widget/ScrollbarDrawing.cpp

   1 /* -*- Mode: C++; c-basic-offset: 2; indent-tabs-mode: nil; tab-width: 2; -*- */
   2 /* vim: set sw=2 ts=8 et 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 "ScrollbarDrawing.h"
   8
   9 #include "mozilla/RelativeLuminanceUtils.h"
  10 #include "mozilla/StaticPrefs_widget.h"
  11 #include "nsContainerFrame.h"
  12 #include "nsDeviceContext.h"
  13 #include "nsIFrame.h"
  14 #include "nsLayoutUtils.h"
  15 #include "nsLookAndFeel.h"
  16 #include "nsNativeTheme.h"
  17
  18 using namespace mozilla::gfx;
  19
  20 namespace mozilla::widget {
  21
  22 using mozilla::RelativeLuminanceUtils;
  23
  24 /* static */
  25 auto ScrollbarDrawing::GetDPIRatioForScrollbarPart(nsPresContext* aPc)
  26     -> DPIRatio {
  27   if (auto* rootPc = aPc->GetRootPresContext()) {
  28     if (nsCOMPtr<nsIWidget> widget = rootPc->GetRootWidget()) {
  29       return widget->GetDefaultScale();
  30     }
  31   }
  32   return DPIRatio(
  33       float(AppUnitsPerCSSPixel()) /
  34       float(aPc->DeviceContext()->AppUnitsPerDevPixelAtUnitFullZoom()));
  35 }
  36
  37 /*static*/
  38 nsIFrame* ScrollbarDrawing::GetParentScrollbarFrame(nsIFrame* aFrame) {
  39   // Walk our parents to find a scrollbar frame
  40   nsIFrame* scrollbarFrame = aFrame;
  41   do {
  42     if (scrollbarFrame->IsScrollbarFrame()) {
  43       break;
  44     }
  45   } while ((scrollbarFrame = scrollbarFrame->GetParent()));
  46
  47   // We return null if we can't find a parent scrollbar frame
  48   return scrollbarFrame;
  49 }
  50
  51 /*static*/
  52 bool ScrollbarDrawing::IsParentScrollbarRolledOver(nsIFrame* aFrame) {
  53   nsIFrame* scrollbarFrame = GetParentScrollbarFrame(aFrame);
  54   return nsLookAndFeel::GetInt(LookAndFeel::IntID::UseOverlayScrollbars) != 0
  55              ? nsNativeTheme::CheckBooleanAttr(scrollbarFrame, nsGkAtoms::hover)
  56              : nsNativeTheme::GetContentState(scrollbarFrame,
  57                                               StyleAppearance::None)
  58                    .HasState(NS_EVENT_STATE_HOVER);
  59 }
  60
  61 /*static*/
  62 bool ScrollbarDrawing::IsParentScrollbarHoveredOrActive(nsIFrame* aFrame) {
  63   nsIFrame* scrollbarFrame = GetParentScrollbarFrame(aFrame);
  64   return scrollbarFrame && scrollbarFrame->GetContent()
  65                                ->AsElement()
  66                                ->State()
  67                                .HasAtLeastOneOfStates(NS_EVENT_STATE_HOVER |
  68                                                       NS_EVENT_STATE_ACTIVE);
  69 }
  70
  71 /*static*/
  72 bool ScrollbarDrawing::IsScrollbarWidthThin(const ComputedStyle& aStyle) {
  73   auto scrollbarWidth = aStyle.StyleUIReset()->ScrollbarWidth();
  74   return scrollbarWidth == StyleScrollbarWidth::Thin;
  75 }
  76
  77 /*static*/
