/* This Source Code Form is subject to the terms of the Mozilla Public * License, v. 2.0. If a copy of the MPL was not distributed with this * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ //! The layout task. Performs layout on the DOM, builds display lists and sends them to be //! painted. #![allow(unsafe_code)] use animation; use app_units::Au; use azure::azure::AzColor; use canvas_traits::CanvasMsg; use construct::ConstructionResult; use context::{SharedLayoutContext, StylistWrapper, heap_size_of_local_context}; use cssparser::ToCss; use data::LayoutDataWrapper; use display_list_builder::ToGfxColor; use euclid::Matrix4; use euclid::point::Point2D; use euclid::rect::Rect; use euclid::scale_factor::ScaleFactor; use euclid::size::Size2D; use flow::{self, Flow, ImmutableFlowUtils, MutableFlowUtils, MutableOwnedFlowUtils}; use flow_ref::{self, FlowRef}; use fnv::FnvHasher; use fragment::{Fragment, FragmentBorderBoxIterator, SpecificFragmentInfo}; use gfx::display_list::{ClippingRegion, DisplayList, LayerInfo, OpaqueNode, StackingContext}; use gfx::font_cache_task::FontCacheTask; use gfx::font_context; use gfx::paint_task::{LayoutToPaintMsg, PaintLayer}; use gfx_traits::color; use incremental::{LayoutDamageComputation, REFLOW, REFLOW_ENTIRE_DOCUMENT, REPAINT}; use ipc_channel::ipc::{self, IpcReceiver, IpcSender}; use ipc_channel::router::ROUTER; use layout_debug; use layout_traits::LayoutTaskFactory; use log; use msg::compositor_msg::{Epoch, LayerId, ScrollPolicy}; use msg::constellation_msg::Msg as ConstellationMsg; use msg::constellation_msg::{ConstellationChan, Failure, PipelineId}; use net_traits::image_cache_task::{ImageCacheChan, ImageCacheResult, ImageCacheTask}; use opaque_node::OpaqueNodeMethods; use parallel::{self, WorkQueueData}; use profile_traits::mem::{self, Report, ReportKind, ReportsChan}; use profile_traits::time::{TimerMetadataFrameType, TimerMetadataReflowType}; use profile_traits::time::{self, TimerMetadata, profile}; use query::{LayoutRPCImpl, process_content_box_request, process_content_boxes_request}; use query::{MarginPadding, MarginRetrievingFragmentBorderBoxIterator, PositionProperty}; use query::{PositionRetrievingFragmentBorderBoxIterator, Side}; use script::dom::node::LayoutData; use script::layout_interface::Animation; use script::layout_interface::{LayoutChan, LayoutRPC, OffsetParentResponse}; use script::layout_interface::{Msg, NewLayoutTaskInfo, Reflow, ReflowGoal, ReflowQueryType}; use script::layout_interface::{ScriptLayoutChan, ScriptReflow, TrustedNodeAddress}; use script_traits::{ConstellationControlMsg, LayoutControlMsg, OpaqueScriptLayoutChannel}; use selectors::parser::PseudoElement; use sequential; use serde_json; use std::borrow::ToOwned; use std::collections::HashMap; use std::collections::hash_state::DefaultState; use std::mem::transmute; use std::ops::{Deref, DerefMut, Drop}; use std::sync::atomic::{AtomicUsize, Ordering}; use std::sync::mpsc::{channel, Sender, Receiver}; use std::sync::{Arc, Mutex, MutexGuard}; use string_cache::Atom; use style::computed_values::{self, filter, mix_blend_mode}; use style::media_queries::{Device, MediaType}; use style::properties::longhands::{display, position}; use style::properties::style_structs; use style::selector_matching::{Stylist, USER_OR_USER_AGENT_STYLESHEETS}; use style::stylesheets::{CSSRuleIteratorExt, Stylesheet}; use style::values::AuExtensionMethods; use url::Url; use util::geometry::{MAX_RECT, ZERO_POINT}; use util::ipc::OptionalIpcSender; use util::logical_geometry::LogicalPoint; use util::mem::HeapSizeOf; use util::opts; use util::task::spawn_named_with_send_on_failure; use util::task_state; use util::workqueue::WorkQueue; use wrapper::{LayoutNode, ThreadSafeLayoutNode}; /// The number of screens of data we're allowed to generate display lists for in each direction. pub const DISPLAY_PORT_SIZE_FACTOR: i32 = 8; /// The number of screens we have to traverse before we decide to generate new display lists. const DISPLAY_PORT_THRESHOLD_SIZE_FACTOR: i32 = 4; /// Mutable data belonging to the LayoutTask. /// /// This needs to be protected by a mutex so we can do fast RPCs. pub struct LayoutTaskData { /// The channel on which messages can be sent to the constellation. pub constellation_chan: ConstellationChan, /// The root stacking context. pub stacking_context: Option>, /// Performs CSS selector matching and style resolution. pub stylist: Box, /// A queued response for the union of the content boxes of a node. pub content_box_response: Rect, /// A queued response for the content boxes of a node. pub content_boxes_response: Vec>, /// A queued response for the client {top, left, width, height} of a node in pixels. pub client_rect_response: Rect, /// A queued response for the resolved style property of an element. pub resolved_style_response: Option, /// A queued response for the offset parent/rect of a node. pub offset_parent_response: OffsetParentResponse, } /// Information needed by the layout task. pub struct LayoutTask { /// The ID of the pipeline that we belong to. pub id: PipelineId, /// The URL of the pipeline that we belong to. pub url: Url, /// Is the current reflow of an iframe, as opposed to a root window? pub is_iframe: bool, /// The port on which we receive messages from the script task. pub port: Receiver, /// The port on which we receive messages from the constellation. pub pipeline_port: Receiver, /// The port on which we receive messages from the image cache image_cache_receiver: Receiver, /// The channel on which the image cache can send messages to ourself. image_cache_sender: ImageCacheChan, /// The port on which we receive messages from the font cache task. font_cache_receiver: Receiver<()>, /// The channel on which the font cache can send messages to us. font_cache_sender: Sender<()>, /// The channel on which we or others can send messages to ourselves. pub chan: LayoutChan, /// The channel on which messages can be sent to the constellation. pub constellation_chan: ConstellationChan, /// The channel on which messages can be sent to the script task. pub script_chan: Sender, /// The channel on which messages can be sent to the painting task. pub paint_chan: OptionalIpcSender, /// The channel on which messages can be sent to the time profiler. pub time_profiler_chan: time::ProfilerChan, /// The channel on which messages can be sent to the memory profiler. pub mem_profiler_chan: mem::ProfilerChan, /// The channel on which messages can be sent to the image cache. pub image_cache_task: ImageCacheTask, /// Public interface to the font cache task. pub font_cache_task: FontCacheTask, /// Is this the first reflow in this LayoutTask? pub first_reflow: bool, /// To receive a canvas renderer associated to a layer, this message is propagated /// to the paint chan pub canvas_layers_receiver: Receiver<(LayerId, IpcSender)>, pub canvas_layers_sender: Sender<(LayerId, IpcSender)>, /// The workers that we use for parallel operation. parallel_traversal: Option>, /// Starts at zero, and increased by one every time a layout completes. /// This can be used to easily check for invalid stale data. generation: u32, /// A channel on which new animations that have been triggered by style recalculation can be /// sent. new_animations_sender: Sender, /// Receives newly-discovered animations. new_animations_receiver: Receiver, /// The number of Web fonts that have been requested but not yet loaded. outstanding_web_fonts: Arc, /// The root of the flow tree. root_flow: Option, /// The position and size of the visible rect for each layer. We do not build display lists /// for any areas more than `DISPLAY_PORT_SIZE_FACTOR` screens away from this area. visible_rects: Arc, DefaultState>>, /// The list of currently-running animations. running_animations: Arc>>, /// A counter for epoch messages epoch: Epoch, /// The size of the viewport. This may be different from the size of the screen due to viewport /// constraints. viewport_size: Size2D, /// A mutex to allow for fast, read-only RPC of layout's internal data /// structures, while still letting the LayoutTask modify them. /// /// All the other elements of this struct are read-only. pub rw_data: Arc>, } impl LayoutTaskFactory for LayoutTask { /// Spawns a new layout task. fn create(_phantom: Option<&mut LayoutTask>, id: PipelineId, url: Url, is_iframe: bool, chan: OpaqueScriptLayoutChannel, pipeline_port: IpcReceiver, constellation_chan: ConstellationChan, failure_msg: Failure, script_chan: Sender, paint_chan: OptionalIpcSender, image_cache_task: ImageCacheTask, font_cache_task: FontCacheTask, time_profiler_chan: time::ProfilerChan, mem_profiler_chan: mem::ProfilerChan, shutdown_chan: Sender<()>) { let ConstellationChan(con_chan) = constellation_chan.clone(); spawn_named_with_send_on_failure(format!("LayoutTask {:?}", id), task_state::LAYOUT, move || { { // Ensures layout task is destroyed before we send shutdown message let sender = chan.sender(); let layout_chan = LayoutChan(sender); let layout = LayoutTask::new(id, url, is_iframe, chan.receiver(), layout_chan.clone(), pipeline_port, constellation_chan, script_chan, paint_chan, image_cache_task, font_cache_task, time_profiler_chan, mem_profiler_chan.clone()); let reporter_name = format!("layout-reporter-{}", id); mem_profiler_chan.run_with_memory_reporting(|| { layout.start(); }, reporter_name, layout_chan.0, Msg::CollectReports); } shutdown_chan.send(()).unwrap(); }, ConstellationMsg::Failure(failure_msg), con_chan); } } /// The `LayoutTask` `rw_data` lock must remain locked until the first reflow, /// as RPC calls don't make sense until then. Use this in combination with /// `LayoutTask::lock_rw_data` and `LayoutTask::return_rw_data`. pub enum RWGuard<'a> { /// If the lock was previously held, from when the task started. Held(MutexGuard<'a, LayoutTaskData>), /// If the lock was just used, and has been returned since there has been /// a reflow already. Used(MutexGuard<'a, LayoutTaskData>), } impl<'a> Deref for RWGuard<'a> { type Target = LayoutTaskData; fn deref(&self) -> &LayoutTaskData { match *self { RWGuard::Held(ref x) => &**x, RWGuard::Used(ref x) => &**x, } } } impl<'a> DerefMut for RWGuard<'a> { fn deref_mut(&mut self) -> &mut LayoutTaskData { match *self { RWGuard::Held(ref mut x) => &mut **x, RWGuard::Used(ref mut x) => &mut **x, } } } struct RwData<'a, 'b: 'a> { rw_data: &'b Arc>, possibly_locked_rw_data: &'a mut Option>, } impl<'a, 'b: 'a> RwData<'a, 'b> { /// If no reflow has happened yet, this will just return the lock in /// `possibly_locked_rw_data`. Otherwise, it will acquire the `rw_data` lock. /// /// If you do not wish RPCs to remain blocked, just drop the `RWGuard` /// returned from this function. If you _do_ wish for them to remain blocked, /// use `block`. fn lock(&mut self) -> RWGuard<'b> { match self.possibly_locked_rw_data.take() { None => RWGuard::Used(self.rw_data.lock().unwrap()), Some(x) => RWGuard::Held(x), } } /// If no reflow has ever been triggered, this will keep the lock, locked /// (and saved in `possibly_locked_rw_data`). If it has been, the lock will /// be unlocked. fn block(&mut self, rw_data: RWGuard<'b>) { match rw_data { RWGuard::Used(x) => drop(x), RWGuard::Held(x) => *self.possibly_locked_rw_data = Some(x), } } } fn add_font_face_rules(stylesheet: &Stylesheet, device: &Device, font_cache_task: &FontCacheTask, font_cache_sender: &Sender<()>, outstanding_web_fonts_counter: &Arc) { for font_face in stylesheet.effective_rules(&device).font_face() { for source in &font_face.sources { if opts::get().load_webfonts_synchronously { let (sender, receiver) = channel(); font_cache_task.add_web_font(font_face.family.clone(), (*source).clone(), sender); receiver.recv().unwrap(); } else { outstanding_web_fonts_counter.fetch_add(1, Ordering::SeqCst); font_cache_task.add_web_font(font_face.family.clone(), (*source).clone(), (*font_cache_sender).clone()); } } } } impl LayoutTask { /// Creates a new `LayoutTask` structure. fn new(id: PipelineId, url: Url, is_iframe: bool, port: Receiver, chan: LayoutChan, pipeline_port: IpcReceiver, constellation_chan: ConstellationChan, script_chan: Sender, paint_chan: OptionalIpcSender, image_cache_task: ImageCacheTask, font_cache_task: FontCacheTask, time_profiler_chan: time::ProfilerChan, mem_profiler_chan: mem::ProfilerChan) -> LayoutTask { let device = Device::new( MediaType::Screen, opts::get().initial_window_size.as_f32() * ScaleFactor::new(1.0)); let parallel_traversal = if opts::get().layout_threads != 1 { Some(WorkQueue::new("LayoutWorker", task_state::LAYOUT, opts::get().layout_threads)) } else { None }; // Create the channel