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(const nsPresContext* aPc)
  26     -> DPIRatio {
  27   DPIRatio ratio(
  28       float(AppUnitsPerCSSPixel()) /
  29       float(aPc->DeviceContext()->AppUnitsPerDevPixelAtUnitFullZoom()));
  30   if (aPc->IsPrintPreview()) {
  31     ratio.scale *= aPc->GetPrintPreviewScaleForSequenceFrameOrScrollbars();
  32   }
  33   if (mKind == Kind::Cocoa) {
  34     return DPIRatio(ratio.scale >= 2.0f ? 2.0f : 1.0f);
  35   }
  36   return ratio;
  37 }
  38
  39 /*static*/
  40 nsIFrame* ScrollbarDrawing::GetParentScrollbarFrame(nsIFrame* aFrame) {
  41   // Walk our parents to find a scrollbar frame
  42   nsIFrame* scrollbarFrame = aFrame;
  43   do {
  44     if (scrollbarFrame->IsScrollbarFrame()) {
  45       break;
  46     }
  47   } while ((scrollbarFrame = scrollbarFrame->GetParent()));
  48
  49   // We return null if we can't find a parent scrollbar frame
  50   return scrollbarFrame;
  51 }
  52
  53 /*static*/
  54 bool ScrollbarDrawing::IsParentScrollbarRolledOver(nsIFrame* aFrame) {
  55   nsIFrame* scrollbarFrame = GetParentScrollbarFrame(aFrame);
  56   return aFrame->PresContext()->UseOverlayScrollbars()
  57              ? nsNativeTheme::CheckBooleanAttr(scrollbarFrame, nsGkAtoms::hover)
  58              : nsNativeTheme::GetContentState(scrollbarFrame,
  59                                               StyleAppearance::None)
  60                    .HasState(ElementState::HOVER);
  61 }
  62
  63 /*static*/
  64 bool ScrollbarDrawing::IsParentScrollbarHoveredOrActive(nsIFrame* aFrame) {
  65   nsIFrame* scrollbarFrame = GetParentScrollbarFrame(aFrame);
  66   return scrollbarFrame &&
  67          scrollbarFrame->GetContent()
  68              ->AsElement()
  69              ->State()
  70              .HasAtLeastOneOfStates(ElementState::HOVER | ElementState::ACTIVE);
  71 }
  72
  73 /*static*/
  74 bool ScrollbarDrawing::IsScrollbarWidthThin(const ComputedStyle& aStyle) {
  75   auto scrollbarWidth = aStyle.StyleUIReset()->ScrollbarWidth();
  76   return scrollbarWidth == StyleScrollbarWidth::Thin;
  77 }
  78
  79 /*static*/
  80 bool ScrollbarDrawing::IsScrollbarWidthThin(nsIFrame* aFrame) {
  81   ComputedStyle* style = nsLayoutUtils::StyleForScrollbar(aFrame);
  82   return IsScrollbarWidthThin(*style);
  83 }
  84
  85 CSSIntCoord ScrollbarDrawing::GetCSSScrollbarSize(StyleScrollbarWidth aWidth,
  86                                                   Overlay aOverlay) const {
  87   return mScrollbarSize[aWidth == StyleScrollbarWidth::Thin]
  88                        [aOverlay == Overlay::Yes];
  89 }
  90
  91 void ScrollbarDrawing::ConfigureScrollbarSize(StyleScrollbarWidth aWidth,
  92                                               Overlay aOverlay,
  93                                               CSSIntCoord aSize) {
  94   mScrollbarSize[aWidth == StyleScrollbarWidth::Thin]
  95                 [aOverlay == Overlay::Yes] = aSize;
  96 }
  97
  98 void ScrollbarDrawing::ConfigureScrollbarSize(CSSIntCoord aSize) {
  99   ConfigureScrollbarSize(StyleScrollbarWidth::Auto, Overlay::No, aSize);
 100   ConfigureScrollbarSize(StyleScrollbarWidth::Auto, Overlay::Yes, aSize);
 101   ConfigureScrollbarSize(StyleScrollbarWidth::Thin, Overlay::No, aSize / 2);
 102   ConfigureScrollbarSize(StyleScrollbarWidth::Thin, Overlay::Yes, aSize / 2);
 103 }
 104
 105 LayoutDeviceIntCoord ScrollbarDrawing::GetScrollbarSize(
 106     const nsPresContext* aPresContext, StyleScrollbarWidth aWidth,
 107     Overlay aOverlay) {
 108   return (CSSCoord(GetCSSScrollbarSize(aWidth, aOverlay)) *
