auto merge of #646 : kmcallister/servo/incremental-layout, r=metajack

This is a first attempt at incremental layout.  When recomputing styles, we compare old and new CSS properties to determine which layout steps can be skipped.

Since I'm new to Servo I'm not sure that my code matches the idioms of the project.  Please don't hold back with review comments :)

src/components/gfx/font_context.rs

@@ -134,11 +134,8 @@ impl<'self> FontContext {
             let transformed_family_name = self.transform_family(family_name);
             debug!("(create font group) transformed family is `%s`", transformed_family_name);
 
-            let result = match self.font_list {
-                Some(ref fl) => {
-                    fl.find_font_in_family(transformed_family_name, style)
-                },
-                None => None,
+            let result = do self.font_list.chain_ref |fl| {
+                fl.find_font_in_family(transformed_family_name, style)
             };
 
             let mut found = false;
@@ -162,11 +159,8 @@ impl<'self> FontContext {
         let last_resort = FontList::get_last_resort_font_families();
 
         for last_resort.iter().advance |family| {
-            let result = match self.font_list {
-                Some(ref fl) => {
-                    fl.find_font_in_family(*family, style)
-                },
-                None => None,
+            let result = do self.font_list.chain_ref |fl| {
+                fl.find_font_in_family(*family, style)
             };
 
             for result.iter().advance |font_entry| {

src/components/gfx/opts.rs

@@ -78,11 +78,9 @@ pub fn from_cmdline_args(args: &[~str]) -> Opts {
         None => 1,      // FIXME: Number of cores.
     };
 
-    let profiler_period: Option<float> =
-        // if only flag is present, default to 5 second period
-        match getopts::opt_default(&opt_match, "p", "5") {
-        Some(period) => Some(float::from_str(period).get()),
-        None => None,
+    // if only flag is present, default to 5 second period
+    let profiler_period = do getopts::opt_default(&opt_match, "p", "5").map |period| {
+        float::from_str(*period).get()
     };
 
     let exit_after_load = getopts::opt_present(&opt_match, "x");

src/components/main/css/matching.rs

@@ -6,6 +6,7 @@
 
 use css::node_util::NodeUtil;
 use css::select_handler::NodeSelectHandler;
+use layout::incremental;
 
 use script::dom::node::{AbstractNode, LayoutView};
 use newcss::complete::CompleteSelectResults;
@@ -31,6 +32,13 @@ impl MatchMethods for AbstractNode<LayoutView> {
             let incomplete_results = select_ctx.select_style(self, &select_handler);
             // Combine this node's results with its parent's to resolve all inherited values
             let complete_results = compose_results(*self, incomplete_results);
+
+            // If there was an existing style, compute the damage that
+            // incremental layout will need to fix.
+            if self.have_css_select_results() {
+                let damage = incremental::compute_damage(self, self.get_css_select_results(), &complete_results);
+                self.set_restyle_damage(damage);
+            }
             self.set_css_select_results(complete_results);
         }
 

src/components/main/css/node_style.rs

@@ -5,13 +5,15 @@
 // Style retrieval from DOM elements.
 
 use css::node_util::NodeUtil;
+use layout::incremental::RestyleDamage;
 
 use newcss::complete::CompleteStyle;
 use script::dom::node::{AbstractNode, LayoutView};
 
 /// Node mixin providing `style` method that returns a `NodeStyle`
 pub trait StyledNode {
     fn style(&self) -> CompleteStyle;
+    fn restyle_damage(&self) -> RestyleDamage;
 }
 
 impl StyledNode for AbstractNode<LayoutView> {
@@ -20,4 +22,8 @@ impl StyledNode for AbstractNode<LayoutView> {
         let results = self.get_css_select_results();
         results.computed_style()
     }
+
+    fn restyle_damage(&self) -> RestyleDamage {
+        self.get_restyle_damage()
+    }
 }

src/components/main/css/node_util.rs

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use layout::aux::LayoutAuxMethods;
+use layout::incremental::RestyleDamage;
 
 use std::cast::transmute;
 use newcss::complete::CompleteSelectResults;
@@ -11,6 +12,10 @@ use script::dom::node::{AbstractNode, LayoutView};
 pub trait NodeUtil<'self> {
     fn get_css_select_results(self) -> &'self CompleteSelectResults;
     fn set_css_select_results(self, decl: CompleteSelectResults);
+    fn have_css_select_results(self) -> bool;
+
+    fn get_restyle_damage(self) -> RestyleDamage;
+    fn set_restyle_damage(self, damage: RestyleDamage);
 }
 
 impl<'self> NodeUtil<'self> for AbstractNode<LayoutView> {
@@ -32,6 +37,11 @@ impl<'self> NodeUtil<'self> for AbstractNode<LayoutView> {
         }
     }
 