on which new animations can be sent. let (new_animations_sender, new_animations_receiver) = channel(); let (canvas_layers_sender, canvas_layers_receiver) = channel(); // Proxy IPC messages from the pipeline to the layout thread. let pipeline_receiver = ROUTER.route_ipc_receiver_to_new_mpsc_receiver(pipeline_port); // Ask the router to proxy IPC messages from the image cache task to the layout thread. let (ipc_image_cache_sender, ipc_image_cache_receiver) = ipc::channel().unwrap(); let image_cache_receiver = ROUTER.route_ipc_receiver_to_new_mpsc_receiver(ipc_image_cache_receiver); let (font_cache_sender, font_cache_receiver) = channel(); let stylist = box Stylist::new(device); let outstanding_web_fonts_counter = Arc::new(AtomicUsize::new(0)); for stylesheet in &*USER_OR_USER_AGENT_STYLESHEETS { add_font_face_rules(stylesheet, &stylist.device, &font_cache_task, &font_cache_sender, &outstanding_web_fonts_counter); } LayoutTask { id: id, url: url, is_iframe: is_iframe, port: port, pipeline_port: pipeline_receiver, chan: chan, script_chan: script_chan, constellation_chan: constellation_chan.clone(), paint_chan: paint_chan, time_profiler_chan: time_profiler_chan, mem_profiler_chan: mem_profiler_chan, image_cache_task: image_cache_task, font_cache_task: font_cache_task, first_reflow: true, image_cache_receiver: image_cache_receiver, image_cache_sender: ImageCacheChan(ipc_image_cache_sender), font_cache_receiver: font_cache_receiver, font_cache_sender: font_cache_sender, canvas_layers_receiver: canvas_layers_receiver, canvas_layers_sender: canvas_layers_sender, parallel_traversal: parallel_traversal, generation: 0, new_animations_sender: new_animations_sender, new_animations_receiver: new_animations_receiver, outstanding_web_fonts: outstanding_web_fonts_counter, root_flow: None, visible_rects: Arc::new(HashMap::with_hash_state(Default::default())), running_animations: Arc::new(HashMap::new()), epoch: Epoch(0), viewport_size: Size2D::new(Au(0), Au(0)), rw_data: Arc::new(Mutex::new( LayoutTaskData { constellation_chan: constellation_chan, stacking_context: None, stylist: stylist, content_box_response: Rect::zero(), content_boxes_response: Vec::new(), client_rect_response: Rect::zero(), resolved_style_response: None, offset_parent_response: OffsetParentResponse::empty(), })), } } /// Starts listening on the port. fn start(mut self) { let rw_data = self.rw_data.clone(); let mut possibly_locked_rw_data = Some(rw_data.lock().unwrap()); let mut rw_data = RwData { rw_data: &rw_data, possibly_locked_rw_data: &mut possibly_locked_rw_data, }; while self.handle_request(&mut rw_data) { // Loop indefinitely. } } // Create a layout context for use in building display lists, hit testing, &c. fn build_shared_layout_context(&self, rw_data: &LayoutTaskData, screen_size_changed: bool, url: &Url, goal: ReflowGoal) -> SharedLayoutContext { SharedLayoutContext { image_cache_task: self.image_cache_task.clone(), image_cache_sender: Mutex::new(self.image_cache_sender.clone()), viewport_size: self.viewport_size.clone(), screen_size_changed: screen_size_changed, font_cache_task: Mutex::new(self.font_cache_task.clone()), canvas_layers_sender: Mutex::new(self.canvas_layers_sender.clone()), stylist: StylistWrapper(&*rw_data.stylist), url: (*url).clone(), visible_rects: self.visible_rects.clone(), generation: self.generation, new_animations_sender: Mutex::new(self.new_animations_sender.clone()), goal: goal, running_animations: self.running_animations.clone(), } } /// Receives and dispatches messages from the script and constellation tasks fn handle_request<'a, 'b>(&mut self, possibly_locked_rw_data: &mut RwData<'a, 'b>) -> bool { enum Request { FromPipeline(LayoutControlMsg), FromScript(Msg), FromImageCache, FromFontCache, } let request = { let port_from_script = &self.port; let port_from_pipeline = &self.pipeline_port; let port_from_image_cache = &self.image_cache_receiver; let port_from_font_cache = &self.font_cache_receiver; select! { msg = port_from_pipeline.recv() => { Request::FromPipeline(msg.unwrap()) }, msg = port_from_script.recv() => { Request::FromScript(msg.unwrap()) }, msg = port_from_image_cache.recv() => { msg.unwrap(); Request::FromImageCache }, msg = port_from_font_cache.recv() => { msg.unwrap(); Request::FromFontCache } } }; match request { Request::FromPipeline(LayoutControlMsg::SetVisibleRects(new_visible_rects)) => { self.handle_request_helper(Msg::SetVisibleRects(new_visible_rects), possibly_locked_rw_data) }, Request::FromPipeline(LayoutControlMsg::TickAnimations) => { self.handle_request_helper(Msg::TickAnimations, possibly_locked_rw_data) }, Request::FromPipeline(LayoutControlMsg::GetCurrentEpoch(sender)) => { self.handle_request_helper(Msg::GetCurrentEpoch(sender), possibly_locked_rw_data) }, Request::FromPipeline(LayoutControlMsg::GetWebFontLoadState(sender)) => { self.handle_request_helper(Msg::GetWebFontLoadState(sender), possibly_locked_rw_data) }, Request::FromPipeline(LayoutControlMsg::ExitNow) => { self.handle_request_helper(Msg::ExitNow, possibly_locked_rw_data) }, Request::FromScript(msg) => { self.handle_request_helper(msg, possibly_locked_rw_data) }, Request::FromImageCache => { self.repaint(possibly_locked_rw_data) }, Request::FromFontCache => { let _rw_data = possibly_locked_rw_data.lock(); self.outstanding_web_fonts.fetch_sub(1, Ordering::SeqCst); font_context::invalidate_font_caches(); self.script_chan.send(ConstellationControlMsg::WebFontLoaded(self.id)).unwrap(); true }, } } /// Repaint the scene, without performing style matching. This is typically /// used when an image arrives asynchronously and triggers a relayout and /// repaint. /// TODO: In the future we could detect if the image size hasn't changed /// since last time and avoid performing a complete layout pass. fn repaint<'a, 'b>(&mut self, possibly_locked_rw_data: &mut RwData<'a, 'b>) -> bool { let mut rw_data = possibly_locked_rw_data.lock(); let reflow_info = Reflow { goal: ReflowGoal::ForDisplay, page_clip_rect: MAX_RECT, }; let mut layout_context = self.build_shared_layout_context(&*rw_data, false, &self.url, reflow_info.goal); self.perform_post_style_recalc_layout_passes(&reflow_info, &mut *rw_data, &mut layout_context); true } /// Receives and dispatches messages from other tasks. fn handle_request_helper<'a, 'b>(&mut