Add layout debugger support to layout_2020

components/layout_thread_2020/lib.rs

@@ -36,6 +36,7 @@ use ipc_channel::ipc::{self, IpcReceiver, IpcSender};
 use ipc_channel::router::ROUTER;
 use layout::context::LayoutContext;
 use layout::display_list::{DisplayListBuilder, WebRenderImageInfo};
+use layout::layout_debug;
 use layout::query::{
     process_content_box_request, process_content_boxes_request, LayoutRPCImpl, LayoutThreadData,
 };
@@ -175,7 +176,7 @@ pub struct LayoutThread {
     box_tree_root: RefCell<Option<BoxTreeRoot>>,
 
     /// The root of the fragment tree.
-    fragment_tree_root: RefCell<Option<FragmentTreeRoot>>,
+    fragment_tree_root: RefCell<Option<Arc<FragmentTreeRoot>>>,
 
     /// The document-specific shared lock used for author-origin stylesheets
     document_shared_lock: Option<SharedRwLock>,
@@ -234,6 +235,10 @@ pub struct LayoutThread {
 
     /// Emits notifications when there is a relayout.
     relayout_event: bool,
+
+    /// True if each step of layout is traced to an external JSON file
+    /// for debugging purposes.
+    trace_layout: bool,
 }
 
 impl LayoutThreadFactory for LayoutThread {
@@ -266,7 +271,7 @@ impl LayoutThreadFactory for LayoutThread {
         dump_rule_tree: bool,
         relayout_event: bool,
         _nonincremental_layout: bool,
-        _trace_layout: bool,
+        trace_layout: bool,
         dump_flow_tree: bool,
     ) {
         thread::Builder::new()
@@ -314,6 +319,7 @@ impl LayoutThreadFactory for LayoutThread {
                         dump_style_tree,
                         dump_rule_tree,
                         dump_flow_tree,
+                        trace_layout,
                     );
 
                     let reporter_name = format!("layout-reporter-{}", id);
@@ -482,6 +488,7 @@ impl LayoutThread {
         dump_style_tree: bool,
         dump_rule_tree: bool,
         dump_flow_tree: bool,
+        trace_layout: bool,
     ) -> LayoutThread {
         // Let webrender know about this pipeline by sending an empty display list.
         webrender_api_sender.send_initial_transaction(webrender_document, id.to_webrender());
@@ -567,6 +574,7 @@ impl LayoutThread {
             dump_style_tree,
             dump_rule_tree,
             dump_flow_tree,
+            trace_layout,
         }
     }
 
@@ -866,9 +874,9 @@ impl LayoutThread {
             self.dump_style_tree,
             self.dump_rule_tree,
             self.relayout_event,
-            true,  // nonincremental_layout
-            false, // trace_layout
-            self.dump_flow_tree,
+            true,              // nonincremental_layout
+            self.trace_layout, // trace_layout
+            self.dump_flow_tree, // dump_flow_tree
         );
     }
 
@@ -1165,7 +1173,7 @@ impl LayoutThread {
                 run_layout()
             };
             *self.box_tree_root.borrow_mut() = Some(box_tree);
-            *self.fragment_tree_root.borrow_mut() = Some(fragment_tree);
+            *self.fragment_tree_root.borrow_mut() = Some(Arc::new(fragment_tree));
         }
 
         for element in elements_with_snapshot {
@@ -1195,7 +1203,7 @@ impl LayoutThread {
         // Perform post-style recalculation layout passes.
         if let Some(root) = &*self.fragment_tree_root.borrow() {
             self.perform_post_style_recalc_layout_passes(
-                root,
+                root.clone(),
                 &data.reflow_goal,
                 Some(&document),
                 &mut layout_context,
@@ -1358,7 +1366,7 @@ impl LayoutThread {
             let mut layout_context = self.build_layout_context(guards, false, &snapshots, origin);
 
             self.perform_post_style_recalc_layout_passes(
-                root,
+                root.clone(),
                 &ReflowGoal::TickAnimations,
                 None,
                 &mut layout_context,
@@ -1369,7 +1377,7 @@ impl LayoutThread {
 
     fn perform_post_style_recalc_layout_passes(
         &self,
-        fragment_tree: &FragmentTreeRoot,
+        fragment_tree: Arc<FragmentTreeRoot>,
         reflow_goal: &ReflowGoal,
         document: Option<&ServoLayoutDocument>,
         context: &mut LayoutContext,
@@ -1384,6 +1392,11 @@ impl LayoutThread {
                 .needs_paint_from_layout();
             return;
         }
+
+        if self.trace_layout {
+            layout_debug::begin_trace(fragment_tree.clone());
+        }
+
         if let Some(document) = document {
             document.will_paint();
         }
@@ -1426,6 +1439,10 @@ impl LayoutThread {
             display_list.wr.finalize(),
         );
 
+        if self.trace_layout {
+            layout_debug::end_trace(self.generation.get());
+        }
+
         self.generation.set(self.generation.get() + 1);
     }