1 files changed, 144 insertions, 0 deletions
diff --git a/gfx/2d/CGTextDrawing.h b/gfx/2d/CGTextDrawing.h
new file mode 100644
index 000000000..b9e3b374a
--- /dev/null
+++ b/gfx/2d/CGTextDrawing.h
@@ -0,0 +1,144 @@
+/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+#ifndef _MOZILLA_GFX_SKIACGPOPUPDRAWER_H
+#define _MOZILLA_GFX_SKIACGPOPUPDRAWER_H
+
+#include <ApplicationServices/ApplicationServices.h>
+#include "nsDebug.h"
+#include "mozilla/Vector.h"
+#include "ScaledFontMac.h"
+#include "PathCG.h"
+#include <dlfcn.h>
+
+// This is used when we explicitly need CG to draw text to support things such
+// as vibrancy and subpixel AA on transparent backgrounds. The current use cases
+// are really only to enable Skia to support drawing text in those situations.
+
+namespace mozilla {
+namespace gfx {
+
+typedef void (*CGContextSetFontSmoothingBackgroundColorFunc) (CGContextRef cgContext, CGColorRef color);
+
+static CGContextSetFontSmoothingBackgroundColorFunc
+GetCGContextSetFontSmoothingBackgroundColorFunc()
+{
+  static CGContextSetFontSmoothingBackgroundColorFunc func = nullptr;
+  static bool lookedUpFunc = false;
+  if (!lookedUpFunc) {
+    func = (CGContextSetFontSmoothingBackgroundColorFunc)dlsym(
+      RTLD_DEFAULT, "CGContextSetFontSmoothingBackgroundColor");
+    lookedUpFunc = true;
+  }
+  return func;
+}
+
+static CGColorRef
+ColorToCGColor(CGColorSpaceRef aColorSpace, const Color& aColor)
+{
+  CGFloat components[4] = {aColor.r, aColor.g, aColor.b, aColor.a};
+  return CGColorCreate(aColorSpace, components);
+}
+
+static bool
+SetFontSmoothingBackgroundColor(CGContextRef aCGContext, CGColorSpaceRef aColorSpace,
+                                const GlyphRenderingOptions* aRenderingOptions)
+{
+  if (aRenderingOptions) {
+    Color fontSmoothingBackgroundColor =
+      static_cast<const GlyphRenderingOptionsCG*>(aRenderingOptions)->FontSmoothingBackgroundColor();
+    if (fontSmoothingBackgroundColor.a > 0) {
+      CGContextSetFontSmoothingBackgroundColorFunc setFontSmoothingBGColorFunc =
+        GetCGContextSetFontSmoothingBackgroundColorFunc();
+      if (setFontSmoothingBGColorFunc) {
+        CGColorRef color = ColorToCGColor(aColorSpace, fontSmoothingBackgroundColor);
+        setFontSmoothingBGColorFunc(aCGContext, color);
+        CGColorRelease(color);
+        return true;
+      }
+    }
+  }
+
+  return false;
+}
+
+// Font rendering with a non-transparent font smoothing background color
+// can leave pixels in our buffer where the rgb components exceed the alpha
+// component. When this happens we need to clean up the data afterwards.
+// The purpose of this is probably the following: Correct compositing of
+// subpixel anti-aliased fonts on transparent backgrounds requires
+// different alpha values per RGB component. Usually, premultiplied color
+// values are derived by multiplying all components with the same per-pixel
+// alpha value. However, if you multiply each component with a *different*
+// alpha, and set the alpha component of the pixel to, say, the average
+// of the alpha values that you used during the premultiplication of the
+// RGB components, you can trick OVER compositing into doing a simplified
+// form of component alpha compositing. (You just need to make sure to
+// clamp the components of the result pixel to [0,255] afterwards.)
+static void
+EnsureValidPremultipliedData(CGContextRef aContext,
+                             CGRect aTextBounds = CGRectInfinite)
+{
+  if (CGBitmapContextGetBitsPerPixel(aContext) != 32 ||
+      CGBitmapContextGetAlphaInfo(aContext) != kCGImageAlphaPremultipliedFirst) {
+    return;
+  }
+
+  uint8_t* bitmapData = (uint8_t*)CGBitmapContextGetData(aContext);
+  CGRect bitmapBounds = CGRectMake(0, 0, CGBitmapContextGetWidth(aContext), CGBitmapContextGetHeight(aContext));
+  int stride = CGBitmapContextGetBytesPerRow(aContext);
+
+  CGRect bounds = CGRectIntersection(bitmapBounds, aTextBounds);
+  int startX = bounds.origin.x;
+  int endX = startX + bounds.size.width;
+  MOZ_ASSERT(endX <= bitmapBounds.size.width);
+
+
+  // CGRect assume that our origin is the bottom left.
+  // The data assumes that the origin is the top left.
+  // Have to switch the Y axis so that our coordinates are correct
+  int startY = bitmapBounds.size.height - (bounds.origin.y + bounds.size.height);
+  int endY = startY + bounds.size.height;
+  MOZ_ASSERT(endY <= (int)CGBitmapContextGetHeight(aContext));
+
+  for (int y = startY; y < endY; y++) {
+    for (int x = startX; x < endX; x++) {
+      int i = y * stride + x * 4;
+      uint8_t a = bitmapData[i + 3];
+
+      bitmapData[i + 0] = std::min(a, bitmapData[i+0]);
+      bitmapData[i + 1] = std::min(a, bitmapData[i+1]);
+      bitmapData[i + 2] = std::min(a, bitmapData[i+2]);
+    }
+  }
+}
+
+static CGRect
+ComputeGlyphsExtents(CGRect *bboxes, CGPoint *positions, CFIndex count, float scale)
+{
+  CGFloat x1, x2, y1, y2;
+  if (count < 1)
+    return CGRectZero;
+
+  x1 = bboxes[0].origin.x + positions[0].x;
+  x2 = bboxes[0].origin.x + positions[0].x + scale*bboxes[0].size.width;
+  y1 = bboxes[0].origin.y + positions[0].y;
+  y2 = bboxes[0].origin.y + positions[0].y + scale*bboxes[0].size.height;
+
+  // accumulate max and minimum coordinates
+  for (int i = 1; i < count; i++) {
+    x1 = std::min(x1, bboxes[i].origin.x + positions[i].x);
+    y1 = std::min(y1, bboxes[i].origin.y + positions[i].y);
+    x2 = std::max(x2, bboxes[i].origin.x + positions[i].x + scale*bboxes[i].size.width);
+    y2 = std::max(y2, bboxes[i].origin.y + positions[i].y + scale*bboxes[i].size.height);
+  }
+
+  CGRect extents = {{x1, y1}, {x2-x1, y2-y1}};
+  return extents;
+}
+
+} // namespace gfx
+} // namespace mozilla
+
+#endif