Implemented a more robust and transparent scheme for making

sure that iconphoto images are not blended with a black background.

FossilOrigin-Name: f73e7d222226c063d238608005411b38126d37da08db5760c0de02f7027e0475

3 files changed, 14 insertions, 16 deletions

diff --git a/macosx/tkMacOSXDraw.c b/macosx/tkMacOSXDraw.c
index 3d21507..90ebd54 100644
--- a/macosx/tkMacOSXDraw.c
+++ b/macosx/tkMacOSXDraw.c
@@ -440,8 +440,10 @@ TkMacOSXGetNSImageWithTkImage(
     int height)
 {
     Pixmap pixmap = Tk_GetPixmap(display, None, width, height, 0);
+    MacDrawable *macDraw = (MacDrawable *) pixmap;
     NSImage *nsImage;
 
+    macDraw->flags |= TK_DO_NOT_BLEND;
     Tk_RedrawImage(image, 0, 0, width, height, pixmap, 0, 0);
     nsImage = CreateNSImageWithPixmap(pixmap, width, height);
     Tk_FreePixmap(display, pixmap);
diff --git a/macosx/tkMacOSXImage.c b/macosx/tkMacOSXImage.c
index 02e8c54..adcb0f5 100644
--- a/macosx/tkMacOSXImage.c
+++ b/macosx/tkMacOSXImage.c
@@ -160,25 +160,20 @@ XGetImage(
     unsigned int bytes_per_row, size, row, n, m;
     unsigned int scalefactor=1, scaled_height=height, scaled_width=width;
     NSWindow *win = TkMacOSXDrawableWindow(drawable);
-    TkWindow *winPtr = TkMacOSXGetTkWindow(win);
+    MacDrawable *macDraw = ((MacDrawable*)drawable);
     static enum {unknown, no, yes} has_retina = unknown;
 
-    if (win && !winPtr) {
+    if (macDraw->flags & TK_DO_NOT_BLEND) {
 	/*
-	 * If this drawable has an associated NSWindow but does not have an
-	 * associated Tk window then it must be a dock icon.  We are being
-	 * called by TkImgPhotoDisplay because it is displaying a photoimage
-	 * with an alpha channel, e.g. one generated from a png file, as the
-	 * dock icon.  It is asking us to create a pixmap for the rectangle
-	 * where the image will be drawn so that it can blend the photoimage
-	 * with its background using the alpha values.  But in the case of a
-	 * dock icon, that background will be black, not transparent as it
-	 * should be.
-	 *
-	 * By returning NULL here, we force TkImgPhotoDisplay to give up on
-	 * trying to blend, and just copy the image pixels to the screen.  That
-	 * does the right thing for a dock icon, as it happens.
-	 */ 
+	 * When called by TkImgPhotoDisplay we are being asked to return a
+	 * background image to be blended with the photoimage using its alpha
+	 * channel, if it has one.  Returning NULL here makes TkImgPhotoDisplay
+	 * simply copy the image data, including the alpha channel, rather than
+	 * do any blending.  For example, when creating an iconphoto from a
+	 * photoimage with transparency we will be passed a newly created
+	 * pixmap filled with black pixels.  These should not be blended with
+	 * the pixels in the photoimage.
+	 */
 	return NULL;
     }
 
diff --git a/macosx/tkMacOSXInt.h b/macosx/tkMacOSXInt.h
index 6971e26..eb280a6 100644
--- a/macosx/tkMacOSXInt.h
+++ b/macosx/tkMacOSXInt.h
@@ -87,6 +87,7 @@ typedef struct TkWindowPrivate MacDrawable;
 #define TK_IS_PIXMAP		0x20
 #define TK_IS_BW_PIXMAP		0x40
 #define TK_DO_NOT_DRAW          0x80
+#define TK_DO_NOT_BLEND         0x100
 /*
  * I am reserving TK_EMBEDDED = 0x100 in the MacDrawable flags
  * This is defined in tk.h. We need to duplicate the TK_EMBEDDED flag in the