[webkit-reviews] review requested: [Bug 93292] [Chromium] Pinch Zoom prototype tracking issue. : [Attachment 163466] Working V1 prototype.

[bugzilla-daemon at webkit.org]

Jeff Timanus <twiz at chromium.org> has asked  for review:
Bug 93292: [Chromium] Pinch Zoom prototype tracking issue.
https://bugs.webkit.org/show_bug.cgi?id=93292

Attachment 163466: Working V1 prototype.
https://bugs.webkit.org/attachment.cgi?id=163466&action=review

------- Additional Comments from Jeff Timanus <twiz at chromium.org>
Patch that corrects the screen-space scrolling issues that were present in
previous patches.  

The problem was that the page-scale was being applied to the scroll delta, but
because all scrolling is now in layout space, this factor is not needed.  Note
that I haven't tested this change extensively with --force-device-scale-factor,
so there may be lurking issues.

Given the previous comments on NPAPI scaling, I think that this patch
represents a reasonable state for an initial check-in, on which we can
iterate/bug-fix.  I'm thinking something along the lines of #if
USE(COMPOSITOR_PINCH_ZOOM) to selectively enable the patch.  I will need some
guidance on how to best test this behaviour.

I will start a separate patch to see if I can remove the use of
LayerChromium::boundsContainPageScale(...).  If we can submit this patch with a
conditional #define, then removing boundsContainPageScale may not be a strict
prerequisite.

Question:  Do we need to preserve the CSS-transform based pinch implementation,
even after this patch has fully landed and is enabled?