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script: Do not run layout in a thread (#31346)

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* 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 commit is contained in:
Martin Robinson 2024-02-23 09:14:10 +01:00 • committed by GitHub
parent 4849ba901e
commit 9c0561536d
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GPG key ID: B5690EEEBB952194
44 changed files with 636 additions and 1253 deletions
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150
components/script/dom/window.rs
View file

@ -10,7 +10,7 @@ use std::default::Default;
use std::io::{stderr, stdout, Write};
use std::ptr::NonNull;
use std::rc::Rc;
use std::sync::atomic::{AtomicBool, Ordering};
use std::sync::atomic::Ordering;
use std::sync::{Arc, Mutex};
use std::{cmp, env, mem};
@ -26,7 +26,7 @@ use dom_struct::dom_struct;
use embedder_traits::{EmbedderMsg, PromptDefinition, PromptOrigin, PromptResult};
use euclid::default::{Point2D as UntypedPoint2D, Rect as UntypedRect};
use euclid::{Point2D, Rect, Scale, Size2D, Vector2D};
use ipc_channel::ipc::IpcSender;
use ipc_channel::ipc::{self, IpcSender};
use ipc_channel::router::ROUTER;
use js::conversions::ToJSValConvertible;
use js::jsapi::{GCReason, Heap, JSAutoRealm, JSObject, StackFormat, JSPROP_ENUMERATE, JS_GC};
@ -47,13 +47,13 @@ use num_traits::ToPrimitive;
use parking_lot::Mutex as ParkMutex;
use profile_traits::ipc as ProfiledIpc;
use profile_traits::mem::ProfilerChan as MemProfilerChan;
use profile_traits::time::{ProfilerChan as TimeProfilerChan, ProfilerMsg};
use profile_traits::time::ProfilerChan as TimeProfilerChan;
use script_layout_interface::message::{Msg, QueryMsg, Reflow, ReflowGoal, ScriptReflow};
use script_layout_interface::rpc::{
ContentBoxResponse, ContentBoxesResponse, LayoutRPC, NodeScrollIdResponse,
ResolvedStyleResponse, TextIndexResponse,
};
use script_layout_interface::{PendingImageState, TrustedNodeAddress};
use script_layout_interface::{Layout, PendingImageState, TrustedNodeAddress};
use script_traits::webdriver_msg::{WebDriverJSError, WebDriverJSResult};
use script_traits::{
ConstellationControlMsg, DocumentState, HistoryEntryReplacement, LoadData, ScriptMsg,
@ -237,19 +237,6 @@ pub struct Window {
#[ignore_malloc_size_of = "Rc<T> is hard"]
js_runtime: DomRefCell<Option<Rc<Runtime>>>,
/// A handle for communicating messages to the layout thread.
///
/// This channel shouldn't be accessed directly, but through `Window::layout_chan()`,
/// which returns `None` if there's no layout thread anymore.
#[ignore_malloc_size_of = "channels are hard"]
#[no_trace]
layout_chan: Sender<Msg>,
/// A handle to perform RPC calls into the layout, quickly.
#[ignore_malloc_size_of = "trait objects are hard"]
#[no_trace]
layout_rpc: Box<dyn LayoutRPC + Send + 'static>,
/// The current size of the window, in pixels.
#[no_trace]
window_size: Cell<WindowSizeData>,
@ -339,10 +326,6 @@ pub struct Window {
/// It is used to avoid sending idle message more than once, which is unneccessary.
has_sent_idle_message: Cell<bool>,
/// Flag that indicates if the layout thread is busy handling a request.