  78 bool ScrollbarDrawing::IsScrollbarWidthThin(nsIFrame* aFrame) {
  79   ComputedStyle* style = nsLayoutUtils::StyleForScrollbar(aFrame);
  80   return IsScrollbarWidthThin(*style);
  81 }
  82
  83 auto ScrollbarDrawing::GetScrollbarSizes(nsPresContext* aPresContext,
  84                                          StyleScrollbarWidth aWidth, Overlay)
  85     -> ScrollbarSizes {
  86   uint32_t h = GetHorizontalScrollbarHeight();
  87   uint32_t w = GetVerticalScrollbarWidth();
  88   if (aWidth == StyleScrollbarWidth::Thin) {
  89     h /= 2;
  90     w /= 2;
  91   }
  92   auto dpi = GetDPIRatioForScrollbarPart(aPresContext);
  93   return {(CSSCoord(w) * dpi).Rounded(), (CSSCoord(h) * dpi).Rounded()};
  94 }
  95
  96 auto ScrollbarDrawing::GetScrollbarSizes(nsPresContext* aPresContext,
  97                                          nsIFrame* aFrame) -> ScrollbarSizes {
  98   auto* style = nsLayoutUtils::StyleForScrollbar(aFrame);
  99   auto width = style->StyleUIReset()->ScrollbarWidth();
 100   auto overlay =
 101       aPresContext->UseOverlayScrollbars() ? Overlay::Yes : Overlay::No;
 102   return GetScrollbarSizes(aPresContext, width, overlay);
 103 }
 104
 105 bool ScrollbarDrawing::IsScrollbarTrackOpaque(nsIFrame* aFrame) {
 106   auto trackColor = ComputeScrollbarTrackColor(
 107       aFrame, *nsLayoutUtils::StyleForScrollbar(aFrame),
 108       aFrame->PresContext()->Document()->GetDocumentState(),
 109       Colors(aFrame, StyleAppearance::ScrollbartrackVertical));
 110   return trackColor.a == 1.0f;
 111 }
 112
 113 sRGBColor ScrollbarDrawing::ComputeScrollbarTrackColor(
 114     nsIFrame* aFrame, const ComputedStyle& aStyle,
 115     const EventStates& aDocumentState, const Colors& aColors) {
 116   if (aColors.HighContrast()) {
 117     return aColors.System(StyleSystemColor::Window);
 118   }
 119   const nsStyleUI* ui = aStyle.StyleUI();
 120   if (ui->mScrollbarColor.IsColors()) {
 121     return sRGBColor::FromABGR(
 122         ui->mScrollbarColor.AsColors().track.CalcColor(aStyle));
 123   }
 124   static constexpr sRGBColor sDefaultDarkTrackColor =
 125       sRGBColor::FromU8(20, 20, 25, 77);
 126   static constexpr sRGBColor sDefaultTrackColor(
 127       gfx::sRGBColor::UnusualFromARGB(0xfff0f0f0));
 128
 129   auto systemColor =
 130       aDocumentState.HasAllStates(NS_DOCUMENT_STATE_WINDOW_INACTIVE)
 131           ? StyleSystemColor::ThemedScrollbarInactive
 132           : StyleSystemColor::ThemedScrollbar;
 133   return aColors.SystemOrElse(systemColor, [&] {
 134     return aColors.IsDark() ? sDefaultDarkTrackColor : sDefaultTrackColor;
 135   });
 136 }
 137
 138 // Don't use the theme color for dark scrollbars if it's not a color (if it's
 139 // grey-ish), as that'd either lack enough contrast, or be close to what we'd do
 140 // by default anyways.
