layout: Implement flow tree dumping with RUST_LOG=debug is on.

r? @pcwalton

components/layout/layout_task.rs

@@ -30,6 +30,7 @@ use gfx::render_task::{RenderInitMsg, RenderChan, RenderLayer};
 use gfx::{render_task, color};
 use layout_traits;
 use layout_traits::{LayoutControlMsg, LayoutTaskFactory};
+use log;
 use script::dom::bindings::js::JS;
 use script::dom::node::{ElementNodeTypeId, LayoutDataRef, Node};
 use script::dom::element::{HTMLBodyElementTypeId, HTMLHtmlElementTypeId};
@@ -566,7 +567,9 @@ impl LayoutTask {
 
         debug!("layout: received layout request for: {:s}", data.url.serialize());
         debug!("layout: parsed Node tree");
-        debug!("{:?}", node.dump());
+        if log_enabled!(log::DEBUG) {
+            node.dump();
+        }
 
         let mut rw_data = self.lock_rw_data(possibly_locked_rw_data);
 

components/layout/traversal.rs

@@ -266,7 +266,7 @@ impl PreorderFlow for FlowTreeVerification {
     fn process(&mut self, flow: &mut Flow) {
         let base = flow::base(flow);
         if !base.flags.is_leaf() && !base.flags.is_nonleaf() {
-            println("flow tree verification failed: flow wasn't a leaf or a nonleaf!");
+            println!("flow tree verification failed: flow wasn't a leaf or a nonleaf!");
             flow.dump();
             fail!("flow tree verification failed")
         }

components/layout/wrapper.rs

@@ -126,11 +126,6 @@ pub trait TLayoutNode {
 
     /// Returns the first child of this node.
     fn first_child(&self) -> Option<Self>;
-
-    /// Dumps this node tree, for debugging.
-    fn dump(&self) {
-        // TODO(pcwalton): Reimplement this in a way that's safe for layout to call.
-    }
 }
 
 /// A wrapper so that layout can access only the methods that it should have access to. Layout must
@@ -206,6 +201,28 @@ impl<'ln> LayoutNode<'ln> {
         })
     }
 
+    pub fn dump(self) {
+        self.dump_indent(0);
+    }
+
+    fn dump_indent(self, indent: uint) {
+        let mut s = String::new();
+        for _ in range(0, indent) {
+            s.push_str("  ");
+        }
+
+        s.push_str(self.debug_str().as_slice());
+        error!("{:s}", s);
+
+        for kid in self.children() {
+            kid.dump_indent(indent + 1);
+        }
+    }
+
+    fn debug_str(self) -> String {
+        format!("{}: dirty={}", self.type_id(), self.is_dirty())
+    }
+
     pub fn flow_debug_id(self) -> uint {
         let layout_data_ref = self.borrow_layout_data();
         match *layout_data_ref {

components/script/dom/element.rs

@@ -73,7 +73,7 @@ impl Reflectable for Element {
     }
 }
 
-#[deriving(PartialEq)]
+#[deriving(PartialEq, Show)]
 #[jstraceable]
 pub enum ElementTypeId {
     HTMLElementTypeId,
@@ -1172,4 +1172,3 @@ impl<'a> style::TElement<'a> for JSRef<'a, Element> {
         }
     }
 }
-

components/script/dom/node.rs

@@ -251,7 +251,7 @@ impl LayoutDataRef {
 }
 
 /// The different types of nodes.
-#[deriving(PartialEq)]
+#[deriving(PartialEq, Show)]
 #[jstraceable]
 pub enum NodeTypeId {
     DoctypeNodeTypeId,