Bug 364221 - "[cairo] bad page scrolling performance with large background images" [p=alfredkayser@nl.ibm.com (Alfred Kayser) / vladimir@pobox.com (Vladimir Vukicevic [vlad]) r=stuart sr=tor a=blocking1.9+]

gfx/src/thebes/nsThebesImage.cpp

@@ -66,6 +66,7 @@ nsThebesImage::nsThebesImage()
       mDecoded(0,0,0,0),
       mImageComplete(PR_FALSE),
       mSinglePixel(PR_FALSE),
+      mFormatChanged(PR_FALSE),
       mAlphaDepth(0)
 {
     static PRBool hasCheckedOptimize = PR_FALSE;
@@ -254,6 +255,8 @@ nsThebesImage::Optimize(nsIDeviceContext* aContext)
     if (ShouldUseImageSurfaces())
         return NS_OK;
 
+    mOptSurface = nsnull;
+
 #ifdef XP_WIN
     // we need to special-case windows here, because windows has
     // a distinction between DIB and DDB and we want to use DDBs as much
@@ -288,21 +291,22 @@ nsThebesImage::Optimize(nsIDeviceContext* aContext)
                 mOptSurface = wsurf;
             }
         }
-
-        if (!mOptSurface) {
-            // just use the DIB
+        if (!mOptSurface && !mFormatChanged) {
+            // just use the DIB if the format has not changed
             mOptSurface = mWinSurface;
         }
-    } else {
-        mOptSurface = gfxPlatform::GetPlatform()->OptimizeImage(mImageSurface);
     }
-
-    mWinSurface = nsnull;
-#else
-    mOptSurface = gfxPlatform::GetPlatform()->OptimizeImage(mImageSurface);
 #endif
 
-    mImageSurface = nsnull;
+    if (mOptSurface == nsnull)
+        mOptSurface = gfxPlatform::GetPlatform()->OptimizeImage(mImageSurface, mFormat);
+
+    if (mOptSurface) {
+        mImageSurface = nsnull;
+#ifdef XP_WIN
+        mWinSurface = nsnull;
+#endif
+    }
 
     return NS_OK;
 }
@@ -636,6 +640,8 @@ nsThebesImage::ShouldUseImageSurfaces()
 void
 nsThebesImage::SetHasNoAlpha()
 {
-    if (mFormat == gfxASurface::ImageFormatARGB32)
+    if (mFormat == gfxASurface::ImageFormatARGB32) {
         mFormat = gfxASurface::ImageFormatRGB24;
+        mFormatChanged = PR_TRUE;
+    }
 }

gfx/src/thebes/nsThebesImage.h

@@ -142,6 +142,7 @@ protected:
     nsRect mDecoded;
     PRPackedBool mImageComplete;
     PRPackedBool mSinglePixel;
+    PRPackedBool mFormatChanged;
 #ifdef XP_WIN
     PRPackedBool mIsDDBSurface;
 #endif

gfx/thebes/public/gfxPlatform.h

@@ -87,15 +87,14 @@ public:
 
     /**
      * Create an offscreen surface of the given dimensions
-     * and image format.  If fastPixelAccess is TRUE,
-     * create a surface that is optimized for rapid pixel
-     * changing.
+     * and image format.
      */
     virtual already_AddRefed<gfxASurface> CreateOffscreenSurface(const gfxIntSize& size,
                                                                  gfxASurface::gfxImageFormat imageFormat) = 0;
 
 
-    virtual already_AddRefed<gfxASurface> OptimizeImage(gfxImageSurface *aSurface);
+    virtual already_AddRefed<gfxASurface> OptimizeImage(gfxImageSurface *aSurface,
+                                                        gfxASurface::gfxImageFormat format);
 
     /*
      * Font bits

gfx/thebes/src/gfxPlatform.cpp

@@ -195,15 +195,13 @@ gfxPlatform::SetUseGlitz(PRBool use)
 }
 
 already_AddRefed<gfxASurface>
-gfxPlatform::OptimizeImage(gfxImageSurface *aSurface)
+gfxPlatform::OptimizeImage(gfxImageSurface *aSurface,
+                           gfxASurface::gfxImageFormat format)
 {
     const gfxIntSize& surfaceSize = aSurface->GetSize();
 
-    gfxASurface::gfxImageFormat realFormat = aSurface->Format();
-
-    nsRefPtr<gfxASurface> optSurface = CreateOffscreenSurface(surfaceSize, realFormat);
-
-    if (!optSurface)
+    nsRefPtr<gfxASurface> optSurface = CreateOffscreenSurface(surfaceSize, format);
+    if (!optSurface || optSurface->CairoStatus() != 0)
         return nsnull;
 
     nsRefPtr<gfxContext> tmpCtx(new gfxContext(optSurface));

modules/libpr0n/decoders/gif/nsGIFDecoder2.cpp

@@ -121,6 +121,7 @@ nsGIFDecoder2::nsGIFDecoder2()
   , mLastFlushedPass(0)
   , mOldColor(0)
   , mGIFOpen(PR_FALSE)
+  , mSawTransparency(PR_FALSE)
 {
   // Clear out the structure, excluding the arrays
   memset(&mGIFStruct, 0, sizeof(mGIFStruct));
@@ -380,6 +381,11 @@ void nsGIFDecoder2::EndImageFrame()
 				  mGIFStruct.screen_height - realFrameHeight);
       mObserver->OnDataAvailable(nsnull, mImageFrame, &r);
     }
+    // This transparency check is only valid for first frame
+    if (mGIFStruct.is_transparent && !mSawTransparency) {
+      nsCOMPtr<nsIImage> img(do_GetInterface(mImageFrame));
+      img->SetHasNoAlpha();
+    }
   }
   mCurrentRow = mLastFlushedRow = -1;
   mCurrentPass = mLastFlushedPass = 0;
@@ -458,6 +464,17 @@ PRUint32 nsGIFDecoder2::OutputRow()
       *--to = cmap[*--from];
     }
   
+    // check for alpha (only for first frame)
+    if (mGIFStruct.is_transparent && !mSawTransparency) {
+      const PRUint32 *rgb = (PRUint32*)rowp;
+      for (PRUint32 i = mGIFStruct.width; i > 0; i--) {
+        if (*rgb++ == 0) {
+          mSawTransparency = PR_TRUE;
+          break;
+        }
+      }
+    }
+
     // Duplicate rows
     if (drow_end > drow_start) {
       // irow is the current row filled

modules/libpr0n/decoders/gif/nsGIFDecoder2.h

@@ -99,6 +99,7 @@ private:
   PRUint8 mCurrentPass;
   PRUint8 mLastFlushedPass;
   PRPackedBool mGIFOpen;
+  PRPackedBool mSawTransparency;
 
   gif_struct mGIFStruct;
 };