Adding upstream version 2.10.36.upstream/2.10.36

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

1 files changed, 1025 insertions, 0 deletions

diff --git a/app/display/gimpdisplayshell-transform.c b/app/display/gimpdisplayshell-transform.c
new file mode 100644
index 0000000..f9cd2e5
--- /dev/null
+++ b/app/display/gimpdisplayshell-transform.c
@@ -0,0 +1,1025 @@
+/* GIMP - The GNU Image Manipulation Program
+ * Copyright (C) 1995 Spencer Kimball and Peter Mattis
+ *
+ * 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 <math.h>
+
+#include <gegl.h>
+#include <gtk/gtk.h>
+
+#include "libgimpmath/gimpmath.h"
+
+#include "display-types.h"
+
+#include "core/gimpboundary.h"
+#include "core/gimpdrawable.h"
+#include "core/gimpimage.h"
+#include "core/gimp-utils.h"
+
+#include "gimpdisplay.h"
+#include "gimpdisplayshell.h"
+#include "gimpdisplayshell-scroll.h"
+#include "gimpdisplayshell-transform.h"
+
+
+/*  local function prototypes  */
+
+static void gimp_display_shell_transform_xy_f_noround (GimpDisplayShell *shell,
+                                                       gdouble           x,
+                                                       gdouble           y,
+                                                       gdouble          *nx,
+                                                       gdouble          *ny);
+
+/*  public functions  */
+
+/**
+ * gimp_display_shell_zoom_coords:
+ * @shell:          a #GimpDisplayShell
+ * @image_coords:   image coordinates
+ * @display_coords: returns the corresponding display coordinates
+ *
+ * Zooms from image coordinates to display coordinates, so that
+ * objects can be rendered at the correct points on the display.
+ **/
+void
+gimp_display_shell_zoom_coords (GimpDisplayShell *shell,
+                                const GimpCoords *image_coords,
+                                GimpCoords       *display_coords)
+{
+  g_return_if_fail (GIMP_IS_DISPLAY_SHELL (shell));
+  g_return_if_fail (image_coords != NULL);
+  g_return_if_fail (display_coords != NULL);
+
+  *display_coords = *image_coords;
+
+  display_coords->x = SCALEX (shell, image_coords->x);
+  display_coords->y = SCALEY (shell, image_coords->y);
+
+  display_coords->x -= shell->offset_x;
+  display_coords->y -= shell->offset_y;
+}
+
+/**
+ * gimp_display_shell_unzoom_coords:
+ * @shell:          a #GimpDisplayShell
+ * @display_coords: display coordinates
+ * @image_coords:   returns the corresponding image coordinates
+ *
+ * Zooms from display coordinates to image coordinates, so that
+ * points on the display can be mapped to points in the image.
+ **/
+void
+gimp_display_shell_unzoom_coords (GimpDisplayShell *shell,
+                                  const GimpCoords *display_coords,
+                                  GimpCoords       *image_coords)
+{
+  g_return_if_fail (GIMP_IS_DISPLAY_SHELL (shell));
+  g_return_if_fail (display_coords != NULL);
+  g_return_if_fail (image_coords != NULL);
+
+  *image_coords = *display_coords;
+
+  image_coords->x += shell->offset_x;
+  image_coords->y += shell->offset_y;
+
+  image_coords->x /= shell->scale_x;
+  image_coords->y /= shell->scale_y;
+}
+
+/**
+ * gimp_display_shell_zoom_xy:
+ * @shell:
+ * @x:
+ * @y:
+ * @nx:
+ * @ny:
+ *
+ * Zooms an image coordinate to a shell coordinate.
+ **/
+void
+gimp_display_shell_zoom_xy (GimpDisplayShell *shell,
+                            gdouble           x,
+                            gdouble           y,
+                            gint             *nx,
+                            gint             *ny)
+{
+  gint64 tx;
+  gint64 ty;
+
+  g_return_if_fail (GIMP_IS_DISPLAY_SHELL (shell));
+  g_return_if_fail (nx != NULL);
+  g_return_if_fail (ny != NULL);
+
+  tx = x * shell->scale_x;
+  ty = y * shell->scale_y;
+
+  tx -= shell->offset_x;
+  ty -= shell->offset_y;
+
+  /*  The projected coordinates might overflow a gint in the case of
+   *  big images at high zoom levels, so we clamp them here to avoid
+   *  problems.
+   */
+  *nx = CLAMP (tx, G_MININT, G_MAXINT);
+  *ny = CLAMP (ty, G_MININT, G_MAXINT);
+}
+
+/**
+ * gimp_display_shell_unzoom_xy:
+ * @shell:       a #GimpDisplayShell
+ * @x:           x coordinate in display coordinates
+ * @y:           y coordinate in display coordinates
+ * @nx:          returns x oordinate in image coordinates
+ * @ny:          returns y coordinate in image coordinates
+ * @round:       if %TRUE, round the results to the nearest integer;
+ *               if %FALSE, simply cast them to @gint.