 109           GetDPIRatioForScrollbarPart(aPresContext))
 110       .Rounded();
 111 }
 112
 113 LayoutDeviceIntCoord ScrollbarDrawing::GetScrollbarSize(
 114     const nsPresContext* aPresContext, nsIFrame* aFrame) {
 115   auto* style = nsLayoutUtils::StyleForScrollbar(aFrame);
 116   auto width = style->StyleUIReset()->ScrollbarWidth();
 117   auto overlay =
 118       aPresContext->UseOverlayScrollbars() ? Overlay::Yes : Overlay::No;
 119   return GetScrollbarSize(aPresContext, width, overlay);
 120 }
 121
 122 bool ScrollbarDrawing::IsScrollbarTrackOpaque(nsIFrame* aFrame) {
 123   auto trackColor = ComputeScrollbarTrackColor(
 124       aFrame, *nsLayoutUtils::StyleForScrollbar(aFrame),
 125       aFrame->PresContext()->Document()->State(),
 126       Colors(aFrame, StyleAppearance::ScrollbartrackVertical));
 127   return trackColor.a == 1.0f;
 128 }
 129
 130 sRGBColor ScrollbarDrawing::ComputeScrollbarTrackColor(
 131     nsIFrame* aFrame, const ComputedStyle& aStyle,
 132     const DocumentState& aDocumentState, const Colors& aColors) {
 133   if (aColors.HighContrast()) {
 134     return aColors.System(StyleSystemColor::Window);
 135   }
 136   const nsStyleUI* ui = aStyle.StyleUI();
 137   if (ui->mScrollbarColor.IsColors()) {
 138     return sRGBColor::FromABGR(
 139         ui->mScrollbarColor.AsColors().track.CalcColor(aStyle));
 140   }
 141   static constexpr sRGBColor sDefaultDarkTrackColor =
 142       sRGBColor::FromU8(20, 20, 25, 77);
 143   static constexpr sRGBColor sDefaultTrackColor(
 144       gfx::sRGBColor::UnusualFromARGB(0xfff0f0f0));
 145
 146   auto systemColor = aDocumentState.HasAllStates(DocumentState::WINDOW_INACTIVE)
 147                          ? StyleSystemColor::ThemedScrollbarInactive
 148                          : StyleSystemColor::ThemedScrollbar;
 149   return aColors.SystemOrElse(systemColor, [&] {
 150     return aColors.IsDark() ? sDefaultDarkTrackColor : sDefaultTrackColor;
 151   });
 152 }
 153
 154 // Don't use the theme color for dark scrollbars if it's not a color (if it's
 155 // grey-ish), as that'd either lack enough contrast, or be close to what we'd do
 156 // by default anyways.
 157 sRGBColor ScrollbarDrawing::ComputeScrollbarThumbColor(
 158     nsIFrame* aFrame, const ComputedStyle& aStyle,
 159     const ElementState& aElementState, const DocumentState& aDocumentState,
 160     const Colors& aColors) {
 161   const nsStyleUI* ui = aStyle.StyleUI();
 162   if (ui->mScrollbarColor.IsColors()) {
 163     return sRGBColor::FromABGR(ThemeColors::AdjustUnthemedScrollbarThumbColor(
 164         ui->mScrollbarColor.AsColors().thumb.CalcColor(aStyle), aElementState));
 165   }
 166
 167   auto systemColor = [&] {
 168     if (aDocumentState.HasState(DocumentState::WINDOW_INACTIVE)) {
 169       return StyleSystemColor::ThemedScrollbarThumbInactive;
 170     }
 171     if (aElementState.HasState(ElementState::ACTIVE)) {
 172       if (aColors.HighContrast()) {
 173         return StyleSystemColor::Selecteditem;
 174       }
 175       return StyleSystemColor::ThemedScrollbarThumbActive;
 176     }
 177     if (aElementState.HasState(ElementState::HOVER)) {
 178       if (aColors.HighContrast()) {
 179         return StyleSystemColor::Selecteditem;
 180       }
 181       return StyleSystemColor::ThemedScrollbarThumbHover;
 182     }
 183     if (aColors.HighContrast()) {
 184       return StyleSystemColor::Windowtext;
 185     }
 186     return StyleSystemColor::ThemedScrollbarThumb;
 187   }();
 188
 189   return aColors.SystemOrElse(systemColor, [&] {
 190     const nscolor unthemedColor = aColors.IsDark() ? NS_RGBA(249, 249, 250, 102)
