Bug 1764201 Part 2: Make Gecko_MediaFeatures_VideoDynamicRange check per-screen HDR. r=emilio

This makes all platforms report video-dynamic-range:high if the screen
most closely associated with the document (according to the logic of
nsDeviceContext::FindScreen) is HDR capable.

This removes the LookAndFeel id for VideoDynamicRange, since it is only
used by Gecko_MediaFeatures_VideoDynamicRange, which is being modified
here to use the nsDeviceContext instead.

It also removes gfxPlatform::supportsHDR and its implementations, as it
is no longer used.

Differential Revision: https://phabricator.services.mozilla.com/D203329

gfx/src/nsDeviceContext.cpp

@@ -208,6 +208,16 @@ uint16_t nsDeviceContext::GetScreenOrientationAngle() {
   return screen->GetOrientationAngle();
 }
 
+bool nsDeviceContext::GetScreenIsHDR() {
+  RefPtr<widget::Screen> screen = FindScreen();
+  if (!screen) {
+    auto& screenManager = ScreenManager::GetSingleton();
+    screen = screenManager.GetPrimaryScreen();
+    MOZ_ASSERT(screen);
+  }
+  return screen->GetIsHDR();
+}
+
 nsresult nsDeviceContext::GetDeviceSurfaceDimensions(nscoord& aWidth,
                                                      nscoord& aHeight) {
   if (IsPrinterContext()) {

gfx/src/nsDeviceContext.h

@@ -149,6 +149,11 @@ class nsDeviceContext final {
    */
   uint16_t GetScreenOrientationAngle();
 
+  /**
+   * Get the status of HDR support of the associated screen.
+   */
+  bool GetScreenIsHDR();
+
   /**
    * Get the size of the displayable area of the output device
    * in app units.

gfx/thebes/gfxPlatform.cpp

@@ -1064,6 +1064,13 @@ void gfxPlatform::ReportTelemetry() {
     mozilla::glean::gfx_display::count.Set(screenCount);
     mozilla::glean::gfx_display::primary_height.Set(rect.Height());
     mozilla::glean::gfx_display::primary_width.Set(rect.Width());
+
+    // Check if any screen known by screenManager supports HDR.
+    bool supportsHDR = false;
+    for (const auto& screen : screenManager.CurrentScreenList()) {
+      supportsHDR |= screen->GetIsHDR();
+    }
+    Telemetry::ScalarSet(Telemetry::ScalarID::GFX_SUPPORTS_HDR, supportsHDR);
   }
 
   nsString adapterDesc;
@@ -1120,10 +1127,6 @@ void gfxPlatform::ReportTelemetry() {
       NS_ConvertUTF16toUTF8(adapterDriverDate));
 
   mozilla::glean::gfx_status::headless.Set(IsHeadless());
-
-  MOZ_ASSERT(gPlatform, "Need gPlatform to generate some telemetry.");
-  Telemetry::ScalarSet(Telemetry::ScalarID::GFX_SUPPORTS_HDR,
-                       gPlatform->SupportsHDR());
 }
 
 static bool IsFeatureSupported(long aFeature, bool aDefault) {

gfx/thebes/gfxPlatform.h

@@ -811,8 +811,6 @@ class gfxPlatform : public mozilla::layers::MemoryPressureListener {
 
   static bool UseDesktopZoomingScrollbars();
 
-  virtual bool SupportsHDR() { return false; }
-
  protected:
   gfxPlatform();
   virtual ~gfxPlatform();

gfx/thebes/gfxPlatformMac.cpp

@@ -965,27 +965,6 @@ gfxPlatformMac::CreateGlobalHardwareVsyncSource() {
 #endif
 }
 
-bool gfxPlatformMac::SupportsHDR() {
-  // HDR has 3 requirements:
-  // 1) high peak brightness
-  // 2) high contrast ratio
-  // 3) color depth > 24
-  if (GetScreenDepth() <= 24) {
-    return false;
-  }
-
-#ifdef MOZ_WIDGET_UIKIT
-  return false;
-#elif defined(EARLY_BETA_OR_EARLIER)
-  // Screen is capable. Is the OS capable?
-  // More-or-less supported in Catalina.
-  return true;
-#else
-  // Definitely supported in Big Sur.
-  return nsCocoaFeatures::OnBigSurOrLater();
-#endif
-}
-
 nsTArray<uint8_t> gfxPlatformMac::GetPlatformCMSOutputProfileData() {
   nsTArray<uint8_t> prefProfileData = GetPrefCMSOutputProfileData();
   if (!prefProfileData.IsEmpty()) {

gfx/thebes/gfxPlatformMac.h

@@ -76,8 +76,6 @@ class gfxPlatformMac : public gfxPlatform {
 
   static bool CheckVariationFontSupport();
 
