Send array of paint rects and bitmaps as opposed to a Union

chrome/browser/renderer_host/backing_store_x.cc

Index: chrome/browser/renderer_host/backing_store_x.cc
===================================================================
--- chrome/browser/renderer_host/backing_store_x.cc	(revision 17347)
+++ chrome/browser/renderer_host/backing_store_x.cc	(working copy)
@@ -77,17 +77,23 @@
 }
 
 void BackingStore::PaintRectWithoutXrender(TransportDIB* bitmap,
-                                           const gfx::Rect &bitmap_rect) {
-  const int width = bitmap_rect.width();
-  const int height = bitmap_rect.height();
-  Pixmap pixmap = XCreatePixmap(display_, root_window_, width, height,
-                                visual_depth_);
+                                           const gfx::Rect& bitmap_rect,
+                                           const gfx::Rect& paint_rect) {
+  DCHECK(bitmap_rect.Contains(paint_rect) &&
+         paint_rect.x() < kMaxBitmapLengthAllowed &&
+         paint_rect.y() < kMaxBitmapLengthAllowed);
+  const int paint_width = paint_rect.width();
+  const int paint_height = paint_rect.height();
+  Pixmap pixmap = XCreatePixmap(display_, root_window_, paint_width,
+                                paint_height, visual_depth_);
 
+  const int bitmap_width = bitmap_rect.width();
+  const int bitmap_height = bitmap_rect.height();
   XImage image;
   memset(&image, 0, sizeof(image));
 
-  image.width = width;
-  image.height = height;
+  image.width = bitmap_width;
+  image.height = bitmap_height;
   image.format = ZPixmap;
   image.byte_order = LSBFirst;
   image.bitmap_unit = 8;
@@ -96,16 +102,18 @@
   image.green_mask = 0xff00;
   image.blue_mask = 0xff0000;
 
+  const int x_offset = paint_rect.x() - bitmap_rect.x();
+  const int y_offset = paint_rect.y() - bitmap_rect.y();
   if (pixmap_bpp_ == 32) {
     // If the X server depth is already 32-bits, then our job is easy.
     image.depth = visual_depth_;
     image.bits_per_pixel = 32;
-    image.bytes_per_line = width * 4;
+    image.bytes_per_line = bitmap_width * 4;
     image.data = static_cast<char*>(bitmap->memory());
 
     XPutImage(display_, pixmap, static_cast<GC>(pixmap_gc_), &image,
-              0, 0 /* source x, y */, 0, 0 /* dest x, y */,
-              width, height);
+              x_offset, y_offset /* source x, y */, 0, 0 /* dest x, y */,
+              paint_width, paint_height);
   } else if (pixmap_bpp_ == 24) {
     // In this case we just need to strip the alpha channel out of each
     // pixel. This is the case which covers VNC servers since they don't
@@ -114,48 +122,64 @@
     // It's possible to use some fancy SSE tricks here, but since this is the
     // slow path anyway, we do it slowly.
 
-    uint8_t* bitmap24 = static_cast<uint8_t*>(malloc(3 * width * height));
+    uint8_t* bitmap24 = static_cast<uint8_t*>(malloc(3 * paint_width *
+                                                     paint_height));
     const uint32_t* bitmap_in = static_cast<const uint32_t*>(bitmap->memory());
-    for (int y = 0; y < height; ++y) {
-      for (int x = 0; x < width; ++x) {
+    const int x_limit = paint_rect.right() - bitmap_rect.x();
+    const int y_limit = paint_rect.bottom() - bitmap_rect.y();
+    const int row_length = bitmap_width;
+    bitmap_in += row_length * y_offset;
+    for (int y = y_offset; y < y_limit; ++y) {
+      bitmap_in += x_offset;
+      for (int x = x_offset; x < x_limit; ++x) {
         const uint32_t pixel = *(bitmap_in++);
         bitmap24[0] = (pixel >> 16) & 0xff;
         bitmap24[1] = (pixel >> 8) & 0xff;
         bitmap24[2] = pixel & 0xff;
         bitmap24 += 3;
       }
+      bitmap_in += row_length - x_limit;
     }
 