+ *
+ * Zoom from display coordinates to image coordinates, so that
+ * points on the display can be mapped to the corresponding points
+ * in the image.
+ **/
+void
+gimp_display_shell_unzoom_xy (GimpDisplayShell *shell,
+                              gint              x,
+                              gint              y,
+                              gint             *nx,
+                              gint             *ny,
+                              gboolean          round)
+{
+  gint64 tx;
+  gint64 ty;
+
+  g_return_if_fail (GIMP_IS_DISPLAY_SHELL (shell));
+  g_return_if_fail (nx != NULL);
+  g_return_if_fail (ny != NULL);
+
+  if (round)
+    {
+      tx = SIGNED_ROUND (((gdouble) x + shell->offset_x) / shell->scale_x);
+      ty = SIGNED_ROUND (((gdouble) y + shell->offset_y) / shell->scale_y);
+    }
+  else
+    {
+      tx = ((gint64) x + shell->offset_x) / shell->scale_x;
+      ty = ((gint64) y + shell->offset_y) / shell->scale_y;
+    }
+
+  *nx = CLAMP (tx, G_MININT, G_MAXINT);
+  *ny = CLAMP (ty, G_MININT, G_MAXINT);
+}
+
+/**
+ * gimp_display_shell_zoom_xy_f:
+ * @shell: a #GimpDisplayShell
+ * @x:     image x coordinate of point
+ * @y:     image y coordinate of point
+ * @nx:    returned shell canvas x coordinate
+ * @ny:    returned shell canvas y coordinate
+ *
+ * Zooms from image coordinates to display shell canvas
+ * coordinates.
+ **/
+void
+gimp_display_shell_zoom_xy_f (GimpDisplayShell *shell,
+                              gdouble           x,
+                              gdouble           y,
+                              gdouble          *nx,
+                              gdouble          *ny)
+{
+  g_return_if_fail (GIMP_IS_DISPLAY_SHELL (shell));
+  g_return_if_fail (nx != NULL);
+  g_return_if_fail (ny != NULL);
+
+  *nx = SCALEX (shell, x) - shell->offset_x;
+  *ny = SCALEY (shell, y) - shell->offset_y;
+}
+
+/**
+ * gimp_display_shell_unzoom_xy_f:
+ * @shell:       a #GimpDisplayShell
+ * @x:           x coordinate in display coordinates
+ * @y:           y coordinate in display coordinates
+ * @nx:          place to return x coordinate in image coordinates
+ * @ny:          place to return y coordinate in image coordinates
+ *
+ * This function is identical to gimp_display_shell_unzoom_xy(),
+ * except that the input and output coordinates are doubles rather than
+ * ints, and consequently there is no option related to rounding.
+ **/
+void
+gimp_display_shell_unzoom_xy_f (GimpDisplayShell *shell,
+                                gdouble           x,
+                                gdouble           y,
+                                gdouble          *nx,
+                                gdouble          *ny)
+{
+  g_return_if_fail (GIMP_IS_DISPLAY_SHELL (shell));
+  g_return_if_fail (nx != NULL);
+  g_return_if_fail (ny != NULL);
+
+  *nx = (x + shell->offset_x) / shell->scale_x;
+  *ny = (y + shell->offset_y) / shell->scale_y;
+}
+
+/**
+ * gimp_display_shell_zoom_segments:
+ * @shell:       a #GimpDisplayShell
+ * @src_segs:    array of segments in image coordinates
+ * @dest_segs:   returns the corresponding segments in display coordinates
+ * @n_segs:      number of segments
+ *
+ * Zooms from image coordinates to display coordinates, so that
+ * objects can be rendered at the correct points on the display.
+ **/
+void
+gimp_display_shell_zoom_segments (GimpDisplayShell   *shell,
+                                  const GimpBoundSeg *src_segs,
+                                  GimpSegment        *dest_segs,
+                                  gint                n_segs,
+                                  gdouble             offset_x,
+                                  gdouble             offset_y)
+{
+  gint i;
+
+  g_return_if_fail (GIMP_IS_DISPLAY_SHELL (shell));
+
+  for (i = 0; i < n_segs ; i++)
+    {
+      gdouble x1, x2;
+      gdouble y1, y2;
+
+      x1 = src_segs[i].x1 + offset_x;
+      x2 = src_segs[i].x2 + offset_x;
+      y1 = src_segs[i].y1 + offset_y;
+      y2 = src_segs[i].y2 + offset_y;
+
+      dest_segs[i].x1 = SCALEX (shell, x1) - shell->offset_x;
+      dest_segs[i].x2 = SCALEX (shell, x2) - shell->offset_x;
+      dest_segs[i].y1 = SCALEY (shell, y1) - shell->offset_y;
+      dest_segs[i].y2 = SCALEY (shell, y2) - shell->offset_y;
+    }
+}
+
+/**
+ * gimp_display_shell_rotate_coords:
+ * @shell:          a #GimpDisplayShell
+ * @image_coords:   unrotated display coordinates
+ * @display_coords: returns the corresponding rotated display coordinates
+ *
+ * Rotates from unrotated display coordinates to rotated display
+ * coordinates, so that objects can be rendered at the correct points
+ * on the display.
