Adding upstream version 2.10.36.upstream/2.10.36

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

1 files changed, 914 insertions, 0 deletions

diff --git a/app/operations/layer-modes/gimpoperationlayermode.c b/app/operations/layer-modes/gimpoperationlayermode.c
new file mode 100644
index 0000000..db74ed5
--- /dev/null
+++ b/app/operations/layer-modes/gimpoperationlayermode.c
@@ -0,0 +1,914 @@
+/* GIMP - The GNU Image Manipulation Program
+ * Copyright (C) 1995 Spencer Kimball and Peter Mattis
+ *
+ * gimpoperationlayermode.c
+ * Copyright (C) 2008 Michael Natterer <mitch@gimp.org>
+ * Copyright (C) 2008 Martin Nordholts <martinn@svn.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-plugin.h>
+#include <cairo.h>
+#include <gdk-pixbuf/gdk-pixbuf.h>
+
+#include "libgimpbase/gimpbase.h"
+
+#include "../operations-types.h"
+
+#include "gimp-layer-modes.h"
+#include "gimpoperationlayermode.h"
+#include "gimpoperationlayermode-composite.h"
+
+
+/* the maximum number of samples to process in one go.  used to limit
+ * the size of the buffers we allocate on the stack.
+ */
+#define GIMP_COMPOSITE_BLEND_MAX_SAMPLES ((1 << 18) /* 256 KiB */  /      \
+                                          16 /* bytes per pixel */ /      \
+                                          2  /* max number of buffers */)
+
+/* number of consecutive unblended samples (whose source or destination alpha
+ * is zero) above which to split the blending process, in order to avoid
+ * performing too many unnecessary conversions.
+ */
+#define GIMP_COMPOSITE_BLEND_SPLIT_THRESHOLD 32
+
+
+enum
+{
+  PROP_0,
+  PROP_LAYER_MODE,
+  PROP_OPACITY,
+  PROP_BLEND_SPACE,
+  PROP_COMPOSITE_SPACE,
+  PROP_COMPOSITE_MODE
+};
+
+
+typedef void (* CompositeFunc) (const gfloat *in,
+                                const gfloat *layer,
+                                const gfloat *comp,
+                                const gfloat *mask,
+                                float         opacity,
+                                gfloat       *out,
+                                gint          samples);
+
+
+static void            gimp_operation_layer_mode_set_property        (GObject                *object,
+                                                                      guint                   property_id,
+                                                                      const GValue           *value,
+                                                                      GParamSpec             *pspec);
+static void            gimp_operation_layer_mode_get_property        (GObject                *object,
+                                                                      guint                   property_id,
+                                                                      GValue                 *value,
+                                                                      GParamSpec             *pspec);
+
+static void            gimp_operation_layer_mode_prepare             (GeglOperation          *operation);
+static GeglRectangle   gimp_operation_layer_mode_get_bounding_box    (GeglOperation          *operation);
+static gboolean        gimp_operation_layer_mode_parent_process      (GeglOperation          *operation,
+                                                                      GeglOperationContext   *context,
+                                                                      const gchar            *output_prop,
+                                                                      const GeglRectangle    *result,
+                                                                      gint                    level);
+
+static gboolean        gimp_operation_layer_mode_process             (GeglOperation          *operation,
+                                                                      void                   *in,
+                                                                      void                   *layer,
+                                                                      void                   *mask,
+                                                                      void                   *out,
+                                                                      glong                   samples,
+                                                                      const GeglRectangle    *roi,
+                                                                      gint                    level);
+
+static gboolean        gimp_operation_layer_mode_real_parent_process (GeglOperation          *operation,
+                                                                      GeglOperationContext   *context,
+                                                                      const gchar            *output_prop,
+                                                                      const GeglRectangle    *result,
+                                                                      gint                    level);
