Improve DISPOSE_PREVIOUS in gif_load slightly

* src/image.c (gif_load): Tweak how DISPOSE_PREVIOUS is handled.
It's still not right, but it's less glaringly wrong.

1 files changed, 8 insertions, 0 deletions

diff --git a/src/image.c b/src/image.c
index 530819eab9d..45de7ae83d3 100644
--- a/src/image.c
+++ b/src/image.c
@@ -9115,6 +9115,14 @@ gif_load (struct frame *f, struct image *img)
       if (disposal == DISPOSAL_UNSPECIFIED)
         disposal = DISPOSE_DO_NOT;
 
+      /* This is not quite correct -- the specification is unclear,
+         but I think we're supposed to restore to the frame before the
+         previous frame?  And we don't have that data at this point.
+         But DISPOSE_DO_NOT is less wrong than substituting the
+         background, so do that for now.  */
+      if (disposal == DISPOSE_PREVIOUS)
+        disposal = DISPOSE_DO_NOT;
+
       gif_color_map = subimage->ImageDesc.ColorMap;
       if (!gif_color_map)
         gif_color_map = gif->SColorMap;