+ **/
+void
+gimp_display_shell_rotate_coords (GimpDisplayShell *shell,
+                                  const GimpCoords *unrotated_coords,
+                                  GimpCoords       *rotated_coords)
+{
+  g_return_if_fail (GIMP_IS_DISPLAY_SHELL (shell));
+  g_return_if_fail (unrotated_coords != NULL);
+  g_return_if_fail (rotated_coords != NULL);
+
+  *rotated_coords = *unrotated_coords;
+
+  if (shell->rotate_transform)
+    cairo_matrix_transform_point (shell->rotate_transform,
+                                  &rotated_coords->x,
+                                  &rotated_coords->y);
+}
+
+/**
+ * gimp_display_shell_unrotate_coords:
+ * @shell:          a #GimpDisplayShell
+ * @display_coords: rotated display coordinates
+ * @image_coords:   returns the corresponding unrotated display coordinates
+ *
+ * Rotates from rotated display coordinates to unrotated display coordinates.
+ **/
+void
+gimp_display_shell_unrotate_coords (GimpDisplayShell *shell,
+                                    const GimpCoords *rotated_coords,
+                                    GimpCoords       *unrotated_coords)
+{
+  g_return_if_fail (GIMP_IS_DISPLAY_SHELL (shell));
+  g_return_if_fail (rotated_coords != NULL);
+  g_return_if_fail (unrotated_coords != NULL);
+
+  *unrotated_coords = *rotated_coords;
+
+  if (shell->rotate_untransform)
+    cairo_matrix_transform_point (shell->rotate_untransform,
+                                  &unrotated_coords->x,
+                                  &unrotated_coords->y);
+}
+
+/**
+ * gimp_display_shell_rotate_xy:
+ * @shell:
+ * @x:
+ * @y:
+ * @nx:
+ * @ny:
+ *
+ * Rotates an unrotated display coordinate to a rotated shell coordinate.
+ **/
+void
+gimp_display_shell_rotate_xy (GimpDisplayShell *shell,
+                              gdouble           x,
+                              gdouble           y,
+                              gint             *nx,
+                              gint             *ny)
+{
+  gint64 tx;
+  gint64 ty;
+
+  g_return_if_fail (GIMP_IS_DISPLAY_SHELL (shell));
+  g_return_if_fail (nx != NULL);
+  g_return_if_fail (ny != NULL);
+
+  if (shell->rotate_transform)
+    cairo_matrix_transform_point (shell->rotate_transform, &x, &y);
+
+  tx = x;
+  ty = y;
+
+  /*  The projected coordinates might overflow a gint in the case of
+   *  big images at high zoom levels, so we clamp them here to avoid
+   *  problems.
+   */
+  *nx = CLAMP (tx, G_MININT, G_MAXINT);
+  *ny = CLAMP (ty, G_MININT, G_MAXINT);
+}
+
+/**
+ * gimp_display_shell_unrotate_xy:
+ * @shell:       a #GimpDisplayShell
+ * @x:           x coordinate in rotated display coordinates
+ * @y:           y coordinate in rotated display coordinates
+ * @nx:          returns x oordinate in unrotated display coordinates
+ * @ny:          returns y coordinate in unrotated display coordinates
+ *
+ * Rotate from rotated display coordinates to unrotated display
+ * coordinates.
+ **/
+void
+gimp_display_shell_unrotate_xy (GimpDisplayShell *shell,
+                                gint              x,
+                                gint              y,
+                                gint             *nx,
+                                gint             *ny)
+{
+  g_return_if_fail (GIMP_IS_DISPLAY_SHELL (shell));
+  g_return_if_fail (nx != NULL);
+  g_return_if_fail (ny != NULL);
+
+  if (shell->rotate_untransform)
+    {
+      gdouble fx = x;
+      gdouble fy = y;
+
+      cairo_matrix_transform_point (shell->rotate_untransform, &fx, &fy);
+
+      *nx = CLAMP (fx, G_MININT, G_MAXINT);
+      *ny = CLAMP (fy, G_MININT, G_MAXINT);
+    }
+  else
+    {
+      *nx = x;
+      *ny = y;
+    }
+}
+
+/**
+ * gimp_display_shell_rotate_xy_f:
+ * @shell: a #GimpDisplayShell
+ * @x:     image x coordinate of point
+ * @y:     image y coordinate of point
+ * @nx:    returned shell canvas x coordinate
+ * @ny:    returned shell canvas y coordinate
+ *
+ * Rotates from untransformed display coordinates to rotated display
+ * coordinates.
