layout/style/nsMediaFeatures.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 /* the features that media queries can test */
   8
   9 #include "nsGkAtoms.h"
  10 #include "nsStyleConsts.h"
  11 #include "nsPresContext.h"
  12 #include "nsCSSProps.h"
  13 #include "nsCSSValue.h"
  14 #include "mozilla/LookAndFeel.h"
  15 #include "nsDeviceContext.h"
  16 #include "nsIBaseWindow.h"
  17 #include "nsIDocShell.h"
  18 #include "nsIPrintSettings.h"
  19 #include "mozilla/dom/Document.h"
  20 #include "mozilla/dom/DocumentInlines.h"
  21 #include "mozilla/dom/BrowsingContextBinding.h"
  22 #include "mozilla/dom/ScreenBinding.h"
  23 #include "nsIWidget.h"
  24 #include "nsContentUtils.h"
  25 #include "mozilla/RelativeLuminanceUtils.h"
  26 #include "mozilla/StaticPrefs_browser.h"
  27 #include "mozilla/StyleSheet.h"
  28 #include "mozilla/StyleSheetInlines.h"
  29 #include "mozilla/GeckoBindings.h"
  30 #include "PreferenceSheet.h"
  31 #include "nsGlobalWindowOuter.h"
  32 #ifdef XP_WIN
  33 #  include "mozilla/WindowsVersion.h"
  34 #endif
  35
  36 using namespace mozilla;
  37 using mozilla::dom::DisplayMode;
  38 using mozilla::dom::Document;
  39
  40 // A helper for four features below
  41 static nsSize GetSize(const Document& aDocument) {
  42   nsPresContext* pc = aDocument.GetPresContext();
  43
  44   // Per spec, return a 0x0 viewport if we're not being rendered. See:
  45   //
  46   //  * https://github.com/w3c/csswg-drafts/issues/571
  47   //  * https://github.com/whatwg/html/issues/1813
  48   //
  49   if (!pc) {
  50     return {};
  51   }
  52
  53   if (pc->IsRootPaginatedDocument()) {
  54     // We want the page size, including unprintable areas and margins.
  55     //
  56     // FIXME(emilio, bug 1414600): Not quite!
  57     return pc->GetPageSize();
  58   }
  59
  60   return pc->GetVisibleArea().Size();
  61 }
  62
  63 // A helper for three features below.
  64 static nsSize GetDeviceSize(const Document& aDocument) {
  65   if (aDocument.ShouldResistFingerprinting(RFPTarget::CSSDeviceSize)) {
  66     return GetSize(aDocument);
  67   }
  68
  69   // Media queries in documents in an RDM pane should use the simulated
  70   // device size.
  71   Maybe<CSSIntSize> deviceSize =
  72       nsGlobalWindowOuter::GetRDMDeviceSize(aDocument);
  73   if (deviceSize.isSome()) {
  74     return CSSPixel::ToAppUnits(deviceSize.value());
  75   }
  76
  77   nsPresContext* pc = aDocument.GetPresContext();
  78   // NOTE(emilio): We should probably figure out how to return an appropriate
  79   // device size here, though in a multi-screen world that makes no sense
  80   // really.
  81   if (!pc) {
  82     return {};
  83   }
  84
  85   if (pc->IsRootPaginatedDocument()) {
  86     // We want the page size, including unprintable areas and margins.
  87     // XXX The spec actually says we want the "page sheet size", but
  88     // how is that different?
  89     return pc->GetPageSize();
  90   }
  91
  92   nsSize size;
  93   pc->DeviceContext()->GetDeviceSurfaceDimensions(size.width, size.height);
  94   return size;
  95 }
  96
  97 bool Gecko_MediaFeatures_IsResourceDocument(const Document* aDocument) {
  98   return aDocument->IsResourceDoc();
  99 }
 100
 101 bool Gecko_MediaFeatures_ShouldAvoidNativeTheme(const Document* aDocument) {
 102   return aDocument->ShouldAvoidNativeTheme();
 103 }
 104
 105 bool Gecko_MediaFeatures_UseOverlayScrollbars(const Document* aDocument) {
 106   nsPresContext* pc = aDocument->GetPresContext();
 107   return pc && pc->UseOverlayScrollbars();
 108 }
 109
 110 static nsDeviceContext* GetDeviceContextFor(const Document* aDocument) {
 111   nsPresContext* pc = aDocument->GetPresContext();
 112   if (!pc) {
 113     return nullptr;
 114   }
 115
 116   // It would be nice to call nsLayoutUtils::GetDeviceContextForScreenInfo here,
 117   // except for two things:  (1) it can flush, and flushing is bad here, and (2)
 118   // it doesn't really get us consistency in multi-monitor situations *anyway*.
