Bug 612840. Part 1: Remove CONTENT_NO_TEXT flag since it's not really used. Also remove ShouldRetainTransparentSurface and related code; we'll assume that when text is over opaque pixels in an RGBA surface we can always paint it with subpixel AA --- and make it so in later patches. r=vlad

gfx/layers/Layers.cpp

@@ -443,9 +443,6 @@ Layer::PrintInfo(nsACString& aTo, const char* aPrefix)
   if (GetContentFlags() & CONTENT_OPAQUE) {
     aTo += " [opaqueContent]";
   }
-  if (GetContentFlags() & CONTENT_NO_TEXT) {
-    aTo += " [noText]";
-  }
   if (GetContentFlags() & CONTENT_NO_TEXT_OVER_TRANSPARENT) {
     aTo += " [noTextOverTransparent]";
   }

gfx/layers/Layers.h

@@ -481,20 +481,13 @@ public:
      * SetVisibleRegion) will be filled with opaque content.
      */
     CONTENT_OPAQUE = 0x01,
-    /**
-     * ThebesLayers only!
-     * If this is set, the caller is promising that the visible region
-     * contains no text at all. If this is set,
-     * CONTENT_NO_TEXT_OVER_TRANSPARENT will also be set.
-     */
-    CONTENT_NO_TEXT = 0x02,
     /**
      * ThebesLayers only!
      * If this is set, the caller is promising that the visible region
      * contains no text over transparent pixels (any text, if present,
      * is over fully opaque pixels).
      */
-    CONTENT_NO_TEXT_OVER_TRANSPARENT = 0x04
+    CONTENT_NO_TEXT_OVER_TRANSPARENT = 0x02
   };
   /**
    * CONSTRUCTION PHASE ONLY

gfx/layers/basic/BasicLayers.cpp

@@ -439,32 +439,6 @@ ClipToContain(gfxContext* aContext, const nsIntRect& aRect)
   aContext->SetMatrix(currentMatrix);
 }
 
-static PRBool
-ShouldRetainTransparentSurface(PRUint32 aContentFlags,
-                               gfxASurface* aTargetSurface)
-{
-  if (aContentFlags & Layer::CONTENT_NO_TEXT)
-    return PR_TRUE;
-
-  switch (aTargetSurface->GetTextQualityInTransparentSurfaces()) {
-  case gfxASurface::TEXT_QUALITY_OK:
-    return PR_TRUE;
-  case gfxASurface::TEXT_QUALITY_OK_OVER_OPAQUE_PIXELS:
-    // Retain the buffer if all text is over opaque pixels. Otherwise,
-    // don't retain the buffer, in the hope that the backbuffer has
-    // opaque pixels where our layer does not.
-    return (aContentFlags & Layer::CONTENT_NO_TEXT_OVER_TRANSPARENT) != 0;
-  case gfxASurface::TEXT_QUALITY_BAD:
-    // If the backbuffer is opaque, then draw directly into it to get
-    // subpixel AA. If the backbuffer is not an opaque format, then we won't get
-    // subpixel AA by drawing into it, so we might as well retain.
-    return aTargetSurface->GetContentType() != gfxASurface::CONTENT_COLOR;
-  default:
-    NS_ERROR("Unknown quality type");
-    return PR_TRUE;
-  }
-}
-
 static nsIntRegion
 IntersectWithClip(const nsIntRegion& aRegion, gfxContext* aContext)
 {
@@ -495,7 +469,7 @@ BasicThebesLayer::Paint(gfxContext* aContext,
 
   if (!BasicManager()->IsRetained() ||
       (opacity == 1.0 && !canUseOpaqueSurface &&
-       !ShouldRetainTransparentSurface(mContentFlags, targetSurface) &&
+       !(mContentFlags & CONTENT_NO_TEXT_OVER_TRANSPARENT) &&
        !MustRetainContent())) {
     mValidRegion.SetEmpty();
     mBuffer.Clear();

gfx/thebes/gfxASurface.h

@@ -160,39 +160,6 @@ public:
       return nsnull;
     }
 
-    enum TextQuality {
-        /**
-         * TEXT_QUALITY_OK means that text is always rendered to a
-         * transparent surface just as well as it would be rendered to an
-         * opaque surface. This would normally only be true if
-         * subpixel antialiasing is disabled or if the platform's
-         * transparent surfaces support component alpha.
-         */
-        TEXT_QUALITY_OK,
-        /**
-         * TEXT_QUALITY_OK_OVER_OPAQUE_PIXELS means that text is rendered
-         * to a transparent surface just as well as it would be rendered to an
-         * opaque surface, but only if all the pixels the text is drawn
-         * over already have opaque alpha values.
-         */
-        TEXT_QUALITY_OK_OVER_OPAQUE_PIXELS,
-        /**
-         * TEXT_QUALITY_BAD means that text is rendered
-         * to a transparent surface worse than it would be rendered to an
-         * opaque surface, even if all the pixels the text is drawn
-         * over already have opaque alpha values.
-         */
-        TEXT_QUALITY_BAD
-    };
-    /**
-     * Determine how well text would be rendered in transparent surfaces that
-     * are similar to this surface.
-     */
-    virtual TextQuality GetTextQualityInTransparentSurfaces()
-    {
-        return TEXT_QUALITY_BAD;
-    }
-
     int CairoStatus();
 