#[ignore_malloc_size_of = "Arc<T> is hard"]
layout_is_busy: Arc<AtomicBool>,
/// Emits notifications when there is a relayout.
relayout_event: bool,
@ -519,8 +502,8 @@ impl Window {
}
pub fn pending_image_notification(&self, response: PendingImageResponse) {
//XXXjdm could be more efficient to send the responses to the layout thread,
// rather than making the layout thread talk to the image cache to
//XXXjdm could be more efficient to send the responses to layout,
// rather than making layout talk to the image cache to
// obtain the same data.
let mut images = self.pending_layout_images.borrow_mut();
let nodes = images.entry(response.id);
@ -1676,7 +1659,7 @@ impl Window {
// objects removed from the tree that haven't been collected
// yet). There should not be any such DOM nodes with layout
// data, but if there are, then when they are dropped, they
// will attempt to send a message to the closed layout thread.
// will attempt to send a message to layout.
// This causes memory safety issues, because the DOM node uses
// the layout channel from its window, and the window has
// already been GC'd. For nodes which do not have a live
@ -1803,18 +1786,14 @@ impl Window {
ScriptThread::handle_tick_all_animations_for_testing(pipeline_id);
}
/// Reflows the page unconditionally if possible and not suppressed. This
/// method will wait for the layout thread to complete (but see the `TODO`
/// below). If there is no window size yet, the page is presumed invisible
/// and no reflow is performed. If reflow is suppressed, no reflow will be
/// performed for ForDisplay goals.
///
/// TODO(pcwalton): Only wait for style recalc, since we have
/// off-main-thread layout.
/// Reflows the page unconditionally if possible and not suppressed. This method will wait for
/// the layout to complete. If there is no window size yet, the page is presumed invisible and
/// no reflow is performed. If reflow is suppressed, no reflow will be performed for ForDisplay
/// goals.
///
/// Returns true if layout actually happened, false otherwise.
#[allow(unsafe_code)]
pub fn force_reflow(
pub(crate) fn force_reflow(
&self,
reflow_goal: ReflowGoal,
reason: ReflowReason,
@ -1905,14 +1884,7 @@ impl Window {
animations: document.animations().sets.clone(),
};
match self.layout_chan() {
Some(layout_chan) => layout_chan
.send(Msg::Reflow(reflow))
.expect("Layout thread disconnected"),
None => return false,
};
debug!("script: layout forked");
let _ = self.with_layout(move |layout| layout.process(Msg::Reflow(reflow)));
let complete = match join_port.try_recv() {
Err(TryRecvError::Empty) => {
@ -1921,11 +1893,11 @@ impl Window {
},
Ok(reflow_complete) => reflow_complete,
Err(TryRecvError::Disconnected) => {
panic!("Layout thread failed while script was waiting for a result.");
panic!("Layout failed while script was waiting for a result.");
},
};
debug!("script: layout joined");
debug!("script: layout complete");
// Pending reflows require display, so only reset the pending reflow count if this reflow
// was to be displayed.
@ -1968,17 +1940,12 @@ impl Window {
}
document.update_animations_post_reflow();
self.update_constellation_epoch();
true
}
/// Reflows the page if it's possible to do so and the page is dirty. This
/// method will wait for the layout thread to complete (but see the `TODO`
/// below). If there is no window size yet, the page is presumed invisible
/// and no reflow is performed.
///
/// TODO(pcwalton): Only wait for style recalc, since we have
/// off-main-thread layout.
/// Reflows the page if it's possible to do so and the page is dirty.
///
/// Returns true if layout actually happened, false otherwise.
