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Minimal test - lines (39, 54)

Code

ComputedStyle* ScrollbarUtil::GetCustomScrollbarStyle(nsIFrame* aFrame,
                                                      bool* aDarkScrollbar) {
  ComputedStyle* style = nsLayoutUtils::StyleForScrollbar(aFrame);
  if (style->StyleUI()->HasCustomScrollbars()) {
    return style;
  }
  bool useDarkScrollbar = !StaticPrefs::widget_disable_dark_scrollbar() &&
                          nsNativeTheme::IsDarkBackground(aFrame);
  if (useDarkScrollbar || IsScrollbarWidthThin(style)) {
    if (aDarkScrollbar) {
      *aDarkScrollbar = useDarkScrollbar;
    }
    return style;
  }
  return nullptr;
}

Minimal test - lines (86, 117)

Code

nscolor ScrollbarUtil::GetScrollbarArrowColor(nscolor aButtonColor) {
  // In Windows 10 scrollbar, there are several gray colors used:
  //
  // State  | Background (lum) | Arrow   | Contrast
  // -------+------------------+---------+---------
  // Normal | Gray 240 (87.1%) | Gray 96 |     5.5
  // Hover  | Gray 218 (70.1%) | Black   |    15.0
  // Active | Gray 96  (11.7%) | White   |     6.3
  //
  // Contrast value is computed based on the definition in
  // https://www.w3.org/TR/WCAG20/#contrast-ratiodef
  //
  // This function is written based on these values.

  float luminance = RelativeLuminanceUtils::Compute(aButtonColor);
  // Color with luminance larger than 0.72 has contrast ratio over 4.6
  // to color with luminance of gray 96, so this value is chosen for
  // this range. It is the luminance of gray 221.
  if (luminance >= 0.72) {
    // ComputeRelativeLuminanceFromComponents(96). That function cannot
    // be constexpr because of std::pow.
    const float GRAY96_LUMINANCE = 0.117f;
    return RelativeLuminanceUtils::Adjust(aButtonColor, GRAY96_LUMINANCE);
  }
  // The contrast ratio of a color to black equals that to white when its
  // luminance is around 0.18, with a contrast ratio ~4.6 to both sides,
  // thus the value below. It's the lumanince of gray 118.
  if (luminance >= 0.18) {
    return NS_RGBA(0, 0, 0, NS_GET_A(aButtonColor));
  }
  return NS_RGBA(255, 255, 255, NS_GET_A(aButtonColor));
}

Minimal test - lines (33, 36)

Code

bool ScrollbarUtil::IsScrollbarWidthThin(nsIFrame* aFrame) {
  ComputedStyle* style = nsLayoutUtils::StyleForScrollbar(aFrame);
  return IsScrollbarWidthThin(style);
}

Minimal test - lines (57, 83)

Code

nscolor ScrollbarUtil::GetScrollbarButtonColor(nscolor aTrackColor,
                                               EventStates aStates) {
  // See numbers in GetScrollbarArrowColor.
  // This function is written based on ratios between values listed there.

  bool isActive = aStates.HasState(NS_EVENT_STATE_ACTIVE);
  bool isHover = aStates.HasState(NS_EVENT_STATE_HOVER);
  if (!isActive && !isHover) {
    return aTrackColor;
  }
  float luminance = RelativeLuminanceUtils::Compute(aTrackColor);
  if (isActive) {
    if (luminance >= 0.18f) {
      luminance *= 0.134f;
    } else {
      luminance /= 0.134f;
      luminance = std::min(luminance, 1.0f);
    }
  } else {
    if (luminance >= 0.18f) {
      luminance *= 0.805f;
    } else {
      luminance /= 0.805f;
    }
  }
  return RelativeLuminanceUtils::Adjust(aTrackColor, luminance);
}

Minimal test - lines (136, 153)

Code

nscolor ScrollbarUtil::GetScrollbarThumbColor(nsIFrame* aFrame,
                                              EventStates aEventStates) {
  bool darkScrollbar = false;
  ComputedStyle* style = GetCustomScrollbarStyle(aFrame, &darkScrollbar);
  nscolor color =
      darkScrollbar ? NS_RGBA(249, 249, 250, 102) : NS_RGB(205, 205, 205);
  if (style) {
    const nsStyleUI* ui = style->StyleUI();
    auto* customColors = ui->mScrollbarColor.IsAuto()
                             ? nullptr
                             : &ui->mScrollbarColor.AsColors();
    if (customColors) {
      color = customColors->thumb.CalcColor(*style);
    }
  }
  return nsNativeBasicTheme::AdjustUnthemedScrollbarThumbColor(color,
                                                               aEventStates);
}

Minimal test - lines (27, 30)

Code

bool ScrollbarUtil::IsScrollbarWidthThin(ComputedStyle* aStyle) {
  auto scrollbarWidth = aStyle->StyleUIReset()->mScrollbarWidth;
  return scrollbarWidth == StyleScrollbarWidth::Thin;
}

Minimal test - lines (120, 133)

Code

nscolor ScrollbarUtil::GetScrollbarTrackColor(nsIFrame* aFrame) {
  bool darkScrollbar = false;
  ComputedStyle* style = GetCustomScrollbarStyle(aFrame, &darkScrollbar);
  if (style) {
    const nsStyleUI* ui = style->StyleUI();
    auto* customColors = ui->mScrollbarColor.IsAuto()
                             ? nullptr
                             : &ui->mScrollbarColor.AsColors();
    if (customColors) {
      return customColors->track.CalcColor(*style);
    }
  }
  return darkScrollbar ? NS_RGBA(20, 20, 25, 77) : NS_RGB(240, 240, 240);
}