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_UseOverlayScrollbars(const Document* aDocument) {
 102   nsPresContext* pc = aDocument->GetPresContext();
 103   return pc && pc->UseOverlayScrollbars();
 104 }
 105
 106 static nsDeviceContext* GetDeviceContextFor(const Document* aDocument) {
 107   nsPresContext* pc = aDocument->GetPresContext();
 108   if (!pc) {
 109     return nullptr;
 110   }
 111
 112   // It would be nice to call nsLayoutUtils::GetDeviceContextForScreenInfo here,
 113   // except for two things:  (1) it can flush, and flushing is bad here, and (2)
 114   // it doesn't really get us consistency in multi-monitor situations *anyway*.
 115   return pc->DeviceContext();
 116 }
 117
 118 void Gecko_MediaFeatures_GetDeviceSize(const Document* aDocument,
 119                                        nscoord* aWidth, nscoord* aHeight) {
 120   nsSize size = GetDeviceSize(*aDocument);
 121   *aWidth = size.width;
 122   *aHeight = size.height;
 123 }
 124
 125 int32_t Gecko_MediaFeatures_GetMonochromeBitsPerPixel(
 126     const Document* aDocument) {
 127   // The default bits per pixel for a monochrome device. We could propagate this
 128   // further to nsIPrintSettings, but Gecko doesn't actually know this value
 129   // from the hardware, so it seems silly to do so.
 130   static constexpr int32_t kDefaultMonochromeBpp = 8;
 131
 132   nsPresContext* pc = aDocument->GetPresContext();
 133   if (!pc) {
 134     return 0;
 135   }
 136   nsIPrintSettings* ps = pc->GetPrintSettings();
 137   if (!ps) {
 138     return 0;
 139   }
 140   bool color = true;
 141   ps->GetPrintInColor(&color);
 142   return color ? 0 : kDefaultMonochromeBpp;
 143 }
 144
 145 dom::ScreenColorGamut Gecko_MediaFeatures_ColorGamut(
 146     const Document* aDocument) {
 147   auto colorGamut = dom::ScreenColorGamut::Srgb;
 148   if (!aDocument->ShouldResistFingerprinting(RFPTarget::CSSColorInfo)) {
 149     if (auto* dx = GetDeviceContextFor(aDocument)) {
 150       colorGamut = dx->GetColorGamut();
 151     }
 152   }
 153   return colorGamut;
 154 }
 155
 156 int32_t Gecko_MediaFeatures_GetColorDepth(const Document* aDocument) {
 157   if (Gecko_MediaFeatures_GetMonochromeBitsPerPixel(aDocument) != 0) {
 158     // If we're a monochrome device, then the color depth is zero.
 159     return 0;
 160   }
 161
 162   // Use depth of 24 when resisting fingerprinting, or when we're not being
 163   // rendered.
 164   int32_t depth = 24;
 165
 166   if (!aDocument->ShouldResistFingerprinting(RFPTarget::CSSColorInfo)) {
 167     if (nsDeviceContext* dx = GetDeviceContextFor(aDocument)) {
 168       depth = dx->GetDepth();
 169     }
 170   }
 171
 172   // The spec says to use bits *per color component*, so divide by 3,
 173   // and round down, since the spec says to use the smallest when the
 174   // color components differ.
 175   return depth / 3;
 176 }
 177
 178 float Gecko_MediaFeatures_GetResolution(const Document* aDocument) {
 179   // We're returning resolution in terms of device pixels per css pixel, since
 180   // that is the preferred unit for media queries of resolution. This avoids
 181   // introducing precision error from conversion to and from less-used
 182   // physical units like inches.
 183   nsPresContext* pc = aDocument->GetPresContext();
 184   if (!pc) {
 185     return 1.;
 186   }
 187
 188   if (pc->GetOverrideDPPX() > 0.) {
 189     return pc->GetOverrideDPPX();
 190   }
 191
 192   if (aDocument->ShouldResistFingerprinting(RFPTarget::CSSResolution)) {
 193     return pc->DeviceContext()->GetFullZoom();
 194   }
 195   // Get the actual device pixel ratio, which also takes zoom into account.