 191                                                    : NS_RGB(0xcd, 0xcd, 0xcd);
 192
 193     return sRGBColor::FromABGR(ThemeColors::AdjustUnthemedScrollbarThumbColor(
 194         unthemedColor, aElementState));
 195   });
 196 }
 197
 198 template <typename PaintBackendData>
 199 bool ScrollbarDrawing::DoPaintDefaultScrollbar(
 200     PaintBackendData& aPaintData, const LayoutDeviceRect& aRect,
 201     ScrollbarKind aScrollbarKind, nsIFrame* aFrame, const ComputedStyle& aStyle,
 202     const ElementState& aElementState, const DocumentState& aDocumentState,
 203     const Colors& aColors, const DPIRatio& aDpiRatio) {
 204   const bool overlay = aFrame->PresContext()->UseOverlayScrollbars();
 205   if (overlay && !aElementState.HasAtLeastOneOfStates(ElementState::HOVER |
 206                                                       ElementState::ACTIVE)) {
 207     return true;
 208   }
 209   const auto color =
 210       ComputeScrollbarTrackColor(aFrame, aStyle, aDocumentState, aColors);
 211   if (overlay && mKind == Kind::Win11) {
 212     LayoutDeviceCoord radius =
 213         (aScrollbarKind == ScrollbarKind::Horizontal ? aRect.height
 214                                                      : aRect.width) /
 215         2.0f;
 216     ThemeDrawing::PaintRoundedRectWithRadius(aPaintData, aRect, color,
 217                                              sRGBColor(), 0, radius / aDpiRatio,
 218                                              aDpiRatio);
 219   } else {
 220     ThemeDrawing::FillRect(aPaintData, aRect, color);
 221   }
 222   return true;
 223 }
 224
 225 bool ScrollbarDrawing::PaintScrollbar(
 226     DrawTarget& aDrawTarget, const LayoutDeviceRect& aRect,
 227     ScrollbarKind aScrollbarKind, nsIFrame* aFrame, const ComputedStyle& aStyle,
 228     const ElementState& aElementState, const DocumentState& aDocumentState,
 229     const Colors& aColors, const DPIRatio& aDpiRatio) {
 230   return DoPaintDefaultScrollbar(aDrawTarget, aRect, aScrollbarKind, aFrame,
 231                                  aStyle, aElementState, aDocumentState, aColors,
 232                                  aDpiRatio);
 233 }
 234
 235 bool ScrollbarDrawing::PaintScrollbar(
 236     WebRenderBackendData& aWrData, const LayoutDeviceRect& aRect,
 237     ScrollbarKind aScrollbarKind, nsIFrame* aFrame, const ComputedStyle& aStyle,
 238     const ElementState& aElementState, const DocumentState& aDocumentState,
 239     const Colors& aColors, const DPIRatio& aDpiRatio) {
 240   return DoPaintDefaultScrollbar(aWrData, aRect, aScrollbarKind, aFrame, aStyle,
 241                                  aElementState, aDocumentState, aColors,
 242                                  aDpiRatio);
 243 }
 244
 245 template <typename PaintBackendData>
 246 bool ScrollbarDrawing::DoPaintDefaultScrollCorner(
 247     PaintBackendData& aPaintData, const LayoutDeviceRect& aRect,
 248     ScrollbarKind aScrollbarKind, nsIFrame* aFrame, const ComputedStyle& aStyle,
 249     const DocumentState& aDocumentState, const Colors& aColors,
 250     const DPIRatio& aDpiRatio) {
 251   auto scrollbarColor =
 252       ComputeScrollbarTrackColor(aFrame, aStyle, aDocumentState, aColors);
 253   ThemeDrawing::FillRect(aPaintData, aRect, scrollbarColor);
 254   return true;
 255 }
 256
 257 bool ScrollbarDrawing::PaintScrollCorner(
 258     DrawTarget& aDrawTarget, const LayoutDeviceRect& aRect,
 259     ScrollbarKind aScrollbarKind, nsIFrame* aFrame, const ComputedStyle& aStyle,
 260     const DocumentState& aDocumentState, const Colors& aColors,
 261     const DPIRatio& aDpiRatio) {
