Create an X window overlay with static ID for GL contexts.

This code creates an X window that overlays where tab contents are drawn. The handle associated with this window never changes (unlike the X window associated with a GTK widget that is created and destroyed whenever the widget is realized and unrealized respectively).  This is helpful when creating a GL context associated with an X window. Also, having a floating overlay allows us to handle detaching GPU accelerated tabs.

This code seems to have uncovered a race condition within the GPU process. When a tab that uses accelerated compositing is detached (e.g. http://webkit.org/blog/386/3d-transforms/), the tab contents often don't get displayed even though the tab is redrawn.  A slight delay of about 100ms in the GPU process on the call to glXSwapBuffers (in gl_context_linux.cc) fixes this. To witness that GL can draw to the overlay after delay, try it with a tab with constant animation (e.g. http://webkit.org/blog-files/3d-transforms/poster-circle.html).

I've written a bare bones test (about 150 lines of C) of the overlay technique, and it requires no such delay b/w reparenting the glXSwapBuffers. I've also confirmed that there is no synchronization issues w.r.t. the X server between my patch and GL draw commands. I propose filing a new bug for the race, if this patch gets accepted.

BUG=53345,56419
TEST=Open two tabs, one with GPU rendered content (http://webkit.org/blog/386/3d-transforms/). Detach the tab with GPU rendered content.  GPU process shouldn't crash.

Review URL: http://codereview.chromium.org/3509004
Patch from Jonathan Backer <backer@google.com>.

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@61561 0039d316-1c4b-4281-b951-d872f2087c98

0 files changed, 0 insertions, 0 deletions