+ **/
+void
+gimp_display_shell_rotate_xy_f (GimpDisplayShell *shell,
+                                gdouble           x,
+                                gdouble           y,
+                                gdouble          *nx,
+                                gdouble          *ny)
+{
+  g_return_if_fail (GIMP_IS_DISPLAY_SHELL (shell));
+  g_return_if_fail (nx != NULL);
+  g_return_if_fail (ny != NULL);
+
+  *nx = x;
+  *ny = y;
+
+  if (shell->rotate_transform)
+    cairo_matrix_transform_point (shell->rotate_transform, nx, ny);
+}
+
+/**
+ * gimp_display_shell_unrotate_xy_f:
+ * @shell:       a #GimpDisplayShell
+ * @x:           x coordinate in rotated display coordinates
+ * @y:           y coordinate in rotated display coordinates
+ * @nx:          place to return x coordinate in unrotated display coordinates
+ * @ny:          place to return y coordinate in unrotated display  coordinates
+ *
+ * This function is identical to gimp_display_shell_unrotate_xy(),
+ * except that the input and output coordinates are doubles rather
+ * than ints.
+ **/
+void
+gimp_display_shell_unrotate_xy_f (GimpDisplayShell *shell,
+                                  gdouble           x,
+                                  gdouble           y,
+                                  gdouble          *nx,
+                                  gdouble          *ny)
+{
+  g_return_if_fail (GIMP_IS_DISPLAY_SHELL (shell));
+  g_return_if_fail (nx != NULL);
+  g_return_if_fail (ny != NULL);
+
+  *nx = x;
+  *ny = y;
+
+  if (shell->rotate_untransform)
+    cairo_matrix_transform_point (shell->rotate_untransform, nx, ny);
+}
+
+void
+gimp_display_shell_rotate_bounds (GimpDisplayShell *shell,
+                                  gdouble           x1,
+                                  gdouble           y1,
+                                  gdouble           x2,
+                                  gdouble           y2,
+                                  gdouble          *nx1,
+                                  gdouble          *ny1,
+                                  gdouble          *nx2,
+                                  gdouble          *ny2)
+{
+
+  g_return_if_fail (GIMP_IS_DISPLAY_SHELL (shell));
+
+  if (shell->rotate_transform)
+    {
+      gdouble tx1 = x1;
+      gdouble ty1 = y1;
+      gdouble tx2 = x1;
+      gdouble ty2 = y2;
+      gdouble tx3 = x2;
+      gdouble ty3 = y1;
+      gdouble tx4 = x2;
+      gdouble ty4 = y2;
+
+      cairo_matrix_transform_point (shell->rotate_transform, &tx1, &ty1);
+      cairo_matrix_transform_point (shell->rotate_transform, &tx2, &ty2);
+      cairo_matrix_transform_point (shell->rotate_transform, &tx3, &ty3);
+      cairo_matrix_transform_point (shell->rotate_transform, &tx4, &ty4);
+
+      *nx1 = MIN4 (tx1, tx2, tx3, tx4);
+      *ny1 = MIN4 (ty1, ty2, ty3, ty4);
+      *nx2 = MAX4 (tx1, tx2, tx3, tx4);
+      *ny2 = MAX4 (ty1, ty2, ty3, ty4);
+    }
+  else
+    {
+      *nx1 = x1;
+      *ny1 = y1;
+      *nx2 = x2;
+      *ny2 = y2;
+    }
+}
+
+void
+gimp_display_shell_unrotate_bounds (GimpDisplayShell *shell,
+                                    gdouble           x1,
+                                    gdouble           y1,
+                                    gdouble           x2,
+                                    gdouble           y2,
+                                    gdouble          *nx1,
+                                    gdouble          *ny1,
+                                    gdouble          *nx2,
+                                    gdouble          *ny2)
+{
+  g_return_if_fail (GIMP_IS_DISPLAY_SHELL (shell));
+
+  if (shell->rotate_untransform)
+    {
+      gdouble tx1 = x1;
+      gdouble ty1 = y1;
+      gdouble tx2 = x1;
+      gdouble ty2 = y2;
+      gdouble tx3 = x2;
+      gdouble ty3 = y1;
+      gdouble tx4 = x2;
+      gdouble ty4 = y2;
+
+      cairo_matrix_transform_point (shell->rotate_untransform, &tx1, &ty1);
+      cairo_matrix_transform_point (shell->rotate_untransform, &tx2, &ty2);
+      cairo_matrix_transform_point (shell->rotate_untransform, &tx3, &ty3);
+      cairo_matrix_transform_point (shell->rotate_untransform, &tx4, &ty4);
+
+      *nx1 = MIN4 (tx1, tx2, tx3, tx4);
+      *ny1 = MIN4 (ty1, ty2, ty3, ty4);
+      *nx2 = MAX4 (tx1, tx2, tx3, tx4);
+      *ny2 = MAX4 (ty1, ty2, ty3, ty4);
+    }
+  else
+    {
+      *nx1 = x1;
+      *ny1 = y1;
+      *nx2 = x2;
+      *ny2 = y2;
+    }
+}
+
+/**
+ * gimp_display_shell_transform_coords:
+ * @shell:          a #GimpDisplayShell
+ * @image_coords:   image coordinates
+ * @display_coords: returns the corresponding display coordinates
+ *
+ * Transforms from image coordinates to display coordinates, so that
+ * objects can be rendered at the correct points on the display.
