the pivot instead.
+       */
+      pivot.x = private->prev_tcx;
+      pivot.y = private->prev_tcy;
+
+      fixedpivot = TRUE;
+    }
+
+  /* move */
+  if (handle == GIMP_TRANSFORM_HANDLE_CENTER)
+    {
+      if (private->constrain_move)
+        {
+          /* snap to 45 degree vectors from starting point */
+          gdouble angle = 16.0 * calcangle ((GimpVector2) { 1.0, 0.0 },
+                                            d) / (2.0 * G_PI);
+          gdouble dist  = norm (d) / sqrt (2);
+
+          if (angle < 1.0 || angle >= 15.0)
+            d.y = 0;
+          else if (angle < 3.0)
+            d.y = -(d.x = dist);
+          else if (angle < 5.0)
+            d.x = 0;
+          else if (angle < 7.0)
+            d.x = d.y = -dist;
+          else if (angle < 9.0)
+            d.y = 0;
+          else if (angle < 11.0)
+            d.x = -(d.y = dist);
+          else if (angle < 13.0)
+            d.x = 0;
+          else if (angle < 15.0)
+            d.x = d.y = dist;
+        }
+
+      for (i = 0; i < 4; i++)
+        newpos[i] = vectoradd (oldpos[i], d);
+    }
+
+  /* rotate */
+  if (handle == GIMP_TRANSFORM_HANDLE_ROTATION)
+    {
+      gdouble angle = calcangle (vectorsubtract (cur, pivot),
+                                 vectorsubtract (mouse, pivot));
+
+      if (private->constrain_rotate)
+        {
+          /* round to 15 degree multiple */
+          angle /= 2 * G_PI / 24.0;
+          angle = round (angle);
+          angle *= 2 * G_PI / 24.0;
+        }
+
+      for (i = 0; i < 4; i++)
+        newpos[i] = vectoradd (pivot,
+                               rotate2d (vectorsubtract (oldpos[i], pivot),
+                                         angle));
+
+      fixedpivot = TRUE;
+    }
+
+  /* move rotation axis */
+  if (handle == GIMP_TRANSFORM_HANDLE_PIVOT)
+    {
+      pivot = vectoradd (pivot, d);
+
+      if (private->cornersnap)
+        {
+          /* snap to corner points and center */
+          gint    closest = 0;
+          gdouble closest_dist = G_MAXDOUBLE, dist;
+
+          for (i = 0; i < 5; i++)
+            {
+              dist = norm (vectorsubtract (pivot, oldpos[i]));
+              if (dist < closest_dist)
+                {
+                  closest_dist = dist;
+                  closest = i;
+                }
+            }
+
+          if (closest_dist *
+              gimp_tool_widget_get_shell (widget)->scale_x < 50)
+            {
+              pivot = oldpos[closest];
+            }
+        }
+
+      fixedpivot = TRUE;
+    }
+
+  /* scaling via corner */
+  if (handle == GIMP_TRANSFORM_HANDLE_NW ||
+      handle == GIMP_TRANSFORM_HANDLE_NE ||
+      handle == GIMP_TRANSFORM_HANDLE_SE ||
+      handle == GIMP_TRANSFORM_HANDLE_SW)
+    {
+      /* Scaling through scale handles means translating one corner point,
+       * with all sides at constant angles.
+       */
+
+      gint this, left, right, opposite;
+
+      /* 0: northwest, 1: northeast, 2: southwest, 3: southeast */
+      if (handle == GIMP_TRANSFORM_HANDLE_NW)
+        {
+          this = 0; left = 1; right = 2; opposite = 3;
+        }
+      else if (handle == GIMP_TRANSFORM_HANDLE_NE)
+        {
+          this = 1; left = 3; right = 0; opposite = 2;
+        }
+      else if (handle == GIMP_TRANSFORM_HANDLE_SW)
+        {
+          this = 2; left = 0; right = 3; opposite = 1;
+        }
+      else if (handle == GIMP_TRANSFORM_HANDLE_SE)
+        {
+          this = 3; left = 2; right = 1; opposite = 0;
+        }
+      else
+        gimp_assert_not_reached ();
+
+      /* when the keep aspect transformation constraint is enabled,
+       * the translation shall only be along the diagonal that runs
+       * trough this corner point.
+       */
+      if (private->constrain_scale)
+        {
+          /* restrict to movement along the diagonal */
+          GimpVector2 diag = vectorsubtract (oldpos[this], oldpos[opposite]);
+
+          d = vectorproject (d, diag);
+        }
+
+      /* Move the corner being interacted with */
+      /*    rp---------tp
+       *   /           /\ <- d, the interaction vector
+       *  /           /  tp
+       * op----------/
+       *
+       */
+      newpos[this] = vectoradd (oldpos[this], d);
+
+      /* Where the corner to the right and left would go, need these to form
+       * lines to intersect with the sides */
+      /*    rp----------/
+       *   /\          /\
+       *  /  nr       /  nt
+       * op----------lp
+       *              \
+       *               nl
+       */
+
+      newpos[right] = vectoradd (oldpos[right], d);
+      newpos[left]  = vectoradd (oldpos[left], d);
+
+      /* Now we just need to find the intersection of op-rp and nr-nt.
