b=480088; use a single cached data block for painting with image surfaces on Windows CE; r=stuart

widget/src/windows/nsWindow.cpp

@@ -169,6 +169,11 @@
 // out to the bounding-box if there are more
 #define MAX_RECTS_IN_REGION 100
 
+#ifdef PAINT_USE_IMAGE_SURFACE
+static nsAutoPtr<PRUint8> gSharedSurfaceData;
+static gfxIntSize gSharedSurfaceSize;
+#endif
+
 /*
  * WinCE helpers
  */
@@ -6075,10 +6080,37 @@ PRBool nsWindow::OnPaint(HDC aDC)
         targetSurface = new gfxWindowsSurface(hDC);
       }
 #elif defined(PAINT_USE_IMAGE_SURFACE)
+      if (!gSharedSurfaceData) {
+        gSharedSurfaceSize.height = GetSystemMetrics(SM_CYSCREEN);
+        gSharedSurfaceSize.width = GetSystemMetrics(SM_CXSCREEN);
+        gSharedSurfaceData = (PRUint8*) malloc(gSharedSurfaceSize.width * gSharedSurfaceSize.height * 4);
+      }
+
       gfxIntSize surfaceSize(ps.rcPaint.right - ps.rcPaint.left,
                              ps.rcPaint.bottom - ps.rcPaint.top);
-      nsRefPtr<gfxImageSurface> targetSurface = new gfxImageSurface(surfaceSize,
-                                                                    gfxASurface::ImageFormatRGB24);
+
+      nsRefPtr<gfxImageSurface> targetSurface;
+
+      if (!gSharedSurfaceData ||
+          surfaceSize.width > gSharedSurfaceSize.width ||
+          surfaceSize.height > gSharedSurfaceSize.height)
+      {
+#ifdef DEBUG_vladimir
+          RETAILMSG(1, (L"OnPaint: Paint area bigger than screen! Screen %dx%d, surface %dx%d, HWND %p\r\n", gSharedSurfaceSize.width, gSharedSurfaceSize.height, surfaceSize.width, surfaceSize.height, mWnd));
+#endif
+
+          // allocate a new oversize surface; hopefully this will just be a one-time thing,
+          // and we should really fix whatever's doing it!
+          targetSurface = new gfxImageSurface(surfaceSize, gfxASurface::ImageFormatRGB24);
+      } else {
+          // don't use the shared surface directly; instead, create a new one
+          // that just reuses its buffer.
+          targetSurface = new gfxImageSurface(gSharedSurfaceData.get(),
+                                              surfaceSize,
+                                              surfaceSize.width * 4,
+                                              gfxASurface::ImageFormatRGB24);
+      }
+
       if (targetSurface && !targetSurface->CairoStatus()) {
         targetSurface->SetDeviceOffset(gfxPoint(-ps.rcPaint.left, -ps.rcPaint.top));
       }