Bug 1922506: Implement CanvasRenderingContext2D::GetDebugInfo. r=tjr,jgilbert,webidl,smaug

For our data collection efforts, we want to be able to tell whether a canvas we are reading is HW accelerated or not. For that reason, we want to implement CanvasRenderingContext2D::GetDebugInfo. We are only really interested in isAccelerated property, but added 3 other properties that might be useful in the future, or for other developers.

Differential Revision: https://phabricator.services.mozilla.com/D224495

dom/canvas/CanvasRenderingContext2D.cpp

@@ -1128,6 +1128,30 @@ void CanvasRenderingContext2D::GetContextAttributes(
   // those just keep their default values.
 }
 
+void CanvasRenderingContext2D::GetDebugInfo(
+    bool aEnsureTarget, CanvasRenderingContext2DDebugInfo& aDebugInfo,
+    ErrorResult& aError) {
+  if (aEnsureTarget && !EnsureTarget(aError)) {
+    return;
+  }
+
+  if (!mBufferProvider) {
+    aError.ThrowInvalidStateError("No buffer provider available");
+    return;
+  }
+
+  if (!mTarget) {
+    aError.ThrowInvalidStateError("No target available");
+    return;
+  }
+
+  aDebugInfo = CanvasRenderingContext2DDebugInfo();
+  aDebugInfo.mIsAccelerated = mBufferProvider->IsAccelerated();
+  aDebugInfo.mIsShared = mBufferProvider->IsShared();
+  aDebugInfo.mBackendType = static_cast<int8_t>(mTarget->GetBackendType());
+  aDebugInfo.mDrawTargetType = static_cast<int8_t>(mTarget->GetType());
+}
+
 CanvasRenderingContext2D::ColorStyleCacheEntry
 CanvasRenderingContext2D::ParseColorSlow(const nsACString& aString) {
   ColorStyleCacheEntry result{nsCString(aString)};

dom/canvas/CanvasRenderingContext2D.h

@@ -99,6 +99,10 @@ class CanvasRenderingContext2D : public nsICanvasRenderingContextInternal,
 
   void GetContextAttributes(CanvasRenderingContext2DSettings& aSettings) const;
 
+  void GetDebugInfo(bool aEnsureTarget,
+                    CanvasRenderingContext2DDebugInfo& aDebugInfo,
+                    ErrorResult& aError);
+
   void OnMemoryPressure() override;
   void OnBeforePaintTransaction() override;
   void OnDidPaintTransaction() override;

dom/webidl/CanvasRenderingContext2D.webidl

@@ -35,10 +35,21 @@ dictionary CanvasRenderingContext2DSettings {
   // whether or not we're planning to do a lot of readback operations
   boolean willReadFrequently = false;
 
-  [Func="nsRFPService::IsSoftwareRenderingOptionExposed"]
+  [Func="nsRFPService::IsSystemPrincipalOrAboutFingerprintingProtection"]
   boolean forceSoftwareRendering = false;
 };
 
+[GenerateInit]
+dictionary CanvasRenderingContext2DDebugInfo {
+  required boolean isAccelerated;
+
+  required boolean isShared;
+
+  required byte backendType;
+
+  required byte drawTargetType;
+};
+
 dictionary HitRegionOptions {
   Path2D? path = null;
   DOMString id = "";
@@ -64,6 +75,9 @@ interface CanvasRenderingContext2D {
 
   CanvasRenderingContext2DSettings getContextAttributes();
 
+  [Throws, Func="nsRFPService::IsSystemPrincipalOrAboutFingerprintingProtection"]
+  CanvasRenderingContext2DDebugInfo getDebugInfo(optional boolean ensureTarget = false);
+
   // Show the caret if appropriate when drawing
   [Func="CanvasUtils::HasDrawWindowPrivilege"]
   const unsigned long DRAWWINDOW_DRAW_CARET   = 0x01;

dom/webidl/WebGLRenderingContext.webidl

@@ -53,7 +53,7 @@ dictionary WebGLContextAttributes {
     GLboolean failIfMajorPerformanceCaveat = false;
     WebGLPowerPreference powerPreference = "default";
 
-    [Func="nsRFPService::IsSoftwareRenderingOptionExposed"]
+    [Func="nsRFPService::IsSystemPrincipalOrAboutFingerprintingProtection"]
     GLboolean forceSoftwareRendering = false;
 };
 

toolkit/components/resistfingerprinting/nsRFPService.cpp

@@ -1919,8 +1919,8 @@ bool nsRFPService::CheckSuspiciousFingerprintingActivity(
 }
 
 /* static */
-bool nsRFPService::IsSoftwareRenderingOptionExposed(JSContext* aCx,
-                                                    JSObject* aObj) {
+bool nsRFPService::IsSystemPrincipalOrAboutFingerprintingProtection(
+    JSContext* aCx, JSObject* aObj) {
   if (!NS_IsMainThread()) {
     return false;
   }

toolkit/components/resistfingerprinting/nsRFPService.h

@@ -223,7 +223,8 @@ class nsRFPService final : public nsIObserver, public nsIRFPService {
       bool aIsPrivateMode, RFPTarget aTarget,
       const Maybe<RFPTarget>& aOverriddenFingerprintingSettings);
 
-  static bool IsSoftwareRenderingOptionExposed(JSContext*, JSObject*);
+  static bool IsSystemPrincipalOrAboutFingerprintingProtection(JSContext*,
+                                                               JSObject*);
 
   // --------------------------------------------------------------------------
   static double TimerResolution(RTPCallerType aRTPCallerType);