Introduce XGetImage() for GrabWindowSnapshot() in ChromeOS.

ui/aura/root_window_host_linux.cc

Index: ui/aura/root_window_host_linux.cc
diff --git a/ui/aura/root_window_host_linux.cc b/ui/aura/root_window_host_linux.cc
index 4f42775ff14aa9e8c40e44b6a4b72b2f86672dab..97e8c0d68b6f972bdcc9bfb4b06913bf8a7fef3c 100644
--- a/ui/aura/root_window_host_linux.cc
+++ b/ui/aura/root_window_host_linux.cc
@@ -6,6 +6,7 @@
 
 #include <X11/Xatom.h>
 #include <X11/Xcursor/Xcursor.h>
+#include <X11/Xlib.h>
 #include <X11/cursorfont.h>
 #include <X11/extensions/XInput2.h>
 #include <X11/extensions/Xfixes.h>
@@ -29,6 +30,7 @@
 #include "ui/base/view_prop.h"
 #include "ui/base/x/x11_util.h"
 #include "ui/compositor/layer.h"
+#include "ui/gfx/codec/png_codec.h"
 #include "ui/gfx/image/image.h"
 
 using std::max;
@@ -804,6 +806,25 @@ void RootWindowHostLinux::SetFocusWhenShown(bool focus_when_shown) {
   }
 }
 
+bool RootWindowHostLinux::GrabSnapshot(
+    std::vector<unsigned char>* png_representation,
+    const gfx::Rect& snapshot_bounds) {
+  XImage* image = XGetImage(
+      xdisplay_, xwindow_,
+      snapshot_bounds.x(), snapshot_bounds.y(),
+      snapshot_bounds.width(), snapshot_bounds.height(),
+      AllPlanes, ZPixmap);
+
+  unsigned char* data = reinterpret_cast<unsigned char*>(image->data);
+  gfx::PNGCodec::Encode(data, gfx::PNGCodec::FORMAT_BGRA,

[Daniel Erat, 2012/05/15 23:35:08]

I don't think it's safe to assume the image format like this.  In the old X
window manager for Chrome OS, I had to check byte_order to determine whether it
was BGR or RGB:

http://git.chromium.org/gitweb/?p=chromiumos/platform/window_manager.git;a=bl...

[Jun Mukai, 2012/05/16 18:07:43]

Wrote a simple detector.  Thanks for pointing.

+                        snapshot_bounds.size(),
+                        image->width * image->bits_per_pixel / 8,
+                        true, std::vector<gfx::PNGCodec::Comment>(),
+                        png_representation);
+  XFree(image);
+  return true;
+}
+
 void RootWindowHostLinux::PostNativeEvent(
     const base::NativeEvent& native_event) {
   DCHECK(xwindow_);