widget/ThemeColors.cpp

   1 /* -*- Mode: C++; tab-width: 40; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* This Source Code Form is subject to the terms of the Mozilla Public
   3  * License, v. 2.0. If a copy of the MPL was not distributed with this
   4  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   5
   6 #include "ThemeColors.h"
   7
   8 #include "mozilla/RelativeLuminanceUtils.h"
   9 #include "mozilla/StaticPrefs_widget.h"
  10 #include "ThemeDrawing.h"
  11 #include "nsNativeTheme.h"
  12
  13 using namespace mozilla::gfx;
  14
  15 namespace mozilla::widget {
  16
  17 struct ColorPalette {
  18   ColorPalette(nscolor aAccent, nscolor aForeground);
  19
  20   constexpr ColorPalette(sRGBColor aAccent, sRGBColor aForeground,
  21                          sRGBColor aLight, sRGBColor aDark, sRGBColor aDarker)
  22       : mAccent(aAccent),
  23         mForeground(aForeground),
  24         mAccentLight(aLight),
  25         mAccentDark(aDark),
  26         mAccentDarker(aDarker) {}
  27
  28   constexpr static ColorPalette Default() {
  29     return ColorPalette(
  30         sDefaultAccent, sDefaultAccentText,
  31         sRGBColor::UnusualFromARGB(0x4d008deb),  // Luminance: 25.04791%
  32         sRGBColor::UnusualFromARGB(0xff0250bb),  // Luminance: 9.33808%
  33         sRGBColor::UnusualFromARGB(0xff054096)   // Luminance: 5.90106%
  34     );
  35   }
  36
  37   // Ensure accent color is opaque by blending with white. This serves two
  38   // purposes: On one hand, it avoids surprises if we overdraw. On the other, it
  39   // makes our math below make more sense, as we want to match the browser
  40   // style, which has an opaque accent color.
  41   static nscolor EnsureOpaque(nscolor aAccent) {
  42     if (NS_GET_A(aAccent) != 0xff) {
  43       return NS_ComposeColors(NS_RGB(0xff, 0xff, 0xff), aAccent);
  44     }
  45     return aAccent;
  46   }
  47
  48   static nscolor GetLight(nscolor aAccent) {
  49     // The luminance from the light color divided by the one of the accent color
  50     // in the default palette.
  51     constexpr float kLightLuminanceScale = 25.048f / 13.693f;
  52     const float lightLuminanceAdjust = ThemeColors::ScaleLuminanceBy(
  53         RelativeLuminanceUtils::Compute(aAccent), kLightLuminanceScale);
  54     nscolor lightColor =
  55         RelativeLuminanceUtils::Adjust(aAccent, lightLuminanceAdjust);
  56     return NS_RGBA(NS_GET_R(lightColor), NS_GET_G(lightColor),
  57                    NS_GET_B(lightColor), 0x4d);
  58   }
  59
  60   static nscolor GetDark(nscolor aAccent) {
  61     // Same deal as above (but without the alpha).
  62     constexpr float kDarkLuminanceScale = 9.338f / 13.693f;
  63     const float darkLuminanceAdjust = ThemeColors::ScaleLuminanceBy(
  64         RelativeLuminanceUtils::Compute(aAccent), kDarkLuminanceScale);
  65     return RelativeLuminanceUtils::Adjust(aAccent, darkLuminanceAdjust);
  66   }
  67
  68   static nscolor GetDarker(nscolor aAccent) {
  69     // Same deal as above.
  70     constexpr float kDarkerLuminanceScale = 5.901f / 13.693f;
  71     const float darkerLuminanceAdjust = ThemeColors::ScaleLuminanceBy(
  72         RelativeLuminanceUtils::Compute(aAccent), kDarkerLuminanceScale);
  73     return RelativeLuminanceUtils::Adjust(aAccent, darkerLuminanceAdjust);
  74   }
  75
  76   sRGBColor mAccent;
  77   sRGBColor mForeground;
  78
  79   // Note that depending on the exact accent color, lighter/darker might really
  80   // be inverted.