+       *    rp----------/
+       *   /           /
+       *  /  nr==========nt
+       * op----------/
+       *
+       */
+      newpos[right] = lineintersect (newpos[right], newpos[this],
+                                     oldpos[opposite], oldpos[right]);
+      newpos[left]  = lineintersect (newpos[left], newpos[this],
+                                     oldpos[opposite], oldpos[left]);
+      /*    /-----------/
+       *   /           /
+       *  rp============nt
+       * op----------/
+       *
+       */
+
+      /*
+       *
+       *  /--------------/
+       * /--------------/
+       *
+       */
+
+      if (private->frompivot_scale &&
+          transform_is_convex (newpos) &&
+          transform_is_convex (oldpos))
+        {
+          /* transform the pivot point before the interaction and
+           * after, and move everything by this difference
+           */
+          //TODO the handle doesn't actually end up where the mouse cursor is
+          GimpVector2 delta = get_pivot_delta (grid, oldpos, newpos, pivot);
+          for (i = 0; i < 4; i++)
+            newpos[i] = vectorsubtract (newpos[i], delta);
+
+          fixedpivot = TRUE;
+        }
+    }
+
+  /* scaling via sides */
+  if (handle == GIMP_TRANSFORM_HANDLE_N ||
+      handle == GIMP_TRANSFORM_HANDLE_E ||
+      handle == GIMP_TRANSFORM_HANDLE_S ||
+      handle == GIMP_TRANSFORM_HANDLE_W)
+    {
+      gint        this_l, this_r, opp_l, opp_r;
+      GimpVector2 side_l, side_r, midline;
+
+      /* 0: northwest, 1: northeast, 2: southwest, 3: southeast */
+      if (handle == GIMP_TRANSFORM_HANDLE_N)
+        {
+          this_l = 1; this_r = 0;
+        }
+      else if (handle == GIMP_TRANSFORM_HANDLE_E)
+        {
+          this_l = 3; this_r = 1;
+        }
+      else if (handle == GIMP_TRANSFORM_HANDLE_S)
+        {
+          this_l = 2; this_r = 3;
+        }
+      else if (handle == GIMP_TRANSFORM_HANDLE_W)
+        {
+          this_l = 0; this_r = 2;
+        }
+      else
+        gimp_assert_not_reached ();
+
+      opp_l = 3 - this_r; opp_r = 3 - this_l;
+
+      side_l = vectorsubtract (oldpos[opp_l], oldpos[this_l]);
+      side_r = vectorsubtract (oldpos[opp_r], oldpos[this_r]);
+      midline = vectoradd (side_l, side_r);
+
+      /* restrict to movement along the midline */
+      d = vectorproject (d, midline);
+
+      if (private->constrain_scale)
+        {
+          GimpVector2 before, after, effective_pivot = pivot;
+          gdouble     distance;
+
+          if (! private->frompivot_scale)
+            {
+              /* center of the opposite side is pivot */
+              effective_pivot = scalemult (vectoradd (oldpos[opp_l],
+                                                      oldpos[opp_r]), 0.5);
+            }
+
+          /* get the difference between the distance from the pivot to
+           * where interaction started and the distance from the pivot
+           * to where cursor is now, and scale all corners distance
+           * from the pivot with this factor
+           */
+          before = vectorsubtract (effective_pivot, mouse);
+          after = vectorsubtract (effective_pivot, cur);
+          after = vectorproject (after, before);
+
+          distance = 0.5 * (after.x / before.x + after.y / before.y);
+
+          for (i = 0; i < 4; i++)
+            newpos[i] = vectoradd (effective_pivot,
+                                   scalemult (vectorsubtract (oldpos[i],
+                                                              effective_pivot),
+                                              distance));
+        }
+      else
+        {
+          /* just move the side */
+          newpos[this_l] = vectoradd (oldpos[this_l], d);
+          newpos[this_r] = vectoradd (oldpos[this_r], d);
+        }
+
+      if (! private->constrain_scale   &&
+          private->frompivot_scale     &&
+          transform_is_convex (newpos) &&
+          transform_is_convex (oldpos))
+        {
+          GimpVector2 delta = get_pivot_delta (grid, oldpos, newpos, pivot);
+          for (i = 0; i < 4; i++)
+            newpos[i] = vectorsubtract (newpos[i], delta);
+
+          fixedpivot = TRUE;
+        }
+    }
+
+  /* shear */
+  if (handle == GIMP_TRANSFORM_HANDLE_N_S ||
+      handle == GIMP_TRANSFORM_HANDLE_E_S ||
+      handle == GIMP_TRANSFORM_HANDLE_S_S ||
+      handle == GIMP_TRANSFORM_HANDLE_W_S)
+    {
+      gint this_l, this_r;
+
+      /* set up indices for this edge and the opposite edge */
+      if (handle == GIMP_TRANSFORM_HANDLE_N_S)
+        {
+          this_l = 1; this_r = 0;
+        }
+      else if (handle == GIMP_TRANSFORM_HANDLE_W_S)
+        {
