Calling scroll() on an element which is not rendered (by a parent with
display: none) would previously cause a crash. In fact, we should
terminate the algorithm
[https://drafts.csswg.org/cssom-view/#dom-element-scroll] at step 10 in
this situation.
The fix hinges on implementing Element::has_css_layout_box() correctly,
rather than just returning true in all cases as we did previously.
Fixes#19430.
Unify background placement code
Merges the implementations for background-image placement
from gradients and images. Add missing parts and fix bugs.
Now supported are the CSS properties:
* background-attachment (except for local value, see #19650)
* background-clip
* background-origin
* background-position-x/y
* background-repeat
* background-size
It should be noted that backgrounds are not clipped to
rounded border corners.
(This was done before but worked only in simple cases)
See: #19649
This solves the following issues:
closes#19626closes#16657closes#19482 (examples from http://lea.verou.me/css3patterns/ are rendered perfectly but the round border is completely ignored now)
closes#19577
- `./mach build -d` does not report any errors
- `./mach test-tidy` does not report any errors
I enabled a few tests with the first commit but I have written about a dozen manual tests I will try to turn into ref tests either before or after this patch lands.
@bors-servo try
The relationship between the different inputs is visualized in this flowchart:

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Use background-size, background-position properties to render
CSS gradients.
Some cleanup in display_list_builder.rs related to gradient
calculations.
Adds two wpt tests for tiled gradients.
Note: For now even gradients with background-repeat: no-repeat
are repeated. Sometimes the gradient is not repeated everywhere.
Enable vars-background-shorthand-001.html CSS test.