We are moving toward an architecture where the browser owns a single
process that holds the GPU context, so Skia resources can be shared
across every renderer and WebContent processes can be sandboxed away
from direct GPU access. A dedicated Compositor helper process is the
first step. The earlier commits laid the foundation; this one turns the
helper on as a selectable backend, gated behind
--enable-compositor-process so the existing in-process path stays the
shipping default.
Default topology -- one compositor per WebContent, in-process:
+---------+
| Browser |
+---------+
/ | \
v v v
+---+ +---+ +---+ each WebContent runs its own
|WC | |WC | |WC | CompositorThread on a dedicated
|+C+| |+C+| |+C+| thread, with its own GPU context.
+---+ +---+ +---+
Opt-in topology -- one single-threaded Compositor, shared by all WCs:
+---------+ control +-------------------+
| Browser |<----------->| Compositor |
+---------+ | (single thread, |
/ | \ | single GPU ctx, |
v v v data | shared by all |
[WC] [WC] [WC] ---------->| connected WCs) |
+-------------------+
Three IPC channels carry the work in the opt-in topology. The
existing Browser<->WebContent channel gains context allocation.
A new Browser<->Compositor channel carries context lifetime,
viewport, UI input, and presentation acks plus backing-store and
frame upcalls. A new WebContent<->Compositor channel carries
display lists, scroll state, video, compositor surfaces, async
scrolling, presentation, and screenshots, with upcalls for
delegated input and compositor loss.
These IPC methods should be expanded in the future to allow WebContent
to specify what UI elements should be kept/removed, for example, the
navigation UI.
The set_viewport_size and set_device_pixel_ratio IPC messages were sent
separately, potentially causing a race condition when the DPR changes
(e.g. moving a window between screens): the DPR message would arrive
and use a stale viewport size, computing a temporarily wrong CSS
viewport. Combine both into a single set_viewport IPC that updates the
device viewport size and DPR together.
When multiple views share a WebContent process (e.g. parent and child
views created via window.open()), we need to notify ALL of them when
the process crashes, not just one.
Previously, each view would overwrite the single crash callback on
WebContentClient, so only the last view to initialize would be notified.
This adds WebContentClient::notify_all_views_of_crash() which iterates
over all registered views and notifies each one. Child views also now
propagate crashes to their parent, and can be disconnected between
tests to prevent stale crashes from affecting subsequent tests.
Clipboard handling largely has nothing to do with the individual web
views. Rather, we interact with the system clipboard at the application
level. So let's move these implementations to the Application.
We currently create a separate headless-browser application to serve two
purposes:
1. Allow headless browsing to take a screenshot of a page or print its
layout tree / internal text.
2. Run the LibWeb test framework.
This patch migrates (1) to the main Ladybird executable. The --headless
flag enables this mode. This matches the behavior of other browsers, and
means we have one less executable to ship at distribution time.
We want to avoid creating too many AppKit / Qt facilities in headless
mode. So this involves some shuffling of application init to ensure we
don't create them until after we've parsed the command line arguments.
Namely, we avoid creating the NSApp in AppKit and QCoreApplication in
Qt. Doing so also requires that we don't create the application event
loop until we've parsed the command line as well, because the loop we
create depends on whether we're creating those UI facilities.