self, request: Msg, possibly_locked_rw_data: &mut RwData<'a, 'b>) -> bool { match request { Msg::AddStylesheet(style_info) => { self.handle_add_stylesheet(style_info, possibly_locked_rw_data) } Msg::SetQuirksMode => self.handle_set_quirks_mode(possibly_locked_rw_data), Msg::GetRPC(response_chan) => { response_chan.send(box LayoutRPCImpl(self.rw_data.clone()) as Box).unwrap(); }, Msg::Reflow(data) => { profile(time::ProfilerCategory::LayoutPerform, self.profiler_metadata(), self.time_profiler_chan.clone(), || self.handle_reflow(&data, possibly_locked_rw_data)); }, Msg::TickAnimations => self.tick_all_animations(possibly_locked_rw_data), Msg::ReflowWithNewlyLoadedWebFont => { self.reflow_with_newly_loaded_web_font(possibly_locked_rw_data) } Msg::SetVisibleRects(new_visible_rects) => { self.set_visible_rects(new_visible_rects, possibly_locked_rw_data); } Msg::ReapLayoutData(dead_layout_data) => { unsafe { self.handle_reap_layout_data(dead_layout_data) } } Msg::CollectReports(reports_chan) => { self.collect_reports(reports_chan, possibly_locked_rw_data); }, Msg::GetCurrentEpoch(sender) => { let _rw_data = possibly_locked_rw_data.lock(); sender.send(self.epoch).unwrap(); }, Msg::GetWebFontLoadState(sender) => { let _rw_data = possibly_locked_rw_data.lock(); let outstanding_web_fonts = self.outstanding_web_fonts.load(Ordering::SeqCst); sender.send(outstanding_web_fonts != 0).unwrap(); }, Msg::CreateLayoutTask(info) => { self.create_layout_task(info) } Msg::PrepareToExit(response_chan) => { self.prepare_to_exit(response_chan); return false }, Msg::ExitNow => { debug!("layout: ExitNow received"); self.exit_now(); return false } } true } fn collect_reports<'a, 'b>(&self, reports_chan: ReportsChan, possibly_locked_rw_data: &mut RwData<'a, 'b>) { let mut reports = vec![]; // FIXME(njn): Just measuring the display tree for now. let rw_data = possibly_locked_rw_data.lock(); let stacking_context = rw_data.stacking_context.as_ref(); reports.push(Report { path: path![format!("url({})", self.url), "layout-task", "display-list"], kind: ReportKind::ExplicitJemallocHeapSize, size: stacking_context.map_or(0, |sc| sc.heap_size_of_children()), }); // The LayoutTask has a context in TLS... reports.push(Report { path: path![format!("url({})", self.url), "layout-task", "local-context"], kind: ReportKind::ExplicitJemallocHeapSize, size: heap_size_of_local_context(), }); // ... as do each of the LayoutWorkers, if present. if let Some(ref traversal) = self.parallel_traversal { let sizes = traversal.heap_size_of_tls(heap_size_of_local_context); for (i, size) in sizes.iter().enumerate() { reports.push(Report { path: path![format!("url({})", self.url), format!("layout-worker-{}-local-context", i)], kind: ReportKind::ExplicitJemallocHeapSize, size: *size, }); } } reports_chan.send(reports); } fn create_layout_task(&self, info: NewLayoutTaskInfo) { LayoutTaskFactory::create(None::<&mut LayoutTask>, info.id, info.url.clone(), info.is_parent, info.layout_pair, info.pipeline_port, info.constellation_chan, info.failure, info.script_chan.clone(), *info.paint_chan .downcast::>() .unwrap(), self.image_cache_task.clone(), self.font_cache_task.clone(), self.time_profiler_chan.clone(), self.mem_profiler_chan.clone(), info.layout_shutdown_chan); } /// Enters a quiescent state in which no new messages will be processed until an `ExitNow` is /// received. A pong is immediately sent on the given response channel. fn prepare_to_exit(&mut self, response_chan: Sender<()>) { response_chan.send(()).unwrap(); loop { match self.port.recv().unwrap() { Msg::ReapLayoutData(dead_layout_data) => { unsafe { self.handle_reap_layout_data(dead_layout_data) } } Msg::ExitNow => { debug!("layout task is exiting..."); self.exit_now(); break } Msg::CollectReports(_) => { // Just ignore these messages at this point. } _ => { panic!("layout: unexpected message received after `PrepareToExitMsg`") } } } } /// Shuts down the layout task now. If there are any DOM nodes left, layout will now (safely) /// crash. fn exit_now<'a, 'b>(&mut self) { if let Some(ref mut traversal) = self.parallel_traversal { traversal.shutdown() } let (response_chan, response_port) = ipc::channel().unwrap(); self.paint_chan.send(LayoutToPaintMsg::Exit(response_chan)).unwrap(); response_port.recv().unwrap() } fn handle_add_stylesheet<'a, 'b>(&self, stylesheet: Arc, possibly_locked_rw_data: &mut RwData<'a, 'b>) { // Find all font-face rules and notify the font cache of them. // GWTODO: Need to handle unloading web fonts. let rw_data = possibly_locked_rw_data.lock(); if stylesheet.is_effective_for_device(&rw_data.stylist.device) { add_font_face_rules(&*stylesheet, &rw_data.stylist.device, &self.font_cache_task, &self.font_cache_sender, &self.outstanding_web_fonts); } possibly_locked_rw_data.block(rw_data); } /// Sets quirks mode for the document, causing the quirks mode stylesheet to be used. fn handle_set_quirks_mode<'a, 'b>(&self, possibly_locked_rw_data: &mut RwData<'a, 'b>) { let mut rw_data = possibly_locked_rw_data.lock(); rw_data.stylist.set_quirks_mode(true); possibly_locked_rw_data.block(rw_data); } fn try_get_layout_root(&self, node: LayoutNode) -> Option { let mut layout_data_ref = node.mutate_layout_data(); let layout_data = match layout_data_ref.as_mut() { None => return None, Some(layout_data) => layout_data, }; let result = layout_data.data.flow_construction_result.swap_out(); let mut flow = match result { ConstructionResult::Flow(mut flow, abs_descendants) => { // Note: Assuming that the root has display 'static' (as per // CSS Section 9.3.1). Otherwise, if it were absolutely // positioned, it would return a reference to itself in // `abs_descendants` and would lead to a circular reference. // Set Root as CB for any remaining absolute descendants. flow.set_absolute_descendants(abs_descendants); flow } _ => return None, }; flow_ref::deref_mut(&mut flow).mark_as_root(); Some(flow) } /// Performs layout constraint solving. /// /// This corresponds to `Reflow()` in Gecko and `layout()` in WebKit/Blink and should be /// benchmarked against those two. It is marked `#[inline(never)]` to aid profiling. #[inline(never)] fn solve_constraints(layout_root: &mut FlowRef, shared_layout_context: &SharedLayoutContext) { let _scope = layout_debug_scope!