+static gboolean        gimp_operation_layer_mode_real_process        (GeglOperation          *operation,
+                                                                      void                   *in,
+                                                                      void                   *layer,
+                                                                      void                   *mask,
+                                                                      void                   *out,
+                                                                      glong                   samples,
+                                                                      const GeglRectangle    *roi,
+                                                                      gint                    level);
+
+static gboolean        process_last_node                             (GeglOperation       *operation,
+                                                                      void                *in,
+                                                                      void                *layer,
+                                                                      void                *mask,
+                                                                      void                *out,
+                                                                      glong                samples,
+                                                                      const GeglRectangle *roi,
+                                                                      gint                 level);
+
+
+G_DEFINE_TYPE (GimpOperationLayerMode, gimp_operation_layer_mode,
+               GEGL_TYPE_OPERATION_POINT_COMPOSER3)
+
+#define parent_class gimp_operation_layer_mode_parent_class
+
+
+static const Babl *gimp_layer_color_space_fish[3 /* from */][3 /* to */];
+
+static CompositeFunc composite_union                = gimp_operation_layer_mode_composite_union;
+static CompositeFunc composite_clip_to_backdrop     = gimp_operation_layer_mode_composite_clip_to_backdrop;
+static CompositeFunc composite_clip_to_layer        = gimp_operation_layer_mode_composite_clip_to_layer;
+static CompositeFunc composite_intersection         = gimp_operation_layer_mode_composite_intersection;
+
+static CompositeFunc composite_union_sub            = gimp_operation_layer_mode_composite_union_sub;
+static CompositeFunc composite_clip_to_backdrop_sub = gimp_operation_layer_mode_composite_clip_to_backdrop_sub;
+static CompositeFunc composite_clip_to_layer_sub    = gimp_operation_layer_mode_composite_clip_to_layer_sub;
+static CompositeFunc composite_intersection_sub     = gimp_operation_layer_mode_composite_intersection_sub;
+
+
+static void
+gimp_operation_layer_mode_class_init (GimpOperationLayerModeClass *klass)
+{
+  GObjectClass                     *object_class          = G_OBJECT_CLASS (klass);
+  GeglOperationClass               *operation_class       = GEGL_OPERATION_CLASS (klass);
+  GeglOperationPointComposer3Class *point_composer3_class = GEGL_OPERATION_POINT_COMPOSER3_CLASS (klass);
+
+  gegl_operation_class_set_keys (operation_class,
+                                 "name", "gimp:layer-mode", NULL);
+
+  object_class->set_property        = gimp_operation_layer_mode_set_property;
+  object_class->get_property        = gimp_operation_layer_mode_get_property;
+
+  operation_class->prepare          = gimp_operation_layer_mode_prepare;
+  operation_class->get_bounding_box = gimp_operation_layer_mode_get_bounding_box;
+  operation_class->process          = gimp_operation_layer_mode_parent_process;
+
+  point_composer3_class->process    = gimp_operation_layer_mode_process;
+
+  klass->parent_process             = gimp_operation_layer_mode_real_parent_process;
+  klass->process                    = gimp_operation_layer_mode_real_process;
+  klass->get_affected_region        = NULL;
+
+  g_object_class_install_property (object_class, PROP_LAYER_MODE,
+                                   g_param_spec_enum ("layer-mode",
+                                                      NULL, NULL,
+                                                      GIMP_TYPE_LAYER_MODE,
+                                                      GIMP_LAYER_MODE_NORMAL,
+                                                      GIMP_PARAM_READWRITE |
+                                                      G_PARAM_CONSTRUCT));
+
+  g_object_class_install_property (object_class, PROP_OPACITY,
+                                   g_param_spec_double ("opacity",
+                                                        NULL, NULL,
+                                                        0.0, 1.0, 1.0,
+                                                        GIMP_PARAM_READWRITE |
+                                                        G_PARAM_CONSTRUCT));
+
+  g_object_class_install_property (object_class, PROP_BLEND_SPACE,
