Bug 1732227 - Remove unused layers.componentalpha.enabled pref. r=gfx-reviewers,nical

Differential Revision: https://phabricator.services.mozilla.com/D126446

gfx/layers/LayerManager.cpp

@@ -96,21 +96,6 @@ already_AddRefed<ImageContainer> LayerManager::CreateImageContainer(
   return container.forget();
 }
 
-bool LayerManager::LayersComponentAlphaEnabled() {
-  // If MOZ_GFX_OPTIMIZE_MOBILE is defined, we force component alpha off
-  // and ignore the preference.
-#ifdef MOZ_GFX_OPTIMIZE_MOBILE
-  return false;
-#else
-  return StaticPrefs::
-      layers_componentalpha_enabled_AtStartup_DoNotUseDirectly();
-#endif
-}
-
-bool LayerManager::AreComponentAlphaLayersEnabled() {
-  return LayerManager::LayersComponentAlphaEnabled();
-}
-
 /*static*/
 void LayerManager::LayerUserDataDestroy(void* data) {
   delete static_cast<LayerUserData*>(data);

gfx/layers/LayerManager.h

@@ -239,19 +239,6 @@ class LayerManager : public WindowRenderer {
       const nsTArray<nsIWidget::Configuration>& aConfigurations) {}
   bool IsSnappingEffectiveTransforms() { return mSnapEffectiveTransforms; }
 
-  /**
-   * Returns true if the underlying platform can properly support layers with
-   * SurfaceMode::SURFACE_COMPONENT_ALPHA.
-   */
-  static bool LayersComponentAlphaEnabled();
-
-  /**
-   * Returns true if this LayerManager can properly support layers with
-   * SurfaceMode::SURFACE_COMPONENT_ALPHA. LayerManagers that can't will use
-   * transparent surfaces (and lose subpixel-AA for text).
-   */
-  virtual bool AreComponentAlphaLayersEnabled();
-
   /**
    * Returns true if this LayerManager always requires an intermediate surface
    * to render blend operations.

gfx/layers/Layers.cpp

@@ -540,7 +540,6 @@ ContainerLayer::ContainerLayer(LayerManager* aManager, void* aImplData)
       mInheritedYScale(1.0f),
       mPresShellResolution(1.0f),
       mUseIntermediateSurface(false),
-      mSupportsComponentAlphaChildren(false),
       mMayHaveReadbackChild(false),
       mChildrenChanged(false) {}
 
@@ -993,45 +992,6 @@ void ContainerLayer::DefaultComputeEffectiveTransforms(
   ComputeEffectiveTransformForMaskLayers(aTransformToSurface);
 }
 
-void ContainerLayer::DefaultComputeSupportsComponentAlphaChildren(
-    bool* aNeedsSurfaceCopy) {
-  if (!(GetContentFlags() & Layer::CONTENT_COMPONENT_ALPHA_DESCENDANT) ||
-      !Manager()->AreComponentAlphaLayersEnabled()) {
-    mSupportsComponentAlphaChildren = false;
-    if (aNeedsSurfaceCopy) {
-      *aNeedsSurfaceCopy = false;
-    }
-    return;
-  }
-
-  mSupportsComponentAlphaChildren = false;
-  bool needsSurfaceCopy = false;
-  CompositionOp blendMode = GetEffectiveMixBlendMode();
-  if (UseIntermediateSurface()) {
-    if (GetLocalVisibleRegion().GetNumRects() == 1 &&
-        (GetContentFlags() & Layer::CONTENT_OPAQUE)) {
-      mSupportsComponentAlphaChildren = true;
-    } else {
-      gfx::Matrix transform;
-      if (HasOpaqueAncestorLayer(this) &&
-          GetEffectiveTransform().Is2D(&transform) &&
-          !gfx::ThebesMatrix(transform).HasNonIntegerTranslation() &&
-          blendMode == gfx::CompositionOp::OP_OVER) {
-        mSupportsComponentAlphaChildren = true;
-        needsSurfaceCopy = true;
-      }
-    }
-  } else if (blendMode == gfx::CompositionOp::OP_OVER) {
-    mSupportsComponentAlphaChildren =
-        (GetContentFlags() & Layer::CONTENT_OPAQUE) ||
-        (GetParent() && GetParent()->SupportsComponentAlphaChildren());
-  }
-
-  if (aNeedsSurfaceCopy) {
-    *aNeedsSurfaceCopy = mSupportsComponentAlphaChildren && needsSurfaceCopy;
-  }
-}
-
 void ContainerLayer::ComputeEffectiveTransformsForChildren(
     const Matrix4x4& aTransformToSurface) {
   for (Layer* l = mFirstChild; l; l = l->GetNextSibling()) {
@@ -1039,14 +999,6 @@ void ContainerLayer::ComputeEffectiveTransformsForChildren(
   }
 }
 