+          this_l = 0; this_r = 2;
+        }
+      else if (handle == GIMP_TRANSFORM_HANDLE_S_S)
+        {
+          this_l = 2; this_r = 3;
+        }
+      else if (handle == GIMP_TRANSFORM_HANDLE_E_S)
+        {
+          this_l = 3; this_r = 1;
+        }
+      else
+        gimp_assert_not_reached ();
+
+      if (private->constrain_shear)
+        {
+          /* restrict to movement along the side */
+          GimpVector2 side = vectorsubtract (oldpos[this_r], oldpos[this_l]);
+
+          d = vectorproject (d, side);
+        }
+
+      newpos[this_l] = vectoradd (oldpos[this_l], d);
+      newpos[this_r] = vectoradd (oldpos[this_r], d);
+
+      if (private->frompivot_shear     &&
+          transform_is_convex (newpos) &&
+          transform_is_convex (oldpos))
+        {
+          GimpVector2 delta = get_pivot_delta (grid, oldpos, newpos, pivot);
+          for (i = 0; i < 4; i++)
+            newpos[i] = vectorsubtract (newpos[i], delta);
+
+          fixedpivot = TRUE;
+        }
+    }
+
+  /* perspective transform */
+  if (handle == GIMP_TRANSFORM_HANDLE_NW_P ||
+      handle == GIMP_TRANSFORM_HANDLE_NE_P ||
+      handle == GIMP_TRANSFORM_HANDLE_SE_P ||
+      handle == GIMP_TRANSFORM_HANDLE_SW_P)
+    {
+      gint this, left, right, opposite;
+
+      /* 0: northwest, 1: northeast, 2: southwest, 3: southeast */
+      if (handle == GIMP_TRANSFORM_HANDLE_NW_P)
+        {
+          this = 0; left = 1; right = 2; opposite = 3;
+        }
+      else if (handle == GIMP_TRANSFORM_HANDLE_NE_P)
+        {
+          this = 1; left = 3; right = 0; opposite = 2;
+        }
+      else if (handle == GIMP_TRANSFORM_HANDLE_SW_P)
+        {
+          this = 2; left = 0; right = 3; opposite = 1;
+        }
+      else if (handle == GIMP_TRANSFORM_HANDLE_SE_P)
+        {
+          this = 3; left = 2; right = 1; opposite = 0;
+        }
+      else
+        gimp_assert_not_reached ();
+
+      if (private->constrain_perspective)
+        {
+          /* when the constrain transformation constraint is enabled,
+           * the translation shall only be either along the side
+           * angles of the two sides that run to this corner point, or
+           * along the diagonal that runs trough this corner point.
+           */
+          GimpVector2 proj[4];
+          gdouble     rej[4];
+
+          for (i = 0; i < 4; i++)
+            {
+              if (i == this)
+                continue;
+
+              /* get the vectors along the sides and the diagonal */
+              proj[i] = vectorsubtract (oldpos[this], oldpos[i]);
+
+              /* project d on each candidate vector and see which has
+               * the shortest rejection
+               */
+              proj[i] = vectorproject (d, proj[i]);
+              rej[i] = norm (vectorsubtract (d, proj[i]));
+            }
+
+          if (rej[left] < rej[right] && rej[left] < rej[opposite])
+            d = proj[left];
+          else if (rej[right] < rej[opposite])
+            d = proj[right];
+          else
+            d = proj[opposite];
+        }
+
+      newpos[this] = vectoradd (oldpos[this], d);
+
+      if (private->frompivot_perspective &&
+          transform_is_convex (newpos)   &&
+          transform_is_convex (oldpos))
+        {
+          GimpVector2 delta = get_pivot_delta (grid, oldpos, newpos, pivot);
+
+          for (i = 0; i < 4; i++)
+            newpos[i] = vectorsubtract (newpos[i], delta);
+
+          fixedpivot = TRUE;
+        }
+    }
+
+  /* this will have been set to TRUE if an operation used the pivot in
+   * addition to being a user option
+   */
+  if (! fixedpivot                 &&
+      transform_is_convex (newpos) &&
+      transform_is_convex (oldpos) &&
+      point_is_inside_polygon_pos (oldpos, pivot))
+    {
+      GimpVector2 delta = get_pivot_delta (grid, oldpos, newpos, pivot);
+      pivot = vectoradd (pivot, delta);
+    }
+
+  /* make sure the new coordinates are valid */
+  for (i = 0; i < 4; i++)
+    {
+      if (! isfinite (newpos[i].x) || ! isfinite (newpos[i].y))
+        return;
+    }
+
+  if (! isfinite (pivot.x) || ! isfinite (pivot.y))
+    return;
+
+  for (i = 0; i < 4; i++)
+    {
+      *x[i] = newpos[i].x;
+      *y[i] = newpos[i].y;
+    }
+
+  /* set unconditionally: if options get toggled during operation, we
+   * have to move pivot back
+   */
+  *newpivot_x = pivot.x;
+  *newpivot_y = pivot.y;
+
+  gimp_tool_transform_grid_update_matrix (grid);
+}
+
+static const gchar *
+get_friendly_operation_name (GimpTransformHandle handle)
+{
+  switch (handle)
+    {
+    case GIMP_TRANSFORM_HANDLE_NONE:
+      return "";
+    case GIMP_TRANSFORM_HANDLE_NW_P:
+    case GIMP_TRANSFORM_HANDLE_NE_P:
+    case GIMP_TRANSFORM_HANDLE_SW_P:
+    case GIMP_TRANSFORM_HANDLE_SE_P:
+      return _("Click-Drag to change perspective");
+    case GIMP_TRANSFORM_HANDLE_NW:
+    case GIMP_TRANSFORM_HANDLE_NE:
+    case GIMP_TRANSFORM_HANDLE_SW:
+    case GIMP_TRANSFORM_HANDLE_SE:
+      return _("Click-Drag to scale");
+    case GIMP_TRANSFORM_HANDLE_N:
+    case GIMP_TRANSFORM_HANDLE_S:
+    case GIMP_TRANSFORM_HANDLE_E:
+    case GIMP_TRANSFORM_HANDLE_W:
+      return _("Click-Drag to scale");
+    case GIMP_TRANSFORM_HANDLE_CENTER:
+      return _("Click-Drag to move");
+    case GIMP_TRANSFORM_HANDLE_PIVOT:
+      return _("Click-Drag to move the pivot point");
+    case GIMP_TRANSFORM_HANDLE_N_S:
+    case GIMP_TRANSFORM_HANDLE_S_S:
+    case GIMP_TRANSFORM_HANDLE_E_S:
+    case GIMP_TRANSFORM_HANDLE_W_S:
+      return _("Click-Drag to shear");
+    case GIMP_TRANSFORM_HANDLE_ROTATION:
+      return _("Click-Drag to rotate");
+    default:
+      gimp_assert_not_reached ();
+    }
+}
+
+static GimpTransformHandle
+gimp_tool_transform_get_area_handle (GimpToolTransformGrid *grid,
+                                     const GimpCoords      *coords,
+                                     GimpTransformFunction  function)
+{
+  GimpToolTransformGridPrivate *private = grid->private;
+  GimpTransformHandle           handle  = GIMP_TRANSFORM_HANDLE_NONE;
+
+  switch (function)
+    {
+    case GIMP_TRANSFORM_FUNCTION_NONE:
+      break;
+
+    case GIMP_TRANSFORM_FUNCTION_MOVE:
+      handle = GIMP_TRANSFORM_HANDLE_CENTER;
+      break;
+
+    case GIMP_TRANSFORM_FUNCTION_ROTATE:
+      handle = GIMP_TRANSFORM_HANDLE_ROTATION;
+      break;
+
+    case GIMP_TRANSFORM_FUNCTION_SCALE:
+    case GIMP_TRANSFORM_FUNCTION_PERSPECTIVE:
+      {
+        gdouble closest_dist;
+        gdouble dist;
+
+        dist = gimp_canvas_item_transform_distance_square (private->guides,
+                                                           coords->x, coords->y,
+                                                           private->tx1,
+                                                           private->ty1);
+        closest_dist = dist;
+        if (function == GIMP_TRANSFORM_FUNCTION_PERSPECTIVE)
+          handle = GIMP_TRANSFORM_HANDLE_NW_P;
+        else
+          handle = GIMP_TRANSFORM_HANDLE_NW;
+
+        dist = gimp_canvas_item_transform_distance_square (private->guides,
+                                                           coords->x, coords->y,
+                                                           private->tx2,
+                                                           private->ty2);
+        if (dist < closest_dist)
+          {
+            closest_dist = dist;
+            if (function == GIMP_TRANSFORM_FUNCTION_PERSPECTIVE)
+              handle = GIMP_TRANSFORM_HANDLE_NE_P;
+            else
+              handle = GIMP_TRANSFORM_HANDLE_NE;
+          }
+
+        dist = gimp_canvas_item_transform_distance_square (private->guides,
+                                                           coords->x, coords->y,
+                                                           private->tx3,
+                                                           private->ty3);
+        if (dist < closest_dist)
+          {
+            closest_dist = dist;
+            if (function == GIMP_TRANSFORM_FUNCTION_PERSPECTIVE)
+              handle = GIMP_TRANSFORM_HANDLE_SW_P;
+            else
+              handle = GIMP_TRANSFORM_HANDLE_SW;
+          }
+
+        dist = gimp_canvas_item_transform_distance_square (private->guides,
+                                                           coords->x, coords->y,
+                                                           private->tx4,
+                                                           private->ty4);
+        if (dist < closest_dist)
+          {
+            closest_dist = dist;
+            if (function == GIMP_TRANSFORM_FUNCTION_PERSPECTIVE)
+              handle = GIMP_TRANSFORM_HANDLE_SE_P;
+            else
+              handle = GIMP_TRANSFORM_HANDLE_SE;
+          }
+      }
+      break;
+
+    case GIMP_TRANSFORM_FUNCTION_SHEAR:
+      {
+        gdouble handle_x;
+        gdouble handle_y;
+        gdouble closest_dist;
+        gdouble dist;
+
+        gimp_canvas_handle_get_position (private->handles[GIMP_TRANSFORM_HANDLE_N],
+                                         &handle_x, &handle_y);
+        dist = gimp_canvas_item_transform_distance_square (private->guides,
+                                                           coords->x, coords->y,
+                                                           handle_x, handle_y);
+        closest_dist = dist;