+                                   g_param_spec_enum ("blend-space",
+                                                      NULL, NULL,
+                                                      GIMP_TYPE_LAYER_COLOR_SPACE,
+                                                      GIMP_LAYER_COLOR_SPACE_RGB_LINEAR,
+                                                      GIMP_PARAM_READWRITE |
+                                                      G_PARAM_CONSTRUCT));
+
+
+  g_object_class_install_property (object_class, PROP_COMPOSITE_SPACE,
+                                   g_param_spec_enum ("composite-space",
+                                                      NULL, NULL,
+                                                      GIMP_TYPE_LAYER_COLOR_SPACE,
+                                                      GIMP_LAYER_COLOR_SPACE_RGB_LINEAR,
+                                                      GIMP_PARAM_READWRITE |
+                                                      G_PARAM_CONSTRUCT));
+
+  g_object_class_install_property (object_class, PROP_COMPOSITE_MODE,
+                                   g_param_spec_enum ("composite-mode",
+                                                      NULL, NULL,
+                                                      GIMP_TYPE_LAYER_COMPOSITE_MODE,
+                                                      GIMP_LAYER_COMPOSITE_UNION,
+                                                      GIMP_PARAM_READWRITE |
+                                                      G_PARAM_CONSTRUCT));
+
+  gimp_layer_color_space_fish
+    /* from */ [GIMP_LAYER_COLOR_SPACE_RGB_LINEAR     - 1]
+    /* to   */ [GIMP_LAYER_COLOR_SPACE_RGB_PERCEPTUAL - 1] =
+      babl_fish ("RGBA float", "R'G'B'A float");
+  gimp_layer_color_space_fish
+    /* from */ [GIMP_LAYER_COLOR_SPACE_RGB_LINEAR     - 1]
+    /* to   */ [GIMP_LAYER_COLOR_SPACE_LAB            - 1] =
+      babl_fish ("RGBA float", "CIE Lab alpha float");
+
+  gimp_layer_color_space_fish
+    /* from */ [GIMP_LAYER_COLOR_SPACE_RGB_PERCEPTUAL - 1]
+    /* to   */ [GIMP_LAYER_COLOR_SPACE_RGB_LINEAR     - 1] =
+      babl_fish ("R'G'B'A float", "RGBA float");
+  gimp_layer_color_space_fish
+    /* from */ [GIMP_LAYER_COLOR_SPACE_RGB_PERCEPTUAL - 1]
+    /* to   */ [GIMP_LAYER_COLOR_SPACE_LAB            - 1] =
+      babl_fish ("R'G'B'A float", "CIE Lab alpha float");
+
+  gimp_layer_color_space_fish
+    /* from */ [GIMP_LAYER_COLOR_SPACE_LAB            - 1]
+    /* to   */ [GIMP_LAYER_COLOR_SPACE_RGB_LINEAR     - 1] =
+      babl_fish ("CIE Lab alpha float", "RGBA float");
+  gimp_layer_color_space_fish
+    /* from */ [GIMP_LAYER_COLOR_SPACE_LAB            - 1]
+    /* to   */ [GIMP_LAYER_COLOR_SPACE_RGB_PERCEPTUAL - 1] =
+      babl_fish ("CIE Lab alpha float", "R'G'B'A float");
+
+#if COMPILE_SSE2_INTRINISICS
+  if (gimp_cpu_accel_get_support () & GIMP_CPU_ACCEL_X86_SSE2)
+    composite_clip_to_backdrop = gimp_operation_layer_mode_composite_clip_to_backdrop_sse2;
+#endif
+}
+
+static void
+gimp_operation_layer_mode_init (GimpOperationLayerMode *self)
+{
+}
+
+static void
+gimp_operation_layer_mode_set_property (GObject      *object,
+                                        guint         property_id,
+                                        const GValue *value,
+                                        GParamSpec   *pspec)
+{
+  GimpOperationLayerMode *self = GIMP_OPERATION_LAYER_MODE (object);
+
+  switch (property_id)
+    {
+    case PROP_LAYER_MODE:
+      self->layer_mode = g_value_get_enum (value);
+      break;
+
+    case PROP_OPACITY:
+      self->prop_opacity = g_value_get_double (value);
+      break;
+
+    case PROP_BLEND_SPACE:
+      self->blend_space = g_value_get_enum (value);
+      break;
+
+    case PROP_COMPOSITE_SPACE:
+      self->composite_space = g_value_get_enum (value);
+      break;
+
+    case PROP_COMPOSITE_MODE:
+      self->prop_composite_mode = g_value_get_enum (value);
+      break;
+
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, property_id, pspec);
+      break;
+    }
+}
+
+static void
+gimp_operation_layer_mode_get_property (GObject    *object,
+                                        guint       property_id,
+                                        GValue     *value,
+                                        GParamSpec *pspec)
+{
+  GimpOperationLayerMode *self = GIMP_OPERATION_LAYER_MODE (object);
+
+  switch (property_id)
+    {
+    case PROP_LAYER_MODE:
+      g_value_set_enum (value, self->layer_mode);
+      break;
+
+    case PROP_OPACITY:
+      g_value_set_double (value, self->prop_opacity);
+      break;
+
+    case PROP_BLEND_SPACE:
+      g_value_set_enum (value, self->blend_space);
+      break;
+
+    case PROP_COMPOSITE_SPACE:
+      g_value_set_enum (value, self->composite_space);
+      break;
+
+    case PROP_COMPOSITE_MODE:
+      g_value_set_enum (value, self->prop_composite_mode);
+      break;
+
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, property_id, pspec);
