[Webkit-unassigned] [Bug 169094] [GTK] Rendering glitches in HiDPI in long GitHub Gist pages when focusing the comments textarea

bugzilla-daemon at webkit.org bugzilla-daemon at webkit.org
Sun Apr 9 05:10:48 PDT 2017


Gwang Yoon Hwang <yoon at igalia.com> changed:

           What    |Removed                     |Added
                 CC|                            |yoon at igalia.com

--- Comment #4 from Gwang Yoon Hwang <yoon at igalia.com> ---
This bug was reported to occur only at the HiDPI rendering case. However, when
I made a minimal test case, the test runner with a 1.0 scaled Weston instance
could reproduce this problem.

This bug happens when we are drawing the border of the inline box which has a
complex border (such as dashed, dotted..) with a border radius property.

When we made a change inside of text box, for example, typing space, we are 
going to invalidate the area of the inline box.

While rendering decorations of the render box,
RenderBoxModelObject::paintBorder defines a clip out region to prepare the inner
border to avoid the background bleeding out behind the border.

We are facing a problem from now on. 

The RenderBoxModelObject is going to make a clip to render each side of the
border area. But when we apply this clipping to the cairo context, it seems
cairo context looses the previous clipped out area, which was defined to avoid

It is okay when we draw dashed border side since it is a stroke. But when we
draw a solid border side, it uses fill operation which would fill the whole
quad of the border side with a border color.

I tried to make simple cairo problem to reproduce the problem but it is not so
successful so far.

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