 141 sRGBColor ScrollbarDrawing::ComputeScrollbarThumbColor(
 142     nsIFrame* aFrame, const ComputedStyle& aStyle,
 143     const EventStates& aElementState, const EventStates& aDocumentState,
 144     const Colors& aColors) {
 145   const nsStyleUI* ui = aStyle.StyleUI();
 146   if (ui->mScrollbarColor.IsColors()) {
 147     return sRGBColor::FromABGR(ThemeColors::AdjustUnthemedScrollbarThumbColor(
 148         ui->mScrollbarColor.AsColors().thumb.CalcColor(aStyle), aElementState));
 149   }
 150
 151   auto systemColor = [&] {
 152     if (aDocumentState.HasState(NS_DOCUMENT_STATE_WINDOW_INACTIVE)) {
 153       return StyleSystemColor::ThemedScrollbarThumbInactive;
 154     }
 155     if (aElementState.HasState(NS_EVENT_STATE_ACTIVE)) {
 156       if (aColors.HighContrast()) {
 157         return StyleSystemColor::Selecteditem;
 158       }
 159       return StyleSystemColor::ThemedScrollbarThumbActive;
 160     }
 161     if (aElementState.HasState(NS_EVENT_STATE_HOVER)) {
 162       if (aColors.HighContrast()) {
 163         return StyleSystemColor::Selecteditem;
 164       }
 165       return StyleSystemColor::ThemedScrollbarThumbHover;
 166     }
 167     if (aColors.HighContrast()) {
 168       return StyleSystemColor::Windowtext;
 169     }
 170     return StyleSystemColor::ThemedScrollbarThumb;
 171   }();
 172
 173   return aColors.SystemOrElse(systemColor, [&] {
 174     const nscolor unthemedColor = aColors.IsDark() ? NS_RGBA(249, 249, 250, 102)
 175                                                    : NS_RGB(0xcd, 0xcd, 0xcd);
 176
 177     return sRGBColor::FromABGR(ThemeColors::AdjustUnthemedScrollbarThumbColor(
 178         unthemedColor, aElementState));
 179   });
 180 }
 181
 182 template <typename PaintBackendData>
 183 bool ScrollbarDrawing::DoPaintDefaultScrollbar(
 184     PaintBackendData& aPaintData, const LayoutDeviceRect& aRect,
 185     bool aHorizontal, nsIFrame* aFrame, const ComputedStyle& aStyle,
 186     const EventStates& aElementState, const EventStates& aDocumentState,
 187     const Colors& aColors, const DPIRatio& aDpiRatio) {
 188   if (aFrame->PresContext()->UseOverlayScrollbars() &&
 189       !aElementState.HasAtLeastOneOfStates(NS_EVENT_STATE_HOVER |
 190                                            NS_EVENT_STATE_ACTIVE)) {
 191     return true;
 192   }
 193   auto scrollbarColor =
 194       ComputeScrollbarTrackColor(aFrame, aStyle, aDocumentState, aColors);
 195   ThemeDrawing::FillRect(aPaintData, aRect, scrollbarColor);
 196   return true;
 197 }
 198
 199 bool ScrollbarDrawing::PaintScrollbar(
 200     DrawTarget& aDrawTarget, const LayoutDeviceRect& aRect, bool aHorizontal,
 201     nsIFrame* aFrame, const ComputedStyle& aStyle,
 202     const EventStates& aElementState, const EventStates& aDocumentState,
 203     const Colors& aColors, const DPIRatio& aDpiRatio) {
 204   return DoPaintDefaultScrollbar(aDrawTarget, aRect, aHorizontal, aFrame,
 205                                  aStyle, aElementState, aDocumentState, aColors,
 206                                  aDpiRatio);
 207 }
 208
 209 bool ScrollbarDrawing::PaintScrollbar(
 210     WebRenderBackendData& aWrData, const LayoutDeviceRect& aRect,
 211     bool aHorizontal, nsIFrame* aFrame, const ComputedStyle& aStyle,
 212     const EventStates& aElementState, const EventStates& aDocumentState,
 213     const Colors& aColors, const DPIRatio& aDpiRatio) {
 214   return DoPaintDefaultScrollbar(aWrData, aRect, aHorizontal, aFrame, aStyle,
 215                                  aElementState, aDocumentState, aColors,
 216                                  aDpiRatio);
 217 }
 218
 219 template <typename PaintBackendData>
 220 bool ScrollbarDrawing::DoPaintDefaultScrollCorner(
 221     PaintBackendData& aPaintData, const LayoutDeviceRect& aRect,
 222     nsIFrame* aFrame, const ComputedStyle& aStyle,
 223     const EventStates& aDocumentState, const Colors& aColors,
 224     const DPIRatio& aDpiRatio) {
 225   auto scrollbarColor =
 226       ComputeScrollbarTrackColor(aFrame, aStyle, aDocumentState, aColors);
 227   ThemeDrawing::FillRect(aPaintData, aRect, scrollbarColor);
 228   return true;
 229 }
 230
 231 bool ScrollbarDrawing::PaintScrollCorner(
 232     DrawTarget& aDrawTarget, const LayoutDeviceRect& aRect, nsIFrame* aFrame,
 233     const ComputedStyle& aStyle, const EventStates& aDocumentState,
 234     const Colors& aColors, const DPIRatio& aDpiRatio) {
 235   return DoPaintDefaultScrollCorner(aDrawTarget, aRect, aFrame, aStyle,
 236                                     aDocumentState, aColors, aDpiRatio);
 237 }
 238
 239 bool ScrollbarDrawing::PaintScrollCorner(WebRenderBackendData& aWrData,
 240                                          const LayoutDeviceRect& aRect,
 241                                          nsIFrame* aFrame,
 242                                          const ComputedStyle& aStyle,
 243                                          const EventStates& aDocumentState,
 244                                          const Colors& aColors,
 245                                          const DPIRatio& aDpiRatio) {
 246   return DoPaintDefaultScrollCorner(aWrData, aRect, aFrame, aStyle,
 247                                     aDocumentState, aColors, aDpiRatio);
 248 }
 249
 250 nscolor ScrollbarDrawing::GetScrollbarButtonColor(nscolor aTrackColor,
 251                                                   EventStates aStates) {
 252   // See numbers in GetScrollbarArrowColor.