+      break;
+    }
+}
+
+static void
+gimp_operation_layer_mode_prepare (GeglOperation *operation)
+{
+  GimpOperationLayerMode *self = GIMP_OPERATION_LAYER_MODE (operation);
+  const GeglRectangle    *input_extent;
+  const GeglRectangle    *mask_extent;
+  const Babl             *preferred_format;
+  const Babl             *format;
+
+  self->composite_mode = self->prop_composite_mode;
+
+  if (self->composite_mode == GIMP_LAYER_COMPOSITE_AUTO)
+    {
+      self->composite_mode =
+        gimp_layer_mode_get_composite_mode (self->layer_mode);
+
+      g_warn_if_fail (self->composite_mode != GIMP_LAYER_COMPOSITE_AUTO);
+    }
+
+  self->function       = gimp_layer_mode_get_function       (self->layer_mode);
+  self->blend_function = gimp_layer_mode_get_blend_function (self->layer_mode);
+
+  input_extent = gegl_operation_source_get_bounding_box (operation, "input");
+  mask_extent  = gegl_operation_source_get_bounding_box (operation, "aux2");
+
+  /* if the input pad has data, work as usual. */
+  if (input_extent && ! gegl_rectangle_is_empty (input_extent))
+    {
+      self->is_last_node = FALSE;
+
+      preferred_format = gegl_operation_get_source_format (operation, "input");
+    }
+  /* otherwise, we're the last node (corresponding to the bottom layer).
+   * in this case, we render the layer (as if) using UNION mode.
+   */
+  else
+    {
+      self->is_last_node = TRUE;
+
+      /* if the layer mode doesn't affect the source, use a shortcut
+       * function that only applies the opacity/mask to the layer.
+       */
+      if (! (gimp_operation_layer_mode_get_affected_region (self) &
+             GIMP_LAYER_COMPOSITE_REGION_SOURCE))
+        {
+          self->function = process_last_node;
+        }
+      /* otherwise, use the original process function, but force the
+       * composite mode to UNION.
+       */
+      else
+        {
+          self->composite_mode = GIMP_LAYER_COMPOSITE_UNION;
+        }
+
+      preferred_format = gegl_operation_get_source_format (operation, "aux");
+    }
+
+  self->has_mask = mask_extent && ! gegl_rectangle_is_empty (mask_extent);
+
+  format = gimp_layer_mode_get_format (self->layer_mode,
+                                       self->blend_space,
+                                       self->composite_space,
+                                       self->composite_mode,
+                                       preferred_format);
+
+  gegl_operation_set_format (operation, "input",  format);
+  gegl_operation_set_format (operation, "output", format);
+  gegl_operation_set_format (operation, "aux",    format);
+  gegl_operation_set_format (operation, "aux2",   babl_format ("Y float"));
+}
+
+static GeglRectangle
+gimp_operation_layer_mode_get_bounding_box (GeglOperation *op)
+{
+  GimpOperationLayerMode   *self     = (gpointer) op;
+  GeglRectangle            *in_rect;
+  GeglRectangle            *aux_rect;
+  GeglRectangle            *aux2_rect;
+  GeglRectangle             src_rect = {};
+  GeglRectangle             dst_rect = {};
+  GeglRectangle             result;
+  GimpLayerCompositeRegion  included_region;
+
+  in_rect   = gegl_operation_source_get_bounding_box (op, "input");
+  aux_rect  = gegl_operation_source_get_bounding_box (op, "aux");
+  aux2_rect = gegl_operation_source_get_bounding_box (op, "aux2");
+
+  if (in_rect)
+    dst_rect = *in_rect;
+
+  if (aux_rect)
+    {
+      src_rect = *aux_rect;
+
+      if (aux2_rect)
+        gegl_rectangle_intersect (&src_rect, &src_rect, aux2_rect);
+    }
+
+  if (self->is_last_node)
+    {
+      included_region = GIMP_LAYER_COMPOSITE_REGION_SOURCE;
+    }
+  else
+    {
+      included_region = gimp_layer_mode_get_included_region (self->layer_mode,
+                                                             self->composite_mode);
+    }
+
+  if (self->prop_opacity == 0.0)
+    included_region &= ~GIMP_LAYER_COMPOSITE_REGION_SOURCE;
+
+  gegl_rectangle_intersect (&result, &src_rect, &dst_rect);
+
+  if (included_region & GIMP_LAYER_COMPOSITE_REGION_SOURCE)
+    gegl_rectangle_bounding_box (&result, &result, &src_rect);
+
+  if (included_region & GIMP_LAYER_COMPOSITE_REGION_DESTINATION)
+    gegl_rectangle_bounding_box (&result, &result, &dst_rect);
+
+  return result;
+}
+
+static gboolean
+gimp_operation_layer_mode_parent_process (GeglOperation        *operation,
+                                          GeglOperationContext *context,
+                                          const gchar          *output_prop,
+                                          const GeglRectangle  *result,
+                                          gint                  level)
+{
+  GimpOperationLayerMode *point = GIMP_OPERATION_LAYER_MODE (operation);
+
+  point->opacity = point->prop_opacity;
+
+  /* if we have a mask, but it's not included in the output, pretend the
+   * opacity is 0, so that we don't composite 'aux' over 'input' as if there
+   * was no mask.