+        handle = GIMP_TRANSFORM_HANDLE_N_S;
+
+        gimp_canvas_handle_get_position (private->handles[GIMP_TRANSFORM_HANDLE_W],
+                                         &handle_x, &handle_y);
+        dist = gimp_canvas_item_transform_distance_square (private->guides,
+                                                           coords->x, coords->y,
+                                                           handle_x, handle_y);
+        if (dist < closest_dist)
+          {
+            closest_dist = dist;
+            handle = GIMP_TRANSFORM_HANDLE_W_S;
+          }
+
+        gimp_canvas_handle_get_position (private->handles[GIMP_TRANSFORM_HANDLE_E],
+                                         &handle_x, &handle_y);
+        dist = gimp_canvas_item_transform_distance_square (private->guides,
+                                                           coords->x, coords->y,
+                                                           handle_x, handle_y);
+        if (dist < closest_dist)
+          {
+            closest_dist = dist;
+            handle = GIMP_TRANSFORM_HANDLE_E_S;
+          }
+
+        gimp_canvas_handle_get_position (private->handles[GIMP_TRANSFORM_HANDLE_S],
+                                         &handle_x, &handle_y);
+        dist = gimp_canvas_item_transform_distance_square (private->guides,
+                                                           coords->x, coords->y,
+                                                           handle_x, handle_y);
+        if (dist < closest_dist)
+          {
+            closest_dist = dist;
+            handle = GIMP_TRANSFORM_HANDLE_S_S;
+          }
+      }
+      break;
+    }
+
+  return handle;
+}
+
+GimpHit
+gimp_tool_transform_grid_hit (GimpToolWidget   *widget,
+                              const GimpCoords *coords,
+                              GdkModifierType   state,
+                              gboolean          proximity)
+{
+  GimpToolTransformGrid *grid = GIMP_TOOL_TRANSFORM_GRID (widget);
+  GimpTransformHandle    handle;
+
+  handle = gimp_tool_transform_grid_get_handle_for_coords (grid, coords);
+
+  if (handle != GIMP_TRANSFORM_HANDLE_NONE)
+    return GIMP_HIT_DIRECT;
+
+  return GIMP_HIT_INDIRECT;
+}
+
+void
+gimp_tool_transform_grid_hover (GimpToolWidget   *widget,
+                                const GimpCoords *coords,
+                                GdkModifierType   state,
+                                gboolean          proximity)
+{
+  GimpToolTransformGrid        *grid    = GIMP_TOOL_TRANSFORM_GRID (widget);
+  GimpToolTransformGridPrivate *private = grid->private;
+  GimpTransformHandle           handle;
+
+  handle = gimp_tool_transform_grid_get_handle_for_coords (grid, coords);
+
+  if (handle == GIMP_TRANSFORM_HANDLE_NONE)
+    {
+      /* points passed in clockwise order */
+      if (point_is_inside_polygon (4,
+                                   (gdouble[4]){ private->tx1, private->tx2,
+                                                 private->tx4, private->tx3 },
+                                   (gdouble[4]){ private->ty1, private->ty2,
+                                                 private->ty4, private->ty3 },
+                                   coords->x, coords->y))
+        {
+          handle = gimp_tool_transform_get_area_handle (grid, coords,
+                                                        private->inside_function);
+        }
+      else
+        {
+          handle = gimp_tool_transform_get_area_handle (grid, coords,
+                                                        private->outside_function);
+        }
+    }
+
+  if (handle != GIMP_TRANSFORM_HANDLE_NONE && proximity)
+    {
+      gimp_tool_widget_set_status (widget,
+                                   get_friendly_operation_name (handle));
+    }
+  else
+    {
+      gimp_tool_widget_set_status (widget, NULL);
+    }
+
+  private->handle = handle;
+
+  gimp_tool_transform_grid_update_hilight (grid);
+}
+
+void
+gimp_tool_transform_grid_leave_notify (GimpToolWidget *widget)
+{
+  GimpToolTransformGrid        *grid    = GIMP_TOOL_TRANSFORM_GRID (widget);
+  GimpToolTransformGridPrivate *private = grid->private;
+
+  private->handle = GIMP_TRANSFORM_HANDLE_NONE;
+
+  gimp_tool_transform_grid_update_hilight (grid);
+
+  GIMP_TOOL_WIDGET_CLASS (parent_class)->leave_notify (widget);
+}
+
+static void
+gimp_tool_transform_grid_modifier (GimpToolWidget  *widget,
+                                   GdkModifierType  key)
+{
+  GimpToolTransformGrid        *grid    = GIMP_TOOL_TRANSFORM_GRID (widget);
+  GimpToolTransformGridPrivate *private = grid->private;
+
+  if (key == gimp_get_constrain_behavior_mask ())
+    {
