This change splits the style and layout data in DOM nodes that is
populated by style and layout passes. This makes Servo's data design
more like Gecko's. This allows:
1. Removing the various `StyleAndLayout` data structures used by layout.
2. Removing the `GetStyleAndLayoutData` and
`GetStyleAndOpaqueLayoutData` traits. Accessing style and layout data
are now just functions on the `LayoutNode` and `ThreadSafeLayoutNode`
traits.
3. Styling now doesn't populate layout data. This is is postponed until
layout itself.
4. Allows the DOM wrappers to no longer have to be generic over the
layout data. This data was already stored using `std::any::Any` and
the new code just makes layout responsible for downcasting. Cleaning
up the generic type parameter in the DOM wrappers can happen in a
followup change.
The main benefit to all of this is that we should be able to remove
unsafe creation of `ServoLayoutNode` in layout and
`TrustedLayoutNodeAddress` entirely, because `ServoLayoutNode` will be
able to be passed directly from script to layout. In addition, this
removes one more abstraction layer from the layout DOM wrappers, making
the code a lot more understandable.
Note: This increases the measured size of DOM types, but the same data
is stored. It's simply that before that data was stored behind a heap
pointer.
Instead of the tricky `LayoutRPC` interface, query layout using the
`Layout` trait. This means that now queries will requires calling layout
and then running the query. During layout an enum is used to indicate
what kind of layout is necessary.
This change also removes the mutex-locked `rw_data` from both layout
threads. It's no longer necessary since layout runs synchronously. The
one downside here is that for resolved style queries, we now have to
create two StyleContexts. One for layout and one for the query itself.
The creation of this context should not be very expensive though.
`LayoutRPC` used to be necessary because layout used to run
asynchronously from script, but that no longer happens. With this
change, it becomes possible to safely pass nodes to layout from script
-- a cleanup that can happen in a followup change.
This change also makes two fixes that are necessary to get WOFF2 fonts
working:
1. It adds support for loading web fonts from stylesheets included via
@import rules.
2. It ensure that when web fonts are loaded synchronusly they invalidate
the font cache. This led to incorrect font rendering when running
tests before.
Fixes#31598.
* Updated comment with 'layout_traits' to 'script_layout_interface'
* Rewrap text
* Remove trailing whitespace
---------
Co-authored-by: Martin Robinson <mrobinson@igalia.com>
* script: Do not run layout in a thread
Instead of spawning a thread for layout that almost always runs
synchronously with script, simply run layout in the script thread.
This is a resurrection of #28708, taking just the bits that remove the
layout thread. It's a complex change and thus is just a first step
toward cleaning up the interface between script and layout. Messages are
still passed from script to layout via a `process()` method and script
proxies some messages to layout from other threads as well.
Big changes:
1. Layout is created in the script thread on Document load, thus every
live document is guaranteed to have a layout. This isn't completely
hidden in the interface, but we can safely `unwrap()` on a Document's
layout.
2. Layout configuration is abstracted away into a LayoutConfig struct
and the LayoutFactory is a struct passed around by the Constellation.
This is to avoid having to monomorphize the entire script thread
for each layout.
3. Instead of having the Constellation block on the layout thread to
figure out the current epoch and whether there are pending web fonts
loading, updates are sent synchronously to the Constellation when
rendering to a screenshot. This practically only used by the WPT.
A couple tests start to fail, which is probably inevitable since removing
the layout thread has introduced timing changes in "exit after load" and
screenshot behavior.
Co-authored-by: Josh Matthews <josh@joshmatthews.net>
* Update test expectations
* Fix some issues found during review
* Clarify some comments
* Address review comments
---------
Co-authored-by: Josh Matthews <josh@joshmatthews.net>
This is the start of the organization of types that are in their own
crates in order to break dependency cycles between other crates. The
idea here is that putting these packages into their own directory is the
first step toward cleaning them up. They have grown organically and it
is difficult to explain to new folks where to put new shared types. Many
of these crates contain more than traits or don't contain traits at all.
Notably, `script_traits` isn't touched because it is vendored from
Gecko. Eventually this will move to `third_party`.