 119   return pc->DeviceContext();
 120 }
 121
 122 void Gecko_MediaFeatures_GetDeviceSize(const Document* aDocument,
 123                                        nscoord* aWidth, nscoord* aHeight) {
 124   nsSize size = GetDeviceSize(*aDocument);
 125   *aWidth = size.width;
 126   *aHeight = size.height;
 127 }
 128
 129 int32_t Gecko_MediaFeatures_GetMonochromeBitsPerPixel(
 130     const Document* aDocument) {
 131   // The default bits per pixel for a monochrome device. We could propagate this
 132   // further to nsIPrintSettings, but Gecko doesn't actually know this value
 133   // from the hardware, so it seems silly to do so.
 134   static constexpr int32_t kDefaultMonochromeBpp = 8;
 135
 136   nsPresContext* pc = aDocument->GetPresContext();
 137   if (!pc) {
 138     return 0;
 139   }
 140   nsIPrintSettings* ps = pc->GetPrintSettings();
 141   if (!ps) {
 142     return 0;
 143   }
 144   bool color = true;
 145   ps->GetPrintInColor(&color);
 146   return color ? 0 : kDefaultMonochromeBpp;
 147 }
 148
 149 dom::ScreenColorGamut Gecko_MediaFeatures_ColorGamut(
 150     const Document* aDocument) {
 151   auto colorGamut = dom::ScreenColorGamut::Srgb;
 152   if (!aDocument->ShouldResistFingerprinting(RFPTarget::CSSColorInfo)) {
 153     if (auto* dx = GetDeviceContextFor(aDocument)) {
 154       colorGamut = dx->GetColorGamut();
 155     }
 156   }
 157   return colorGamut;
 158 }
 159
 160 int32_t Gecko_MediaFeatures_GetColorDepth(const Document* aDocument) {
 161   if (Gecko_MediaFeatures_GetMonochromeBitsPerPixel(aDocument) != 0) {
 162     // If we're a monochrome device, then the color depth is zero.
 163     return 0;
 164   }
 165
 166   // Use depth of 24 when resisting fingerprinting, or when we're not being
 167   // rendered.
 168   int32_t depth = 24;
 169
 170   if (!aDocument->ShouldResistFingerprinting(RFPTarget::CSSColorInfo)) {
 171     if (nsDeviceContext* dx = GetDeviceContextFor(aDocument)) {
 172       depth = dx->GetDepth();
 173     }
 174   }
 175
 176   // The spec says to use bits *per color component*, so divide by 3,
 177   // and round down, since the spec says to use the smallest when the
 178   // color components differ.
 179   return depth / 3;
 180 }
 181
 182 float Gecko_MediaFeatures_GetResolution(const Document* aDocument) {
 183   // We're returning resolution in terms of device pixels per css pixel, since
 184   // that is the preferred unit for media queries of resolution. This avoids
 185   // introducing precision error from conversion to and from less-used
 186   // physical units like inches.
 187   nsPresContext* pc = aDocument->GetPresContext();
 188   if (!pc) {
 189     return 1.;
 190   }
 191
 192   if (pc->GetOverrideDPPX() > 0.) {
 193     return pc->GetOverrideDPPX();
 194   }
 195
 196   if (aDocument->ShouldResistFingerprinting(RFPTarget::CSSResolution)) {
 197     return pc->DeviceContext()->GetFullZoom();
 198   }
 199   // Get the actual device pixel ratio, which also takes zoom into account.