 262   return DoPaintDefaultScrollCorner(aDrawTarget, aRect, aScrollbarKind, aFrame,
 263                                     aStyle, aDocumentState, aColors, aDpiRatio);
 264 }
 265
 266 bool ScrollbarDrawing::PaintScrollCorner(
 267     WebRenderBackendData& aWrData, const LayoutDeviceRect& aRect,
 268     ScrollbarKind aScrollbarKind, nsIFrame* aFrame, const ComputedStyle& aStyle,
 269     const DocumentState& aDocumentState, const Colors& aColors,
 270     const DPIRatio& aDpiRatio) {
 271   return DoPaintDefaultScrollCorner(aWrData, aRect, aScrollbarKind, aFrame,
 272                                     aStyle, aDocumentState, aColors, aDpiRatio);
 273 }
 274
 275 nscolor ScrollbarDrawing::GetScrollbarButtonColor(nscolor aTrackColor,
 276                                                   ElementState aStates) {
 277   // See numbers in GetScrollbarArrowColor.
 278   // This function is written based on ratios between values listed there.
 279
 280   bool isActive = aStates.HasState(ElementState::ACTIVE);
 281   bool isHover = aStates.HasState(ElementState::HOVER);
 282   if (!isActive && !isHover) {
 283     return aTrackColor;
 284   }
 285   float luminance = RelativeLuminanceUtils::Compute(aTrackColor);
 286   if (isActive) {
 287     if (luminance >= 0.18f) {
 288       luminance *= 0.134f;
 289     } else {
 290       luminance /= 0.134f;
 291       luminance = std::min(luminance, 1.0f);
 292     }
 293   } else {
 294     if (luminance >= 0.18f) {
 295       luminance *= 0.805f;
 296     } else {
 297       luminance /= 0.805f;
 298     }
 299   }
 300   return RelativeLuminanceUtils::Adjust(aTrackColor, luminance);
 301 }
 302
 303 Maybe<nscolor> ScrollbarDrawing::GetScrollbarArrowColor(nscolor aButtonColor) {
 304   // In Windows 10 scrollbar, there are several gray colors used:
 305   //
 306   // State  | Background (lum) | Arrow   | Contrast
 307   // -------+------------------+---------+---------
 308   // Normal | Gray 240 (87.1%) | Gray 96 |     5.5
 309   // Hover  | Gray 218 (70.1%) | Black   |    15.0
 310   // Active | Gray 96  (11.7%) | White   |     6.3
 311   //
 312   // Contrast value is computed based on the definition in
 313   // https://www.w3.org/TR/WCAG20/#contrast-ratiodef
 314   //
 315   // This function is written based on these values.
 316
 317   if (NS_GET_A(aButtonColor) == 0) {
 318     // If the button color is transparent, because of e.g.
 319     // scrollbar-color: <something> transparent, then use
 320     // the thumb color, which is expected to have enough
 321     // contrast.
 322     return Nothing();
 323   }
 324
 325   float luminance = RelativeLuminanceUtils::Compute(aButtonColor);
 326   // Color with luminance larger than 0.72 has contrast ratio over 4.6
 327   // to color with luminance of gray 96, so this value is chosen for
 328   // this range. It is the luminance of gray 221.
 329   if (luminance >= 0.72) {
 330     // ComputeRelativeLuminanceFromComponents(96). That function cannot
 331     // be constexpr because of std::pow.
 332     const float GRAY96_LUMINANCE = 0.117f;
 333     return Some(RelativeLuminanceUtils::Adjust(aButtonColor, GRAY96_LUMINANCE));
 334   }
 335   // The contrast ratio of a color to black equals that to white when its
 336   // luminance is around 0.18, with a contrast ratio ~4.6 to both sides,
 337   // thus the value below. It's the lumanince of gray 118.
 338   //
 339   // TODO(emilio): Maybe the button alpha is not the best thing to use here and
 340   // we should use the thumb alpha? It seems weird that the color of the arrow
 341   // depends on the opacity of the scrollbar thumb...