 253   // This function is written based on ratios between values listed there.
 254
 255   bool isActive = aStates.HasState(NS_EVENT_STATE_ACTIVE);
 256   bool isHover = aStates.HasState(NS_EVENT_STATE_HOVER);
 257   if (!isActive && !isHover) {
 258     return aTrackColor;
 259   }
 260   float luminance = RelativeLuminanceUtils::Compute(aTrackColor);
 261   if (isActive) {
 262     if (luminance >= 0.18f) {
 263       luminance *= 0.134f;
 264     } else {
 265       luminance /= 0.134f;
 266       luminance = std::min(luminance, 1.0f);
 267     }
 268   } else {
 269     if (luminance >= 0.18f) {
 270       luminance *= 0.805f;
 271     } else {
 272       luminance /= 0.805f;
 273     }
 274   }
 275   return RelativeLuminanceUtils::Adjust(aTrackColor, luminance);
 276 }
 277
 278 Maybe<nscolor> ScrollbarDrawing::GetScrollbarArrowColor(nscolor aButtonColor) {
 279   // In Windows 10 scrollbar, there are several gray colors used:
 280   //
 281   // State  | Background (lum) | Arrow   | Contrast
 282   // -------+------------------+---------+---------
 283   // Normal | Gray 240 (87.1%) | Gray 96 |     5.5
 284   // Hover  | Gray 218 (70.1%) | Black   |    15.0
 285   // Active | Gray 96  (11.7%) | White   |     6.3
 286   //
 287   // Contrast value is computed based on the definition in
 288   // https://www.w3.org/TR/WCAG20/#contrast-ratiodef
 289   //
 290   // This function is written based on these values.
 291
 292   if (NS_GET_A(aButtonColor) == 0) {
 293     // If the button color is transparent, because of e.g.
 294     // scrollbar-color: <something> transparent, then use
 295     // the thumb color, which is expected to have enough
 296     // contrast.
 297     return Nothing();
 298   }
 299
 300   float luminance = RelativeLuminanceUtils::Compute(aButtonColor);
 301   // Color with luminance larger than 0.72 has contrast ratio over 4.6
 302   // to color with luminance of gray 96, so this value is chosen for
 303   // this range. It is the luminance of gray 221.
 304   if (luminance >= 0.72) {
 305     // ComputeRelativeLuminanceFromComponents(96). That function cannot
 306     // be constexpr because of std::pow.
 307     const float GRAY96_LUMINANCE = 0.117f;
 308     return Some(RelativeLuminanceUtils::Adjust(aButtonColor, GRAY96_LUMINANCE));
 309   }
 310   // The contrast ratio of a color to black equals that to white when its
 311   // luminance is around 0.18, with a contrast ratio ~4.6 to both sides,
 312   // thus the value below. It's the lumanince of gray 118.
 313   //
 314   // TODO(emilio): Maybe the button alpha is not the best thing to use here and
 315   // we should use the thumb alpha? It seems weird that the color of the arrow
 316   // depends on the opacity of the scrollbar thumb...
