Implements reflow events debugging.

Start servo with -Z relayout-event and you should have
reflow events printed to the terminal.

components/script/dom/document.rs

@@ -56,7 +56,7 @@ use dom::processinginstruction::ProcessingInstruction;
 use dom::range::Range;
 use dom::treewalker::TreeWalker;
 use dom::uievent::UIEvent;
-use dom::window::{Window, WindowHelpers};
+use dom::window::{Window, WindowHelpers, ReflowReason};
 
 use layout_interface::{HitTestResponse, MouseOverResponse};
 use msg::compositor_msg::ScriptListener;
@@ -523,7 +523,7 @@ impl<'a> DocumentHelpers<'a> for JSRef<'a, Document> {
         el.authentic_click_activation(event);
 
         self.commit_focus_transaction();
-        window.r().reflow(ReflowGoal::ForDisplay, ReflowQueryType::NoQuery);
+        window.r().reflow(ReflowGoal::ForDisplay, ReflowQueryType::NoQuery, ReflowReason::MouseEvent);
     }
 
     /// Return need force reflow or not
@@ -664,7 +664,7 @@ impl<'a> DocumentHelpers<'a> for JSRef<'a, Document> {
             _ => ()
         }
 
-        window.r().reflow(ReflowGoal::ForDisplay, ReflowQueryType::NoQuery);
+        window.r().reflow(ReflowGoal::ForDisplay, ReflowQueryType::NoQuery, ReflowReason::KeyEvent);
     }
 
     fn set_current_script(self, script: Option<JSRef<HTMLScriptElement>>) {

components/script/dom/window.rs

@@ -41,6 +41,7 @@ use net::image_cache_task::ImageCacheTask;
 use net::resource_task::ResourceTask;
 use net::storage_task::StorageTask;
 use util::geometry::{self, Au, MAX_RECT};
+use util::opts;
 use util::str::{DOMString,HTML_SPACE_CHARACTERS};
 
 use geom::{Point2D, Rect, Size2D};
@@ -63,6 +64,19 @@ use std::sync::mpsc::{channel, Receiver};
 use std::sync::mpsc::TryRecvError::{Empty, Disconnected};
 use time;
 
+/// Extra information concerning the reason for reflowing.
+pub enum ReflowReason {
+    CachedPageNeededReflow,
+    FirstLoad,
+    KeyEvent,
+    MouseEvent,
+    Query,
+    ReceivedReflowEvent,
+    Timer,
+    Viewport,
+    WindowResize,
+}
+
 #[dom_struct]
 pub struct Window {
     eventtarget: EventTarget,
@@ -397,7 +411,7 @@ pub trait WindowHelpers {
     fn init_browser_context(self, doc: JSRef<Document>, frame_element: Option<JSRef<Element>>);
     fn load_url(self, href: DOMString);
     fn handle_fire_timer(self, timer_id: TimerId);
-    fn reflow(self, goal: ReflowGoal, query_type: ReflowQueryType);
+    fn reflow(self, goal: ReflowGoal, query_type: ReflowQueryType, reason: ReflowReason);
     fn join_layout(self);
     fn layout(&self) -> &LayoutRPC;
     fn content_box_query(self, content_box_request: TrustedNodeAddress) -> Rect<Au>;
@@ -480,7 +494,7 @@ impl<'a> WindowHelpers for JSRef<'a, Window> {
     /// 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.
-    fn reflow(self, goal: ReflowGoal, query_type: ReflowQueryType) {
+    fn reflow(self, goal: ReflowGoal, query_type: ReflowQueryType, reason: ReflowReason) {
         let document = self.Document().root();
         let root = document.r().GetDocumentElement().root();
         let root = match root.r() {
@@ -511,6 +525,11 @@ impl<'a> WindowHelpers for JSRef<'a, Window> {
 
         let window_size = self.window_size.get();
 
+        // On debug mode, print the reflow event information.
+        if opts::get().relayout_event {
+            debug_reflow_events(&goal, &query_type, &reason);
+        }
+
         // Send new document and relevant styles to layout.
         let reflow = box Reflow {
             document_root: root.to_trusted_node_address(),
@@ -562,14 +581,14 @@ impl<'a> WindowHelpers for JSRef<'a, Window> {
     }
 
     fn content_box_query(self, content_box_request: TrustedNodeAddress) -> Rect<Au> {
-        self.reflow(ReflowGoal::ForScriptQuery, ReflowQueryType::ContentBoxQuery(content_box_request));
+        self.reflow(ReflowGoal::ForScriptQuery, ReflowQueryType::ContentBoxQuery(content_box_request), ReflowReason::Query);
         self.join_layout(); //FIXME: is this necessary, or is layout_rpc's mutex good enough?
         let ContentBoxResponse(rect) = self.layout_rpc.content_box();
         rect
     }
 