("solve_constraints"); sequential::traverse_flow_tree_preorder(layout_root, shared_layout_context); } /// Performs layout constraint solving in parallel. /// /// This corresponds to `Reflow()` in Gecko and `layout()` in WebKit/Blink and should be /// benchmarked against those two. It is marked `#[inline(never)]` to aid profiling. #[inline(never)] fn solve_constraints_parallel(traversal: &mut WorkQueue, layout_root: &mut FlowRef, profiler_metadata: Option, time_profiler_chan: time::ProfilerChan, shared_layout_context: &SharedLayoutContext) { let _scope = layout_debug_scope!("solve_constraints_parallel"); // NOTE: this currently computes borders, so any pruning should separate that // operation out. parallel::traverse_flow_tree_preorder(layout_root, profiler_metadata, time_profiler_chan, shared_layout_context, traversal); } fn process_node_geometry_request(&self, requested_node: TrustedNodeAddress, layout_root: &mut FlowRef) -> Rect { let requested_node: OpaqueNode = OpaqueNodeMethods::from_script_node(requested_node); let mut iterator = FragmentLocatingFragmentIterator::new(requested_node); sequential::iterate_through_flow_tree_fragment_border_boxes(layout_root, &mut iterator); iterator.client_rect } /// Return the resolved value of property for a given (pseudo)element. /// https://drafts.csswg.org/cssom/#resolved-value fn process_resolved_style_request(&self, requested_node: TrustedNodeAddress, pseudo: &Option, property: &Atom, layout_root: &mut FlowRef) -> Option { let node = unsafe { LayoutNode::new(&requested_node) }; let layout_node = ThreadSafeLayoutNode::new(&node); let layout_node = match pseudo { &Some(PseudoElement::Before) => layout_node.get_before_pseudo(), &Some(PseudoElement::After) => layout_node.get_after_pseudo(), _ => Some(layout_node) }; let layout_node = match layout_node { None => { // The pseudo doesn't exist, return nothing. Chrome seems to query // the element itself in this case, Firefox uses the resolved value. // https://www.w3.org/Bugs/Public/show_bug.cgi?id=29006 return None; } Some(layout_node) => layout_node }; let style = &*layout_node.style(); let positioned = match style.get_box().position { position::computed_value::T::relative | /*position::computed_value::T::sticky |*/ position::computed_value::T::fixed | position::computed_value::T::absolute => true, _ => false }; //TODO: determine whether requested property applies to the element. // eg. width does not apply to non-replaced inline elements. // Existing browsers disagree about when left/top/right/bottom apply // (Chrome seems to think they never apply and always returns resolved values). // There are probably other quirks. let applies = true; fn used_value_for_position_property(layout_node: ThreadSafeLayoutNode, layout_root: &mut FlowRef, requested_node: TrustedNodeAddress, property: &Atom) -> Option { let layout_data = layout_node.borrow_layout_data(); let position = layout_data.as_ref().map(|layout_data| { match layout_data.data.flow_construction_result { ConstructionResult::Flow(ref flow_ref, _) => flow::base(flow_ref.deref()).stacking_relative_position, // TODO(dzbarsky) search parents until we find node with a flow ref. // https://github.com/servo/servo/issues/8307 _ => ZERO_POINT } }).unwrap_or(ZERO_POINT); let property = match *property { atom!("bottom") => PositionProperty::Bottom, atom!("top") => PositionProperty::Top, atom!("left") => PositionProperty::Left, atom!("right") => PositionProperty::Right, atom!("width") => PositionProperty::Width, atom!("height") => PositionProperty::Height, _ => unreachable!() }; let requested_node: OpaqueNode = OpaqueNodeMethods::from_script_node(requested_node); let mut iterator = PositionRetrievingFragmentBorderBoxIterator::new(requested_node, property, position); sequential::iterate_through_flow_tree_fragment_border_boxes(layout_root, &mut iterator); iterator.result.map(|r| r.to_css_string()) } // TODO: we will return neither the computed nor used value for margin and padding. // Firefox returns blank strings for the computed value of shorthands, // so this should be web-compatible. match *property { atom!("margin-bottom") | atom!("margin-top") | atom!("margin-left") | atom!("margin-right") | atom!("padding-bottom") | atom!("padding-top") | atom!("padding-left") | atom!("padding-right") if applies && style.get_box().display != display::computed_value::T::none => { let (margin_padding, side) = match *property { atom!("margin-bottom") => (MarginPadding::Margin, Side::Bottom), atom!("margin-top") => (MarginPadding::Margin, Side::Top), atom!("margin-left") => (MarginPadding::Margin, Side::Left), atom!("margin-right") => (MarginPadding::Margin, Side::Right), atom!("padding-bottom") => (MarginPadding::Padding, Side::Bottom), atom!("padding-top") => (MarginPadding::Padding, Side::Top), atom!("padding-left") => (MarginPadding::Padding, Side::Left), atom!("padding-right") => (MarginPadding::Padding, Side::Right), _ => unreachable!() }; let requested_node: OpaqueNode = OpaqueNodeMethods::from_script_node(requested_node); let mut iterator = MarginRetrievingFragmentBorderBoxIterator::new(requested_node, side, margin_padding, style.writing_mode); sequential::iterate_through_flow_tree_fragment_border_boxes(layout_root, &mut iterator); iterator.result.map(|r| r.to_css_string()) }, atom!("bottom") | atom!("top") | atom!("right") | atom!("left") if applies && positioned && style.get_box().display != display::computed_value::T::none => { used_value_for_position_property(layout_node, layout_root, requested_node, property) } atom!("width") | atom!