 196   return float(AppUnitsPerCSSPixel()) /
 197          pc->DeviceContext()->AppUnitsPerDevPixel();
 198 }
 199
 200 static const Document* TopDocument(const Document* aDocument) {
 201   const Document* current = aDocument;
 202   while (const Document* parent = current->GetInProcessParentDocument()) {
 203     current = parent;
 204   }
 205   return current;
 206 }
 207
 208 StyleDisplayMode Gecko_MediaFeatures_GetDisplayMode(const Document* aDocument) {
 209   const Document* rootDocument = TopDocument(aDocument);
 210
 211   nsCOMPtr<nsISupports> container = rootDocument->GetContainer();
 212   if (nsCOMPtr<nsIBaseWindow> baseWindow = do_QueryInterface(container)) {
 213     nsCOMPtr<nsIWidget> mainWidget;
 214     baseWindow->GetMainWidget(getter_AddRefs(mainWidget));
 215     if (mainWidget && mainWidget->SizeMode() == nsSizeMode_Fullscreen) {
 216       return StyleDisplayMode::Fullscreen;
 217     }
 218   }
 219
 220   static_assert(static_cast<int32_t>(DisplayMode::Browser) ==
 221                         static_cast<int32_t>(StyleDisplayMode::Browser) &&
 222                     static_cast<int32_t>(DisplayMode::Minimal_ui) ==
 223                         static_cast<int32_t>(StyleDisplayMode::MinimalUi) &&
 224                     static_cast<int32_t>(DisplayMode::Standalone) ==
 225                         static_cast<int32_t>(StyleDisplayMode::Standalone) &&
 226                     static_cast<int32_t>(DisplayMode::Fullscreen) ==
 227                         static_cast<int32_t>(StyleDisplayMode::Fullscreen),
 228                 "DisplayMode must mach nsStyleConsts.h");
 229
 230   dom::BrowsingContext* browsingContext = aDocument->GetBrowsingContext();
 231   if (!browsingContext) {
 232     return StyleDisplayMode::Browser;
 233   }
 234   return static_cast<StyleDisplayMode>(browsingContext->DisplayMode());
 235 }
 236
 237 bool Gecko_MediaFeatures_MatchesPlatform(StylePlatform aPlatform) {
 238   switch (aPlatform) {
 239 #if defined(XP_WIN)
 240     case StylePlatform::Windows:
 241       return true;
 242 #elif defined(ANDROID)
 243     case StylePlatform::Android:
 244       return true;
 245 #elif defined(MOZ_WIDGET_GTK)
 246     case StylePlatform::Linux:
 247       return true;
 248 #elif defined(XP_MACOSX)
 249     case StylePlatform::Macos:
 250       return true;
 251 #elif defined(XP_IOS)
 252     case StylePlatform::Ios:
 253       return true;
 254 #else
 255 #  error "Unknown platform?"
 256 #endif
 257     default:
 258       return false;
 259   }
 260 }
 261
 262 bool Gecko_MediaFeatures_PrefersReducedMotion(const Document* aDocument) {
 263   if (aDocument->ShouldResistFingerprinting(
 264           RFPTarget::CSSPrefersReducedMotion)) {
 265     return false;
 266   }
 267   return LookAndFeel::GetInt(LookAndFeel::IntID::PrefersReducedMotion, 0) == 1;
 268 }
 269
 270 bool Gecko_MediaFeatures_PrefersReducedTransparency(const Document* aDocument) {
 271   if (aDocument->ShouldResistFingerprinting(
 272           RFPTarget::CSSPrefersReducedTransparency)) {
 273     return false;
 274   }
 275   return LookAndFeel::GetInt(LookAndFeel::IntID::PrefersReducedTransparency,
 276                              0) == 1;
 277 }
 278
 279 StylePrefersColorScheme Gecko_MediaFeatures_PrefersColorScheme(
 280     const Document* aDocument, bool aUseContent) {
 281   auto scheme = aUseContent ? PreferenceSheet::ContentPrefs().mColorScheme
 282                             : aDocument->PreferredColorScheme();
 283   return scheme == ColorScheme::Dark ? StylePrefersColorScheme::Dark
 284                                      : StylePrefersColorScheme::Light;
 285 }
 286
 287 // Neither Linux, Windows, nor Mac have a way to indicate that low contrast is
 288 // preferred so we use the presence of an accessibility theme or forced colors
 289 // as a signal.
