app: add gimp_paint_core_{set_show_all,get_image_pickable}()

GimpPaintCore operates indipendently of a display, and hence needs
to be explictly told when operating in "show all" mode, affecting
the result of paint tools operating in "sample merged" mode.  Add
gimp_paint_core_set_show_all() for that purpose, and call it,
passing the current display's "show all" mode, in GimpPaintTool.
This controls which pickable (the image itself, or its projection)
is used as the sampling source, as per
GimpPaintCore::saved_proj_buffer, and as returned by the new
gimp_paint_core_get_image_pickable() function.

app/paint/gimppaintcore.c

@@ -394,12 +394,18 @@ gimp_paint_core_start (GimpPaintCore     *core,
 
   core->undo_buffer = gimp_gegl_buffer_dup (gimp_drawable_get_buffer (drawable));
 
+  /*  Set the image pickable  */
+  if (! core->show_all)
+    core->image_pickable = GIMP_PICKABLE (image);
+  else
+    core->image_pickable = GIMP_PICKABLE (gimp_image_get_projection (image));
+
   /*  Allocate the saved proj structure  */
   g_clear_object (&core->saved_proj_buffer);
 
   if (core->use_saved_proj)
     {
-      GeglBuffer *buffer = gimp_pickable_get_buffer (GIMP_PICKABLE (image));
+      GeglBuffer *buffer = gimp_pickable_get_buffer (core->image_pickable);
 
       core->saved_proj_buffer = gimp_gegl_buffer_dup (buffer);
     }
@@ -537,6 +543,8 @@ gimp_paint_core_finish (GimpPaintCore *core,
       gimp_image_undo_group_end (image);
     }
 
+  core->image_pickable = NULL;
+
   g_clear_object (&core->undo_buffer);
   g_clear_object (&core->saved_proj_buffer);
 
@@ -620,6 +628,23 @@ gimp_paint_core_interpolate (GimpPaintCore    *core,
                                                  paint_options, time);
 }
 
+void
+gimp_paint_core_set_show_all (GimpPaintCore *core,
+                              gboolean       show_all)
+{
+  g_return_if_fail (GIMP_IS_PAINT_CORE (core));
+
+  core->show_all = show_all;
+}
+
+gboolean
+gimp_paint_core_get_show_all (GimpPaintCore *core)
+{
+  g_return_val_if_fail (GIMP_IS_PAINT_CORE (core), FALSE);
+
+  return core->show_all;
+}
+
 void
 gimp_paint_core_set_current_coords (GimpPaintCore    *core,
                                     const GimpCoords *coords)
@@ -744,6 +769,15 @@ gimp_paint_core_get_paint_buffer (GimpPaintCore    *core,
   return paint_buffer;
 }
 
+GimpPickable *
+gimp_paint_core_get_image_pickable (GimpPaintCore *core)
+{
+  g_return_val_if_fail (GIMP_IS_PAINT_CORE (core), NULL);
+  g_return_val_if_fail (core->image_pickable != NULL, NULL);
+
+  return core->image_pickable;
+}
+
 GeglBuffer *
 gimp_paint_core_get_orig_image (GimpPaintCore *core)
 {

app/paint/gimppaintcore.h

@@ -40,6 +40,8 @@ struct _GimpPaintCore
 
   gchar          *undo_desc;         /*  undo description                    */
 
+  gboolean        show_all;          /*  whether working in show-all mode    */
+
   GimpCoords      start_coords;      /*  the last stroke's endpoint for undo */
 
   GimpCoords      cur_coords;        /*  current coords                      */
@@ -55,6 +57,8 @@ struct _GimpPaintCore
 
   gboolean        use_saved_proj;    /*  keep the unmodified proj around     */
 
+  GimpPickable   *image_pickable;    /*  the image pickable                  */
+
   GeglBuffer     *undo_buffer;       /*  pixels which have been modified     */
   GeglBuffer     *saved_proj_buffer; /*  proj tiles which have been modified */
   GeglBuffer     *canvas_buffer;     /*  the buffer to paint the mask to     */
@@ -146,6 +150,10 @@ void      gimp_paint_core_interpolate               (GimpPaintCore    *core,
                                                      const GimpCoords *coords,
                                                      guint32           time);
 
+void      gimp_paint_core_set_show_all              (GimpPaintCore    *core,
+                                                     gboolean          show_all);
+gboolean  gimp_paint_core_get_show_all              (GimpPaintCore    *core);
+
 void      gimp_paint_core_set_current_coords        (GimpPaintCore    *core,
                                                      const GimpCoords *coords);
 void      gimp_paint_core_get_current_coords        (GimpPaintCore    *core,
@@ -176,6 +184,8 @@ GeglBuffer * gimp_paint_core_get_paint_buffer       (GimpPaintCore    *core,
                                                      gint             *paint_width,
                                                      gint             *paint_height);
 
+GimpPickable * gimp_paint_core_get_image_pickable   (GimpPaintCore    *core);
+
 GeglBuffer * gimp_paint_core_get_orig_image         (GimpPaintCore    *core);
 GeglBuffer * gimp_paint_core_get_orig_proj          (GimpPaintCore    *core);
 

app/tools/gimppainttool-paint.c

@@ -32,6 +32,7 @@
 #include "paint/gimppaintoptions.h"
 
 #include "display/gimpdisplay.h"
+#include "display/gimpdisplayshell.h"
 #include "display/gimpdisplayshell-utils.h"
 
 #include "gimppainttool.h"
@@ -261,6 +262,8 @@ gimp_paint_tool_paint_start (GimpPaintTool     *paint_tool,
   if (gimp_paint_tool_paint_use_thread (paint_tool))
     gimp_drawable_start_paint (drawable);
 
+  gimp_paint_core_set_show_all (core, shell->show_all);
+
   /*  Start the paint core  */
   if (! gimp_paint_core_start (core,
                                drawable, paint_options, &curr_coords,