Bug 346150 Fix setting an image as wallpaper in Cairo builds

patch by bugzilla@mcsmurf.de r=jag sr=jag

xpfe/components/winhooks/nsWindowsHooks.cpp

@@ -847,34 +847,38 @@ WriteBitmap(nsIFile* aFile, gfxIImageFrame* aImage)
   
   PRUint8* bits;
   PRUint32 length;
+  aImage->LockImageData();
   aImage->GetImageData(&bits, &length);
-  if (!bits) return NS_ERROR_FAILURE;
-  
+  if (!bits) {
+      aImage->UnlockImageData();
+      return NS_ERROR_FAILURE;
+  }
+ 
   PRUint32 bpr;
   aImage->GetImageBytesPerRow(&bpr);
   PRInt32 bitCount = bpr/width;
   
   // initialize these bitmap structs which we will later
   // serialize directly to the head of the bitmap file
-  LPBITMAPINFOHEADER bmi = (LPBITMAPINFOHEADER)new BITMAPINFO;
-  bmi->biSize = sizeof(BITMAPINFOHEADER);
-  bmi->biWidth = width;
-  bmi->biHeight = height;
-  bmi->biPlanes = 1;
-  bmi->biBitCount = (WORD)bitCount*8;
-  bmi->biCompression = BI_RGB;
-  bmi->biSizeImage = 0; // don't need to set this if bmp is uncompressed
-  bmi->biXPelsPerMeter = 0;
-  bmi->biYPelsPerMeter = 0;
-  bmi->biClrUsed = 0;
-  bmi->biClrImportant = 0;
+  BITMAPINFOHEADER bmi;
+  bmi.biSize = sizeof(BITMAPINFOHEADER);
+  bmi.biWidth = width;
+  bmi.biHeight = height;
+  bmi.biPlanes = 1;
+  bmi.biBitCount = (WORD)bitCount*8;
+  bmi.biCompression = BI_RGB;
+  bmi.biSizeImage = length;
+  bmi.biXPelsPerMeter = 0;
+  bmi.biYPelsPerMeter = 0;
+  bmi.biClrUsed = 0;
+  bmi.biClrImportant = 0;
   
   BITMAPFILEHEADER bf;
   bf.bfType = 0x4D42; // 'BM'
   bf.bfReserved1 = 0;
   bf.bfReserved2 = 0;
   bf.bfOffBits = sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER);
-  bf.bfSize = bf.bfOffBits + bmi->biSizeImage;
+  bf.bfSize = bf.bfOffBits + bmi.biSizeImage;
 
   // get a file output stream
   nsresult rv;
@@ -888,17 +892,34 @@ WriteBitmap(nsIFile* aFile, gfxIImageFrame* aImage)
     PRUint32 written;
     stream->Write((const char*)&bf, sizeof(BITMAPFILEHEADER), &written);
     if (written == sizeof(BITMAPFILEHEADER)) {
-      stream->Write((const char*)bmi, sizeof(BITMAPINFOHEADER), &written);
+      stream->Write((const char*)&bmi, sizeof(BITMAPINFOHEADER), &written);
       if (written == sizeof(BITMAPINFOHEADER)) {
+#ifndef MOZ_CAIRO_GFX
         stream->Write((const char*)bits, length, &written);
         if (written == length)
           rv = NS_OK;
+#else
+        // write out the image data backwards because the desktop won't
+        // show bitmaps with negative heights for top-to-bottom
+        PRUint32 i = length;
+        rv = NS_OK;
+        do {
+          i -= bpr;
+
+          stream->Write(((const char*)bits) + i, bpr, &written);
+          if (written != bpr) {
+            rv = NS_ERROR_FAILURE;
+            break;
+          }
+        } while (i != 0);
+#endif
       }
     }
   
     stream->Close();
   }
-  
+
+  aImage->UnlockImageData(); 
   return rv;
 }