 290 StylePrefersContrast Gecko_MediaFeatures_PrefersContrast(
 291     const Document* aDocument) {
 292   if (aDocument->ShouldResistFingerprinting(RFPTarget::CSSPrefersContrast)) {
 293     return StylePrefersContrast::NoPreference;
 294   }
 295   const auto& prefs = PreferenceSheet::PrefsFor(*aDocument);
 296   if (!prefs.mUseAccessibilityTheme && prefs.mUseDocumentColors) {
 297     return StylePrefersContrast::NoPreference;
 298   }
 299   const auto& colors = prefs.ColorsFor(ColorScheme::Light);
 300   float ratio = RelativeLuminanceUtils::ContrastRatio(colors.mDefaultBackground,
 301                                                       colors.mDefault);
 302   // https://www.w3.org/TR/WCAG21/#contrast-minimum
 303   if (ratio < 4.5f) {
 304     return StylePrefersContrast::Less;
 305   }
 306   // https://www.w3.org/TR/WCAG21/#contrast-enhanced
 307   if (ratio >= 7.0f) {
 308     return StylePrefersContrast::More;
 309   }
 310   return StylePrefersContrast::Custom;
 311 }
 312
 313 bool Gecko_MediaFeatures_InvertedColors(const Document* aDocument) {
 314   if (aDocument->ShouldResistFingerprinting(RFPTarget::CSSInvertedColors)) {
 315     return false;
 316   }
 317   return LookAndFeel::GetInt(LookAndFeel::IntID::InvertedColors, 0) == 1;
 318 }
 319
 320 StyleScripting Gecko_MediaFeatures_Scripting(const Document* aDocument) {
 321   const auto* doc = aDocument;
 322   if (aDocument->IsStaticDocument()) {
 323     doc = aDocument->GetOriginalDocument();
 324   }
 325
 326   return doc->IsScriptEnabled() ? StyleScripting::Enabled
 327                                 : StyleScripting::None;
 328 }
 329
 330 StyleDynamicRange Gecko_MediaFeatures_DynamicRange(const Document* aDocument) {
 331   // Bug 1759772: Once HDR color is available, update each platform
 332   // LookAndFeel implementation to return StyleDynamicRange::High when
 333   // appropriate.
 334   return StyleDynamicRange::Standard;
 335 }
 336
 337 StyleDynamicRange Gecko_MediaFeatures_VideoDynamicRange(
 338     const Document* aDocument) {
 339   if (aDocument->ShouldResistFingerprinting(RFPTarget::CSSVideoDynamicRange)) {
 340     return StyleDynamicRange::Standard;
 341   }
 342   // video-dynamic-range: high has 3 requirements:
 343   // 1) high peak brightness
 344   // 2) high contrast ratio
 345   // 3) color depth > 24
 346   // We check the color depth requirement before asking the LookAndFeel
 347   // if it is HDR capable.
 348   if (nsDeviceContext* dx = GetDeviceContextFor(aDocument)) {
 349     if (dx->GetDepth() > 24 &&
 350         LookAndFeel::GetInt(LookAndFeel::IntID::VideoDynamicRange)) {
 351       return StyleDynamicRange::High;
 352     }
 353   }
 354
 355   return StyleDynamicRange::Standard;
 356 }
 357
 358 static PointerCapabilities GetPointerCapabilities(const Document* aDocument,
 359                                                   LookAndFeel::IntID aID) {
 360   MOZ_ASSERT(aID == LookAndFeel::IntID::PrimaryPointerCapabilities ||
 361              aID == LookAndFeel::IntID::AllPointerCapabilities);
 362   MOZ_ASSERT(aDocument);
 363
 364   if (dom::BrowsingContext* bc = aDocument->GetBrowsingContext()) {
 365     // The touch-events-override happens only for the Responsive Design Mode so
 366     // that we don't need to care about ResistFingerprinting.
 367     if (bc->TouchEventsOverride() == dom::TouchEventsOverride::Enabled) {
 368       return PointerCapabilities::Coarse;
 369     }
 370   }
 371
 372   // The default value for Desktop is mouse-type pointer, and for Android
 373   // a coarse pointer.
 374   const PointerCapabilities kDefaultCapabilities =
 375 #ifdef ANDROID
 376       PointerCapabilities::Coarse;
 377 #else
 378       PointerCapabilities::Fine | PointerCapabilities::Hover;
 379 #endif
 380   if (aDocument->ShouldResistFingerprinting(
 381           RFPTarget::CSSPointerCapabilities)) {
 382     return kDefaultCapabilities;
 383   }
 384
 385   int32_t intValue;
 386   nsresult rv = LookAndFeel::GetInt(aID, &intValue);
 387   if (NS_FAILED(rv)) {
 388     return kDefaultCapabilities;
 389   }
 390
 391   return static_cast<PointerCapabilities>(intValue);
 392 }
 393
 394 PointerCapabilities Gecko_MediaFeatures_PrimaryPointerCapabilities(
 395     const Document* aDocument) {
 396   return GetPointerCapabilities(aDocument,
 397                                 LookAndFeel::IntID::PrimaryPointerCapabilities);
 398 }
 399
 400 PointerCapabilities Gecko_MediaFeatures_AllPointerCapabilities(
 401     const Document* aDocument) {
 402   return GetPointerCapabilities(aDocument,
 403                                 LookAndFeel::IntID::AllPointerCapabilities);
 404 }
 405
 406 StyleGtkThemeFamily Gecko_MediaFeatures_GtkThemeFamily() {
 407   static_assert(int32_t(StyleGtkThemeFamily::Unknown) == 0);
 408   return StyleGtkThemeFamily(
 409       LookAndFeel::GetInt(LookAndFeel::IntID::GTKThemeFamily));
 410 }