("height") if applies && style.get_box().display != display::computed_value::T::none => { used_value_for_position_property(layout_node, layout_root, requested_node, property) } // FIXME: implement used value computation for line-height ref property => { style.computed_value_to_string(property.as_slice()).ok() } } } fn process_offset_parent_query(&self, requested_node: TrustedNodeAddress, layout_root: &mut FlowRef) -> OffsetParentResponse { let requested_node: OpaqueNode = OpaqueNodeMethods::from_script_node(requested_node); let mut iterator = ParentOffsetBorderBoxIterator::new(requested_node); sequential::iterate_through_flow_tree_fragment_border_boxes(layout_root, &mut iterator); let parent_info_index = iterator.parent_nodes.iter().rposition(|info| info.is_some()); match parent_info_index { Some(parent_info_index) => { let parent = iterator.parent_nodes[parent_info_index].as_ref().unwrap(); let origin = iterator.node_border_box.origin - parent.border_box.origin; let size = iterator.node_border_box.size; OffsetParentResponse { node_address: Some(parent.node_address.to_untrusted_node_address()), rect: Rect::new(origin, size), } } None => { OffsetParentResponse::empty() } } } fn compute_abs_pos_and_build_display_list<'a>(&'a mut self, data: &Reflow, layout_root: &mut FlowRef, shared_layout_context: &mut SharedLayoutContext, rw_data: &mut LayoutTaskData) { let writing_mode = flow::base(&**layout_root).writing_mode; let (metadata, sender) = (self.profiler_metadata(), self.time_profiler_chan.clone()); profile(time::ProfilerCategory::LayoutDispListBuild, metadata.clone(), sender.clone(), || { flow::mut_base(flow_ref::deref_mut(layout_root)).stacking_relative_position = LogicalPoint::zero(writing_mode).to_physical(writing_mode, self.viewport_size); flow::mut_base(flow_ref::deref_mut(layout_root)).clip = ClippingRegion::from_rect(&data.page_clip_rect); match (&mut self.parallel_traversal, opts::get().parallel_display_list_building) { (&mut Some(ref mut traversal), true) => { parallel::build_display_list_for_subtree(layout_root, metadata, sender, shared_layout_context, traversal); } _ => { sequential::build_display_list_for_subtree(layout_root, shared_layout_context); } } if data.goal == ReflowGoal::ForDisplay { debug!("Done building display list."); let root_background_color = get_root_flow_background_color( flow_ref::deref_mut(layout_root)); let root_size = { let root_flow = flow::base(&**layout_root); if rw_data.stylist.viewport_constraints().is_some() { root_flow.position.size.to_physical(root_flow.writing_mode) } else { root_flow.overflow.size } }; let mut display_list = box DisplayList::new(); display_list.append_from(&mut flow::mut_base(flow_ref::deref_mut(layout_root)) .display_list_building_result); let origin = Rect::new(Point2D::new(Au(0), Au(0)), root_size); let stacking_context = Arc::new(StackingContext::new(display_list, &origin, &origin, 0, filter::T::new(Vec::new()), mix_blend_mode::T::normal, Matrix4::identity(), Matrix4::identity(), true, false, None)); if opts::get().dump_display_list { stacking_context.print("DisplayList".to_owned()); } if opts::get().dump_display_list_json { println!("{}", serde_json::to_string_pretty(&stacking_context).unwrap()); } rw_data.stacking_context = Some(stacking_context.clone()); let layer_info = LayerInfo::new(layout_root.layer_id(), ScrollPolicy::Scrollable, None); let paint_layer = PaintLayer::new_with_stacking_context(layer_info, stacking_context, root_background_color); debug!("Layout done!"); self.epoch.next(); self.paint_chan .send(LayoutToPaintMsg::PaintInit(self.epoch, paint_layer)) .unwrap(); } }); } /// The high-level routine that performs layout tasks. fn handle_reflow<'a, 'b>(&mut self, data: &ScriptReflow, possibly_locked_rw_data: &mut RwData<'a, 'b>) { // Make sure that every return path from this method joins the script task, // otherwise the script task will panic. struct AutoJoinScriptTask<'a> { data: &'a ScriptReflow }; impl<'a> Drop for AutoJoinScriptTask<'a> { fn drop(&mut self) { self.data.script_join_chan.send(()).unwrap(); } }; let _ajst = AutoJoinScriptTask { data: data }; let document = unsafe { LayoutNode::new(&data.document) }; let document = document.as_document().unwrap(); let node: LayoutNode = match document.root_node() { None => return, Some(x) => x, }; debug!("layout: received layout request for: {}", self.url.serialize()); if log_enabled!(log::LogLevel::Debug) { node.dump(); } let mut rw_data = possibly_locked_rw_data.lock(); let stylesheets: Vec<&Stylesheet> = data.document_stylesheets.iter().map(|entry| &**entry) .collect(); let stylesheets_changed = data.stylesheets_changed; let initial_viewport = data.window_size.initial_viewport; let old_viewport_size = self.viewport_size; let current_screen_size = Size2D::new(Au::from_f32_px(initial_viewport.width.get()), Au::from_f32_px(initial_viewport.height.get())); // Calculate the actual viewport as per DEVICE-ADAPT ยง 6 let device = Device::new(MediaType::Screen, initial_viewport); rw_data.stylist.set_device(device, &stylesheets); let constraints = rw_data.stylist.viewport_constraints().clone(); self.viewport_size = match constraints { Some(ref constraints) => { debug!("Viewport constraints: {:?}", constraints); // other rules are evaluated against the actual viewport Size2D::new(Au::from_f32_px(constraints.size.width.get()), Au::from_f32_px(constraints.size.height.get())) } None => current_screen_size, }; // Handle conditions where the entire flow tree is invalid. let viewport_size_changed = self.viewport_size != old_viewport_size; if viewport_size_changed { if let Some(constraints) = constraints { // let the constellation know about the viewport constraints let ConstellationChan(ref constellation_chan) = rw_data.constellation_chan; constellation_chan.send(ConstellationMsg::ViewportConstrained( self.id, constraints)).unwrap(); } } // If the entire flow tree is invalid, then it will be reflowed anyhow. let needs_dirtying = rw_data.stylist.update(&stylesheets, stylesheets_changed); let needs_reflow = viewport_size_changed && !needs_dirtying; unsafe { if needs_dirtying { LayoutTask::dirty_all_nodes(node); } } if needs_reflow { if let Some(mut flow) = self.try_get_layout_root(node) { LayoutTask::reflow_all_nodes(flow_ref::deref_mut(&mut flow)); } } let modified_elements = document.drain_modified_elements(); if !needs_dirtying { for (el, snapshot) in modified_elements { let hint = rw_data.stylist.compute_restyle_hint(&el, &snapshot, el.get_state()); el.note_restyle_hint(hint); } } // Create a layout context for use throughout the following passes. let mut shared_layout_context = self.build_shared_layout_context(&*rw_data, viewport_size_changed, &self.url, data.reflow_info.goal); if node.is_dirty() || node.has_dirty_descendants() { // Recalculate CSS styles and rebuild flows and fragments. profile(time::ProfilerCategory::LayoutStyleRecalc, self.profiler_metadata(), self.time_profiler_chan.clone(), || { // Perform CSS selector matching and flow construction. match self.parallel_traversal { None => { sequential::traverse_dom_preorder(node, &shared_layout_context); } Some(ref