+    image.width = paint_width;
+    image.height = paint_height;
     image.depth = visual_depth_;
     image.bits_per_pixel = 24;
-    image.bytes_per_line = width * 3;
+    image.bytes_per_line = paint_width * 3;
     image.data = reinterpret_cast<char*>(bitmap24);
 
     XPutImage(display_, pixmap, static_cast<GC>(pixmap_gc_), &image,
               0, 0 /* source x, y */, 0, 0 /* dest x, y */,
-              width, height);
+              paint_width, paint_height);
 
     free(bitmap24);
   } else if (pixmap_bpp_ == 16) {
     // Some folks have VNC setups which still use 16-bit visuals and VNC
     // doesn't include Xrender.
 
-    uint16_t* bitmap16 = static_cast<uint16_t*>(malloc(2 * width * height));
+    uint16_t* bitmap16 = static_cast<uint16_t*>(malloc(2 * paint_width *
+                                                       paint_height));
     uint16_t* const orig_bitmap16 = bitmap16;
     const uint32_t* bitmap_in = static_cast<const uint32_t*>(bitmap->memory());
-    for (int y = 0; y < height; ++y) {
-      for (int x = 0; x < width; ++x) {
+    const int x_limit = paint_rect.right() - bitmap_rect.x();
+    const int y_limit = paint_rect.bottom() - bitmap_rect.y();
+    const int row_length = bitmap_width;
+    bitmap_in += row_length * y_offset;
+    for (int y = y_offset; y < y_limit; ++y) {
+      bitmap_in += x_offset;
+      for (int x = x_offset; x < x_limit; ++x) {
         const uint32_t pixel = *(bitmap_in++);
         uint16_t out_pixel = ((pixel >> 8) & 0xf800) |
                              ((pixel >> 5) & 0x07e0) |
                              ((pixel >> 3) & 0x001f);
         *(bitmap16++) = out_pixel;
       }
+      bitmap_in += row_length - x_limit;
     }
 
     image.depth = visual_depth_;
     image.bits_per_pixel = 16;
-    image.bytes_per_line = width * 2;
+    image.bytes_per_line = paint_width * 2;
     image.data = reinterpret_cast<char*>(orig_bitmap16);
 
     image.red_mask = 0xf800;
@@ -164,7 +188,7 @@
 
     XPutImage(display_, pixmap, static_cast<GC>(pixmap_gc_), &image,
               0, 0 /* source x, y */, 0, 0 /* dest x, y */,
-              width, height);
+              paint_width, paint_height);
     free(orig_bitmap16);
   } else {
     CHECK(false) << "Sorry, we don't support your visual depth without "
@@ -174,15 +198,19 @@
 
   XCopyArea(display_, pixmap /* source */, pixmap_ /* target */,
             static_cast<GC>(pixmap_gc_),
-            0, 0 /* source x, y */, bitmap_rect.width(), bitmap_rect.height(),
-            bitmap_rect.x(), bitmap_rect.y() /* dest x, y */);
+            0, 0 /* source x, y */, paint_width, paint_height,
+            paint_rect.x(), paint_rect.y() /* dest x, y */);
 
   XFreePixmap(display_, pixmap);
 }
 
 void BackingStore::PaintRect(base::ProcessHandle process,
                              TransportDIB* bitmap,
-                             const gfx::Rect& bitmap_rect) {
+                             const gfx::Rect& bitmap_rect,
+                             const gfx::Rect& paint_rect) {
+  DCHECK(bitmap_rect.Contains(paint_rect) &&
+         paint_rect.x() < kMaxBitmapLengthAllowed &&
+         paint_rect.y() < kMaxBitmapLengthAllowed);
   if (!display_)
     return;
 
