Fix PNGs on macOS (bug#28176)

* src/nsimage.m (ns_load_image): Remove index check.
(EmacsImage::getAnimatedBitmapImageRep): New function.
(EmacsImage::getMetadata): Use getAnimatedBitmapImageRep.
(EmacsImage::setFrame): Use getAnimatedBitmapImageRep and check index
is valid.

1 files changed, 40 insertions, 26 deletions

diff --git a/src/nsimage.m b/src/nsimage.m
index 94b24a3912c..3c81dea67a9 100644
--- a/src/nsimage.m
+++ b/src/nsimage.m
@@ -106,7 +106,7 @@ ns_load_image (struct frame *f, struct image *img,
       return 0;
     }
 
-  if (index < 0 || ![eImg setFrame: index])
+  if (![eImg setFrame: index])
     {
       add_to_log ("Unable to set index %d for image %s", index, img->spec);
       return 0;
@@ -450,49 +450,63 @@ ns_set_alpha (void *img, int x, int y, unsigned char a)
   return stippleMask;
 }
 
-/* If the image has multiple frames, get a count of them and the
-   animation delay, if available. */
-- (Lisp_Object)getMetadata
+/* Find the first NSBitmapImageRep which has multiple frames. */
+- (NSBitmapImageRep *)getAnimatedBitmapImageRep
 {
-  Lisp_Object metadata = Qnil;
-
   for (NSImageRep * r in [self representations])
     {
       if ([r isKindOfClass:[NSBitmapImageRep class]])
         {
           NSBitmapImageRep * bm = (NSBitmapImageRep *)r;
-          int frames = [[bm valueForProperty: NSImageFrameCount] intValue];
-          float delay = [[bm valueForProperty: NSImageCurrentFrameDuration]
-                          floatValue];
-
-          if (frames > 1)
-            metadata = Fcons (Qcount, Fcons (make_number (frames), metadata));
-          if (delay > 0)
-            metadata = Fcons (Qdelay, Fcons (make_float (delay), metadata));
-          break;
+          if ([[bm valueForProperty:NSImageFrameCount] intValue] > 0)
+            return bm;
         }
     }
+  return nil;
+}
+
+/* If the image has multiple frames, get a count of them and the
+   animation delay, if available. */
+- (Lisp_Object)getMetadata
+{
+  Lisp_Object metadata = Qnil;
+
+  NSBitmapImageRep * bm = [self getAnimatedBitmapImageRep];
+
+  if (bm != nil)
+    {
+      int frames = [[bm valueForProperty:NSImageFrameCount] intValue];
+      float delay = [[bm valueForProperty:NSImageCurrentFrameDuration]
+                      floatValue];
+
+      if (frames > 1)
+        metadata = Fcons (Qcount, Fcons (make_number (frames), metadata));
+      if (delay > 0)
+        metadata = Fcons (Qdelay, Fcons (make_float (delay), metadata));
+    }
   return metadata;
 }
 
 /* Attempt to set the animation frame to be displayed. */
 - (BOOL)setFrame: (unsigned int) index
 {
-  for (NSImageRep * r in [self representations])
+  NSBitmapImageRep * bm = [self getAnimatedBitmapImageRep];
+
+  if (bm != nil)
     {
-      if ([r isKindOfClass:[NSBitmapImageRep class]])
-        {
-          NSBitmapImageRep * bm = (NSBitmapImageRep *)r;
-          if ([[bm valueForProperty: NSImageFrameCount] intValue] <= index)
-            continue;
+      int frames = [[bm valueForProperty:NSImageFrameCount] intValue];
 
-          [bm setProperty: NSImageCurrentFrame
-                withValue: [NSNumber numberWithUnsignedInt: index]];
-          return YES;
-        }
+      /* If index is invalid, give up. */
+      if (index < 0 || index > frames)
+        return NO;
+
+      [bm setProperty: NSImageCurrentFrame
+            withValue: [NSNumber numberWithUnsignedInt:index]];
     }
 
-  return NO;
+  /* Setting the frame has succeeded, or the image doesn't have
+     multiple frames. */
+  return YES;
 }
 
 @end