Browsers such as Chrome and Firefox apply an arbitrary scale to the
current font size if `normal` is used for `line-height`. Firefox uses
1.2 while Chrome uses 1.15. Let's go with the latter for now, it's
relatively easy to change if we ever want to go back on that decision.
This also requires updating the expectations for a lot of layout tests.
The upside of this is that it's a bit easier to compare our layout
results to other browsers', especially Chrome.
This reverts commit a73cd88f0c.
Emitting SaveLayer for each paintable made rasterization a lot slower
on every website because now Skia has to allocate enormous amounts of
temporary surfaces. Let's revert it for now and figure how to implement
it with less aggressive SaveLayer usage.
This improves the quality of our font rendering, especially when
animations are involved. Relevant changes:
* Skia fonts have their subpixel flag set, which means that individual
glyphs are rendered at subpixel offsets causing glyph runs as a
whole to look better.
* Fragment offsets are no longer rounded to whole device pixels, and
instead the floating point offset is kept. This allows us to pass
through the floating point baseline position all the way to the Skia
calls, which already expected that to be a float position.
The `scrollable-contains-table.html` ref test needed different table
headings since they would slightly inflate the column size in the test
file, but not the reference.
The main incentive is much better performance. We could have gone a bit
further in optimizing the Skia painter to blit glyphs produced by LibGfx
more efficiently from the glyph atlas, but eventually, we also want Skia
to improve correctness.
This change does not completely replace LibGfx in text handling. It's
still used at all stages, including layout, up until display list
replaying.
Before this change, "background-clip: text" was implemented by saving a
Vector<Gfx::Path> of all glyphs needed to paint a mask for the
background. The issue with this approach was that once glyphs were
extracted into vector paths, the glyph rasterization cache could no
longer be utilized.
With this change, all text required for mask painting is saved in a
nested display list and rasterized as a regular text.
With this change, instead of recording a display list item for each
instance of a repeated background, a new DrawRepeatedImmutableBitmap
type is used. This allows the painter to use optimized repeated image
painting and, when the GPU backend is used, avoid re-uploading the image
texture for each repetition.
Some screenshot tests are affected, but there are no visible
regressions.
https://null.com/games/chainstaff works a lof faster with this change.
Skia painter is visibly faster than LibGfx painter and has more complete
CSS transforms support. With this change:
- On Linux, it will try to use Vulkan-backend with fallback to
CPU-backend
- On macOS it will try to use Metal-backend with fallback to
CPU-backend
- headless-browser always runs with CPU-backend in layout mode
This change will make it easier to disable screenshot comparison tests
on a specific platform or have per-platform expectations.
Additionally, it's nice to be able to tell if a ref-test uses a
screenshot as an expectation by looking at the test path.