-  bool SupportsHDR() override;
-
  protected:
   bool AccelerateLayersByDefault() override;
 

gfx/thebes/gfxWindowsPlatform.cpp

@@ -259,8 +259,7 @@ class D3DSharedTexturesReporter final : public nsIMemoryReporter {
 
 NS_IMPL_ISUPPORTS(D3DSharedTexturesReporter, nsIMemoryReporter)
 
-gfxWindowsPlatform::gfxWindowsPlatform()
-    : mRenderMode(RENDER_GDI), mSupportsHDR(false) {
+gfxWindowsPlatform::gfxWindowsPlatform() : mRenderMode(RENDER_GDI) {
   // If win32k is locked down then we can't use COM STA and shouldn't need it.
   // Also, we won't be using any GPU memory in this process.
   if (!IsWin32kLockedDown()) {
@@ -401,7 +400,6 @@ void gfxWindowsPlatform::InitAcceleration() {
   // CanUseHardwareVideoDecoding depends on DeviceManagerDx state,
   // so update the cached value now.
   UpdateCanUseHardwareVideoDecoding();
-  UpdateSupportsHDR();
 
   // Our ScreenHelperWin also depends on DeviceManagerDx state.
   if (XRE_IsParentProcess() && !gfxPlatform::IsHeadless()) {
@@ -537,53 +535,6 @@ void gfxWindowsPlatform::UpdateRenderMode() {
   }
 }
 
-void gfxWindowsPlatform::UpdateSupportsHDR() {
-  // TODO: This function crashes content processes, for reasons that are not
-  // obvious from the crash reports. For now, this function can only be executed
-  // by the parent process. Therefore SupportsHDR() will always return false for
-  // content processes, as noted in the header.
-  if (!XRE_IsParentProcess()) {
-    return;
-  }
-
-  // Set mSupportsHDR to true if any of the DeviceManager outputs have a BT2020
-  // colorspace with EOTF2084 gamma curve, this indicates the system is sending
-  // an HDR format to at least one monitor.  The colorspace returned by DXGI is
-  // very vague - we only see DXGI_COLOR_SPACE_RGB_FULL_G2084_NONE_P2020 for HDR
-  // and DXGI_COLOR_SPACE_RGB_FULL_G22_NONE_P709 for SDR modes, even if the
-  // monitor is using something like YCbCr444 according to Settings
-  // (System -> Display Settings -> Advanced Display).  To get more specific
-  // info we would need to query the DISPLAYCONFIG values in WinGDI.
-  //
-  // Note that the bit depth used to be checked here, but as of Windows 11 22H2,
-  // HDR is supported with 8bpc for lower bandwidth, where DWM converts to
-  // dithered RGB8 rather than RGB10, which doesn't really matter here.
-  //
-  // This only returns true if there is an HDR display connected at app start,
-  // if the user switches to HDR to watch a video, we won't know that here, and
-  // if no displays are connected we return false (e.g. if Windows Update
-  // restarted a laptop with its lid closed and no external displays, we will
-  // see zero outputs here when the app is restarted automatically).
-  //
-  // It would be better to track if HDR is ever used and report that telemetry
-  // so we know if HDR matters, not just when it is detected at app start.
-  //
-  // Further reading:
-  // https://learn.microsoft.com/en-us/windows/win32/direct3darticles/high-dynamic-range
-  // https://learn.microsoft.com/en-us/windows/win32/api/wingdi/ns-wingdi-displayconfig_sdr_white_level
-  DeviceManagerDx* dx = DeviceManagerDx::Get();
-  nsTArray<DXGI_OUTPUT_DESC1> outputs = dx->EnumerateOutputs();
-
-  for (auto& output : outputs) {
-    if (output.ColorSpace == DXGI_COLOR_SPACE_RGB_FULL_G2084_NONE_P2020) {
-      mSupportsHDR = true;
-      return;
-    }
-  }
-
-  mSupportsHDR = false;
-}
-
 mozilla::gfx::BackendType gfxWindowsPlatform::GetContentBackendFor(
     mozilla::layers::LayersBackend aLayers) {
   mozilla::gfx::BackendType defaultBackend =

gfx/thebes/gfxWindowsPlatform.h

@@ -193,9 +193,6 @@ class gfxWindowsPlatform final : public gfxPlatform {
 
   static bool CheckVariationFontSupport();
 
-  // Always false for content processes.
-  bool SupportsHDR() override { return mSupportsHDR; }
-
  protected:
   bool AccelerateLayersByDefault() override { return true; }
 
