6507d23 introduced a bug when snapshot for iframe is saved in
`PaintNestedDisplayList` and, since display lists are immutable, it's
not possible to update before the next repaint.
This change fixes the issue by moving `ScrollStateSnapshot` for
nested display lists from `PaintNestedDisplayList` to
`HashMap<NonnullRefPtr<DisplayList>, ScrollStateSnapshot>` that is
placed into pending rendering task, making it possible to update
snapshots for all display lists before the next repaint.
This change doesn't have a test because it's really hard to make a ref
test that will specifically check scenario when scroll offset of an
iframe is advanced after display list is cached. We already have
`Tests/LibWeb/Ref/input/scroll-iframe.html` but unfortunately it did
not catch this bug.
Fixes https://github.com/LadybirdBrowser/ladybird/issues/5486
Skia allows you to pass a bounding rect to its saveLayer() function as
an optimization when you know that you won't paint outside those bounds.
Unfortunately, we were passing a too-small rectangle that didn't take
into account transformed descendants, etc.
For now, simply pass null instead of a bounding rect. This way, Skia
figures it out internally. It may allocate larger temporary bitmaps than
needed this way, but at least we get more correct results. I've left
re-enabling the optimization as a FIXME in the code.
This fixes unwanted clipping in various parts of the Discord UI.
Until now, every paint phase of every PaintableBox injected its own
clipping sequence into the display list:
```
before_paint: Save
AddClipRect (1)
...clip rectangles for each containing block with clip...
AddClipRect (N)
paint: ...paint phase items...
after_paint: Restore
```
Because we ran that sequence for every phase of every box, Skia had to
rebuild clip stack `paint_phases * paintable_boxes` times. Worse,
usually most paint phases contribute no visible drawing at all, yet we
still had to emit clipping items because `before_paint()` has no way to
know that in advance.
This change takes a different approach:
- Clip information is now attached as metadata `ClipFrame` to each
DisplayList item.
- `DisplayListPlayer` groups consecutive commands that share a
`ClipFrame`, applying the clip once at the start of the group and
restoring it once at the end.
Going from 10 ms to 5 ms in rasterization on Discord might not sound
like much, but keep in mind that for 60fps we have 16 ms per frame and
there is a lot more work besides display list rasterization we do in
each frame.
* https://discord.com/channels/1247070541085671459/1247090064480014443
- DisplayList items: 81844 -> 3671
- rasterize time: 10 ms -> 5 ms
- record time: 5 ms -> 3 ms
* https://github.com/LadybirdBrowser/ladybird
- DisplayList items: 7902 -> 1176
- rasterize time: 4 ms -> 4 ms
- record time: 3 ms -> 2 ms
Cuts display list size, mostly because now we avoid lots of FillRect
previusly recorded for boxes with transparent background.
Website | DisplayList Items Before | DisplayList Items After
-------------|--------------------------|-------------------------
ladybird.org | 1431 | 1117
null.com | 4714 | 4484
discord.com | 5360 | 4992
Unbalanced save and restore means that effects only relevant to a
stacking context leak outside, which is never expected behavior. Having
a `VERIFY()` for that makes it much easier to catch such issues.
Unbalanced save/restore within display list items recorded for a
paintable means that some state only relevant for the paintable leaks to
subsequent paintables, which is never expected behavior.
When recording the display list for a stacking context, the following
operations (relevant to this bug) happened:
* push a stacking context
* as part of that push a None-value to the scroll frame id stack
* apply filters
* apply masking
* paint recursively
This meant that mask-images were always recorded without scroll frame
id, causing them to be painted without any scroll offset. As a result
mask-images would break as soon as the website using them was scrolled.
Instead, push to the scroll frame id stack later to solve the problem:
* push a stacking context
* apply filters
* apply masking
* push a None-value to the scroll frame id stack
* paint recursively
With this change we save a copy of of scroll state at the time of
recording a display list, instead of actual ScrollState pointer that
could be modifed by the main thread while display list is beings
rasterized on the rendering thread, which leads to a frame painted with
inconsistent scroll state.
Fixes https://github.com/LadybirdBrowser/ladybird/issues/4288
This adds a command for saving the current layer of the canvas.
This is useful for painting content onto a blank background in
isolation and later compositing it onto the canvas.
Instead of trying to manually determine which parts of a bitmap fall
within the box of the `<img>` element, just draw the whole bitmap and
let Skia clip the draw-area to the correct rectangle.
This fixes a bug where the entire bitmap was squashed into the rectangle
of the image box instead of being clipped.
With this change, image rendering is now correct enough to import some
of the WPT tests for object-fit and object-position. To get some good
coverage I have imported all tests for the `<img>` tag. I also wanted to
import a subset of the tests for the `<object>` tag, since those are
passing as well now. Unfortunately, they are flaky for unknown reasons.
This is the second attempt at this bugfix. The prior one was e055927ead
and broke image rendering whenever the page was scrolled. It has
subsequently been reverted in 16b14273d1. Hopefully this time it is not
horribly broken.
Instead of trying to manually determine which parts of a bitmap fall
within the box of the `<img>` element, just draw the whole bitmap and
let Skia clip the draw-area to the correct rectangle.
This fixes a bug where the entire bitmap was squashed into the rectangle
of the image box instead of being clipped.
With this change, image rendering is now correct enough to import some
of the WPT tests for object-fit and object-position. To get some good
coverage I have imported all tests for the `<img>` tag. I also wanted to
import a subset of the tests for the `<object>` tag, since those are
passing as well now. Unfortunately, they are flaky for unknown reasons.
SVGs are rendered with subpixel precision. As such it can happen that
paths are rendered with less than 1px width or height and that they can
have a bounding box thinner than 1px. Due to an optimization such paths
were ignored when painting because their bounding box was incorrectly
calculated to be empty.
As a result horizontal or vertical lines inside SVGs were missing if:
* The SVG is displayed at viewbox size but the lines are defined with
less than 1px.
* The SVG contians 1px-thin lines, but is displayed at a size smaller
than viewbox size.
To prevent this, the bounding box of the path is now enlarged to contain
all pixels that are partially affected.
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.
CSS filters work similarly to canvas filters, so it makes sense to have
Gfx::Filter that can be used by both libraries in an analogous way
as Gfx::Color.
