Changed when blending is used with tile sets: now use blending if the tile set has...

diff --git a/src/main-cocoa.m b/src/main-cocoa.m
index 17a55ba..e04975c 100644 (file)
--- a/src/main-cocoa.m
+++ b/src/main-cocoa.m
@@ -2544,15 +2544,22 @@ static void Term_xtra_cocoa_fresh(AngbandContext* angbandContext)
     int graf_width, graf_height, alphablend;
 
     if (angbandContext->changes->has_pict) {
+       CGImageAlphaInfo ainfo = CGImageGetAlphaInfo(pict_image);
+
        graf_width = current_graphics_mode->cell_width;
        graf_height = current_graphics_mode->cell_height;
        /*
-        * Transparency effect. We really want to check
-        * current_graphics_mode->alphablend, but as of this writing
-        * that's never set, so we do something lame.
+        * As of this writing, a value of zero for
+        * current_graphics_mode->alphablend can mean either that the tile set
+        * doesn't have an alpha channel or it does but it only takes on values
+        * of 0 or 255.  For main-cocoa.m's purposes, the latter is rendered
+        * using the same procedure as if alphablend was nonzero.  The former
+        * is handled differently, but alphablend doesn't distinguish it from
+        * the latter.  So ignore alphablend and directly test whether an
+        * alpha channel is present.
         */
-       /* alphablend = current_graphics_mode->alphablend */
-       alphablend = (graf_width > 8 || graf_height > 8);
+       alphablend = (ainfo & (kCGImageAlphaPremultipliedFirst |
+                              kCGImageAlphaPremultipliedLast)) ? 1 : 0;
     } else {
        graf_width = 0;
        graf_height = 0;