layout/style/StyleColor.cpp

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #include "mozilla/StyleColorInlines.h"
   8
   9 #include "mozilla/ComputedStyle.h"
  10 #include "mozilla/ComputedStyleInlines.h"
  11 #include "nsIFrame.h"
  12 #include "nsStyleStruct.h"
  13
  14 namespace mozilla {
  15
  16 // Blend one RGBA color with another based on a given ratios.
  17 // It is a linear combination of each channel with alpha premultipled.
  18 static nscolor LinearBlendColors(const StyleRGBA& aBg, float aBgRatio,
  19                                  const StyleRGBA& aFg, float aFgRatio) {
  20   constexpr float kFactor = 1.0f / 255.0f;
  21
  22   float p1 = aBgRatio;
  23   float a1 = kFactor * aBg.alpha;
  24   float r1 = a1 * aBg.red;
  25   float g1 = a1 * aBg.green;
  26   float b1 = a1 * aBg.blue;
  27
  28   float p2 = aFgRatio;
  29   float a2 = kFactor * aFg.alpha;
  30   float r2 = a2 * aFg.red;
  31   float g2 = a2 * aFg.green;
  32   float b2 = a2 * aFg.blue;
  33
  34   float a = p1 * a1 + p2 * a2;
  35   if (a <= 0.f) {
  36     return NS_RGBA(0, 0, 0, 0);
  37   }
  38
  39   if (a > 1.f) {
  40     a = 1.f;
  41   }
  42
  43   auto r = ClampColor((p1 * r1 + p2 * r2) / a);
  44   auto g = ClampColor((p1 * g1 + p2 * g2) / a);
  45   auto b = ClampColor((p1 * b1 + p2 * b2) / a);
  46   return NS_RGBA(r, g, b, NSToIntRound(a * 255));
  47 }
  48
  49 template <>
  50 bool StyleColor::MaybeTransparent() const {
  51   // We know that the color is opaque when it's a numeric color with
  52   // alpha == 255.
  53   return ratios != StyleComplexColorRatios::NUMERIC || color.alpha != 255;
  54 }
  55
  56 template <>
  57 nscolor StyleColor::CalcColor(nscolor aColor) const {
  58   return CalcColor(StyleRGBA::FromColor(aColor));
  59 }
  60
  61 template <>
  62 nscolor StyleColor::CalcColor(const StyleRGBA& aForegroundColor) const {
  63   if (ratios == StyleComplexColorRatios::NUMERIC) {
  64     return color.ToColor();
  65   }
  66   if (ratios == StyleComplexColorRatios::CURRENT_COLOR) {
  67     return aForegroundColor.ToColor();
  68   }
  69   return LinearBlendColors(color, ratios.bg, aForegroundColor, ratios.fg);
  70 }
  71
  72 template <>
  73 nscolor StyleColor::CalcColor(const ComputedStyle& aStyle) const {
  74   // Common case that is numeric color, which is pure background, we
  75   // can skip resolving StyleText().
  76   if (ratios == StyleComplexColorRatios::NUMERIC) {
  77     return color.ToColor();
  78   }
  79   return CalcColor(aStyle.StyleText()->mColor);
  80 }
  81
  82 template <>
  83 nscolor StyleColor::CalcColor(const nsIFrame* aFrame) const {
  84   if (ratios == StyleComplexColorRatios::NUMERIC) {
  85     return color.ToColor();
  86   }
  87   return CalcColor(aFrame->StyleText()->mColor);
  88 }
  89
  90 }  // namespace mozilla