Bug 23170 – [Transforms] Hit test issue with large scale() transform

• Component: Layout and Rendering
• Status: RESOLVED FIXED

[Simon Fraser (smfr)]

The attached testcase shows a hit testing issue when an element has a large scale() transform. This is probably a rounding issue.

[Simon Fraser (smfr)]

<rdar://problem/6478048>

[Simon Fraser (smfr)]

Created attachment 26500 [details]
Testcase

[Simon Fraser (smfr)]

To fix this we need to use FloatPoints for hit testing in RenderLayer, and down through RenderObject::hitTest() and RenderObject::nodeAtPoint().

[Allan Sandfeld Jensen]

(In reply to comment #3)
> To fix this we need to use FloatPoints for hit testing in RenderLayer, and down through RenderObject::hitTest() and RenderObject::nodeAtPoint().

Since I added support for transforms to rect-based hit-testing we actually have a floatpoint copy of the point, which is used whenever new transforms are applied.

[Allan Sandfeld Jensen]

Actually this bug does and did not depend on subpixel layout at all. This is all caused by bad rounding. Once the bad rounding is scaled up x60, the last 30px in width and height becomes unhittable.

[Allan Sandfeld Jensen]

Created attachment 156054 [details]
Patch

[WebKit Review Bot]

Comment on attachment 156054 [details]
Patch

Attachment 156054 [details] did not pass chromium-ews (chromium-xvfb):
Output: http://queues.webkit.org/results/13430027

New failing tests:
css1/box_properties/margin_right.html
css2.1/t0803-c5502-mrgn-r-01-c-a.html
css2.1/20110323/absolute-non-replaced-width-007.htm
css1/box_properties/float_elements_in_series.html
css2.1/t0804-c5507-padn-r-01-c-a.html
css1/box_properties/clear_float.html
compositing/reflections/deeply-nested-reflections.html
compositing/reflections/nested-reflection.html
compositing/reflections/nested-reflection-anchor-point.html
css2.1/t0804-c5507-padn-r-00-c-ag.html
compositing/reflections/nested-reflection-transformed2.html
compositing/rtl/rtl-fixed.html
css2.1/20110323/absolute-non-replaced-width-009.htm
compositing/reflections/reflection-ordering.html
css2.1/20110323/absolute-non-replaced-width-012.htm
compositing/reflections/nested-reflection-size-change.html
css2.1/20110323/absolute-non-replaced-width-021.htm
compositing/shadows/shadow-drawing.html
compositing/reflections/nested-reflection-mask-change.html
css2.1/20110323/absolute-non-replaced-width-005.htm
compositing/reflections/nested-reflection-transformed.html
compositing/rtl/rtl-absolute.html
css1/box_properties/float_on_text_elements.html
css1/text_properties/text_align.html
css2.1/20110323/absolute-non-replaced-width-002.htm
compositing/reflections/nested-reflection-opacity.html
css2.1/t0803-c5502-mrgn-r-00-c-ag.html
compositing/reflections/nested-reflection-animated.html

[WebKit Review Bot]

Created attachment 156100 [details]
Archive of layout-test-results from gce-cr-linux-03

The attached test failures were seen while running run-webkit-tests on the chromium-ews.
Bot: gce-cr-linux-03  Port: <class 'webkitpy.common.config.ports.ChromiumXVFBPort'>  Platform: Linux-2.6.39-gcg-201203291735-x86_64-with-Ubuntu-10.04-lucid

[Allan Sandfeld Jensen]

Comment on attachment 156054 [details]
Patch

Needs move investigation, and I will probably leave some of the bugs unfixed to minimize the number of affected test-cases.

[Allan Sandfeld Jensen]

Created attachment 156306 [details]
Patch

Corrected mistake in FractionalLayoutUnit::floor, that resulted in many 1px differences.

[WebKit Review Bot]

Comment on attachment 156306 [details]
Patch

Attachment 156306 [details] did not pass chromium-ews (chromium-xvfb):
Output: http://queues.webkit.org/results/13431312

New failing tests:
fast/block/float/overhanging-tall-block.html
transforms/3d/hit-testing/perspective-clipped.html
fast/html/details-writing-mode.html

[WebKit Review Bot]

Created attachment 156337 [details]
Archive of layout-test-results from gce-cr-linux-06

The attached test failures were seen while running run-webkit-tests on the chromium-ews.
Bot: gce-cr-linux-06  Port: <class 'webkitpy.common.config.ports.ChromiumXVFBPort'>  Platform: Linux-2.6.39-gcg-201203291735-x86_64-with-Ubuntu-10.04-lucid

[WebKit Review Bot]

Comment on attachment 156306 [details]
Patch

Attachment 156306 [details] did not pass chromium-ews (chromium-xvfb):
Output: http://queues.webkit.org/results/13431336

New failing tests:
fast/block/float/overhanging-tall-block.html
transforms/3d/hit-testing/perspective-clipped.html
fast/html/details-writing-mode.html

[WebKit Review Bot]

Created attachment 156357 [details]
Archive of layout-test-results from gce-cr-linux-03

The attached test failures were seen while running run-webkit-tests on the chromium-ews.
Bot: gce-cr-linux-03  Port: <class 'webkitpy.common.config.ports.ChromiumXVFBPort'>  Platform: Linux-2.6.39-gcg-201203291735-x86_64-with-Ubuntu-10.04-lucid

[Allan Sandfeld Jensen]

Created attachment 156362 [details]
Patch

Skip two bening changes in Chromium, and modified one test that was incorrect under higher accuracy

[Build Bot]

Comment on attachment 156362 [details]
Patch

Attachment 156362 [details] did not pass mac-ews (mac):
Output: http://queues.webkit.org/results/13423895

New failing tests:
fast/block/float/overhanging-tall-block.html

[Build Bot]

Created attachment 156430 [details]
Archive of layout-test-results from apple-mac-5

The attached test failures were seen while running run-webkit-tests on the mac-ews.
Bot: apple-mac-5  Port: <class 'webkitpy.common.config.ports.MacPort'>  Platform: Mac OS X 10.7.4

[Allan Sandfeld Jensen]

(In reply to comment #16)
> (From update of attachment 156362 [details])
> Attachment 156362 [details] did not pass mac-ews (mac):
> Output: http://queues.webkit.org/results/13423895
> 
> New failing tests:
> fast/block/float/overhanging-tall-block.html

I will update the mac baseline before landing, but will leave the current patch for review. The logic behind it is unchanged.

[Allan Sandfeld Jensen]

I have split the part of the patch out that corrects floored rounding into bug #93475 and uploaded a patch there. 

The patch here will need to be rebased once that lands. The only remaining part of the patch will be the changes in HitTestResult.cpp.

[Allan Sandfeld Jensen]

Created attachment 157684 [details]
Patch

[WebKit Review Bot]

Comment on attachment 157684 [details]
Patch

Clearing flags on attachment: 157684

Committed r125306: <http://trac.webkit.org/changeset/125306>

[WebKit Review Bot]

All reviewed patches have been landed.  Closing bug.