+   */
+  if (point->has_mask)
+    {
+      GObject  *mask;
+      gboolean  has_mask;
+
+      /* get the raw value.  this does not increase the reference count. */
+      mask = gegl_operation_context_get_object (context, "aux2");
+
+      /* disregard 'mask' if it's not included in the roi. */
+      has_mask =
+        mask &&
+        gegl_rectangle_intersect (NULL,
+                                  gegl_buffer_get_extent (GEGL_BUFFER (mask)),
+                                  result);
+
+      if (! has_mask)
+        point->opacity = 0.0;
+    }
+
+  return GIMP_OPERATION_LAYER_MODE_GET_CLASS (point)->parent_process (
+    operation, context, output_prop, result, level);
+}
+
+static gboolean
+gimp_operation_layer_mode_process (GeglOperation       *operation,
+                                   void                *in,
+                                   void                *layer,
+                                   void                *mask,
+                                   void                *out,
+                                   glong                samples,
+                                   const GeglRectangle *roi,
+                                   gint                 level)
+{
+  return ((GimpOperationLayerMode *) operation)->function (
+    operation, in, layer, mask, out, samples, roi, level);
+}
+
+static gboolean
+gimp_operation_layer_mode_real_parent_process (GeglOperation        *operation,
+                                               GeglOperationContext *context,
+                                               const gchar          *output_prop,
+                                               const GeglRectangle  *result,
+                                               gint                  level)
+{
+  GimpOperationLayerMode   *point = GIMP_OPERATION_LAYER_MODE (operation);
+  GObject                  *input;
+  GObject                  *aux;
+  gboolean                  has_input;
+  gboolean                  has_aux;
+  GimpLayerCompositeRegion  included_region;
+
+  /* get the raw values.  this does not increase the reference count. */
+  input = gegl_operation_context_get_object (context, "input");
+  aux   = gegl_operation_context_get_object (context, "aux");
+
+  /* disregard 'input' if it's not included in the roi. */
+  has_input =
+    input &&
+    gegl_rectangle_intersect (NULL,
+                              gegl_buffer_get_extent (GEGL_BUFFER (input)),
+                              result);
+
+  /* disregard 'aux' if it's not included in the roi, or if it's fully
+   * transparent.
+   */
+  has_aux =
+    aux &&
+    point->opacity != 0.0 &&
+    gegl_rectangle_intersect (NULL,
+                              gegl_buffer_get_extent (GEGL_BUFFER (aux)),
+                              result);
+
+  if (point->is_last_node)
+    {
+      included_region = GIMP_LAYER_COMPOSITE_REGION_SOURCE;
+    }
+  else
+    {
+      included_region = gimp_layer_mode_get_included_region (point->layer_mode,
+                                                             point->composite_mode);
+    }
+
+  /* if there's no 'input' ... */
+  if (! has_input)
+    {
+      /* ... and there's 'aux', and the composite mode includes it (or we're
+       * the last node) ...
+       */
+      if (has_aux && (included_region & GIMP_LAYER_COMPOSITE_REGION_SOURCE))
+        {
+          GimpLayerCompositeRegion affected_region;
+
+          affected_region =
+            gimp_operation_layer_mode_get_affected_region (point);
+
+          /* ... and the op doesn't otherwise affect 'aux', or changes its
+           * alpha ...