 200   return float(AppUnitsPerCSSPixel()) /
 201          pc->DeviceContext()->AppUnitsPerDevPixel();
 202 }
 203
 204 static const Document* TopDocument(const Document* aDocument) {
 205   const Document* current = aDocument;
 206   while (const Document* parent = current->GetInProcessParentDocument()) {
 207     current = parent;
 208   }
 209   return current;
 210 }
 211
 212 StyleDisplayMode Gecko_MediaFeatures_GetDisplayMode(const Document* aDocument) {
 213   const Document* rootDocument = TopDocument(aDocument);
 214
 215   nsCOMPtr<nsISupports> container = rootDocument->GetContainer();
 216   if (nsCOMPtr<nsIBaseWindow> baseWindow = do_QueryInterface(container)) {
 217     nsCOMPtr<nsIWidget> mainWidget;
 218     baseWindow->GetMainWidget(getter_AddRefs(mainWidget));
 219     if (mainWidget && mainWidget->SizeMode() == nsSizeMode_Fullscreen) {
 220       return StyleDisplayMode::Fullscreen;
 221     }
 222   }
 223
 224   static_assert(static_cast<int32_t>(DisplayMode::Browser) ==
 225                         static_cast<int32_t>(StyleDisplayMode::Browser) &&
 226                     static_cast<int32_t>(DisplayMode::Minimal_ui) ==
 227                         static_cast<int32_t>(StyleDisplayMode::MinimalUi) &&
 228                     static_cast<int32_t>(DisplayMode::Standalone) ==
 229                         static_cast<int32_t>(StyleDisplayMode::Standalone) &&
 230                     static_cast<int32_t>(DisplayMode::Fullscreen) ==
 231                         static_cast<int32_t>(StyleDisplayMode::Fullscreen),
 232                 "DisplayMode must mach nsStyleConsts.h");
 233
 234   dom::BrowsingContext* browsingContext = aDocument->GetBrowsingContext();
 235   if (!browsingContext) {
 236     return StyleDisplayMode::Browser;
 237   }
 238   return static_cast<StyleDisplayMode>(browsingContext->DisplayMode());
 239 }
 240
 241 bool Gecko_MediaFeatures_MatchesPlatform(StylePlatform aPlatform) {
 242   switch (aPlatform) {
 243 #if defined(XP_WIN)
 244     case StylePlatform::Windows:
 245       return true;
 246 #elif defined(ANDROID)
 247     case StylePlatform::Android:
 248       return true;
 249 #elif defined(MOZ_WIDGET_GTK)
 250     case StylePlatform::Linux:
 251       return true;
 252 #elif defined(XP_MACOSX)
 253     case StylePlatform::Macos:
 254       return true;
 255 #else
 256 #  error "Unknown platform?"
 257 #endif
 258     default:
 259       return false;
 260   }
 261 }
 262
 263 bool Gecko_MediaFeatures_PrefersReducedMotion(const Document* aDocument) {
 264   if (aDocument->ShouldResistFingerprinting(
 265           RFPTarget::CSSPrefersReducedMotion)) {
 266     return false;
 267   }
 268   return LookAndFeel::GetInt(LookAndFeel::IntID::PrefersReducedMotion, 0) == 1;
 269 }
 270
 271 bool Gecko_MediaFeatures_PrefersReducedTransparency(const Document* aDocument) {
 272   if (aDocument->ShouldResistFingerprinting(
 273           RFPTarget::CSSPrefersReducedTransparency)) {
 274     return false;
 275   }
 276   return LookAndFeel::GetInt(LookAndFeel::IntID::PrefersReducedTransparency,
 277                              0) == 1;
 278 }
 279
 280 StylePrefersColorScheme Gecko_MediaFeatures_PrefersColorScheme(
 281     const Document* aDocument, bool aUseContent) {
 282   auto scheme = aUseContent ? LookAndFeel::PreferredColorSchemeForContent()
 283                             : aDocument->PreferredColorScheme();
 284   return scheme == ColorScheme::Dark ? StylePrefersColorScheme::Dark
 285                                      : StylePrefersColorScheme::Light;
 286 }
 287
 288 // Neither Linux, Windows, nor Mac have a way to indicate that low contrast is
 289 // preferred so we use the presence of an accessibility theme or forced colors
 290 // as a signal.