 342   if (luminance >= 0.18) {
 343     return Some(NS_RGBA(0, 0, 0, NS_GET_A(aButtonColor)));
 344   }
 345   return Some(NS_RGBA(255, 255, 255, NS_GET_A(aButtonColor)));
 346 }
 347
 348 std::pair<sRGBColor, sRGBColor> ScrollbarDrawing::ComputeScrollbarButtonColors(
 349     nsIFrame* aFrame, StyleAppearance aAppearance, const ComputedStyle& aStyle,
 350     const ElementState& aElementState, const DocumentState& aDocumentState,
 351     const Colors& aColors) {
 352   if (aColors.HighContrast()) {
 353     if (aElementState.HasAtLeastOneOfStates(ElementState::ACTIVE |
 354                                             ElementState::HOVER)) {
 355       return aColors.SystemPair(StyleSystemColor::Selecteditem,
 356                                 StyleSystemColor::Buttonface);
 357     }
 358     return aColors.SystemPair(StyleSystemColor::Window,
 359                               StyleSystemColor::Windowtext);
 360   }
 361
 362   auto trackColor =
 363       ComputeScrollbarTrackColor(aFrame, aStyle, aDocumentState, aColors);
 364   nscolor buttonColor =
 365       GetScrollbarButtonColor(trackColor.ToABGR(), aElementState);
 366   auto arrowColor =
 367       GetScrollbarArrowColor(buttonColor)
 368           .map(sRGBColor::FromABGR)
 369           .valueOrFrom([&] {
 370             return ComputeScrollbarThumbColor(aFrame, aStyle, aElementState,
 371                                               aDocumentState, aColors);
 372           });
 373   return {sRGBColor::FromABGR(buttonColor), arrowColor};
 374 }
 375
 376 bool ScrollbarDrawing::PaintScrollbarButton(
 377     DrawTarget& aDrawTarget, StyleAppearance aAppearance,
 378     const LayoutDeviceRect& aRect, ScrollbarKind aScrollbarKind,
 379     nsIFrame* aFrame, const ComputedStyle& aStyle,
 380     const ElementState& aElementState, const DocumentState& aDocumentState,
 381     const Colors& aColors, const DPIRatio&) {
 382   auto [buttonColor, arrowColor] = ComputeScrollbarButtonColors(
 383       aFrame, aAppearance, aStyle, aElementState, aDocumentState, aColors);
 384   aDrawTarget.FillRect(aRect.ToUnknownRect(),
 385                        ColorPattern(ToDeviceColor(buttonColor)));
 386
 387   // Start with Up arrow.
 388   float arrowPolygonX[] = {-4.0f, 0.0f, 4.0f, 4.0f, 0.0f, -4.0f};
 389   float arrowPolygonY[] = {0.0f, -4.0f, 0.0f, 3.0f, -1.0f, 3.0f};
 390
 391   const float kPolygonSize = 17;
 392
 393   const int32_t arrowNumPoints = ArrayLength(arrowPolygonX);
 394   switch (aAppearance) {
 395     case StyleAppearance::ScrollbarbuttonUp:
 396       break;
 397     case StyleAppearance::ScrollbarbuttonDown:
 398       for (int32_t i = 0; i < arrowNumPoints; i++) {
 399         arrowPolygonY[i] *= -1;
 400       }
 401       break;
 402     case StyleAppearance::ScrollbarbuttonLeft:
 403       for (int32_t i = 0; i < arrowNumPoints; i++) {
 404         float temp = arrowPolygonX[i];
 405         arrowPolygonX[i] = arrowPolygonY[i];
 406         arrowPolygonY[i] = temp;
 407       }
 408       break;
 409     case StyleAppearance::ScrollbarbuttonRight:
 410       for (int32_t i = 0; i < arrowNumPoints; i++) {
 411         float temp = arrowPolygonX[i];
 412         arrowPolygonX[i] = arrowPolygonY[i] * -1;
 413         arrowPolygonY[i] = temp;
 414       }
 415       break;
 416     default:
 417       return false;
 418   }
 419   ThemeDrawing::PaintArrow(aDrawTarget, aRect, arrowPolygonX, arrowPolygonY,
 420                            kPolygonSize, arrowNumPoints, arrowColor);
 421   return true;
 422 }
 423
 424 }  // namespace mozilla::widget