[gimp] app: gimp_widget_load_icon() should actually always return a result.

[Jehan <jehanp src gnome org>]

commit 123dcc6f3fda9c562e76885a346c85fdc14d1cc8
Author: Jehan <jehan girinstud io>
Date:   Sun Jun 24 18:21:24 2018 +0200

    app: gimp_widget_load_icon() should actually always return a result.
    
    When the "gimp-wilber-eek" fallback will fail to load, we just create an
    ugly magenta square instead.
    See Mitch's review at #1608.
    
    Master adaptation for commit 32931c4606841ad81d0c647c9d7ea8b977487f0f.

 app/widgets/gimpwidgets-utils.c | 38 ++++++++++++++++++++++++++++++--------
 1 file changed, 30 insertions(+), 8 deletions(-)
---
diff --git a/app/widgets/gimpwidgets-utils.c b/app/widgets/gimpwidgets-utils.c
index f2a9084d1f..f9a89f46b5 100644
--- a/app/widgets/gimpwidgets-utils.c
+++ b/app/widgets/gimpwidgets-utils.c
@@ -328,16 +328,13 @@ gimp_enum_radio_frame_add (GtkFrame  *frame,
  *
  * Loads an icon into a pixbuf with size as close as possible to @size.
  * If icon does not exist or fail to load, the function will fallback to
- * "gimp-wilber-eek" instead to prevent NULL pixbuf.
- * Nevertheless it is still possible for this function to return NULL,
- * in the edge case where "gimp-wilber-eek" is also missing, its file
- * corrupted or maybe other reasons. So calling code must take the NULL
- * return possibility into account.
+ * "gimp-wilber-eek" instead to prevent NULL pixbuf. As a last resort,
+ * if even the fallback failed to load, a magenta @size square will be
+ * returned, so this function is guaranteed to always return a
+ * #GdkPixbuf.
  *
  * Return value: a newly allocated #GdkPixbuf containing @icon_name at
- * size @size or a fallback icon/size. NULL return is a possibility in
- * if neither the requested icon nor fallback could be loaded
- * successfully.
+ * size @size or a fallback icon/size.
  **/
 GdkPixbuf *
 gimp_widget_load_icon (GtkWidget   *widget,
@@ -403,6 +400,31 @@ gimp_widget_load_icon (GtkWidget   *widget,
             pixbuf = gtk_icon_info_load_symbolic_for_context (icon_info,
                                                               gtk_widget_get_style_context (widget),
                                                               NULL, NULL);
+          if (! pixbuf)
+            {
+              /* As last resort, just draw an ugly magenta square. */
+              guchar *data;
+              gint    rowstride = 3 * size;
+              gint    i, j;
+
+              g_printerr ("WARNING: icon '%s' failed to load. Check the files "
+                          "in your icon theme.\n", GIMP_ICON_WILBER_EEK);
+
+              data = g_new (guchar, rowstride * size);
+              for (i = 0; i < size; i++)
+                {
+                  for (j = 0; j < size; j++)
+                    {
+                      data[i * rowstride + j * 3] = 255;
+                      data[i * rowstride + j * 3 + 1] = 0;
+                      data[i * rowstride + j * 3 + 2] = 255;
+                    }
+                }
+              pixbuf = gdk_pixbuf_new_from_data (data, GDK_COLORSPACE_RGB, FALSE,
+                                                 8, size, size, rowstride,
+                                                 (GdkPixbufDestroyNotify) g_free,
+                                                 NULL);
+            }
         }
     }