 317   if (luminance >= 0.18) {
 318     return Some(NS_RGBA(0, 0, 0, NS_GET_A(aButtonColor)));
 319   }
 320   return Some(NS_RGBA(255, 255, 255, NS_GET_A(aButtonColor)));
 321 }
 322
 323 std::pair<sRGBColor, sRGBColor> ScrollbarDrawing::ComputeScrollbarButtonColors(
 324     nsIFrame* aFrame, StyleAppearance aAppearance, const ComputedStyle& aStyle,
 325     const EventStates& aElementState, const EventStates& aDocumentState,
 326     const Colors& aColors) {
 327   if (aColors.HighContrast()) {
 328     if (aElementState.HasAtLeastOneOfStates(NS_EVENT_STATE_ACTIVE |
 329                                             NS_EVENT_STATE_HOVER)) {
 330       return aColors.SystemPair(StyleSystemColor::Selecteditem,
 331                                 StyleSystemColor::Buttonface);
 332     }
 333     return aColors.SystemPair(StyleSystemColor::Window,
 334                               StyleSystemColor::Windowtext);
 335   }
 336
 337   auto trackColor =
 338       ComputeScrollbarTrackColor(aFrame, aStyle, aDocumentState, aColors);
 339   nscolor buttonColor =
 340       GetScrollbarButtonColor(trackColor.ToABGR(), aElementState);
 341   auto arrowColor =
 342       GetScrollbarArrowColor(buttonColor)
 343           .map(sRGBColor::FromABGR)
 344           .valueOrFrom([&] {
 345             return ComputeScrollbarThumbColor(aFrame, aStyle, aElementState,
 346                                               aDocumentState, aColors);
 347           });
 348   return {sRGBColor::FromABGR(buttonColor), arrowColor};
 349 }
 350
 351 bool ScrollbarDrawing::PaintScrollbarButton(
 352     DrawTarget& aDrawTarget, StyleAppearance aAppearance,
 353     const LayoutDeviceRect& aRect, nsIFrame* aFrame,
 354     const ComputedStyle& aStyle, const EventStates& aElementState,
 355     const EventStates& aDocumentState, const Colors& aColors, const DPIRatio&) {
 356   auto [buttonColor, arrowColor] = ComputeScrollbarButtonColors(
 357       aFrame, aAppearance, aStyle, aElementState, aDocumentState, aColors);
 358   aDrawTarget.FillRect(aRect.ToUnknownRect(),
 359                        ColorPattern(ToDeviceColor(buttonColor)));
 360
 361   // Start with Up arrow.
 362   float arrowPolygonX[] = {-4.0f, 0.0f, 4.0f, 4.0f, 0.0f, -4.0f};
 363   float arrowPolygonY[] = {0.0f, -4.0f, 0.0f, 3.0f, -1.0f, 3.0f};
 364
 365   const float kPolygonSize = 17;
 366
 367   const int32_t arrowNumPoints = ArrayLength(arrowPolygonX);
 368   switch (aAppearance) {
 369     case StyleAppearance::ScrollbarbuttonUp:
 370       break;
 371     case StyleAppearance::ScrollbarbuttonDown:
 372       for (int32_t i = 0; i < arrowNumPoints; i++) {
 373         arrowPolygonY[i] *= -1;
 374       }
 375       break;
 376     case StyleAppearance::ScrollbarbuttonLeft:
 377       for (int32_t i = 0; i < arrowNumPoints; i++) {
 378         float temp = arrowPolygonX[i];
 379         arrowPolygonX[i] = arrowPolygonY[i];
 380         arrowPolygonY[i] = temp;
 381       }
 382       break;
 383     case StyleAppearance::ScrollbarbuttonRight:
 384       for (int32_t i = 0; i < arrowNumPoints; i++) {
 385         float temp = arrowPolygonX[i];
 386         arrowPolygonX[i] = arrowPolygonY[i] * -1;
 387         arrowPolygonY[i] = temp;
 388       }
 389       break;
 390     default:
 391       return false;
 392   }
 393   ThemeDrawing::PaintArrow(aDrawTarget, aRect, arrowPolygonX, arrowPolygonY,
 394                            kPolygonSize, arrowNumPoints, arrowColor);
 395   return true;
 396 }
 397
 398 }  // namespace mozilla::widget