-/* static */
-bool ContainerLayer::HasOpaqueAncestorLayer(Layer* aLayer) {
-  for (Layer* l = aLayer->GetParent(); l; l = l->GetParent()) {
-    if (l->GetContentFlags() & Layer::CONTENT_OPAQUE) return true;
-  }
-  return false;
-}
-
 // Note that ContainerLayer::RemoveAllChildren contains an optimized
 // version of this code; if you make changes to ContainerLayer::DidRemoveChild
 // consider whether the matching changes need to be made to

gfx/layers/Layers.h

@@ -151,12 +151,6 @@ class Layer {
      */
     CONTENT_COMPONENT_ALPHA = 0x02,
 
-    /**
-     * If this is set then one of the descendant layers of this one has
-     * CONTENT_COMPONENT_ALPHA set.
-     */
-    CONTENT_COMPONENT_ALPHA_DESCENDANT = 0x04,
-
     /**
      * If this is set then this layer is part of a preserve-3d group, and should
      * be sorted with sibling layers that are also part of the same group.
@@ -1482,20 +1476,6 @@ class ContainerLayer : public Layer {
    */
   bool HasMultipleChildren();
 
-  /**
-   * Returns true if this container supports children with component alpha.
-   * Should only be called while painting a child of this layer.
-   */
-  bool SupportsComponentAlphaChildren() {
-    return mSupportsComponentAlphaChildren;
-  }
-
-  /**
-   * Returns true if aLayer or any layer in its parent chain has the opaque
-   * content flag set.
-   */
-  static bool HasOpaqueAncestorLayer(Layer* aLayer);
-
   void SetChildrenChanged(bool aVal) { mChildrenChanged = aVal; }
 
   // If |aRect| is null, the entire layer should be considered invalid for
@@ -1547,17 +1527,6 @@ class ContainerLayer : public Layer {
   void DefaultComputeEffectiveTransforms(
       const gfx::Matrix4x4& aTransformToSurface);
 
-  /**
-   * A default implementation to compute and set the value for
-   * SupportsComponentAlphaChildren().
-   *
-   * If aNeedsSurfaceCopy is provided, then it is set to true if the caller
-   * needs to copy the background up into the intermediate surface created,
-   * false otherwise.
-   */
-  void DefaultComputeSupportsComponentAlphaChildren(
-      bool* aNeedsSurfaceCopy = nullptr);
-
   /**
    * Loops over the children calling ComputeEffectiveTransforms on them.
    */
@@ -1585,7 +1554,6 @@ class ContainerLayer : public Layer {
   // associated pres shell; for other layers, 1.0.
   float mPresShellResolution;
   bool mUseIntermediateSurface;
-  bool mSupportsComponentAlphaChildren;
   bool mMayHaveReadbackChild;
   // This is updated by ComputeDifferences. This will be true if we need to
   // invalidate the intermediate surface.

modules/libpref/init/StaticPrefList.yaml

@@ -6332,20 +6332,6 @@
   value: true
   mirror: always
 
-- name: layers.componentalpha.enabled
-  type: bool
-#ifdef MOZ_GFX_OPTIMIZE_MOBILE
-  # Nb: we ignore this pref if MOZ_GFX_OPTIMIZE_MOBILE is defined, as if this
-  # pref was always false. But we go to the effort of setting it to false so
-  # that telemetry's reporting of the pref value is more likely to reflect what
-  # the code is doing.
-  value: false
-#else
-  value: true
-#endif
-  mirror: once
-  do_not_use_directly: true
-
 - name: layers.d3d11.force-warp
   type: bool
   value: false

toolkit/components/telemetry/app/TelemetryEnvironment.jsm

@@ -300,7 +300,6 @@ const DEFAULT_ENVIRONMENT_PREFS = new Map([
   ["layers.async-pan-zoom.enabled", { what: RECORD_PREF_VALUE }],
   ["layers.async-video-oop.enabled", { what: RECORD_PREF_VALUE }],
   ["layers.async-video.enabled", { what: RECORD_PREF_VALUE }],
-  ["layers.componentalpha.enabled", { what: RECORD_PREF_VALUE }],
   ["layers.d3d11.disable-warp", { what: RECORD_PREF_VALUE }],
   ["layers.d3d11.force-warp", { what: RECORD_PREF_VALUE }],
   [