/// This return value is useful for script queries, that wait for a lock
@ -2032,12 +1999,24 @@ impl Window {
elem.has_class(&atom!("reftest-wait"), CaseSensitivity::CaseSensitive)
});
let pending_web_fonts = self
.with_layout(move |layout| layout.waiting_for_web_fonts_to_load())
.unwrap();
let has_sent_idle_message = self.has_sent_idle_message.get();
let is_ready_state_complete = document.ReadyState() == DocumentReadyState::Complete;
let pending_images = self.pending_layout_images.borrow().is_empty();
let pending_images = !self.pending_layout_images.borrow().is_empty();
if !has_sent_idle_message && is_ready_state_complete && !reftest_wait && pending_images
if !has_sent_idle_message &&
is_ready_state_complete &&
!reftest_wait &&
!pending_images &&
!pending_web_fonts
{
debug!(
"{:?}: Sending DocumentState::Idle to Constellation",
self.pipeline_id()
);
let event = ScriptMsg::SetDocumentState(DocumentState::Idle);
self.send_to_constellation(event);
self.has_sent_idle_message.set(true);
@ -2047,13 +2026,28 @@ impl Window {
issued_reflow
}
pub fn layout_reflow(&self, query_msg: QueryMsg) -> bool {
if self.layout_is_busy.load(Ordering::Relaxed) {
let url = self.get_url().into_string();
self.time_profiler_chan()
.send(ProfilerMsg::BlockedLayoutQuery(url));
/// If writing a screenshot, synchronously update the layout epoch that it set
/// in the constellation.
pub(crate) fn update_constellation_epoch(&self) {
if !self.prepare_for_screenshot {
return;
}
let epoch = self
.with_layout(move |layout| layout.current_epoch())
.unwrap();
debug!(
"{:?}: Updating constellation epoch: {epoch:?}",
self.pipeline_id()
);
let (sender, receiver) = ipc::channel().expect("Failed to create IPC channel!");
let event = ScriptMsg::SetLayoutEpoch(epoch, sender);
self.send_to_constellation(event);
receiver.recv().unwrap();
}
pub fn layout_reflow(&self, query_msg: QueryMsg) -> bool {
self.reflow(
ReflowGoal::LayoutQuery(query_msg, time::precise_time_ns()),
ReflowReason::Query,
@ -2069,18 +2063,18 @@ impl Window {
)) {
return None;
}
self.layout_rpc.resolved_font_style()
self.layout_rpc().resolved_font_style()
}
pub fn layout(&self) -> &dyn LayoutRPC {
&*self.layout_rpc
pub fn layout_rpc(&self) -> Box<dyn LayoutRPC> {
self.with_layout(|layout| layout.rpc()).unwrap()
}
pub fn content_box_query(&self, node: &Node) -> Option<UntypedRect<Au>> {
if !self.layout_reflow(QueryMsg::ContentBoxQuery(node.to_opaque())) {
return None;
}
let ContentBoxResponse(rect) = self.layout_rpc.content_box();
let ContentBoxResponse(rect) = self.layout_rpc().content_box();
rect
}
@ -2088,7 +2082,7 @@ impl Window {
if !self.layout_reflow(QueryMsg::ContentBoxesQuery(node.to_opaque())) {
return vec![];
}
let ContentBoxesResponse(rects) = self.layout_rpc.content_boxes();
let ContentBoxesResponse(rects) = self.layout_rpc().content_boxes();
rects
}
@ -2096,7 +2090,7 @@ impl Window {
if !self.layout_reflow(QueryMsg::ClientRectQuery(node.to_opaque())) {
return Rect::zero();
}
self.layout_rpc.node_geometry().client_rect
self.layout_rpc().node_geometry().client_rect
}
/// Find the scroll area of the given node, if it is not None. If the node
@ -2106,7 +2100,7 @@ impl Window {
if !self.layout_reflow(QueryMsg::ScrollingAreaQuery(opaque)) {
return Rect::zero();
}
self.layout_rpc.scrolling_area().client_rect
self.layout_rpc().scrolling_area().client_rect
}
pub fn scroll_offset_query(&self, node: &Node) -> Vector2D<f32, LayoutPixel> {
@ -2129,7 +2123,7 @@ impl Window {
.borrow_mut()
.insert(node.to_opaque(), Vector2D::new(x_ as f32, y_ as f32));
let NodeScrollIdResponse(scroll_id) = self.layout_rpc.node_scroll_id();
let NodeScrollIdResponse(scroll_id) = self.layout_rpc().node_scroll_id();
// Step 12
self.perform_a_scroll(
@ -2150,7 +2144,7 @@ impl Window {
if !self.layout_reflow(QueryMsg::ResolvedStyleQuery(element, pseudo, property)) {
return DOMString::new();
}
let ResolvedStyleResponse(resolved) = self.layout_rpc.resolved_style();
let ResolvedStyleResponse(resolved) = self.layout_rpc().resolved_style();
DOMString::from(resolved)
}
@ -2161,7 +2155,7 @@ impl Window {
if !self.layout_reflow(QueryMsg::InnerWindowDimensionsQuery(browsing_context)) {
return None;
}
self.layout_rpc.inner_window_dimensions()
self.layout_rpc().inner_window_dimensions()
}
#[allow(unsafe_code)]
@ -2172,7 +2166,7 @@ impl Window {
// FIXME(nox): Layout can reply with a garbage value which doesn't
// actually correspond to an element, that's unsound.
