[gimp/gimp-2-10] Issue #4174 - Crash when using the Foreground Select tool with an offset drawable

[Ell <ell src gnome org>]

commit 7a29aca3092dc3d5b11b86c677a66525f9407aa3
Author: Ell <ell_se yahoo com>
Date:   Mon Feb 3 21:09:52 2020 +0200

    Issue #4174 - Crash when using the Foreground Select tool with an offset drawable
    
    In the Foreground Select tool, use the drawable bounds (including
    its offset) as the trimap buffer extents, which is now supported by
    the rest of the code.  This is both more streamlined, and works
    around a GEGL bug (independently fixed by commit
    gegl@378cd512c35fe2eb255492f90b503a67ab38d7a3), causing
    gegl:matting-global to segfault when the drawable and trimap bounds
    are differnet.
    
    (cherry picked from commit 666d0845e152618245bf9fcb31957678e16af4bd)

 app/tools/gimpforegroundselecttool.c | 41 +++++++++++++++++++-----------------
 1 file changed, 22 insertions(+), 19 deletions(-)
---
diff --git a/app/tools/gimpforegroundselecttool.c b/app/tools/gimpforegroundselecttool.c
index b4b7982a3f..480cff1670 100644
--- a/app/tools/gimpforegroundselecttool.c
+++ b/app/tools/gimpforegroundselecttool.c
@@ -912,6 +912,7 @@ gimp_foreground_select_tool_confirm (GimpPolygonSelectTool *poly_sel,
   GimpForegroundSelectTool *fg_select = GIMP_FOREGROUND_SELECT_TOOL (poly_sel);
   GimpImage                *image     = gimp_display_get_image (display);
   GimpDrawable             *drawable  = gimp_image_get_active_drawable (image);
+  GimpItem                 *item      = GIMP_ITEM (drawable);
 
   if (drawable && fg_select->state == MATTING_STATE_FREE_SELECT)
     {
@@ -924,9 +925,10 @@ gimp_foreground_select_tool_confirm (GimpPolygonSelectTool *poly_sel,
       gimp_scan_convert_add_polyline (scan_convert, n_points, points, TRUE);
 
       fg_select->trimap =
-        gegl_buffer_new (GEGL_RECTANGLE (0, 0,
-                                         gimp_image_get_width  (image),
-                                         gimp_image_get_height (image)),
+        gegl_buffer_new (GEGL_RECTANGLE (gimp_item_get_offset_x (item),
+                                         gimp_item_get_offset_y (item),
+                                         gimp_item_get_width    (item),
+                                         gimp_item_get_height   (item)),
                          gimp_image_get_mask_format (image));
 
       gimp_scan_convert_render_value (scan_convert, fg_select->trimap,
@@ -1301,10 +1303,13 @@ gimp_foreground_select_undo_new (GeglBuffer          *trimap,
                                  gint                stroke_width)
 
 {
-  StrokeUndo *undo;
-  gint        x1, y1, x2, y2;
-  gint        width, height;
-  gint        i;
+  StrokeUndo          *undo;
+  const GeglRectangle *extent;
+  gint                 x1, y1, x2, y2;
+  gint                 width, height;
+  gint                 i;
+
+  extent = gegl_buffer_get_extent (trimap);
 
   x1 = G_MAXINT;
   y1 = G_MAXINT;
@@ -1326,10 +1331,10 @@ gimp_foreground_select_undo_new (GeglBuffer          *trimap,
   x2 += (stroke_width + 1) / 2;
   y2 += (stroke_width + 1) / 2;
 
-  x1 = MAX (x1, 0);
-  y1 = MAX (y1, 0);
-  x2 = MIN (x2, gegl_buffer_get_width  (trimap));
-  y2 = MIN (y2, gegl_buffer_get_height (trimap));
+  x1 = MAX (x1, extent->x);
+  y1 = MAX (y1, extent->y);
+  x2 = MIN (x2, extent->x + extent->width);
+  y2 = MIN (y2, extent->x + extent->height);
 
   width  = x2 - x1;
   height = y2 - y1;
@@ -1338,13 +1343,13 @@ gimp_foreground_select_undo_new (GeglBuffer          *trimap,
     return NULL;
 
   undo = g_slice_new0 (StrokeUndo);
-  undo->saved_trimap = gegl_buffer_new (GEGL_RECTANGLE (0, 0, width, height),
+  undo->saved_trimap = gegl_buffer_new (GEGL_RECTANGLE (x1, y1, width, height),
                                         gegl_buffer_get_format (trimap));
 
   gimp_gegl_buffer_copy (
     trimap,             GEGL_RECTANGLE (x1, y1, width, height),
     GEGL_ABYSS_NONE,
-    undo->saved_trimap, GEGL_RECTANGLE (0, 0, width, height));
+    undo->saved_trimap, NULL);
 
   undo->trimap_x = x1;
   undo->trimap_y = y1;
@@ -1371,15 +1376,13 @@ gimp_foreground_select_undo_pop (StrokeUndo *undo,
                          GEGL_RECTANGLE (undo->trimap_x, undo->trimap_y,
                                          width, height),
                          GEGL_ABYSS_NONE,
-                         undo->saved_trimap,
-                         GEGL_RECTANGLE (0, 0, width, height));
+                         undo->saved_trimap, NULL);
 
   gimp_gegl_buffer_copy (buffer,
-                         GEGL_RECTANGLE (0, 0, width, height),
-                         GEGL_ABYSS_NONE,
-                         trimap,
                          GEGL_RECTANGLE (undo->trimap_x, undo->trimap_y,
-                                         width, height));
+                                         width, height),
+                         GEGL_ABYSS_NONE,
+                         trimap, NULL);
 
   g_object_unref (buffer);
 }