+    /// Does this node have a computed style yet?
+    fn have_css_select_results(self) -> bool {
+        self.has_layout_data() && self.layout_data().style.is_some()
+    }
+
     /// Update the computed style of an HTML element with a style specified by CSS.
     fn set_css_select_results(self, decl: CompleteSelectResults) {
         if !self.has_layout_data() {
@@ -40,4 +50,30 @@ impl<'self> NodeUtil<'self> for AbstractNode<LayoutView> {
 
         self.layout_data().style = Some(decl);
     }
+
+    /// Get the description of how to account for recent style changes.
+    /// This is a simple bitfield and fine to copy by value.
+    fn get_restyle_damage(self) -> RestyleDamage {
+        // For DOM elements, if we haven't computed damage yet, assume the worst.
+        // Other nodes don't have styles.
+        let default = if self.is_element() {
+            RestyleDamage::all()
+        } else {
+            RestyleDamage::none()
+        };
+
+        if !self.has_layout_data() {
+            return default;
+        }
+        self.layout_data().restyle_damage.get_or_default(default)
+    }
+
+    /// Set the restyle damage field.
+    fn set_restyle_damage(self, damage: RestyleDamage) {
+        if !self.has_layout_data() {
+            fail!(~"set_restyle_damage() called on a node without aux data!");
+        }
+
+        self.layout_data().restyle_damage = Some(damage);
+    }
 }

src/components/main/css/select_handler.rs

@@ -30,17 +30,14 @@ impl SelectHandler<AbstractNode<LayoutView>> for NodeSelectHandler {
 
     fn named_parent_node(&self, node: &AbstractNode<LayoutView>, name: &str)
                          -> Option<AbstractNode<LayoutView>> {
-        match node.parent_node() {
-            Some(parent) => {
-                do with_node_name(parent) |node_name| {
-                    if eq_slice(name, node_name) {
-                        Some(parent)
-                    } else {
-                        None
-                    }
+        do node.parent_node().chain |parent| {
+            do with_node_name(parent) |node_name| {
+                if eq_slice(name, node_name) {
+                    Some(parent)
+                } else {
+                    None
                 }
             }
-            None => None
         }
     }
 

src/components/main/layout/aux.rs

@@ -5,6 +5,7 @@
 //! Code for managing the layout data in the DOM.
 
 use layout::flow::FlowContext;
+use layout::incremental::RestyleDamage;
 
 use newcss::complete::CompleteSelectResults;
 use script::dom::node::{AbstractNode, LayoutView};
@@ -15,6 +16,9 @@ pub struct LayoutData {
     /// The results of CSS styling for this node.
     style: Option<CompleteSelectResults>,
 
+    /// Description of how to account for recent style changes.
+    restyle_damage: Option<RestyleDamage>,
+
     /// The CSS flow that this node is associated with.
     flow: Option<FlowContext>,
 }
@@ -24,6 +28,7 @@ impl LayoutData {
     pub fn new() -> LayoutData {
         LayoutData {
             style: None,
+            restyle_damage: None,
             flow: None,
         }
     }

src/components/main/layout/box_builder.rs

@@ -356,14 +356,8 @@ impl LayoutTreeBuilder {
                               sibling_generator: Option<@mut BoxGenerator>)
                               -> Option<(@mut BoxGenerator, @mut BoxGenerator)> {
 