+ **/
+void
+gimp_display_shell_transform_coords (GimpDisplayShell *shell,
+                                     const GimpCoords *image_coords,
+                                     GimpCoords       *display_coords)
+{
+  g_return_if_fail (GIMP_IS_DISPLAY_SHELL (shell));
+  g_return_if_fail (image_coords != NULL);
+  g_return_if_fail (display_coords != NULL);
+
+  *display_coords = *image_coords;
+
+  display_coords->x = SCALEX (shell, image_coords->x);
+  display_coords->y = SCALEY (shell, image_coords->y);
+
+  display_coords->x -= shell->offset_x;
+  display_coords->y -= shell->offset_y;
+
+  if (shell->rotate_transform)
+    cairo_matrix_transform_point (shell->rotate_transform,
+                                  &display_coords->x,
+                                  &display_coords->y);
+}
+
+/**
+ * gimp_display_shell_untransform_coords:
+ * @shell:          a #GimpDisplayShell
+ * @display_coords: display coordinates
+ * @image_coords:   returns the corresponding image coordinates
+ *
+ * Transforms from display coordinates to image coordinates, so that
+ * points on the display can be mapped to points in the image.
+ **/
+void
+gimp_display_shell_untransform_coords (GimpDisplayShell *shell,
+                                       const GimpCoords *display_coords,
+                                       GimpCoords       *image_coords)
+{
+  g_return_if_fail (GIMP_IS_DISPLAY_SHELL (shell));
+  g_return_if_fail (display_coords != NULL);
+  g_return_if_fail (image_coords != NULL);
+
+  *image_coords = *display_coords;
+
+  if (shell->rotate_untransform)
+    cairo_matrix_transform_point (shell->rotate_untransform,
+                                  &image_coords->x,
+                                  &image_coords->y);
+
+  image_coords->x += shell->offset_x;
+  image_coords->y += shell->offset_y;
+
+  image_coords->x /= shell->scale_x;
+  image_coords->y /= shell->scale_y;
+
+  image_coords->xscale  = shell->scale_x;
+  image_coords->yscale  = shell->scale_y;
+  image_coords->angle   = shell->rotate_angle / 360.0;
+  image_coords->reflect = shell->flip_horizontally ^ shell->flip_vertically;
+
+  if (shell->flip_vertically)
+    image_coords->angle += 0.5;
+}
+
+/**
+ * gimp_display_shell_transform_xy:
+ * @shell:
+ * @x:
+ * @y:
+ * @nx:
+ * @ny:
+ *
+ * Transforms an image coordinate to a shell coordinate.
+ **/
+void
+gimp_display_shell_transform_xy (GimpDisplayShell *shell,
+                                 gdouble           x,
+                                 gdouble           y,
+                                 gint             *nx,
+                                 gint             *ny)
+{
+  gint64 tx;
+  gint64 ty;
+
+  g_return_if_fail (GIMP_IS_DISPLAY_SHELL (shell));
+  g_return_if_fail (nx != NULL);
+  g_return_if_fail (ny != NULL);
+
+  tx = x * shell->scale_x;
+  ty = y * shell->scale_y;
+
+  tx -= shell->offset_x;
+  ty -= shell->offset_y;
+
+  if (shell->rotate_transform)
+    {
+      gdouble fx = tx;
+      gdouble fy = ty;
+
+      cairo_matrix_transform_point (shell->rotate_transform, &fx, &fy);
+
+      tx = fx;
+      ty = fy;
+    }
+
+  /*  The projected coordinates might overflow a gint in the case of
+   *  big images at high zoom levels, so we clamp them here to avoid
+   *  problems.
