[GTK] REGRESSION: Broken scrolling on element.io with async scrolling

[Alice Mikhaylenko]

Created attachment 421176 [details]
Screen recording

See the recording. It's reproducible with http://svn.webkit.org/repository/webkit/trunk@273230. though it started a lot earlier.

I'm pretty sure it can be reproduced elsewhere, and maybe even already has a bug filed, but can't find anything right now.

[Alice Mikhaylenko]

Created attachment 421178 [details]
Screenshot of a zoomed in page

Oh, I've missed a very important detail: it seems to only happen on HiDPI OR when the page is zoomed in via pinch zoom.

[Alice Mikhaylenko]

Seems it also happens in the inspector, in the "All Layers" list.

[Alice Mikhaylenko]

Found the cause. In `Source/WebCore/platform/graphics/texmap/TextureMapperLayer.cpp`, 

```cpp
        clipTransform.translate(options.offset.width() + m_state.boundsOrigin.x(),
            options.offset.height() + m_state.boundsOrigin.y());
```

the origin coords should be multiplied by the scale factors (both page and device).

[Chris Lord]

Created attachment 429280 [details]
Patch

[Alice Mikhaylenko]

I can confirm it works, both with scale factor and page zooming.

[EWS]

Committed r277855 (237997@main): <https://commits.webkit.org/237997@main>

All reviewed patches have been landed. Closing bug and clearing flags on attachment 429280 [details].