Stop converting between CSS and device pixels as part of rendering - the
display list should be as simple as possible, so convert to DevicePixels
once when constructing the display list.
Instead of rendering text glyphs into a separate mask surface and using
clipShader, paint the backgrounds first and then composite the text
glyphs via saveLayer with SkBlendMode::kDstIn. Skia's saveLayer
automatically sizes its backing at device resolution including CSS
transforms, so no manual scale computation is needed.
Fixes pixelation when zooming in on clipped backgrounds on e.g. the
title of https://modern-css.com/.
We should decide at a later stage, when we've calculated the final
background painting area, whether that area is empty and we can skip
painting the background.
Fixes#7973
Previously, both mask and clip-path were rendered to separate mutable
Gfx::Bitmap objects which forced CPU rasterization. They were then
combined using a CPU pixel-by-pixel operation before being returned
as an ImmutableBitmap.
Instead of including mask in the final bitmap as already rasterized
images, we now use display lists which opens opportunity to utilize
GPU if available.
Bitmap::apply_mask() and ApplyMaskBitmap display list command are no
longer used and have been removed.
Integrate AccumulatedVisualContext with display list recording and
playback. This is the main commit of the refactoring that delivers the
architectural improvements enabled by AccumulatedVisualContext.
Recording changes:
Each display list command now stores a single
RefPtr<AccumulatedVisualContext> instead of separate scroll_frame_id
and ClipFrame. The recorder simply captures the current accumulated
context when appending commands.
The before_paint()/after_paint() hooks that pushed/popped scroll frame
IDs are replaced by directly setting accumulated_visual_context on the
recorder before painting each element.
Playback changes:
The display list player now uses LCA (Lowest Common Ancestor) based
traversal to switch between visual contexts efficiently. When
transitioning from context A to context B:
1. Find the LCA of A and B in the context tree
2. Pop (restore) states back to the LCA depth
3. Push (save + apply) states from LCA down to B
This approach minimizes redundant save/restore operations. For example,
when rendering siblings that share a common scroll container, the
player keeps that scroll state applied and only switches the divergent
parts of their context chains.
Key deletions:
- Remove translate_by() from all 45 display list commands - commands
are now immutable
- Remove transform/perspective fields from PushStackingContext -
transforms are tracked via AccumulatedVisualContext
- Remove push_scroll_frame_id()/pop_scroll_frame_id() from
DisplayListRecorder
- Remove before_paint()/after_paint() hooks from Paintable
- Merge ApplyOpacity, ApplyCompositeAndBlendingOperator, ApplyFilter
into single ApplyEffects command
Stacking context painting changes:
The StackingContext::paint() method is significantly simplified.
Instead of building a PushStackingContextParams struct with transform
matrices and pushing/popping stacking contexts, it now:
1. Sets the accumulated visual context (which already contains
transforms)
2. Applies effects (opacity, blend mode, filters) if needed
3. Applies clip path if needed
4. Paints the content
5. Restores state
The visual state management that was interleaved throughout the
painting code is now handled uniformly by the context tree.
This function used layout node pointer to check if it's corresponding to
viewport. There is no need for that, since `is_viewport_paintable()`
does exactly the same check without going through layout node.
...instead of `auto` Lengths.
This also fixes interpolating between two `auto` `<bg-size>`s, which
fixes a lot of animation tests for both `background-size` and `mask`.
We can use BorderRadiiData::as_corners() to avoid converting the corners
one by one. Instead of passing all four corners one by one, use a
reference to CornerRadii.
No functional changes.
These will be used for the mask-repeat property as well in an upcoming
commit, hence the more generic names. Also, this more closely matches
the names used in the spec.
PaintContext dates back to a time when display lists didn't exist and it
truly represented "paint context". Renaming it to better align with its
current role.
Having a setter for `device_pixels_per_css_pixel` was confusing because
display lists are immutable, so it doesn't make sense to override this
value after the display list has been created.
In the upcoming change, device pixel conversion of ClipFrame will
happen during display list replay, where PaintContext is not available,
so let’s move it out of PaintContext.
`paint_background()` is invoked for each PaintableBox, so by avoiding
save/restore pair emitted for each call, we substantially decrease
display list size.
Website | DisplayList Items Before | DisplayList Items After
-------------|--------------------------|-------------------------
ladybird.org | 2753 | 1431
null.com | 5298 | 4714
discord.com | 6598 | 5360
We're able to efficiently draw repeated bitmaps through Skia, but for
backgrounds we only did so if the background was `repeat-x` _and_
`repeat-y`, and not if just one was set. This meant that for backgrounds
that were only repeating in one direction, we were taking the slow path.
Turns out that this slow path also produced graphical artifacts when
zooming in and out, so let's not do that :^)
This is a improved version of a73cd88f0c
The old commit was reverted in 552dd18696
The new version only paints an element into a new layer if background
blend modes other than normal are used. The rasterization performance
of most websites should therefore not suffer.
Co-Authored-By: Alexander Kalenik <kalenik.aliaksandr@gmail.com>
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 reduces the number of `.cpp` files that need to be recompiled when
one of the below header files changes as follows:
Painting/Command.h: 1030 -> 61
Painting/DisplayList.h: 1030 -> 60
Painting/DisplayListRecorder.h: 557 -> 59
The existing `::unite_horizontally()` and `::unite_vertically()` tests
did not properly test the edge cases where left/top in the Rect were
updated, so they get re-arranged a bit.
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.