     fn content_boxes_query(self, content_boxes_request: TrustedNodeAddress) -> Vec<Rect<Au>> {
-        self.reflow(ReflowGoal::ForScriptQuery, ReflowQueryType::ContentBoxesQuery(content_boxes_request));
+        self.reflow(ReflowGoal::ForScriptQuery, ReflowQueryType::ContentBoxesQuery(content_boxes_request), ReflowReason::Query);
         self.join_layout(); //FIXME: is this necessary, or is layout_rpc's mutex good enough?
         let ContentBoxesResponse(rects) = self.layout_rpc.content_boxes();
         rects
@@ -609,7 +628,7 @@ impl<'a> WindowHelpers for JSRef<'a, Window> {
 
     fn handle_fire_timer(self, timer_id: TimerId) {
         self.timers.fire_timer(timer_id, self);
-        self.reflow(ReflowGoal::ForDisplay, ReflowQueryType::NoQuery);
+        self.reflow(ReflowGoal::ForDisplay, ReflowQueryType::NoQuery, ReflowReason::Timer);
     }
 
     fn set_fragment_name(self, fragment: Option<String>) {
@@ -715,7 +734,6 @@ impl<'a> WindowHelpers for JSRef<'a, Window> {
     fn freeze(self) {
         self.timers.suspend();
     }
-
 }
 
 impl Window {
@@ -798,3 +816,31 @@ fn should_move_clip_rect(clip_rect: Rect<Au>, new_viewport: Rect<f32>) -> bool{
     (clip_rect.origin.y - new_viewport.origin.y).abs() <= viewport_scroll_margin.height ||
     (clip_rect.max_y() - new_viewport.max_y()).abs() <= viewport_scroll_margin.height
 }
+
+fn debug_reflow_events(goal: &ReflowGoal, query_type: &ReflowQueryType, reason: &ReflowReason) {
+    let mut debug_msg = String::from_str("****");
+    match *goal {
+        ReflowGoal::ForDisplay => debug_msg.push_str("\tForDisplay"),
+        ReflowGoal::ForScriptQuery => debug_msg.push_str("\tForScriptQuery"),
+    }
+
+    match *query_type {
+        ReflowQueryType::NoQuery => debug_msg.push_str("\tNoQuery"),
+        ReflowQueryType::ContentBoxQuery(_n) => debug_msg.push_str("\tContentBoxQuery"),
+        ReflowQueryType::ContentBoxesQuery(_n) => debug_msg.push_str("\tContentBoxesQuery"),
+    }
+
+    match *reason {
+        ReflowReason::CachedPageNeededReflow => debug_msg.push_str("\tCachedPageNeededReflow"),
+        ReflowReason::FirstLoad => debug_msg.push_str("\tFirstLoad"),
+        ReflowReason::KeyEvent => debug_msg.push_str("\tKeyEvent"),
+        ReflowReason::MouseEvent => debug_msg.push_str("\tMouseEvent"),
+        ReflowReason::Query => debug_msg.push_str("\tQuery"),
+        ReflowReason::ReceivedReflowEvent => debug_msg.push_str("\tReceivedReflowEvent"),
+        ReflowReason::Timer => debug_msg.push_str("\tTimer"),
+        ReflowReason::Viewport => debug_msg.push_str("\tViewport"),
+        ReflowReason::WindowResize => debug_msg.push_str("\tWindowResize"),
+    }
+
+    println!("{}", debug_msg);
+}

components/script/script_task.rs

@@ -36,7 +36,7 @@ use dom::event::{Event, EventHelpers};
 use dom::uievent::UIEvent;
 use dom::eventtarget::EventTarget;
 use dom::node::{self, Node, NodeHelpers, NodeDamage, window_from_node};
-use dom::window::{Window, WindowHelpers, ScriptHelpers};
+use dom::window::{Window, WindowHelpers, ScriptHelpers, ReflowReason};
 use dom::worker::{Worker, TrustedWorkerAddress};
 use parse::html::{HTMLInput, parse_html};
 use layout_interface::{ScriptLayoutChan, LayoutChan, ReflowGoal, ReflowQueryType};
@@ -697,7 +697,7 @@ impl ScriptTask {
                 let window = inner_page.window().root();
                 if window.r().set_page_clip_rect_with_new_viewport(rect) {
                     let page = get_page(page, id);
-                    self.force_reflow(&*page);
+                    self.force_reflow(&*page, ReflowReason::Viewport);
                 }
                 return;
             }
@@ -771,7 +771,7 @@ impl ScriptTask {
 
         let needed_reflow = page.set_reflow_status(false);
         if needed_reflow {
-            self.force_reflow(&*page);
+            self.force_reflow(&*page, ReflowReason::CachedPageNeededReflow);
         }
     }
 
