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:
<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/19651)
<!-- Reviewable:end -->
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.
