Bug 1403989 - Automatically treat black menu icons as templates, so that they get drawn inverted in hovered menuitems. r=jrmuizel,spohl

MozReview-Commit-ID: Bn69Ij0BfRa

--HG--
extra : rebase_source : 9d2d7d0797d89d0b7cf6685d29e458795f518e9d
extra : source : 7b389e4f44679c086a4a510da264f2f0531267ec

widget/cocoa/nsCocoaUtils.h

@@ -271,10 +271,14 @@ public:
       The caller owns the <code>CGImageRef</code>. 
       @param aFrame the frame to convert
       @param aResult the resulting CGImageRef
+      @param aIsEntirelyBlack an outparam that, if non-null, will be set to a
+                              bool that indicates whether the RGB values on all
+                              pixels are zero
       @return NS_OK if the conversion worked, NS_ERROR_FAILURE otherwise
    */
   static nsresult CreateCGImageFromSurface(SourceSurface* aSurface,
-                                           CGImageRef* aResult);
+                                           CGImageRef* aResult,
+                                           bool* aIsEntirelyBlack = nullptr);
   
   /** Creates a Cocoa <code>NSImage</code> from a <code>CGImageRef</code>.
       Copies the pixel data from the <code>CGImageRef</code> into a new <code>NSImage</code>.

widget/cocoa/nsCocoaUtils.mm

@@ -361,8 +361,28 @@ void data_ss_release_callback(void *aDataSourceSurface,
   }
 }
 
+// This function assumes little endian byte order.
+static bool
+ComputeIsEntirelyBlack(const DataSourceSurface::MappedSurface& aMap,
+                       const IntSize& aSize)
+{
+  for (int32_t y = 0; y < aSize.height; y++) {
+    size_t rowStart = y * aMap.mStride;
+    for (int32_t x = 0; x < aSize.width; x++) {
+      size_t index = rowStart + x * 4;
+      if (aMap.mData[index + 0] != 0 ||
+          aMap.mData[index + 1] != 0 ||
+          aMap.mData[index + 2] != 0) {
+        return false;
+      }
+    }
+  }
+  return true;
+}
+
 nsresult nsCocoaUtils::CreateCGImageFromSurface(SourceSurface* aSurface,
-                                                CGImageRef* aResult)
+                                                CGImageRef* aResult,
+                                                bool* aIsEntirelyBlack)
 {
   RefPtr<DataSourceSurface> dataSurface;
 
@@ -390,6 +410,10 @@ nsresult nsCocoaUtils::CreateCGImageFromSurface(SourceSurface* aSurface,
   }
   // The Unmap() call happens in data_ss_release_callback
 
+  if (aIsEntirelyBlack) {
+    *aIsEntirelyBlack = ComputeIsEntirelyBlack(map, dataSurface->GetSize());
+  }
+
   // Create a CGImageRef with the bits from the image, taking into account
   // the alpha ordering and endianness of the machine so we don't have to
   // touch the bits ourselves.

widget/cocoa/nsMenuItemIconX.mm

@@ -355,7 +355,9 @@ nsMenuItemIconX::OnFrameComplete(imgIRequest* aRequest)
   }
 
   CGImageRef origImage = NULL;
-  nsresult rv = nsCocoaUtils::CreateCGImageFromSurface(surface, &origImage);
+  bool isEntirelyBlack = false;
+  nsresult rv = nsCocoaUtils::CreateCGImageFromSurface(surface, &origImage,
+                                                       &isEntirelyBlack);
   if (NS_FAILED(rv) || !origImage) {
     [mNativeMenuItem setImage:nil];
     return NS_ERROR_FAILURE;
@@ -388,6 +390,14 @@ nsMenuItemIconX::OnFrameComplete(imgIRequest* aRequest)
     return NS_ERROR_FAILURE;
   }
 
+  // If all the color channels in the image are black, treat the image as a
+  // template. This will cause macOS to use the image's alpha channel as a mask
+  // and it will fill it with a color that looks good in the context that it's
+  // used in. For example, for regular menu items, the image will be black, but
+  // when the menu item is hovered (and its background is blue), it will be
+  // filled with white.
+  [newImage setTemplate:isEntirelyBlack];
+
   [newImage setSize:NSMakeSize(kIconWidth, kIconHeight)];
   [mNativeMenuItem setImage:newImage];