[gimp/gimp-2-10] Issue #2436 - Crash after downsizing canvas

[Ell <ell src gnome org>]

commit 4f27efc4a0b12dfa573691caf2bad374891d1d74
Author: Ell <ell_se yahoo com>
Date:   Fri Nov 2 21:36:22 2018 -0400

    Issue #2436 - Crash after downsizing canvas
    
    In gimp_view_renderer_drawable_render(), avoid overflow in preview-
    area calculation.  This prevents erroneously setting 'scaling_up'
    to FALSE while upscaling the drawable by a very large amount, which
    can lead to the creation of a very large GimpTempBuf for the
    preview, causing memory allocation to fail.
    
    (cherry picked from commit 0cdbe91e5ad0ae22e69ef5eb4f8e76a80c99a724)

 app/widgets/gimpviewrendererdrawable.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)
---
diff --git a/app/widgets/gimpviewrendererdrawable.c b/app/widgets/gimpviewrendererdrawable.c
index 4b35ed1650..273ef92208 100644
--- a/app/widgets/gimpviewrendererdrawable.c
+++ b/app/widgets/gimpviewrendererdrawable.c
@@ -234,8 +234,9 @@ gimp_view_renderer_drawable_render (GimpViewRenderer *renderer,
                                        &scaling_up);
     }
 
-  if ((view_width * view_height) <
-      (gimp_item_get_width (item) * gimp_item_get_height (item) * 4))
+  if (((gint64) view_width * (gint64) view_height) <
+      ((gint64) gimp_item_get_width  (item) *
+       (gint64) gimp_item_get_height (item) * 4))
     scaling_up = FALSE;
 
   if (scaling_up && image && ! renderer->is_popup)