This is a step toward the renderer-per-WebView goal. It moves various
details out of `IOCompositor`.
- Image output: This is moved to servoshell as now applications can
access the image contents of a `WebView` via
`RenderingContext::read_to_image`. Most options for this are moved to
`ServoShellPreferences` apart from `wait_for_stable_image` as this
requires a specific kind of coordination in the `ScriptThread` that is
also very expensive. Instead, paint is now simply delayed until a
stable image is reached and `WebView::paint()` returns a boolean.
Maybe this can be revisited in the future.
- Shutdown: Shutdown is now managed by libservo itself. Shutdown state
is shared between the compositor and `Servo` instance. In the future,
this sharing might be unecessary.
- `CompositeTarget` has been removed entirely. This no longer needs to
be passed when creating a Servo instance.
Signed-off-by: Martin Robinson <mrobinson@igalia.com>
Co-authored-by: Ngo Iok Ui (Wu Yu Wei) <yuweiwu@pm.me>
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