+   */
+  *nx = CLAMP (tx, G_MININT, G_MAXINT);
+  *ny = CLAMP (ty, G_MININT, G_MAXINT);
+}
+
+/**
+ * gimp_display_shell_untransform_xy:
+ * @shell:       a #GimpDisplayShell
+ * @x:           x coordinate in display coordinates
+ * @y:           y coordinate in display coordinates
+ * @nx:          returns x oordinate in image coordinates
+ * @ny:          returns y coordinate in image coordinates
+ * @round:       if %TRUE, round the results to the nearest integer;
+ *               if %FALSE, simply cast them to @gint.
+ *
+ * Transform from display coordinates to image coordinates, so that
+ * points on the display can be mapped to the corresponding points
+ * in the image.
+ **/
+void
+gimp_display_shell_untransform_xy (GimpDisplayShell *shell,
+                                   gint              x,
+                                   gint              y,
+                                   gint             *nx,
+                                   gint             *ny,
+                                   gboolean          round)
+{
+  gint64 tx;
+  gint64 ty;
+
+  g_return_if_fail (GIMP_IS_DISPLAY_SHELL (shell));
+  g_return_if_fail (nx != NULL);
+  g_return_if_fail (ny != NULL);
+
+  if (shell->rotate_untransform)
+    {
+      gdouble fx = x;
+      gdouble fy = y;
+
+      cairo_matrix_transform_point (shell->rotate_untransform, &fx, &fy);
+
+      x = fx;
+      y = fy;
+    }
+
+  if (round)
+    {
+      tx = SIGNED_ROUND (((gdouble) x + shell->offset_x) / shell->scale_x);
+      ty = SIGNED_ROUND (((gdouble) y + shell->offset_y) / shell->scale_y);
+    }
+  else
+    {
+      tx = ((gint64) x + shell->offset_x) / shell->scale_x;
+      ty = ((gint64) y + shell->offset_y) / shell->scale_y;
+    }
+
+  *nx = CLAMP (tx, G_MININT, G_MAXINT);
+  *ny = CLAMP (ty, G_MININT, G_MAXINT);
+}
+
+/**
+ * gimp_display_shell_transform_xy_f:
+ * @shell: a #GimpDisplayShell
+ * @x:     image x coordinate of point
+ * @y:     image y coordinate of point
+ * @nx:    returned shell canvas x coordinate
+ * @ny:    returned shell canvas y coordinate
+ *
+ * Transforms from image coordinates to display shell canvas
+ * coordinates.
+ **/
+void
+gimp_display_shell_transform_xy_f (GimpDisplayShell *shell,
+                                   gdouble           x,
+                                   gdouble           y,
+                                   gdouble          *nx,
+                                   gdouble          *ny)
+{
+  g_return_if_fail (GIMP_IS_DISPLAY_SHELL (shell));
+  g_return_if_fail (nx != NULL);
+  g_return_if_fail (ny != NULL);
+
+  *nx = SCALEX (shell, x) - shell->offset_x;
+  *ny = SCALEY (shell, y) - shell->offset_y;
+
+  if (shell->rotate_transform)
+    cairo_matrix_transform_point (shell->rotate_transform, nx, ny);
+}
+
+/**
+ * gimp_display_shell_untransform_xy_f:
+ * @shell:       a #GimpDisplayShell
+ * @x:           x coordinate in display coordinates
+ * @y:           y coordinate in display coordinates
+ * @nx:          place to return x coordinate in image coordinates
+ * @ny:          place to return y coordinate in image coordinates
+ *
+ * This function is identical to gimp_display_shell_untransform_xy(),
+ * except that the input and output coordinates are doubles rather than
+ * ints, and consequently there is no option related to rounding.