  81   sRGBColor mAccentLight;
  82   sRGBColor mAccentDark;
  83   sRGBColor mAccentDarker;
  84 };
  85
  86 static nscolor GetAccentColor(bool aBackground, ColorScheme aScheme) {
  87   auto useStandins = LookAndFeel::UseStandins(
  88       !StaticPrefs::widget_non_native_theme_use_theme_accent());
  89   return ColorPalette::EnsureOpaque(
  90       LookAndFeel::Color(aBackground ? LookAndFeel::ColorID::Accentcolor
  91                                      : LookAndFeel::ColorID::Accentcolortext,
  92                          aScheme, useStandins));
  93 }
  94
  95 static ColorPalette sDefaultLightPalette = ColorPalette::Default();
  96 static ColorPalette sDefaultDarkPalette = ColorPalette::Default();
  97
  98 ColorPalette::ColorPalette(nscolor aAccent, nscolor aForeground) {
  99   mAccent = sRGBColor::FromABGR(aAccent);
 100   mForeground = sRGBColor::FromABGR(aForeground);
 101   mAccentLight = sRGBColor::FromABGR(GetLight(aAccent));
 102   mAccentDark = sRGBColor::FromABGR(GetDark(aAccent));
 103   mAccentDarker = sRGBColor::FromABGR(GetDarker(aAccent));
 104 }
 105
 106 ThemeAccentColor::ThemeAccentColor(const ComputedStyle& aStyle,
 107                                    ColorScheme aScheme) {
 108   const auto& color = aStyle.StyleUI()->mAccentColor;
 109   if (color.IsColor()) {
 110     mAccentColor.emplace(
 111         ColorPalette::EnsureOpaque(color.AsColor().CalcColor(aStyle)));
 112   } else {
 113     MOZ_ASSERT(color.IsAuto());
 114     mDefaultPalette = aScheme == ColorScheme::Light ? &sDefaultLightPalette
 115                                                     : &sDefaultDarkPalette;
 116   }
 117 }
 118
 119 sRGBColor ThemeAccentColor::Get() const {
 120   if (!mAccentColor) {
 121     return mDefaultPalette->mAccent;
 122   }
 123   return sRGBColor::FromABGR(*mAccentColor);
 124 }
 125
 126 sRGBColor ThemeAccentColor::GetForeground() const {
 127   if (!mAccentColor) {
 128     return mDefaultPalette->mForeground;
 129   }
 130   return sRGBColor::FromABGR(
 131       ThemeColors::ComputeCustomAccentForeground(*mAccentColor));
 132 }
 133
 134 sRGBColor ThemeAccentColor::GetLight() const {
 135   if (!mAccentColor) {
 136     return mDefaultPalette->mAccentLight;
 137   }
 138   return sRGBColor::FromABGR(ColorPalette::GetLight(*mAccentColor));
 139 }
 140
 141 sRGBColor ThemeAccentColor::GetDark() const {
 142   if (!mAccentColor) {
 143     return mDefaultPalette->mAccentDark;
 144   }
 145   return sRGBColor::FromABGR(ColorPalette::GetDark(*mAccentColor));
 146 }
 147
 148 sRGBColor ThemeAccentColor::GetDarker() const {
 149   if (!mAccentColor) {
 150     return mDefaultPalette->mAccentDarker;
 151   }
 152   return sRGBColor::FromABGR(ColorPalette::GetDarker(*mAccentColor));
 153 }
 154
 155 bool ThemeColors::ShouldBeHighContrast(const nsPresContext& aPc) {
 156   // We make sure that we're drawing backgrounds, since otherwise layout will
 157   // darken our used text colors etc anyways, and that can cause contrast issues
 158   // with dark high-contrast themes.
 159   return aPc.GetBackgroundColorDraw() &&
 160          PreferenceSheet::PrefsFor(*aPc.Document())
 161              .NonNativeThemeShouldBeHighContrast();
 162 }
 163
 164 ColorScheme ThemeColors::ColorSchemeForWidget(const nsIFrame* aFrame,
 165                                               StyleAppearance aAppearance,
 166                                               bool aHighContrast) {
 167   if (!nsNativeTheme::IsWidgetScrollbarPart(aAppearance)) {
 168     return LookAndFeel::ColorSchemeForFrame(aFrame);
 169   }
 170   // Scrollbars are a bit tricky. Their used color-scheme depends on whether the
 171   // background they are on is light or dark.