@@ -190,10 +218,16 @@
     return;
 
   if (!use_render_)
-    return PaintRectWithoutXrender(bitmap, bitmap_rect);
+    return PaintRectWithoutXrender(bitmap, bitmap_rect, paint_rect);
 
-  const int width = bitmap_rect.width();
-  const int height = bitmap_rect.height();
+  const int paint_width = paint_rect.width();
+  const int paint_height = paint_rect.height();
+
+  // The values for the position of the source rect within the bitmap when
+  // we render the composite depends on the usage of shared memory or not.
+  int src_x = 0;
+  int src_y = 0;
+
   Picture picture;
   Pixmap pixmap;
 
@@ -211,8 +245,11 @@
     // difference between the |data| pointer and the address of the mapping in
     // |shminfo|. Since both are NULL, the offset will be calculated to be 0,
     // which is correct for us.
-    pixmap = XShmCreatePixmap(display_, root_window_, NULL, &shminfo, width,
-                              height, 32);
+    pixmap = XShmCreatePixmap(display_, root_window_, NULL, &shminfo,
+                              bitmap_rect.width(), bitmap_rect.height(), 32);
+    // Since we use the whole source bitmap, we must offset the source.
+    src_x = paint_rect.x() - bitmap_rect.x();
+    src_y = paint_rect.y() - bitmap_rect.y();
   } else {
     // No shared memory support, we have to copy the bitmap contents to the X
     // server. Xlib wraps the underlying PutImage call behind several layers of
@@ -221,34 +258,36 @@
     XImage image;
     memset(&image, 0, sizeof(image));
 
-    image.width = width;
-    image.height = height;
+    image.width = paint_width;
+    image.height = paint_height;
     image.depth = 32;
     image.bits_per_pixel = 32;
     image.format = ZPixmap;
     image.byte_order = LSBFirst;
     image.bitmap_unit = 8;
     image.bitmap_bit_order = LSBFirst;
-    image.bytes_per_line = width * 4;
+    image.bytes_per_line = paint_width * 4;
     image.red_mask = 0xff;
     image.green_mask = 0xff00;
     image.blue_mask = 0xff0000;
+    // TODO(agl): check if we can make this more efficient.
     image.data = static_cast<char*>(bitmap->memory());
 
-    pixmap = XCreatePixmap(display_, root_window_, width, height, 32);
+    pixmap = XCreatePixmap(display_, root_window_, paint_width, paint_height,
+                           32);
     GC gc = XCreateGC(display_, pixmap, 0, NULL);
-    XPutImage(display_, pixmap, gc, &image,
-              0, 0 /* source x, y */, 0, 0 /* dest x, y */,
-              width, height);
+    XPutImage(display_, pixmap, gc, &image, paint_rect.x() - bitmap_rect.x(),
+              paint_rect.y() - bitmap_rect.y() /* source x, y */,
+               0, 0 /* dest x, y */, paint_width, paint_height);
     XFreeGC(display_, gc);
   }
 
   picture = x11_util::CreatePictureFromSkiaPixmap(display_, pixmap);
   XRenderComposite(display_, PictOpSrc, picture /* source */, 0 /* mask */,
-                   picture_ /* dest */, 0, 0 /* source x, y */,
+                   picture_ /* dest */, src_x, src_y /* source x, y */,
                    0, 0 /* mask x, y */,
-                   bitmap_rect.x(), bitmap_rect.y() /* target x, y */,
-                   width, height);
+                   paint_rect.x(), paint_rect.y() /* target x, y */,
+                   paint_width, paint_height);
 
   // In the case of shared memory, we wait for the composite to complete so that
   // we are sure that the X server has finished reading.
@@ -295,7 +334,7 @@
     }
   }
 
-  PaintRect(process, bitmap, bitmap_rect);
+  PaintRect(process, bitmap, bitmap_rect, bitmap_rect);
 }
 
 void BackingStore::ShowRect(const gfx::Rect& rect, XID target) {