Bug 1299741 part 4 - Add StyleComplexColor type for storing color combining numeric color and currentcolor. r=dbaron

MozReview-Commit-ID: I6DaSaMCgtH

--HG--
extra : rebase_source : 0ad610a40431e74a540714491be35ad444fd4372

layout/style/StyleComplexColor.h

@@ -0,0 +1,51 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* 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/. */
+
+/* represent a color combines a numeric color and currentcolor */
+
+#ifndef mozilla_StyleComplexColor_h_
+#define mozilla_StyleComplexColor_h_
+
+#include "nsColor.h"
+
+namespace mozilla {
+
+/**
+ * This struct represents a combined color from a numeric color and
+ * the current foreground color (currentcolor keyword).
+ * Conceptually, the formula is "color * (1 - p) + currentcolor * p"
+ * where p is mForegroundRatio. See mozilla::LinearBlendColors for
+ * the actual algorithm.
+ */
+struct StyleComplexColor
+{
+  nscolor mColor;
+  uint8_t mForegroundRatio;
+
+  StyleComplexColor() {}
+  StyleComplexColor(nscolor aColor, uint_fast8_t aForegroundRatio)
+    : mColor(aColor), mForegroundRatio(aForegroundRatio) {}
+
+  static StyleComplexColor FromColor(nscolor aColor)
+    { return StyleComplexColor(aColor, 0); }
+  static StyleComplexColor CurrentColor()
+    { return StyleComplexColor(NS_RGBA(0, 0, 0, 0), 255); }
+
+  bool IsNumericColor() const { return mForegroundRatio == 0; }
+  bool IsCurrentColor() const { return mForegroundRatio == 255; }
+
+  bool operator==(const StyleComplexColor& aOther) const {
+    return mForegroundRatio == aOther.mForegroundRatio &&
+           (IsCurrentColor() || mColor == aOther.mColor);
+  }
+  bool operator!=(const StyleComplexColor& aOther) const {
+    return !(*this == aOther);
+  }
+};
+
+}
+
+#endif // mozilla_StyleComplexColor_h_

layout/style/moz.build

@@ -100,6 +100,7 @@ EXPORTS.mozilla += [
     'SheetType.h',
     'StyleAnimationValue.h',
     'StyleBackendType.h',
+    'StyleComplexColor.h',
     'StyleContextSource.h',
     'StyleSetHandle.h',
     'StyleSetHandleInlines.h',

layout/style/nsStyleStruct.h

@@ -18,6 +18,7 @@
 #include "mozilla/Maybe.h"
 #include "mozilla/SheetType.h"
 #include "mozilla/StaticPtr.h"
+#include "mozilla/StyleComplexColor.h"
 #include "mozilla/StyleStructContext.h"
 #include "mozilla/UniquePtr.h"
 #include "nsColor.h"
@@ -480,6 +481,11 @@ struct MOZ_NEEDS_MEMMOVABLE_MEMBERS nsStyleColor
     MOZ_COUNT_DTOR(nsStyleColor);
   }
 
+  nscolor CalcComplexColor(const mozilla::StyleComplexColor& aColor) const {
+    return mozilla::LinearBlendColors(aColor.mColor, mColor,
+                                      aColor.mForegroundRatio);
+  }
+
   nsChangeHint CalcDifference(const nsStyleColor& aNewData) const;
   static nsChangeHint MaxDifference() {
     return nsChangeHint_RepaintFrame;