-        fn is_root(node: AbstractNode<LayoutView>) -> bool {
-            match node.parent_node() {
-                None => true,
-                Some(_) => false
-            }
-        }
         let display = if node.is_element() {
-            match node.style().display(is_root(node)) {
+            match node.style().display(node.is_root()) {
                 CSSDisplayNone => return None, // tree ends here if 'display: none'
                 // TODO(eatkinson) these are hacks so that the code doesn't crash
                 // when unsupported display values are used. They should be deleted
@@ -390,11 +384,8 @@ impl LayoutTreeBuilder {
             }
         };
 
-        let sibling_flow: Option<FlowContext> = match sibling_generator {
-            None => None,
-            Some(gen) => Some(gen.flow)
-        };
-
+        let sibling_flow: Option<FlowContext> = sibling_generator.map(|gen| gen.flow);
+
         // TODO(eatkinson): use the value of the float property to
         // determine whether to float left or right.
         let is_float = if (node.is_element()) {

src/components/main/layout/float_context.rs

@@ -291,10 +291,7 @@ impl FloatContextBase{
             }
         }
 
-        match max_height {
-            None => None,
-            Some(h) => Some(h + self.offset.y)
-        }
+        max_height.map(|h| h + self.offset.y)
     }
 
     /// Given necessary info, finds the closest place a box can be positioned

src/components/main/layout/flow.rs

@@ -32,6 +32,8 @@ use layout::context::LayoutContext;
 use layout::display_list_builder::{DisplayListBuilder, ExtraDisplayListData};
 use layout::inline::{InlineFlowData};
 use layout::float_context::{FloatContext, Invalid, FloatType};
+use layout::incremental::RestyleDamage;
+use css::node_style::StyledNode;
 
 use std::cell::Cell;
 use std::uint;
@@ -45,6 +47,7 @@ use servo_util::tree::{TreeNode, TreeNodeRef, TreeUtils};
 
 /// The type of the formatting context and data specific to each context, such as line box
 /// structures or float lists.
+#[deriving(Clone)]
 pub enum FlowContext {
     AbsoluteFlow(@mut FlowData), 
     BlockFlow(@mut BlockFlowData),
@@ -64,12 +67,6 @@ pub enum FlowContextType {
     Flow_Table
 }
 
-impl Clone for FlowContext {
-    fn clone(&self) -> FlowContext {
-        *self
-    }
-}
-
 impl FlowContext {
     pub fn teardown(&self) {
         match *self {
@@ -84,6 +81,9 @@ impl FlowContext {
 
     /// Like traverse_preorder, but don't end the whole traversal if the callback
     /// returns false.
+    //
+    // FIXME: Unify this with traverse_preorder_prune, which takes a separate
+    // 'prune' function.
     fn partially_traverse_preorder(&self, callback: &fn(FlowContext) -> bool) {
         if !callback((*self).clone()) {
             return;
@@ -157,6 +157,7 @@ impl TreeNodeRef<FlowData> for FlowContext {
 /// `CommonFlowInfo`?
 pub struct FlowData {
     node: AbstractNode<LayoutView>,
+    restyle_damage: RestyleDamage,
 
     parent: Option<FlowContext>,
     first_child: Option<FlowContext>,
@@ -225,6 +226,7 @@ impl FlowData {
     pub fn new(id: int, node: AbstractNode<LayoutView>) -> FlowData {
         FlowData {
             node: node,
+            restyle_damage: node.restyle_damage(),
 
             parent: None,
             first_child: None,
@@ -264,6 +266,15 @@ impl<'self> FlowContext {
         }
     }
 
+    /// A convenience method to return the restyle damage of this flow. Fails if the flow is
+    /// currently being borrowed mutably.
+    #[inline(always)]
+    pub fn restyle_damage(&self) -> RestyleDamage {
+        do self.with_base |info| {
+            info.restyle_damage
+        }
+    }
+
     pub fn inline(&self) -> @mut InlineFlowData {
         match *self {
             InlineFlow(info) => info,
@@ -448,7 +459,8 @@ impl<'self> FlowContext {
         };
 
         do self.with_base |base| {
-            fmt!("f%? %? floats %? size %?", base.id, repr, base.num_floats, base.position)
+            fmt!("f%? %? floats %? size %? damage %?", base.id, repr, base.num_floats,
+                 base.position, base.restyle_damage)
         }
     }
 }