 291 StylePrefersContrast Gecko_MediaFeatures_PrefersContrast(
 292     const Document* aDocument) {
 293   if (aDocument->ShouldResistFingerprinting(RFPTarget::CSSPrefersContrast)) {
 294     return StylePrefersContrast::NoPreference;
 295   }
 296   const auto& prefs = PreferenceSheet::PrefsFor(*aDocument);
 297   if (!prefs.mUseAccessibilityTheme && prefs.mUseDocumentColors) {
 298     return StylePrefersContrast::NoPreference;
 299   }
 300   const auto& colors = prefs.ColorsFor(ColorScheme::Light);
 301   float ratio = RelativeLuminanceUtils::ContrastRatio(colors.mDefaultBackground,
 302                                                       colors.mDefault);
 303   // https://www.w3.org/TR/WCAG21/#contrast-minimum
 304   if (ratio < 4.5f) {
 305     return StylePrefersContrast::Less;
 306   }
 307   // https://www.w3.org/TR/WCAG21/#contrast-enhanced
 308   if (ratio >= 7.0f) {
 309     return StylePrefersContrast::More;
 310   }
 311   return StylePrefersContrast::Custom;
 312 }
 313
 314 bool Gecko_MediaFeatures_InvertedColors(const Document* aDocument) {
 315   if (aDocument->ShouldResistFingerprinting(RFPTarget::CSSInvertedColors)) {
 316     return false;
 317   }
 318   return LookAndFeel::GetInt(LookAndFeel::IntID::InvertedColors, 0) == 1;
 319 }
 320
 321 StyleScripting Gecko_MediaFeatures_Scripting(const Document* aDocument) {
 322   const auto* doc = aDocument;
 323   if (aDocument->IsStaticDocument()) {
 324     doc = aDocument->GetOriginalDocument();
 325   }
 326
 327   return doc->IsScriptEnabled() ? StyleScripting::Enabled
 328                                 : StyleScripting::None;
 329 }
 330
 331 StyleDynamicRange Gecko_MediaFeatures_DynamicRange(const Document* aDocument) {
 332   // Bug 1759772: Once HDR color is available, update each platform
 333   // LookAndFeel implementation to return StyleDynamicRange::High when
 334   // appropriate.
 335   return StyleDynamicRange::Standard;
 336 }
 337
 338 StyleDynamicRange Gecko_MediaFeatures_VideoDynamicRange(
 339     const Document* aDocument) {
 340   if (aDocument->ShouldResistFingerprinting(RFPTarget::CSSVideoDynamicRange)) {
 341     return StyleDynamicRange::Standard;
 342   }
 343   // video-dynamic-range: high has 3 requirements:
 344   // 1) high peak brightness
 345   // 2) high contrast ratio
 346   // 3) color depth > 24
 347   // We check the color depth requirement before asking the LookAndFeel
 348   // if it is HDR capable.
 349   if (nsDeviceContext* dx = GetDeviceContextFor(aDocument)) {
 350     if (dx->GetDepth() > 24 &&
 351         LookAndFeel::GetInt(LookAndFeel::IntID::VideoDynamicRange)) {
 352       return StyleDynamicRange::High;
 353     }
 354   }
 355
 356   return StyleDynamicRange::Standard;
 357 }
 358
 359 static PointerCapabilities GetPointerCapabilities(const Document* aDocument,
 360                                                   LookAndFeel::IntID aID) {
 361   MOZ_ASSERT(aID == LookAndFeel::IntID::PrimaryPointerCapabilities ||
 362              aID == LookAndFeel::IntID::AllPointerCapabilities);
 363   MOZ_ASSERT(aDocument);
 364
 365   if (dom::BrowsingContext* bc = aDocument->GetBrowsingContext()) {
 366     // The touch-events-override happens only for the Responsive Design Mode so
 367     // that we don't need to care about ResistFingerprinting.
 368     if (bc->TouchEventsOverride() == dom::TouchEventsOverride::Enabled) {
 369       return PointerCapabilities::Coarse;
 370     }
 371   }
 372
 373   // The default value for Desktop is mouse-type pointer, and for Android
 374   // a coarse pointer.
 375   const PointerCapabilities kDefaultCapabilities =
 376 #ifdef ANDROID
 377       PointerCapabilities::Coarse;
 378 #else
 379       PointerCapabilities::Fine | PointerCapabilities::Hover;
 380 #endif
 381   if (aDocument->ShouldResistFingerprinting(
 382           RFPTarget::CSSPointerCapabilities)) {
 383     return kDefaultCapabilities;
 384   }
 385
 386   int32_t intValue;
 387   nsresult rv = LookAndFeel::GetInt(aID, &intValue);
 388   if (NS_FAILED(rv)) {
 389     return kDefaultCapabilities;
 390   }
 391
 392   return static_cast<PointerCapabilities>(intValue);
 393 }
 394
 395 PointerCapabilities Gecko_MediaFeatures_PrimaryPointerCapabilities(
 396     const Document* aDocument) {
 397   return GetPointerCapabilities(aDocument,
 398                                 LookAndFeel::IntID::PrimaryPointerCapabilities);
 399 }
 400
 401 PointerCapabilities Gecko_MediaFeatures_AllPointerCapabilities(
 402     const Document* aDocument) {
 403   return GetPointerCapabilities(aDocument,
 404                                 LookAndFeel::IntID::AllPointerCapabilities);
 405 }