+           */
+          if (! (affected_region & GIMP_LAYER_COMPOSITE_REGION_SOURCE) &&
+              point->opacity == 1.0                                    &&
+              ! gegl_operation_context_get_object (context, "aux2"))
+            {
+              /* pass 'aux' directly as output; */
+              gegl_operation_context_set_object (context, "output", aux);
+              return TRUE;
+            }
+
+          /* otherwise, if the op affects 'aux', or changes its alpha, process
+           * it even though there's no 'input';
+           */
+        }
+      /* otherwise, there's no 'aux', or the composite mode doesn't include it,
+       * and so ...
+       */
+      else
+        {
+          /* ... the output is empty. */
+          gegl_operation_context_set_object (context, "output", NULL);
+          return TRUE;
+        }
+    }
+  /* otherwise, if there's 'input' but no 'aux' ... */
+  else if (! has_aux)
+    {
+      /* ... and the composite mode includes 'input' ... */
+      if (included_region & GIMP_LAYER_COMPOSITE_REGION_DESTINATION)
+        {
+          GimpLayerCompositeRegion affected_region;
+
+          affected_region =
+            gimp_operation_layer_mode_get_affected_region (point);
+
+          /* ... and the op doesn't otherwise affect 'input' ... */
+          if (! (affected_region & GIMP_LAYER_COMPOSITE_REGION_DESTINATION))
+            {
+              /* pass 'input' directly as output; */
+              gegl_operation_context_set_object (context, "output", input);
+              return TRUE;
+            }
+
+          /* otherwise, if the op affects 'input', process it even though
+           * there's no 'aux';
+           */
+        }
+
+      /* otherwise, the output is fully transparent, but we process it anyway
+       * to maintain the 'input' color values.
+       */
+    }
+
+  /* FIXME: we don't actually handle the case where one of the inputs
+   * is NULL -- it'll just segfault.  'input' is not expected to be NULL,
+   * but 'aux' might be, currently.
+   */
+  if (! input || ! aux)
+    {
+      GObject *empty = G_OBJECT (gegl_buffer_new (NULL, NULL));
+
+      if (! input) gegl_operation_context_set_object (context, "input", empty);
+      if (! aux)   gegl_operation_context_set_object (context, "aux",   empty);
+
+      if (! input && ! aux)
+        gegl_object_set_has_forked (G_OBJECT (empty));
+
+      g_object_unref (empty);
+    }
+
+  /* chain up, which will create the needed buffers for our actual
+   * process function
+   */
+  return GEGL_OPERATION_CLASS (parent_class)->process (operation, context,
+                                                       output_prop, result,
+                                                       level);
+}
+
+static gboolean
+gimp_operation_layer_mode_real_process (GeglOperation       *operation,
+                                        void                *in_p,
+                                        void                *layer_p,
+                                        void                *mask_p,
+                                        void                *out_p,
+                                        glong                samples,
+                                        const GeglRectangle *roi,
+                                        gint                 level)
+{
+  GimpOperationLayerMode *layer_mode              = (gpointer) operation;
+  gfloat                 *in                      = in_p;
+  gfloat                 *out                     = out_p;
+  gfloat                 *layer                   = layer_p;
+  gfloat                 *mask                    = mask_p;
+  gfloat                  opacity                 = layer_mode->opacity;
+  GimpLayerColorSpace     blend_space             = layer_mode->blend_space;
+  GimpLayerColorSpace     composite_space         = layer_mode->composite_space;
+  GimpLayerCompositeMode  composite_mode          = layer_mode->composite_mode;
+  GimpLayerModeBlendFunc  blend_function          = layer_mode->blend_function;
+  gboolean                composite_needs_in_color;
+  gfloat                 *blend_in;
+  gfloat                 *blend_layer;
+  gfloat                 *blend_out;
+  const Babl             *composite_to_blend_fish = NULL;
+  const Babl             *blend_to_composite_fish = NULL;
+
+  /* make sure we don't process more than GIMP_COMPOSITE_BLEND_MAX_SAMPLES
+   * at a time, so that we don't overflow the stack if we allocate buffers
+   * on it.  note that this has to be done with a nested function call,
+   * because alloca'd buffers remain for the duration of the stack frame.
