Don't paint empty scrollbar parts

Don't paint empty scrollbar parts

BUG=496846
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=196610

[Xianzhu, 2015-06-05 20:42:03]

wangxianzhu@chromium.org changed reviewers:
+ chrishtr@chromium.org, pdr@chromium.org

[chrishtr, 2015-06-05 22:50:09]

https://codereview.chromium.org/1154993004/diff/1/Source/core/paint/Scrollabl...
File Source/core/paint/ScrollableAreaPainter.cpp (right):

https://codereview.chromium.org/1154993004/diff/1/Source/core/paint/Scrollabl...
Source/core/paint/ScrollableAreaPainter.cpp:31: if
(!absRect.intersects(damageRect))
Why is this ok? I thought we had to paint all or none now?

[chrishtr, 2015-06-05 22:50:09]

https://codereview.chromium.org/1154993004/diff/1/Source/core/paint/Scrollabl...
File Source/core/paint/ScrollableAreaPainter.cpp (right):

https://codereview.chromium.org/1154993004/diff/1/Source/core/paint/Scrollabl...
Source/core/paint/ScrollableAreaPainter.cpp:31: if
(!absRect.intersects(damageRect))
Why is this ok? I thought we had to paint all or none now?

[Xianzhu, 2015-06-05 22:56:55]

https://codereview.chromium.org/1154993004/diff/1/Source/core/paint/Scrollabl...
File Source/core/paint/ScrollableAreaPainter.cpp (right):

https://codereview.chromium.org/1154993004/diff/1/Source/core/paint/Scrollabl...
Source/core/paint/ScrollableAreaPainter.cpp:31: if
(!absRect.intersects(damageRect))
On 2015/06/05 22:50:09, chrishtr wrote:
> Why is this ok? I thought we had to paint all or none now?

We paint all or none for non-custom parts. For custom parts, we paint them as
normal LayoutBlocks which use the custom layout objects as display item clients.

[chrishtr, 2015-06-05 22:59:11]

https://codereview.chromium.org/1154993004/diff/1/Source/core/paint/Scrollabl...
File Source/core/paint/ScrollableAreaPainter.cpp (right):

https://codereview.chromium.org/1154993004/diff/1/Source/core/paint/Scrollabl...
Source/core/paint/ScrollableAreaPainter.cpp:31: if
(!absRect.intersects(damageRect))
On 2015/06/05 at 22:56:54, Xianzhu wrote:
> On 2015/06/05 22:50:09, chrishtr wrote:
> > Why is this ok? I thought we had to paint all or none now?
> 
> We paint all or none for non-custom parts. For custom parts, we paint them as
normal LayoutBlocks which use the custom layout objects as display item clients.

OK, then...

https://codereview.chromium.org/1154993004/diff/1/Source/core/paint/Scrollabl...
Source/core/paint/ScrollableAreaPainter.cpp:37: if
(!RuntimeEnabledFeatures::slimmingPaintEnabled() &&
!absRect.intersects(damageRect))
Why condition on slimming paint here?

[Xianzhu, 2015-06-05 23:04:41]

https://codereview.chromium.org/1154993004/diff/1/Source/core/paint/Scrollabl...
File Source/core/paint/ScrollableAreaPainter.cpp (right):

https://codereview.chromium.org/1154993004/diff/1/Source/core/paint/Scrollabl...
Source/core/paint/ScrollableAreaPainter.cpp:37: if
(!RuntimeEnabledFeatures::slimmingPaintEnabled() &&
!absRect.intersects(damageRect))
On 2015/06/05 22:59:11, chrishtr wrote:
> Why condition on slimming paint here?

This is the non-custom path. In slimming paint mode, we need to paint the whole
part regardless of damageRect.

(This has the same logic as paintScrollCorner. I missed this method in
https://codereview.chromium.org/1142283006/).

[chrishtr, 2015-06-05 23:10:09]

The CQ bit was checked by chrishtr@chromium.org

[chrishtr, 2015-06-05 23:10:10]

lgtm

[commit-bot: I haz the power, 2015-06-05 23:10:35]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1154993004/1

[commit-bot: I haz the power, 2015-06-05 23:13:52]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=196610