+      g_object_set (widget,
+                    "frompivot-scale",       ! private->frompivot_scale,
+                    "frompivot-shear",       ! private->frompivot_shear,
+                    "frompivot-perspective", ! private->frompivot_perspective,
+                    NULL);
+    }
+  else if (key == gimp_get_extend_selection_mask ())
+    {
+      g_object_set (widget,
+                    "cornersnap",            ! private->cornersnap,
+                    "constrain-move",        ! private->constrain_move,
+                    "constrain-scale",       ! private->constrain_scale,
+                    "constrain-rotate",      ! private->constrain_rotate,
+                    "constrain-shear",       ! private->constrain_shear,
+                    "constrain-perspective", ! private->constrain_perspective,
+                    NULL);
+    }
+}
+
+static void
+gimp_tool_transform_grid_hover_modifier (GimpToolWidget  *widget,
+                                         GdkModifierType  key,
+                                         gboolean         press,
+                                         GdkModifierType  state)
+{
+  GimpToolTransformGrid        *grid    = GIMP_TOOL_TRANSFORM_GRID (widget);
+  GimpToolTransformGridPrivate *private = grid->private;
+  GimpCoords                    coords  = { 0.0, };
+
+  gimp_tool_transform_grid_modifier (widget, key);
+
+  if (private->button_down)
+    {
+      /*  send a non-motion to update the grid with the new constraints  */
+      coords.x = private->curx;
+      coords.y = private->cury;
+      gimp_tool_transform_grid_motion (widget, &coords, 0, state);
+    }
+}
+
+static gboolean
+gimp_tool_transform_grid_get_cursor (GimpToolWidget     *widget,
+                                     const GimpCoords   *coords,
+                                     GdkModifierType     state,
+                                     GimpCursorType     *cursor,
+                                     GimpToolCursorType *tool_cursor,
+                                     GimpCursorModifier *modifier)
+{
+  GimpToolTransformGrid        *grid    = GIMP_TOOL_TRANSFORM_GRID (widget);
+  GimpToolTransformGridPrivate *private = grid->private;
+  gdouble                       angle[9];
+  gint                          i;
+  GimpCursorType                map[8];
+  GimpVector2                   pos[4], this, that;
+  gboolean                      flip       = FALSE;
+  gboolean                      side       = FALSE;
+  gboolean                      set_cursor = TRUE;
+
+  map[0] = GIMP_CURSOR_CORNER_TOP_LEFT;
+  map[1] = GIMP_CURSOR_CORNER_TOP;
+  map[2] = GIMP_CURSOR_CORNER_TOP_RIGHT;
+  map[3] = GIMP_CURSOR_CORNER_RIGHT;
+  map[4] = GIMP_CURSOR_CORNER_BOTTOM_RIGHT;
+  map[5] = GIMP_CURSOR_CORNER_BOTTOM;
+  map[6] = GIMP_CURSOR_CORNER_BOTTOM_LEFT;
+  map[7] = GIMP_CURSOR_CORNER_LEFT;
+
+  get_handle_geometry (grid, pos, angle);
+
+  for (i = 0; i < 8; i++)
+    angle[i] = round (angle[i] * 180.0 / G_PI / 45.0);
+
+  switch (private->handle)
+    {
+    case GIMP_TRANSFORM_HANDLE_NW_P:
+    case GIMP_TRANSFORM_HANDLE_NW:
+      i = (gint) angle[4] + 0;
+      this = pos[0];
+      that = pos[3];
+      break;
+
+    case GIMP_TRANSFORM_HANDLE_NE_P:
+    case GIMP_TRANSFORM_HANDLE_NE:
+      i = (gint) angle[5] + 2;
+      this = pos[1];
+      that = pos[2];
+      break;
+
+    case GIMP_TRANSFORM_HANDLE_SW_P:
+    case GIMP_TRANSFORM_HANDLE_SW:
+      i = (gint) angle[6] + 6;
+      this = pos[2];
+      that = pos[1];
+      break;
+
+    case GIMP_TRANSFORM_HANDLE_SE_P:
+    case GIMP_TRANSFORM_HANDLE_SE:
+      i = (gint) angle[7] + 4;
+      this = pos[3];
+      that = pos[0];
+      break;
+
+    case GIMP_TRANSFORM_HANDLE_N:
+    case GIMP_TRANSFORM_HANDLE_N_S:
+      i = (gint) angle[0] + 1;
+      this = vectoradd (pos[0], pos[1]);
+      that = vectoradd (pos[2], pos[3]);
+      side = TRUE;
+      break;
+
+    case GIMP_TRANSFORM_HANDLE_S:
+    case GIMP_TRANSFORM_HANDLE_S_S:
+      i = (gint) angle[1] + 5;
+      this = vectoradd (pos[2], pos[3]);
+      that = vectoradd (pos[0], pos[1]);
+      side = TRUE;
+      break;
+
+    case GIMP_TRANSFORM_HANDLE_E:
+    case GIMP_TRANSFORM_HANDLE_E_S:
+      i = (gint) angle[2] + 3;
+      this = vectoradd (pos[1], pos[3]);
+      that = vectoradd (pos[0], pos[2]);
+      side = TRUE;
+      break;
+
+    case GIMP_TRANSFORM_HANDLE_W:
+    case GIMP_TRANSFORM_HANDLE_W_S:
+      i = (gint) angle[3] + 7;
+      this = vectoradd (pos[0], pos[2]);
+      that = vectoradd (pos[1], pos[3]);
+      side = TRUE;
+      break;
+
+    default:
+      set_cursor = FALSE;
+      break;
+    }
+
+  if (set_cursor)
+    {
+      i %= 8;
+
+      switch (map[i])