mut traversal) => { parallel::traverse_dom_preorder(node, &shared_layout_context, traversal); } } }); // Retrieve the (possibly rebuilt) root flow. self.root_flow = self.try_get_layout_root(node); } // Send new canvas renderers to the paint task while let Ok((layer_id, renderer)) = self.canvas_layers_receiver.try_recv() { // Just send if there's an actual renderer self.paint_chan.send(LayoutToPaintMsg::CanvasLayer(layer_id, renderer)).unwrap(); } // Perform post-style recalculation layout passes. self.perform_post_style_recalc_layout_passes(&data.reflow_info, &mut rw_data, &mut shared_layout_context); if let Some(mut root_flow) = self.root_flow.clone() { match data.query_type { ReflowQueryType::ContentBoxQuery(node) => rw_data.content_box_response = process_content_box_request(node, &mut root_flow), ReflowQueryType::ContentBoxesQuery(node) => rw_data.content_boxes_response = process_content_boxes_request(node, &mut root_flow), ReflowQueryType::NodeGeometryQuery(node) => rw_data.client_rect_response = self.process_node_geometry_request(node, &mut root_flow), ReflowQueryType::ResolvedStyleQuery(node, ref pseudo, ref property) => { rw_data.resolved_style_response = self.process_resolved_style_request(node, pseudo, property, &mut root_flow) } ReflowQueryType::OffsetParentQuery(node) => rw_data.offset_parent_response = self.process_offset_parent_query(node, &mut root_flow), ReflowQueryType::NoQuery => {} } } } fn set_visible_rects<'a, 'b>(&mut self, new_visible_rects: Vec<(LayerId, Rect)>, possibly_locked_rw_data: &mut RwData<'a, 'b>) -> bool { let mut rw_data = possibly_locked_rw_data.lock(); // First, determine if we need to regenerate the display lists. This will happen if the // layers have moved more than `DISPLAY_PORT_THRESHOLD_SIZE_FACTOR` away from their last // positions. let mut must_regenerate_display_lists = false; let mut old_visible_rects = HashMap::with_hash_state(Default::default()); let inflation_amount = Size2D::new(self.viewport_size.width * DISPLAY_PORT_THRESHOLD_SIZE_FACTOR, self.viewport_size.height * DISPLAY_PORT_THRESHOLD_SIZE_FACTOR); for &(ref layer_id, ref new_visible_rect) in &new_visible_rects { match self.visible_rects.get(layer_id) { None => { old_visible_rects.insert(*layer_id, *new_visible_rect); } Some(old_visible_rect) => { old_visible_rects.insert(*layer_id, *old_visible_rect); if !old_visible_rect.inflate(inflation_amount.width, inflation_amount.height) .intersects(new_visible_rect) { must_regenerate_display_lists = true; } } } } if !must_regenerate_display_lists { // Update `visible_rects` in case there are new layers that were discovered. self.visible_rects = Arc::new(old_visible_rects); return true } debug!("regenerating display lists!"); for &(ref layer_id, ref new_visible_rect) in &new_visible_rects { old_visible_rects.insert(*layer_id, *new_visible_rect); } self.visible_rects = Arc::new(old_visible_rects); // Regenerate the display lists. let reflow_info = Reflow { goal: ReflowGoal::ForDisplay, page_clip_rect: MAX_RECT, }; let mut layout_context = self.build_shared_layout_context(&*rw_data, false, &self.url, reflow_info.goal); self.perform_post_main_layout_passes(&reflow_info, &mut *rw_data, &mut layout_context); true } fn tick_all_animations<'a, 'b>(&mut self, possibly_locked_rw_data: &mut RwData<'a, 'b>) { let mut rw_data = possibly_locked_rw_data.lock(); animation::tick_all_animations(self, &mut rw_data) } pub fn tick_animations(&mut self, rw_data: &mut LayoutTaskData) { let reflow_info = Reflow { goal: ReflowGoal::ForDisplay, page_clip_rect: MAX_RECT, }; let mut layout_context = self.build_shared_layout_context(&*rw_data, false, &self.url, reflow_info.goal); if let Some(mut root_flow) = self.root_flow.clone() { // Perform an abbreviated style recalc that operates without access to the DOM. let animations = &*self.running_animations; profile(time::ProfilerCategory::LayoutStyleRecalc, self.profiler_metadata(), self.time_profiler_chan.clone(), || { animation::recalc_style_for_animations(flow_ref::deref_mut(&mut root_flow), animations) }); } self.perform_post_style_recalc_layout_passes(&reflow_info, &mut *rw_data, &mut layout_context); } fn reflow_with_newly_loaded_web_font<'a, 'b>(&mut self, possibly_locked_rw_data: &mut RwData<'a, 'b>) { let mut rw_data = possibly_locked_rw_data.lock(); font_context::invalidate_font_caches(); let reflow_info = Reflow { goal: ReflowGoal::ForDisplay, page_clip_rect: MAX_RECT, }; let mut layout_context = self.build_shared_layout_context(&*rw_data, false, &self.url, reflow_info.goal); // No need to do a style recalc here. if self.root_flow.is_none() { return } self.perform_post_style_recalc_layout_passes(&reflow_info, &mut *rw_data, &mut layout_context); } fn perform_post_style_recalc_layout_passes<'a>(&'a mut self, data: &Reflow, rw_data: &mut LayoutTaskData, layout_context: &mut SharedLayoutContext) { if let Some(mut root_flow) = self.root_flow.clone() { // Kick off animations if any were triggered, expire completed ones. animation::update_animation_state(&self.constellation_chan, &mut self.running_animations, &self.new_animations_receiver, self.id); profile(time::ProfilerCategory::LayoutRestyleDamagePropagation, self.profiler_metadata(), self.time_profiler_chan.clone(), || { if opts::get().nonincremental_layout || flow_ref::deref_mut(&mut root_flow).compute_layout_damage() .contains(REFLOW_ENTIRE_DOCUMENT) { flow_ref::deref_mut(&mut root_flow).reflow_entire_document() } }); if opts::get().trace_layout { layout_debug::begin_trace(root_flow.clone()); } // Resolve generated content. profile(time::ProfilerCategory::LayoutGeneratedContent, self.profiler_metadata(), self.time_profiler_chan.clone(), || sequential::resolve_generated_content(&mut root_flow, &layout_context)); // Perform the primary layout passes over the flow tree to compute the locations of all // the boxes. profile(time::ProfilerCategory::LayoutMain, self.profiler_metadata(), self.time_profiler_chan.clone(), || { let profiler_metadata = self.profiler_metadata(); match self.parallel_traversal { None => { // Sequential mode. LayoutTask::solve_constraints(&mut root_flow, &layout_context) } Some(ref mut parallel) => { // Parallel mode. LayoutTask::solve_constraints_parallel(parallel, &mut root_flow, profiler_metadata, self.time_profiler_chan.clone(), &*layout_context); } } }); self.perform_post_main_layout_passes(data, rw_data, layout_context); } } fn perform_post_main_layout_passes<'a>(&'a mut self, data: &Reflow, rw_data: &mut LayoutTaskData, layout_context: &mut SharedLayoutContext) { // Build the display list if necessary, and send it to the painter. if let Some(mut root_flow) = self.root_flow.clone() { self.compute_abs_pos_and_build_display_list(data, &mut root_flow, &mut *layout_context, rw_data); self.first_reflow = false; if opts::get().trace_layout { layout_debug::end_trace(); } if opts::get().dump_flow_tree { root_flow.dump(); } self.generation += 1; } } unsafe fn dirty_all_nodes(node: LayoutNode) { for node in node.traverse_preorder() { // TODO(cgaebel): mark nodes which are sensitive to media queries as // "changed": // > node.set_changed(true); node.set_dirty(true); node.set_dirty_descendants(true); } } fn reflow_all_nodes(flow: &mut Flow) { debug!