If Metal context and IOSurface are available, Skia painter will use
Ganesh GPU backend on macOS, which is noticeably faster than the default
CPU backend.
Painting pipeline:
1. (WebContent) Allocate IOSurface for backing store
2. (WebContent) Allocate MTLTexture that wraps IOSurface
3. (WebContent) Paint into MTLTexture using Skia
4. (Browser) Wrap IOSurface into Gfx::Painter and use
QPainter/CoreGraphics to blit backing store into viewport.
Things we should improve in the future:
1. Upload textures for images in advance instead of doing that before
every repaint.
2. Teach AppKit client to read directly from IOSurface instead of
copying.
There is no functional change here, but they added an error message to
the install output to indicate what host tools need to be installed.
This has tripped some people up, so it seems worth updating to.
This change introduces Skia painter available under a flag. It's not
yet match capabilities of Gfx::Painter and is not ready to replace it.
Motivation:
- The current CPU painter is a performance bottleneck on most websites.
Our own GPU painter implementation is very immature and has received
relatively little attention.
- There is ongoing effort on building painter that supports affine
transforms (AffineCommandExecutorCPU) but it is far from being on par
with the default CPU painter. Skia will allow us to immediately get
full transformation support for all painting commands.
GPU painting:
I experimented with Ganesh GPU-backend, however profiling revealed that
without sharing viewport texture between WebContent and Browser
processes, it won't bring much performance improvement compared to
CPU-backend. Therefore, I decided to keep this PR focused on
implementing most of painting commands and switch to GPU-backend in
future changes.
Text rendring:
Skia painter uses glyph bitmaps produced by LibGfx. Using Skia for text
rendering will require large refactoring of the font rendering
subsystem. Currently, it's impossible to construct SkFont right before
rendering because Gfx::VectorFont can't be serialized back into sequence
of bytes.
There is a problem with ugly include paths like:
`#include <core/SkBitmap.h>`.
I would prefer to have skia prefix in the path. There was an attempt to
fix that but PR was rejected https://github.com/microsoft/vcpkg/pull/32660
Regressions compared to Gfx::Painter:
- DrawText is not implemented
- PaintTextShadow is not implemented
- PaintRadialGradient and PaintLinearGradient do not support "transition
hints" and repeat length
- PaintConicGradient is not implemented
- DrawTriangleWave is not implemented
- DrawLine does not account for line style property
- DrawScaledBitmap and DrawScaledImmutableBitmap do not account for
scaling mode property
Rather than removing LibLocale entirely, we will use it as a wrapper
around ICU (which has some C-like interfaces, and uses UTF-16 for its
string types). Using ICU will provide better web compatibility overall,
and will let us implement features we were previously unable to (e.g.
Intl.Collator requires data that is not in the JSON export of the CLDR).
If we get a suggestion from fontconfig, we try those fonts first, before
falling back on the hard coded list of known suitable fonts for each
generic family.
This saves us the trouble of maintaining our own implementation,
and instantly brings us to full WOFF2 feature parity with others.
Co-Authored-By: Andrew Kaster <akaster@serenityos.org>
We will use sqlite3 as a replacement for LibSQL. Using a tried-and-true
database will allow us to avoid maintaining our an incomplete, non-ACID,
and less performant implementation. It also means we do not have to
launch and manage the singleton SQLServer process.