@@ -214,10 +211,7 @@ class gfxWindowsPlatform final : public gfxPlatform {
 
   BackendPrefsData GetBackendPrefs() const override;
 
-  void UpdateSupportsHDR();
-
   RenderMode mRenderMode;
-  bool mSupportsHDR;
 
  private:
   void Init();

layout/style/nsMediaFeatures.cpp

@@ -336,18 +336,20 @@ StyleDynamicRange Gecko_MediaFeatures_DynamicRange(const Document* aDocument) {
 
 StyleDynamicRange Gecko_MediaFeatures_VideoDynamicRange(
     const Document* aDocument) {
-  if (aDocument->ShouldResistFingerprinting(RFPTarget::CSSVideoDynamicRange)) {
+  if (aDocument->ShouldResistFingerprinting(RFPTarget::CSSVideoDynamicRange) ||
+      !StaticPrefs::layout_css_video_dynamic_range_allows_high()) {
     return StyleDynamicRange::Standard;
   }
   // video-dynamic-range: high has 3 requirements:
   // 1) high peak brightness
   // 2) high contrast ratio
   // 3) color depth > 24
-  // We check the color depth requirement before asking the LookAndFeel
-  // if it is HDR capable.
+
+  // As a proxy for those requirements, return 'High' if the screen associated
+  // with the device context claims to be HDR capable.
   if (nsDeviceContext* dx = GetDeviceContextFor(aDocument)) {
-    if (dx->GetDepth() > 24 &&
-        LookAndFeel::GetInt(LookAndFeel::IntID::VideoDynamicRange)) {
+    if (dx->GetScreenIsHDR()) {
+      // bjw
       return StyleDynamicRange::High;
     }
   }

modules/libpref/init/StaticPrefList.yaml

@@ -9396,6 +9396,16 @@
   mirror: always
   rust: true
 
+# Is matching video-dynamic-range: high allowed?
+- name: layout.css.video-dynamic-range.allows-high
+  type: RelaxedAtomicBool
+#if defined(XP_MACOSX) || defined(NIGHTLY_BUILD)
+  value: true
+#else
+  value: false
+#endif
+  mirror: always
+
 # Whether frame visibility tracking is enabled globally.
 - name: layout.framevisibility.enabled
   type: bool

toolkit/components/resistfingerprinting/nsUserCharacteristics.cpp

@@ -57,8 +57,6 @@ int MaxTouchPoints() {
 
 // ==================================================================
 void PopulateCSSProperties() {
-  glean::characteristics::video_dynamic_range.Set(
-      LookAndFeel::GetInt(LookAndFeel::IntID::VideoDynamicRange));
   glean::characteristics::prefers_reduced_transparency.Set(
       LookAndFeel::GetInt(LookAndFeel::IntID::PrefersReducedTransparency));
   glean::characteristics::prefers_reduced_motion.Set(
@@ -110,6 +108,8 @@ void PopulateScreenProperties() {
   const LayoutDeviceIntRect rect = screen->GetRect();
   glean::characteristics::screen_height.Set(rect.Height());
   glean::characteristics::screen_width.Set(rect.Width());
+
+  glean::characteristics::video_dynamic_range.Set(screen->GetIsHDR());
 }
 
 void PopulateMissingFonts() {

widget/LookAndFeel.h

@@ -300,7 +300,6 @@ class LookAndFeel {
      * 1: High
      */
     DynamicRange,
-    VideoDynamicRange,
 
     /** Whether XUL panel animations are enabled. */
     PanelAnimations,

widget/cocoa/nsLookAndFeel.mm

@@ -469,14 +469,6 @@ nsresult nsLookAndFeel::NativeGetInt(IntID aID, int32_t& aResult) {
       aResult = NSWorkspace.sharedWorkspace
                     .accessibilityDisplayShouldIncreaseContrast;
       break;
-    case IntID::VideoDynamicRange: {
-      // If the platform says it supports HDR, then we claim to support
-      // video-dynamic-range.
-      gfxPlatform* platform = gfxPlatform::GetPlatform();
-      MOZ_ASSERT(platform);
-      aResult = platform->SupportsHDR();
-      break;
-    }
     case IntID::PanelAnimations:
       aResult = 1;
       break;

widget/nsXPLookAndFeel.cpp

@@ -187,7 +187,6 @@ static const char sIntPrefs[][45] = {
     "ui.titlebarRadius",
     "ui.titlebarButtonSpacing",
     "ui.dynamicRange",
-    "ui.videoDynamicRange",
     "ui.panelAnimations",
     "ui.hideCursorWhileTyping",
     "ui.gtkThemeFamily",