+ **/
+void
+gimp_display_shell_untransform_xy_f (GimpDisplayShell *shell,
+                                     gdouble           x,
+                                     gdouble           y,
+                                     gdouble          *nx,
+                                     gdouble          *ny)
+{
+  g_return_if_fail (GIMP_IS_DISPLAY_SHELL (shell));
+  g_return_if_fail (nx != NULL);
+  g_return_if_fail (ny != NULL);
+
+  if (shell->rotate_untransform)
+    cairo_matrix_transform_point (shell->rotate_untransform, &x, &y);
+
+  *nx = (x + shell->offset_x) / shell->scale_x;
+  *ny = (y + shell->offset_y) / shell->scale_y;
+}
+
+void
+gimp_display_shell_transform_bounds (GimpDisplayShell *shell,
+                                     gdouble           x1,
+                                     gdouble           y1,
+                                     gdouble           x2,
+                                     gdouble           y2,
+                                     gdouble          *nx1,
+                                     gdouble          *ny1,
+                                     gdouble          *nx2,
+                                     gdouble          *ny2)
+{
+  g_return_if_fail (GIMP_IS_DISPLAY_SHELL (shell));
+  g_return_if_fail (nx1 != NULL);
+  g_return_if_fail (ny1 != NULL);
+  g_return_if_fail (nx2 != NULL);
+  g_return_if_fail (ny2 != NULL);
+
+  if (shell->rotate_transform)
+    {
+      gdouble tx1, ty1;
+      gdouble tx2, ty2;
+      gdouble tx3, ty3;
+      gdouble tx4, ty4;
+
+      gimp_display_shell_transform_xy_f_noround (shell, x1, y1, &tx1, &ty1);
+      gimp_display_shell_transform_xy_f_noround (shell, x1, y2, &tx2, &ty2);
+      gimp_display_shell_transform_xy_f_noround (shell, x2, y1, &tx3, &ty3);
+      gimp_display_shell_transform_xy_f_noround (shell, x2, y2, &tx4, &ty4);
+
+      *nx1 = MIN4 (tx1, tx2, tx3, tx4);
+      *ny1 = MIN4 (ty1, ty2, ty3, ty4);
+      *nx2 = MAX4 (tx1, tx2, tx3, tx4);
+      *ny2 = MAX4 (ty1, ty2, ty3, ty4);
+    }
+  else
+    {
+      gimp_display_shell_transform_xy_f_noround (shell, x1, y1, nx1, ny1);
+      gimp_display_shell_transform_xy_f_noround (shell, x2, y2, nx2, ny2);
+    }
+}
+
+void
+gimp_display_shell_untransform_bounds (GimpDisplayShell *shell,
+                                       gdouble           x1,
+                                       gdouble           y1,
+                                       gdouble           x2,
+                                       gdouble           y2,
+                                       gdouble          *nx1,
+                                       gdouble          *ny1,
+                                       gdouble          *nx2,
+                                       gdouble          *ny2)
+{
+  g_return_if_fail (GIMP_IS_DISPLAY_SHELL (shell));
+  g_return_if_fail (nx1 != NULL);
+  g_return_if_fail (ny1 != NULL);
+  g_return_if_fail (nx2 != NULL);
+  g_return_if_fail (ny2 != NULL);
+
+  if (shell->rotate_untransform)
+    {
+      gdouble tx1, ty1;
+      gdouble tx2, ty2;
+      gdouble tx3, ty3;
+      gdouble tx4, ty4;
+
+      gimp_display_shell_untransform_xy_f (shell, x1, y1, &tx1, &ty1);
+      gimp_display_shell_untransform_xy_f (shell, x1, y2, &tx2, &ty2);
+      gimp_display_shell_untransform_xy_f (shell, x2, y1, &tx3, &ty3);
+      gimp_display_shell_untransform_xy_f (shell, x2, y2, &tx4, &ty4);
+
+      *nx1 = MIN4 (tx1, tx2, tx3, tx4);
+      *ny1 = MIN4 (ty1, ty2, ty3, ty4);
+      *nx2 = MAX4 (tx1, tx2, tx3, tx4);
+      *ny2 = MAX4 (ty1, ty2, ty3, ty4);
+    }
+  else
+    {
+      gimp_display_shell_untransform_xy_f (shell, x1, y1, nx1, ny1);
+      gimp_display_shell_untransform_xy_f (shell, x2, y2, nx2, ny2);
+    }
+}
+
+/* transforms a bounding box from image-space, uniformly scaled by a factor of
+ * 'scale', to display-space.  this is equivalent to, but more accurate than,
+ * dividing the input by 'scale', and using
+ * gimp_display_shell_transform_bounds(), in particular, in that if 'scale'
+ * equals 'shell->scale_x' or 'shell->scale_y', there is no loss in accuracy
+ * in the corresponding dimension due to scaling (although there might be loss
+ * of accuracy due to rotation or translation.)
+ */
+void
+gimp_display_shell_transform_bounds_with_scale (GimpDisplayShell *shell,
+                                                gdouble           scale,
+                                                gdouble           x1,
+                                                gdouble           y1,
+                                                gdouble           x2,
+                                                gdouble           y2,
+                                                gdouble          *nx1,
+                                                gdouble          *ny1,
+                                                gdouble          *nx2,
+                                                gdouble          *ny2)
+{
+  gdouble factor_x;
+  gdouble factor_y;
+
+  g_return_if_fail (GIMP_IS_DISPLAY_SHELL (shell));
+  g_return_if_fail (scale > 0.0);
+  g_return_if_fail (nx1 != NULL);
+  g_return_if_fail (ny1 != NULL);
+  g_return_if_fail (nx2 != NULL);
+  g_return_if_fail (ny2 != NULL);
+
+  factor_x = shell->scale_x / scale;
+  factor_y = shell->scale_y / scale;
+
+  x1 = x1 * factor_x - shell->offset_x;
+  y1 = y1 * factor_y - shell->offset_y;
+  x2 = x2 * factor_x - shell->offset_x;
+  y2 = y2 * factor_y - shell->offset_y;
+
+  gimp_display_shell_rotate_bounds (shell,
+                                    x1,  y1,  x2,  y2,
+                                    nx1, ny1, nx2, ny2);
+}
+
+/* transforms a bounding box from display-space to image-space, uniformly
+ * scaled by a factor of 'scale'.  this is equivalent to, but more accurate
+ * than, using gimp_display_shell_untransform_bounds(), and multiplying the
+ * output by 'scale', in particular, in that if 'scale' equals 'shell->scale_x'
+ * or 'shell->scale_y', there is no loss in accuracy in the corresponding
+ * dimension due to scaling (although there might be loss of accuracy due to
+ * rotation or translation.)