     /* Make sure that the given dimensions don't overflow a 32-bit signed int

gfx/thebes/gfxD2DSurface.h

@@ -61,13 +61,6 @@ public:
 
     virtual ~gfxD2DSurface();
 
-    virtual TextQuality GetTextQualityInTransparentSurfaces()
-    {
-      // D2D always draws text in transparent surfaces with grayscale-AA,
-      // even if the text is over opaque pixels.
-      return TEXT_QUALITY_BAD;
-    }
-
     void Present();
     void Scroll(const nsIntPoint &aDelta, const nsIntRect &aClip);
 

gfx/thebes/gfxQuartzSurface.h

@@ -57,10 +57,6 @@ public:
 
     virtual already_AddRefed<gfxASurface> CreateSimilarSurface(gfxContentType aType,
                                                                const gfxIntSize& aSize);
-    virtual TextQuality GetTextQualityInTransparentSurfaces()
-    {
-      return TEXT_QUALITY_OK_OVER_OPAQUE_PIXELS;
-    }
 
     virtual const gfxIntSize GetSize() const { return gfxIntSize(mSize.width, mSize.height); }
 

gfx/thebes/gfxWindowsSurface.h

@@ -81,11 +81,6 @@ public:
                                                       const gfxIntSize& size,
                                                       gfxImageFormat format);
 
-    virtual TextQuality GetTextQualityInTransparentSurfaces()
-    {
-      return TEXT_QUALITY_OK_OVER_OPAQUE_PIXELS;
-    }
-
     nsresult BeginPrinting(const nsAString& aTitle, const nsAString& aPrintToFileName);
     nsresult EndPrinting();
     nsresult AbortPrinting();

gfx/thebes/gfxXlibSurface.h

@@ -77,11 +77,6 @@ public:
     virtual already_AddRefed<gfxASurface>
     CreateSimilarSurface(gfxContentType aType, const gfxIntSize& aSize);
 
-    virtual TextQuality GetTextQualityInTransparentSurfaces()
-    {
-      return TEXT_QUALITY_OK_OVER_OPAQUE_PIXELS;
-    }
-
     virtual const gfxIntSize GetSize() const { return mSize; }
 
     Display* XDisplay() { return mDisplay; }

layout/base/FrameLayerBuilder.cpp

@@ -166,7 +166,7 @@ protected:
     ThebesLayerData() :
       mActiveScrolledRoot(nsnull), mLayer(nsnull),
       mIsSolidColorInVisibleRegion(PR_FALSE),
-      mHasText(PR_FALSE), mHasTextOverTransparent(PR_FALSE),
+      mHasTextOverTransparent(PR_FALSE),
       mForceTransparentSurface(PR_FALSE) {}
     /**
      * Record that an item has been added to the ThebesLayer, so we
@@ -236,10 +236,6 @@ protected:
      * True if every pixel in mVisibleRegion will have color mSolidColor.
      */
     PRPackedBool mIsSolidColorInVisibleRegion;
-    /**
-     * True if there is any text visible in the layer.
-     */
-    PRPackedBool mHasText;
     /**
      * True if there is any text visible in the layer that's over
      * transparent pixels in the layer.
@@ -871,7 +867,6 @@ ContainerState::PopThebesLayerData()
   }
   PRUint32 flags =
     ((isOpaque && !data->mForceTransparentSurface) ? Layer::CONTENT_OPAQUE : 0) |
-    (data->mHasText ? 0 : Layer::CONTENT_NO_TEXT) |
     (data->mHasTextOverTransparent ? 0 : Layer::CONTENT_NO_TEXT_OVER_TRANSPARENT);
   layer->SetContentFlags(flags);
 
@@ -934,7 +929,6 @@ ContainerState::ThebesLayerData::Accumulate(nsDisplayListBuilder* aBuilder,
       mOpaqueRegion = tmp;
     }
   } else if (aItem->HasText()) {
-    mHasText = PR_TRUE;
     if (!mOpaqueRegion.Contains(aVisibleRect)) {
       mHasTextOverTransparent = PR_TRUE;
     }