+        {
+        case GIMP_CURSOR_CORNER_TOP_LEFT:
+          if (this.x + this.y > that.x + that.y)
+            flip = TRUE;
+          break;
+        case GIMP_CURSOR_CORNER_TOP:
+          if (this.y > that.y)
+            flip = TRUE;
+          break;
+        case GIMP_CURSOR_CORNER_TOP_RIGHT:
+          if (this.x - this.y < that.x - that.y)
+            flip = TRUE;
+          break;
+        case GIMP_CURSOR_CORNER_RIGHT:
+          if (this.x < that.x)
+            flip = TRUE;
+          break;
+        case GIMP_CURSOR_CORNER_BOTTOM_RIGHT:
+          if (this.x + this.y < that.x + that.y)
+            flip = TRUE;
+          break;
+        case GIMP_CURSOR_CORNER_BOTTOM:
+          if (this.y < that.y)
+            flip = TRUE;
+          break;
+        case GIMP_CURSOR_CORNER_BOTTOM_LEFT:
+          if (this.x - this.y > that.x - that.y)
+            flip = TRUE;
+          break;
+        case GIMP_CURSOR_CORNER_LEFT:
+          if (this.x > that.x)
+            flip = TRUE;
+          break;
+        default:
+          gimp_assert_not_reached ();
+        }
+
+      if (flip)
+        *cursor = map[(i + 4) % 8];
+      else
+        *cursor = map[i];
+
+      if (side)
+        *cursor += 8;
+    }
+
+  /* parent class handles *cursor and *modifier for most handles */
+  switch (private->handle)
+    {
+    case GIMP_TRANSFORM_HANDLE_NONE:
+      *tool_cursor = GIMP_TOOL_CURSOR_NONE;
+      break;
+
+    case GIMP_TRANSFORM_HANDLE_NW_P:
+    case GIMP_TRANSFORM_HANDLE_NE_P:
+    case GIMP_TRANSFORM_HANDLE_SW_P:
+    case GIMP_TRANSFORM_HANDLE_SE_P:
+      *tool_cursor = GIMP_TOOL_CURSOR_PERSPECTIVE;
+      break;
+
+    case GIMP_TRANSFORM_HANDLE_NW:
+    case GIMP_TRANSFORM_HANDLE_NE:
+    case GIMP_TRANSFORM_HANDLE_SW:
+    case GIMP_TRANSFORM_HANDLE_SE:
+    case GIMP_TRANSFORM_HANDLE_N:
+    case GIMP_TRANSFORM_HANDLE_S:
+    case GIMP_TRANSFORM_HANDLE_E:
+    case GIMP_TRANSFORM_HANDLE_W:
+      *tool_cursor = GIMP_TOOL_CURSOR_RESIZE;
+      break;
+
+    case GIMP_TRANSFORM_HANDLE_CENTER:
+      *tool_cursor = GIMP_TOOL_CURSOR_MOVE;
+      break;
+
+    case GIMP_TRANSFORM_HANDLE_PIVOT:
+      *tool_cursor = GIMP_TOOL_CURSOR_ROTATE;
+      *modifier    = GIMP_CURSOR_MODIFIER_MOVE;
+      break;
+
+    case GIMP_TRANSFORM_HANDLE_N_S:
+    case GIMP_TRANSFORM_HANDLE_S_S:
+    case GIMP_TRANSFORM_HANDLE_E_S:
+    case GIMP_TRANSFORM_HANDLE_W_S:
+      *tool_cursor = GIMP_TOOL_CURSOR_SHEAR;
+      break;
+
+    case GIMP_TRANSFORM_HANDLE_ROTATION:
+      *tool_cursor = GIMP_TOOL_CURSOR_ROTATE;
+      break;
+
+    default:
+      g_return_val_if_reached (FALSE);
+    }
+
+  return TRUE;
+}
+
+static GimpTransformHandle
+gimp_tool_transform_grid_get_handle_for_coords (GimpToolTransformGrid *grid,
+                                                const GimpCoords      *coords)
+{
+  GimpToolTransformGridPrivate *private = grid->private;
+  GimpTransformHandle           i;
+
+  for (i = GIMP_TRANSFORM_HANDLE_NONE + 1; i < GIMP_N_TRANSFORM_HANDLES; i++)
+    {
+      if (private->handles[i] &&
+          gimp_canvas_item_hit (private->handles[i], coords->x, coords->y))
+        {
+          return i;
+        }
+    }
+
+  return GIMP_TRANSFORM_HANDLE_NONE;
+}
+
+static void
+gimp_tool_transform_grid_update_hilight (GimpToolTransformGrid *grid)
+{
+  GimpToolTransformGridPrivate *private = grid->private;
+  GimpTransformHandle           handle;
+
+  for (handle = GIMP_TRANSFORM_HANDLE_NONE;
+       handle < GIMP_N_TRANSFORM_HANDLES;
+       handle++)
+    {
+      if (private->handles[handle])
+        {
+          gimp_canvas_item_set_highlight (private->handles[handle],
+                                          handle == private->handle);
+        }
+    }
+}
+
+static void
+gimp_tool_transform_grid_update_box (GimpToolTransformGrid  *grid)
+{
+  GimpToolTransformGridPrivate *private = grid->private;
+
+  gimp_matrix3_transform_point (&private->transform,
+                                private->x1, private->y1,
+                                &private->tx1, &private->ty1);
+  gimp_matrix3_transform_point (&private->transform,
+                                private->x2, private->y1,
+                                &private->tx2, &private->ty2);
+  gimp_matrix3_transform_point (&private->transform,
+                                private->x1, private->y2,
+                                &private->tx3, &private->ty3);
+  gimp_matrix3_transform_point (&private->transform,
+                                private->x2, private->y2,
+                                &private->tx4, &private->ty4);
+
+  /* don't transform pivot */
+  private->tpx = private->pivot_x;
+  private->tpy = private->pivot_y;