+ */
+void
+gimp_display_shell_untransform_bounds_with_scale (GimpDisplayShell *shell,
+                                                  gdouble           scale,
+                                                  gdouble           x1,
+                                                  gdouble           y1,
+                                                  gdouble           x2,
+                                                  gdouble           y2,
+                                                  gdouble          *nx1,
+                                                  gdouble          *ny1,
+                                                  gdouble          *nx2,
+                                                  gdouble          *ny2)
+{
+  gdouble factor_x;
+  gdouble factor_y;
+
+  g_return_if_fail (GIMP_IS_DISPLAY_SHELL (shell));
+  g_return_if_fail (scale > 0.0);
+  g_return_if_fail (nx1 != NULL);
+  g_return_if_fail (ny1 != NULL);
+  g_return_if_fail (nx2 != NULL);
+  g_return_if_fail (ny2 != NULL);
+
+  factor_x = scale / shell->scale_x;
+  factor_y = scale / shell->scale_y;
+
+  gimp_display_shell_unrotate_bounds (shell,
+                                      x1,  y1,  x2,  y2,
+                                      nx1, ny1, nx2, ny2);
+
+  *nx1 = (*nx1 + shell->offset_x) * factor_x;
+  *ny1 = (*ny1 + shell->offset_y) * factor_y;
+  *nx2 = (*nx2 + shell->offset_x) * factor_x;
+  *ny2 = (*ny2 + shell->offset_y) * factor_y;
+}
+
+/**
+ * gimp_display_shell_untransform_viewport:
+ * @shell:  a #GimpDisplayShell
+ * @clip:   whether to clip the result to the image bounds
+ * @x:      returns image x coordinate of display upper left corner
+ * @y:      returns image y coordinate of display upper left corner
+ * @width:  returns width of display measured in image coordinates
+ * @height: returns height of display measured in image coordinates
+ *
+ * This function calculates the part of the image, in image coordinates,
+ * that corresponds to the display viewport.
+ **/
+void
+gimp_display_shell_untransform_viewport (GimpDisplayShell *shell,
+                                         gboolean          clip,
+                                         gint             *x,
+                                         gint             *y,
+                                         gint             *width,
+                                         gint             *height)
+{
+  gdouble x1, y1, x2, y2;
+
+  g_return_if_fail (GIMP_IS_DISPLAY_SHELL (shell));
+
+  gimp_display_shell_untransform_bounds (shell,
+                                         0, 0,
+                                         shell->disp_width, shell->disp_height,
+                                         &x1, &y1,
+                                         &x2, &y2);
+
+  x1 = floor (x1);
+  y1 = floor (y1);
+  x2 = ceil (x2);
+  y2 = ceil (y2);
+
+  if (clip)
+    {
+      GimpImage *image = gimp_display_get_image (shell->display);
+
+      x1 = MAX (x1, 0);
+      y1 = MAX (y1, 0);
+      x2 = MIN (x2, gimp_image_get_width  (image));
+      y2 = MIN (y2, gimp_image_get_height (image));
+    }
+
+  if (x)      *x      = x1;
+  if (y)      *y      = y1;
+  if (width)  *width  = x2 - x1;
+  if (height) *height = y2 - y1;
+}
+
+
+/*  private functions  */
+
+/* Same as gimp_display_shell_transform_xy_f(), but doesn't do any rounding
+ * for the transformed coordinates.
+ */
+static void
+gimp_display_shell_transform_xy_f_noround (GimpDisplayShell *shell,
+                                           gdouble           x,
+                                           gdouble           y,
+                                           gdouble          *nx,
+                                           gdouble          *ny)
+{
+  *nx = shell->scale_x * x - shell->offset_x;
+  *ny = shell->scale_y * y - shell->offset_y;
+
+  if (shell->rotate_transform)
+    cairo_matrix_transform_point (shell->rotate_transform, nx, ny);
+}