("reflowing all nodes!"); flow::mut_base(flow).restyle_damage.insert(REFLOW | REPAINT); for child in flow::child_iter(flow) { LayoutTask::reflow_all_nodes(child); } } /// Handles a message to destroy layout data. Layout data must be destroyed on *this* task /// because the struct type is transmuted to a different type on the script side. unsafe fn handle_reap_layout_data(&self, layout_data: LayoutData) { let _: LayoutDataWrapper = transmute(layout_data); } /// Returns profiling information which is passed to the time profiler. fn profiler_metadata(&self) -> Option { Some(TimerMetadata { url: self.url.serialize(), iframe: if self.is_iframe { TimerMetadataFrameType::IFrame } else { TimerMetadataFrameType::RootWindow }, incremental: if self.first_reflow { TimerMetadataReflowType::FirstReflow } else { TimerMetadataReflowType::Incremental }, }) } } struct FragmentLocatingFragmentIterator { node_address: OpaqueNode, client_rect: Rect, } impl FragmentLocatingFragmentIterator { fn new(node_address: OpaqueNode) -> FragmentLocatingFragmentIterator { FragmentLocatingFragmentIterator { node_address: node_address, client_rect: Rect::zero() } } } struct ParentBorderBoxInfo { node_address: OpaqueNode, border_box: Rect, } struct ParentOffsetBorderBoxIterator { node_address: OpaqueNode, last_level: i32, has_found_node: bool, node_border_box: Rect, parent_nodes: Vec>, } impl ParentOffsetBorderBoxIterator { fn new(node_address: OpaqueNode) -> ParentOffsetBorderBoxIterator { ParentOffsetBorderBoxIterator { node_address: node_address, last_level: -1, has_found_node: false, node_border_box: Rect::zero(), parent_nodes: Vec::new(), } } } impl FragmentBorderBoxIterator for FragmentLocatingFragmentIterator { fn process(&mut self, fragment: &Fragment, _: i32, border_box: &Rect) { let style_structs::Border { border_top_width: top_width, border_right_width: right_width, border_bottom_width: bottom_width, border_left_width: left_width, .. } = *fragment.style.get_border(); self.client_rect.origin.y = top_width.to_px(); self.client_rect.origin.x = left_width.to_px(); self.client_rect.size.width = (border_box.size.width - left_width - right_width).to_px(); self.client_rect.size.height = (border_box.size.height - top_width - bottom_width).to_px(); } fn should_process(&mut self, fragment: &Fragment) -> bool { fragment.node == self.node_address } } // https://drafts.csswg.org/cssom-view/#extensions-to-the-htmlelement-interface impl FragmentBorderBoxIterator for ParentOffsetBorderBoxIterator { fn process(&mut self, fragment: &Fragment, level: i32, border_box: &Rect) { if fragment.node == self.node_address { // Found the fragment in the flow tree that matches the // DOM node being looked for. self.has_found_node = true; self.node_border_box = *border_box; // offsetParent returns null if the node is fixed. if fragment.style.get_box().position == computed_values::position::T::fixed { self.parent_nodes.clear(); } } else if level > self.last_level { // TODO(gw): Is there a less fragile way of checking whether this // fragment is the body element, rather than just checking that // the parent nodes stack contains the root node only? let is_body_element = self.parent_nodes.len() == 1; let is_valid_parent = match (is_body_element, fragment.style.get_box().position, &fragment.specific) { // Spec says it's valid if any of these are true: // 1) Is the body element // 2) Is static position *and* is a table or table cell // 3) Is not static position (true, _, _) | (false, computed_values::position::T::static_, &SpecificFragmentInfo::Table) | (false, computed_values::position::T::static_, &SpecificFragmentInfo::TableCell) | (false, computed_values::position::T::absolute, _) | (false, computed_values::position::T::relative, _) | (false, computed_values::position::T::fixed, _) => true, // Otherwise, it's not a valid parent (false, computed_values::position::T::static_, _) => false, }; let parent_info = if is_valid_parent { Some(ParentBorderBoxInfo { border_box: *border_box, node_address: fragment.node, }) } else { None }; self.parent_nodes.push(parent_info); } else if level < self.last_level { self.parent_nodes.pop(); } } fn should_process(&mut self, _: &Fragment) -> bool { !self.has_found_node } } // The default computed value for background-color is transparent (see // http://dev.w3.org/csswg/css-backgrounds/#background-color). However, we // need to propagate the background color from the root HTML/Body // element (http://dev.w3.org/csswg/css-backgrounds/#special-backgrounds) if // it is non-transparent. The phrase in the spec "If the canvas background // is not opaque, what shows through is UA-dependent." is handled by rust-layers // clearing the frame buffer to white. This ensures that setting a background // color on an iframe element, while the iframe content itself has a default // transparent background color is handled correctly. fn get_root_flow_background_color(flow: &mut Flow) -> AzColor { if !flow.is_block_like() { return color::transparent() } let block_flow = flow.as_mut_block(); let kid = match block_flow.base.children.iter_mut().next() { None => return color::transparent(), Some(kid) => kid, }; if !kid.is_block_like() { return color::transparent() } let kid_block_flow = kid.as_block(); kid_block_flow.fragment .style .resolve_color(kid_block_flow.fragment.style.get_background().background_color) .to_gfx_color() }