Clear root window when the aura root window is moved/resized

Clear root window when the aura root window is moved/resized

Without this, switching display may leave some content on other display.

BUG=152003
TEST=manual: Switch to external/internal monitor doesn't leave the content.
 Manually killed chrome (with /var/run/disable_chrome_restart) and confirmed that the content wasn't cleared.


Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=158757

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=158771

[Daniel Erat, 2012-09-25 19:10:57]

http://codereview.chromium.org/10981024/diff/1/ui/aura/root_window_host_linux.cc
File ui/aura/root_window_host_linux.cc (right):

http://codereview.chromium.org/10981024/diff/1/ui/aura/root_window_host_linux...
ui/aura/root_window_host_linux.cc:523: XSetWindowBackgroundPixmap(xdisplay_,
x_root_window_, None);
it's not obvious to me why this is necessary.  can we just set the root's
background to black at startup when we're running on chrome os and be done with
it?

[oshima, 2012-09-25 19:33:28]

http://codereview.chromium.org/10981024/diff/1/ui/aura/root_window_host_linux.cc
File ui/aura/root_window_host_linux.cc (right):

http://codereview.chromium.org/10981024/diff/1/ui/aura/root_window_host_linux...
ui/aura/root_window_host_linux.cc:523: XSetWindowBackgroundPixmap(xdisplay_,
x_root_window_, None);
On 2012/09/25 19:10:57, Daniel Erat wrote:
> it's not obvious to me why this is necessary.  can we just set the root's
> background to black at startup when we're running on chrome os and be done
with
> it?

According to @marcheu, we intentionally set background pixmap to None, to
to avoid flashing when chrome switching to guest mode, or restarting
chrome due to crash.

[Daniel Erat, 2012-09-25 19:54:41]

http://codereview.chromium.org/10981024/diff/1/ui/aura/root_window_host_linux.cc
File ui/aura/root_window_host_linux.cc (right):

http://codereview.chromium.org/10981024/diff/1/ui/aura/root_window_host_linux...
ui/aura/root_window_host_linux.cc:523: XSetWindowBackgroundPixmap(xdisplay_,
x_root_window_, None);
On 2012/09/25 19:33:28, oshima wrote:
> On 2012/09/25 19:10:57, Daniel Erat wrote:
> > it's not obvious to me why this is necessary.  can we just set the root's
> > background to black at startup when we're running on chrome os and be done
> with
> > it?
> 
> According to @marcheu, we intentionally set background pixmap to None, to
> to avoid flashing when chrome switching to guest mode, or restarting
> chrome due to crash.

Got it, thanks.  Wonder if it'd be cleaner to just use XFillRectangle() here. 
The downside is that you might need to create a GC first.  Yay X.

[oshima, 2012-09-25 20:45:09]

http://codereview.chromium.org/10981024/diff/1/ui/aura/root_window_host_linux.cc
File ui/aura/root_window_host_linux.cc (right):

http://codereview.chromium.org/10981024/diff/1/ui/aura/root_window_host_linux...
ui/aura/root_window_host_linux.cc:523: XSetWindowBackgroundPixmap(xdisplay_,
x_root_window_, None);
On 2012/09/25 19:54:41, Daniel Erat wrote:
> On 2012/09/25 19:33:28, oshima wrote:
> > On 2012/09/25 19:10:57, Daniel Erat wrote:
> > > it's not obvious to me why this is necessary.  can we just set the root's
> > > background to black at startup when we're running on chrome os and be done
> > with
> > > it?
> > 
> > According to @marcheu, we intentionally set background pixmap to None, to
> > to avoid flashing when chrome switching to guest mode, or restarting
> > chrome due to crash.
> 
> Got it, thanks.  Wonder if it'd be cleaner to just use XFillRectangle() here. 
> The downside is that you might need to create a GC first.  Yay X.

Done.

[Daniel Erat, 2012-09-25 20:50:57]

lgtm

[commit-bot: I haz the power, 2012-09-25 21:05:08]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/oshima@chromium.org/10981024/7001

[commit-bot: I haz the power, 2012-09-25 21:05:10]

Presubmit check for 10981024-7001 failed and returned exit status 1.


Running presubmit commit checks ...

** Presubmit ERRORS **
Missing LGTM from an OWNER for files in these directories:
    ui/aura

[oshima, 2012-09-25 21:21:14]

+sky for OWNERS

[sky, 2012-09-25 22:21:12]

LGTM

[commit-bot: I haz the power, 2012-09-26 03:02:30]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/oshima@chromium.org/10981024/7001

[commit-bot: I haz the power, 2012-09-26 06:20:27]

Change committed as 158757