 172   //
 173   // TODO(emilio): This heuristic effectively predates the color-scheme CSS
 174   // property. Perhaps we should check whether the style or the document set
 175   // `color-scheme` to something that isn't `normal`, and if so go through the
 176   // code-path above.
 177   if (aHighContrast) {
 178     return ColorScheme::Light;
 179   }
 180   if (StaticPrefs::widget_disable_dark_scrollbar()) {
 181     return ColorScheme::Light;
 182   }
 183   return nsNativeTheme::IsDarkBackground(const_cast<nsIFrame*>(aFrame))
 184              ? ColorScheme::Dark
 185              : ColorScheme::Light;
 186 }
 187
 188 /*static*/
 189 void ThemeColors::RecomputeAccentColors() {
 190   MOZ_RELEASE_ASSERT(NS_IsMainThread());
 191
 192   sDefaultLightPalette =
 193       ColorPalette(GetAccentColor(true, ColorScheme::Light),
 194                    GetAccentColor(false, ColorScheme::Light));
 195
 196   sDefaultDarkPalette = ColorPalette(GetAccentColor(true, ColorScheme::Dark),
 197                                      GetAccentColor(false, ColorScheme::Dark));
 198 }
 199
 200 /*static*/
 201 nscolor ThemeColors::ComputeCustomAccentForeground(nscolor aColor) {
 202   // Contrast ratio is defined in
 203   // https://www.w3.org/TR/WCAG20/#contrast-ratiodef as:
 204   //
 205   //   (L1 + 0.05) / (L2 + 0.05)
 206   //
 207   // Where L1 is the lighter color, and L2 is the darker one. So we determine
 208   // whether we're dark or light and resolve the equation for the target ratio.
 209   //
 210   // So when lightening:
 211   //
 212   //   L1 = k * (L2 + 0.05) - 0.05
 213   //
 214   // And when darkening:
 215   //
 216   //   L2 = (L1 + 0.05) / k - 0.05
 217   //
 218   const float luminance = RelativeLuminanceUtils::Compute(aColor);
 219
 220   // We generally prefer white unless we can't because the color is really light
 221   // and we can't provide reasonable contrast.
 222   const float ratioWithWhite = 1.05f / (luminance + 0.05f);
 223   const bool canBeWhite =
 224       ratioWithWhite >=
 225       StaticPrefs::layout_css_accent_color_min_contrast_ratio();
 226   if (canBeWhite) {
 227     return NS_RGB(0xff, 0xff, 0xff);
 228   }
 229   const float targetRatio =
 230       StaticPrefs::layout_css_accent_color_darkening_target_contrast_ratio();
 231   const float targetLuminance = (luminance + 0.05f) / targetRatio - 0.05f;
 232   return RelativeLuminanceUtils::Adjust(aColor, targetLuminance);
 233 }
 234
 235 nscolor ThemeColors::AdjustUnthemedScrollbarThumbColor(
 236     nscolor aFaceColor, dom::ElementState aStates) {
 237   // In Windows 10, scrollbar thumb has the following colors:
 238   //
 239   // State  | Color    | Luminance
 240   // -------+----------+----------
 241   // Normal | Gray 205 |     61.0%
 242   // Hover  | Gray 166 |     38.1%
 243   // Active | Gray 96  |     11.7%
 244   //
 245   // This function is written based on the ratios between the values.
 246   bool isActive = aStates.HasState(dom::ElementState::ACTIVE);
 247   bool isHover = aStates.HasState(dom::ElementState::HOVER);
 248   if (!isActive && !isHover) {
 249     return aFaceColor;
 250   }
 251   float luminance = RelativeLuminanceUtils::Compute(aFaceColor);
 252   if (isActive) {
 253     // 11.7 / 61.0
 254     luminance = ScaleLuminanceBy(luminance, 0.192f);
 255   } else {
 256     // 38.1 / 61.0
 257     luminance = ScaleLuminanceBy(luminance, 0.625f);
 258   }
 259   return RelativeLuminanceUtils::Adjust(aFaceColor, luminance);
 260 }
 261
 262 }  // namespace mozilla::widget