+   */
+  while (samples > GIMP_COMPOSITE_BLEND_MAX_SAMPLES)
+    {
+      gimp_operation_layer_mode_real_process (operation,
+                                              in, layer, mask, out,
+                                              GIMP_COMPOSITE_BLEND_MAX_SAMPLES,
+                                              roi, level);
+
+      in      += 4 * GIMP_COMPOSITE_BLEND_MAX_SAMPLES;
+      layer   += 4 * GIMP_COMPOSITE_BLEND_MAX_SAMPLES;
+      if (mask)
+        mask  +=     GIMP_COMPOSITE_BLEND_MAX_SAMPLES;
+      out     += 4 * GIMP_COMPOSITE_BLEND_MAX_SAMPLES;
+
+      samples -= GIMP_COMPOSITE_BLEND_MAX_SAMPLES;
+    }
+
+  composite_needs_in_color =
+    composite_mode == GIMP_LAYER_COMPOSITE_UNION ||
+    composite_mode == GIMP_LAYER_COMPOSITE_CLIP_TO_BACKDROP;
+
+  blend_in    = in;
+  blend_layer = layer;
+  blend_out   = out;
+
+  if (blend_space != GIMP_LAYER_COLOR_SPACE_AUTO)
+    {
+      gimp_assert (composite_space >= 1 && composite_space < 4);
+      gimp_assert (blend_space     >= 1 && blend_space     < 4);
+
+      composite_to_blend_fish = gimp_layer_color_space_fish [composite_space - 1]
+                                                            [blend_space     - 1];
+
+      blend_to_composite_fish = gimp_layer_color_space_fish [blend_space     - 1]
+                                                            [composite_space - 1];
+    }
+
+  /* if we need to convert the samples between the composite and blend
+   * spaces...
+   */
+  if (composite_to_blend_fish)
+    {
+      gint i;
+      gint end;
+
+      if (in != out || composite_needs_in_color)
+        {
+          /* don't convert input in-place if we're not doing in-place output,
+           * or if we're going to need the original input for compositing.
+           */
+          blend_in = g_alloca (sizeof (gfloat) * 4 * samples);
+        }
+      blend_layer  = g_alloca (sizeof (gfloat) * 4 * samples);
+
+      if (in == out) /* in-place detected, avoid clobbering since we need to
+                        read 'in' for the compositing stage  */
+        {
+          if (blend_layer != layer)
+            blend_out = blend_layer;
+          else
+            blend_out = g_alloca (sizeof (gfloat) * 4 * samples);
+        }
+
+      /* samples whose the source or destination alpha is zero are not blended,
+       * and therefore do not need to be converted.  while it's generally
+       * desirable to perform conversion and blending in bulk, when we have
+       * more than a certain number of consecutive unblended samples, the cost
+       * of converting them outweighs the cost of splitting the process around
+       * them to avoid the conversion.
+       */
+
+      i   = ALPHA;
+      end = 4 * samples + ALPHA;
+
+      while (TRUE)
+        {
+          gint first;
+          gint last;
+          gint count;
+
+          /* skip any unblended samples.  the color values of `blend_out` for
+           * these samples are unconstrained, in particular, they may be NaN,
+           * but the alpha values should generally be finite, and specifically
+           * 0 when the source alpha is 0.
+           */
+          while (i < end && (in[i] == 0.0f || layer[i] == 0.0f))
+            {
+              blend_out[i] = 0.0f;
+              i += 4;
+            }
+
+          /* stop if there are no more samples */
+          if (i == end)
+            break;
+
+          /* otherwise, keep scanning the samples until we find
+           * GIMP_COMPOSITE_BLEND_SPLIT_THRESHOLD consecutive unblended
+           * samples.
+           */
+
+          first  = i;
+          i     += 4;
+          last   = i;
+
+          while (i < end && i - last < 4 * GIMP_COMPOSITE_BLEND_SPLIT_THRESHOLD)
+            {
+              gboolean blended;
+
+              blended = (in[i] != 0.0f && layer[i] != 0.0f);
+
+              i += 4;
+              if (blended)
+                last = i;
+            }
+
+          /* convert and blend the samples in the range [first, last) */
+
+          count  = (last - first) / 4;
+          first -= ALPHA;
+
+          babl_process (composite_to_blend_fish,
+                        in + first, blend_in + first, count);
+          babl_process (composite_to_blend_fish,
+                        layer + first, blend_layer + first, count);
+
+          blend_function (operation, blend_in + first, blend_layer + first,
+                          blend_out + first, count);
+
+          babl_process (blend_to_composite_fish,
+                        blend_out + first, blend_out + first, count);
+
+          /* make sure the alpha values of `blend_out` are valid for the
+           * trailing unblended samples.