let response = self.layout_rpc.offset_parent();
let response = self.layout_rpc().offset_parent();
let element = response.node_address.and_then(|parent_node_address| {
let node = unsafe { from_untrusted_node_address(parent_node_address) };
DomRoot::downcast(node)
@ -2188,7 +2182,7 @@ impl Window {
if !self.layout_reflow(QueryMsg::TextIndexQuery(node.to_opaque(), point_in_node)) {
return TextIndexResponse(None);
}
self.layout_rpc.text_index()
self.layout_rpc().text_index()
}
#[allow(unsafe_code)]
@ -2313,12 +2307,8 @@ impl Window {
self.Document().url()
}
pub fn layout_chan(&self) -> Option<&Sender<Msg>> {
if self.is_alive() {
Some(&self.layout_chan)
} else {
None
}
pub fn with_layout<'a, T>(&self, call: impl FnOnce(&mut dyn Layout) -> T) -> Result<T, ()> {
ScriptThread::with_layout(self.pipeline_id(), call)
}
pub fn windowproxy_handler(&self) -> WindowProxyHandler {
@ -2539,7 +2529,6 @@ impl Window {
constellation_chan: ScriptToConstellationChan,
control_chan: IpcSender<ConstellationControlMsg>,
scheduler_chan: IpcSender<TimerSchedulerMsg>,
layout_chan: Sender<Msg>,
pipelineid: PipelineId,
parent_info: Option<PipelineId>,
window_size: WindowSizeData,
@ -2552,7 +2541,6 @@ impl Window {
microtask_queue: Rc<MicrotaskQueue>,
webrender_document: DocumentId,
webrender_api_sender: WebrenderIpcSender,
layout_is_busy: Arc<AtomicBool>,
relayout_event: bool,
prepare_for_screenshot: bool,
unminify_js: bool,
@ -2565,11 +2553,6 @@ impl Window {
gpu_id_hub: Arc<ParkMutex<Identities>>,
inherited_secure_context: Option<bool>,
) -> DomRoot<Self> {
let layout_rpc: Box<dyn LayoutRPC + Send> = {
let (rpc_send, rpc_recv) = unbounded();
layout_chan.send(Msg::GetRPC(rpc_send)).unwrap();
rpc_recv.recv().unwrap()
};
let error_reporter = CSSErrorReporter {
pipelineid,
script_chan: Arc::new(Mutex::new(control_chan)),
@ -2615,8 +2598,6 @@ impl Window {
bluetooth_extra_permission_data: BluetoothExtraPermissionData::new(),
page_clip_rect: Cell::new(MaxRect::max_rect()),
resize_event: Default::default(),
layout_chan,
layout_rpc,
window_size: Cell::new(window_size),
current_viewport: Cell::new(Rect::zero()),
suppress_reflow: Cell::new(true),
@ -2640,7 +2621,6 @@ impl Window {
exists_mut_observer: Cell::new(false),
webrender_api_sender,
has_sent_idle_message: Cell::new(false),
layout_is_busy,
relayout_event,
prepare_for_screenshot,
unminify_js,