@@ -1007,7 +1007,7 @@ impl ScriptTask {
         debug!("kicking off initial reflow of {:?}", final_url);
         document.r().content_changed(NodeCast::from_ref(document.r()),
                                      NodeDamage::OtherNodeDamage);
-        window.r().reflow(ReflowGoal::ForDisplay, ReflowQueryType::NoQuery);
+        window.r().reflow(ReflowGoal::ForDisplay, ReflowQueryType::NoQuery, ReflowReason::FirstLoad);
 
         // No more reflow required
         page.set_reflow_status(false);
@@ -1060,11 +1060,11 @@ impl ScriptTask {
     }
 
     /// Reflows non-incrementally.
-    fn force_reflow(&self, page: &Page) {
+    fn force_reflow(&self, page: &Page, reason: ReflowReason) {
         let document = page.document().root();
         document.r().dirty_all_nodes();
         let window = window_from_node(document.r()).root();
-        window.r().reflow(ReflowGoal::ForDisplay, ReflowQueryType::NoQuery);
+        window.r().reflow(ReflowGoal::ForDisplay, ReflowQueryType::NoQuery, reason);
     }
 
     /// This is the main entry point for receiving and dispatching DOM events.
@@ -1113,7 +1113,7 @@ impl ScriptTask {
                 let mouse_over_targets = &mut *self.mouse_over_targets.borrow_mut();
 
                 if document.r().handle_mouse_move_event(self.js_runtime.ptr, point, mouse_over_targets) {
-                    self.force_reflow(&page)
+                    self.force_reflow(&page, ReflowReason::MouseEvent)
                 }
             }
 
@@ -1151,7 +1151,7 @@ impl ScriptTask {
         let page = get_page(&self.root_page(), pipeline_id);
         let window = page.window().root();
         window.r().set_window_size(new_size);
-        self.force_reflow(&*page);
+        self.force_reflow(&*page, ReflowReason::WindowResize);
 
         let document = page.document().root();
         let fragment_node = window.r().steal_fragment_name()
@@ -1177,7 +1177,7 @@ impl ScriptTask {
     fn handle_reflow_event(&self, pipeline_id: PipelineId) {
         debug!("script got reflow event");
         let page = get_page(&self.root_page(), pipeline_id);
-        self.force_reflow(&*page);
+        self.force_reflow(&*page, ReflowReason::ReceivedReflowEvent);
     }
 
     /// Initiate a non-blocking fetch for a specified resource. Stores the InProgressLoad

components/util/opts.rs

@@ -113,6 +113,9 @@ pub struct Opts {
     /// Dumps the flow tree after a layout.
     pub dump_display_list: bool,
 
+    /// Emits notifications when there is a relayout.
+    pub relayout_event: bool,
+
     /// Whether to show an error when display list geometry escapes flow overflow regions.
     pub validate_display_list_geometry: bool,
 
@@ -136,6 +139,7 @@ pub fn print_debug_usage(app: &str)  {
     print_option("disable-text-aa", "Disable antialiasing of rendered text.");
     print_option("dump-flow-tree", "Print the flow tree after each layout.");
     print_option("dump-display-list", "Print the display list after each layout.");
+    print_option("relayout-event", "Print notifications when there is a relayout.");
     print_option("profile-tasks", "Instrument each task, writing the output to a file.");
     print_option("show-compositor-borders", "Paint borders along layer and tile boundaries.");
     print_option("show-fragment-borders", "Paint borders along fragment boundaries.");
@@ -188,6 +192,7 @@ pub fn default_opts() -> Opts {
         user_agent: None,
         dump_flow_tree: false,
         dump_display_list: false,
+        relayout_event: false,
         validate_display_list_geometry: false,
         profile_tasks: false,
         resources_path: None,
@@ -336,6 +341,7 @@ pub fn from_cmdline_args(args: &[String]) -> bool {
         enable_text_antialiasing: !debug_options.contains(&"disable-text-aa"),
         dump_flow_tree: debug_options.contains(&"dump-flow-tree"),
         dump_display_list: debug_options.contains(&"dump-display-list"),
+        relayout_event: debug_options.contains(&"relayout-event"),
         validate_display_list_geometry: debug_options.contains(&"validate-display-list-geometry"),
         resources_path: opt_match.opt_str("resources-path"),
     };