+           */
+          for (; last < i; last += 4)
+            blend_out[last] = 0.0f;
+        }
+    }
+  else
+    {
+      /* if both blending and compositing use the same color space, things are
+       * much simpler.
+       */
+
+      if (in == out) /* in-place detected, avoid clobbering since we need to
+                        read 'in' for the compositing stage  */
+        {
+          blend_out = g_alloca (sizeof (gfloat) * 4 * samples);
+        }
+
+      blend_function (operation, blend_in, blend_layer, blend_out, samples);
+    }
+
+  if (! gimp_layer_mode_is_subtractive (layer_mode->layer_mode))
+    {
+      switch (composite_mode)
+        {
+        case GIMP_LAYER_COMPOSITE_UNION:
+        case GIMP_LAYER_COMPOSITE_AUTO:
+          composite_union (in, layer, blend_out, mask, opacity,
+                           out, samples);
+          break;
+
+        case GIMP_LAYER_COMPOSITE_CLIP_TO_BACKDROP:
+          composite_clip_to_backdrop (in, layer, blend_out, mask, opacity,
+                                      out, samples);
+          break;
+
+        case GIMP_LAYER_COMPOSITE_CLIP_TO_LAYER:
+          composite_clip_to_layer (in, layer, blend_out, mask, opacity,
+                                   out, samples);
+          break;
+
+        case GIMP_LAYER_COMPOSITE_INTERSECTION:
+          composite_intersection (in, layer, blend_out, mask, opacity,
+                                  out, samples);
+          break;
+        }
+    }
+  else
+    {
+      switch (composite_mode)
+        {
+        case GIMP_LAYER_COMPOSITE_UNION:
+        case GIMP_LAYER_COMPOSITE_AUTO:
+          composite_union_sub (in, layer, blend_out, mask, opacity,
+                               out, samples);
+          break;
+
+        case GIMP_LAYER_COMPOSITE_CLIP_TO_BACKDROP:
+          composite_clip_to_backdrop_sub (in, layer, blend_out, mask, opacity,
+                                          out, samples);
+          break;
+
+        case GIMP_LAYER_COMPOSITE_CLIP_TO_LAYER:
+          composite_clip_to_layer_sub (in, layer, blend_out, mask, opacity,
+                                       out, samples);
+          break;
+
+        case GIMP_LAYER_COMPOSITE_INTERSECTION:
+          composite_intersection_sub (in, layer, blend_out, mask, opacity,
+                                      out, samples);
+          break;
+        }
+    }
+
+  return TRUE;
+}
+
+static gboolean
+process_last_node (GeglOperation       *operation,
+                   void                *in_p,
+                   void                *layer_p,
+                   void                *mask_p,
+                   void                *out_p,
+                   glong                samples,
+                   const GeglRectangle *roi,
+                   gint                 level)
+{
+  gfloat *out     = out_p;
+  gfloat *layer   = layer_p;
+  gfloat *mask    = mask_p;
+  gfloat  opacity = GIMP_OPERATION_LAYER_MODE (operation)->opacity;
+
+  while (samples--)
+    {
+      memcpy (out, layer, 3 * sizeof (gfloat));
+
+      out[ALPHA] = layer[ALPHA] * opacity;
+      if (mask)
+        out[ALPHA] *= *mask++;
+
+      layer += 4;
+      out   += 4;
+    }
+
+  return TRUE;
+}
+
+
+/*  public functions  */
+
+
+GimpLayerCompositeRegion
+gimp_operation_layer_mode_get_affected_region (GimpOperationLayerMode *layer_mode)
+{
+  GimpOperationLayerModeClass *klass;
+
+  g_return_val_if_fail (GIMP_IS_OPERATION_LAYER_MODE (layer_mode),
+                        GIMP_LAYER_COMPOSITE_REGION_INTERSECTION);
+
+  klass = GIMP_OPERATION_LAYER_MODE_GET_CLASS (layer_mode);
+
+  if (klass->get_affected_region)
+    return klass->get_affected_region (layer_mode);
+
+  return GIMP_LAYER_COMPOSITE_REGION_INTERSECTION;
+}