+
+  if (transform_grid_is_convex (grid))
+    {
+      gimp_matrix3_transform_point (&private->transform,
+                                    (private->x1 + private->x2) / 2.0,
+                                    (private->y1 + private->y2) / 2.0,
+                                    &private->tcx, &private->tcy);
+    }
+  else
+    {
+      private->tcx = (private->tx1 +
+                      private->tx2 +
+                      private->tx3 +
+                      private->tx4) / 4.0;
+      private->tcy = (private->ty1 +
+                      private->ty2 +
+                      private->ty3 +
+                      private->ty4) / 4.0;
+    }
+}
+
+static void
+gimp_tool_transform_grid_update_matrix (GimpToolTransformGrid *grid)
+{
+  GimpToolTransformGridPrivate *private = grid->private;
+
+  gimp_matrix3_identity (&private->transform);
+  gimp_transform_matrix_perspective (&private->transform,
+                                     private->x1,
+                                     private->y1,
+                                     private->x2 - private->x1,
+                                     private->y2 - private->y1,
+                                     private->tx1,
+                                     private->ty1,
+                                     private->tx2,
+                                     private->ty2,
+                                     private->tx3,
+                                     private->ty3,
+                                     private->tx4,
+                                     private->ty4);
+
+  private->pivot_x = private->tpx;
+  private->pivot_y = private->tpy;
+
+  g_object_freeze_notify (G_OBJECT (grid));
+  g_object_notify (G_OBJECT (grid), "transform");
+  g_object_notify (G_OBJECT (grid), "pivot-x");
+  g_object_notify (G_OBJECT (grid), "pivot-x");
+  g_object_thaw_notify (G_OBJECT (grid));
+}
+
+static void
+gimp_tool_transform_grid_calc_handles (GimpToolTransformGrid *grid,
+                                       gint                  *handle_w,
+                                       gint                  *handle_h)
+{
+  GimpToolTransformGridPrivate *private = grid->private;
+  gint                          dx1, dy1;
+  gint                          dx2, dy2;
+  gint                          dx3, dy3;
+  gint                          dx4, dy4;
+  gint                          x1, y1;
+  gint                          x2, y2;
+
+  if (! private->dynamic_handle_size)
+    {
+      *handle_w = GIMP_CANVAS_HANDLE_SIZE_LARGE;
+      *handle_h = GIMP_CANVAS_HANDLE_SIZE_LARGE;
+
+      return;
+    }
+
+  gimp_canvas_item_transform_xy (private->guides,
+                                 private->tx1, private->ty1,
+                                 &dx1, &dy1);
+  gimp_canvas_item_transform_xy (private->guides,
+                                 private->tx2, private->ty2,
+                                 &dx2, &dy2);
+  gimp_canvas_item_transform_xy (private->guides,
+                                 private->tx3, private->ty3,
+                                 &dx3, &dy3);
+  gimp_canvas_item_transform_xy (private->guides,
+                                 private->tx4, private->ty4,
+                                 &dx4, &dy4);
+
+  x1 = MIN4 (dx1, dx2, dx3, dx4);
+  y1 = MIN4 (dy1, dy2, dy3, dy4);
+  x2 = MAX4 (dx1, dx2, dx3, dx4);
+  y2 = MAX4 (dy1, dy2, dy3, dy4);
+
+  *handle_w = CLAMP ((x2 - x1) / 3,
+                     MIN_HANDLE_SIZE, GIMP_CANVAS_HANDLE_SIZE_LARGE);
+  *handle_h = CLAMP ((y2 - y1) / 3,
+                     MIN_HANDLE_SIZE, GIMP_CANVAS_HANDLE_SIZE_LARGE);
+}
+
+
+/*  public functions  */
+
+GimpToolWidget *
+gimp_tool_transform_grid_new (GimpDisplayShell  *shell,
+                              const GimpMatrix3 *transform,
+                              gdouble            x1,
+                              gdouble            y1,
+                              gdouble            x2,
+                              gdouble            y2)
+{
+  g_return_val_if_fail (GIMP_IS_DISPLAY_SHELL (shell), NULL);
+
+  return g_object_new (GIMP_TYPE_TOOL_TRANSFORM_GRID,
+                       "shell",      shell,
+                       "transform",  transform,
+                       "x1",         x1,
+                       "y1",         y1,
+                       "x2",         x2,
+                       "y2",         y2,
+                       NULL);
+}
+
+
+/*  protected functions  */
+
+GimpTransformHandle
+gimp_tool_transform_grid_get_handle (GimpToolTransformGrid *grid)
+{
+  g_return_val_if_fail (GIMP_IS_TOOL_TRANSFORM_GRID (grid),
+                        GIMP_TRANSFORM_HANDLE_NONE);
+
+  return grid->private->handle;
+}