auto merge of #2471 : bjz/servo/split-to-width, r=pcwalton

@pcwalton r?

src/components/main/layout/box_.rs

@@ -267,16 +267,6 @@ impl UnscannedTextBoxInfo {
     }
 }
 
-/// Represents the outcome of attempting to split a box.
-pub enum SplitBoxResult {
-    CannotSplit,
-    // in general, when splitting the left or right side can
-    // be zero length, due to leading/trailing trimmable whitespace
-    SplitDidFit(Option<Box>, Option<Box>),
-    SplitDidNotFit(Option<Box>, Option<Box>)
-}
-
-
 /// A box that represents a table column.
 #[deriving(Clone)]
 pub struct TableColumnBoxInfo {
@@ -1097,11 +1087,15 @@ impl Box {
         }
     }
 
-    /// Split box which includes new-line character
-    pub fn split_by_new_line(&self) -> SplitBoxResult {
+    /// Split box which includes new-line character.
+    ///
+    /// A return value of `None` indicates that the box could not be split.
+    /// Otherwise the split boxes are returned. The right boxe is optional due
+    /// to the possibility of it being whitespace.
+    pub fn split_by_new_line(&self) -> Option<(Box, Option<Box>)> {
         match self.specific {
             GenericBox | IframeBox(_) | ImageBox(_) | TableBox | TableCellBox |
-            TableRowBox | TableWrapperBox => CannotSplit,
+            TableRowBox | TableWrapperBox => None,
             TableColumnBox(_) => fail!("Table column boxes do not need to split"),
             UnscannedTextBox(_) => fail!("Unscanned text boxes should have been scanned by now!"),
             ScannedTextBox(ref text_box_info) => {
@@ -1118,7 +1112,7 @@ impl Box {
                     let new_metrics = new_text_box_info.run.metrics_for_range(&left_range);
                     let mut new_box = self.transform(new_metrics.bounding_box.size, ScannedTextBox(new_text_box_info));
                     new_box.new_line_pos = vec!();
-                    Some(new_box)
+                    new_box
                 };
 
                 // Right box is for right text of first founded new-line character.
@@ -1132,16 +1126,20 @@ impl Box {
                     None
                 };
 
-                SplitDidFit(left_box, right_box)
+                Some((left_box, right_box))
             }
         }
     }
 
     /// Attempts to split this box so that its width is no more than `max_width`.
-    pub fn split_to_width(&self, max_width: Au, starts_line: bool) -> SplitBoxResult {
+    ///
+    /// A return value of `None` indicates that the box could not be split.
+    /// Otherwise the split boxes are returned. The left and right boxes are
+    /// optional due to the possibility of them being whitespace.
+    pub fn split_to_width(&self, max_width: Au, starts_line: bool) -> Option<(Option<Box>, Option<Box>)> {
         match self.specific {
             GenericBox | IframeBox(_) | ImageBox(_) | TableBox | TableCellBox |
-            TableRowBox | TableWrapperBox => CannotSplit,
+            TableRowBox | TableWrapperBox => None,
             TableColumnBox(_) => fail!("Table column boxes do not have width"),
             UnscannedTextBox(_) => fail!("Unscanned text boxes should have been scanned by now!"),
             ScannedTextBox(ref text_box_info) => {
@@ -1214,28 +1212,30 @@ impl Box {
                     }
                 }
 
-                let left_box = if left_range.length() > CharIndex(0) {
-                    let new_text_box_info = ScannedTextBoxInfo::new(text_box_info.run.clone(), left_range);
-                    let width = new_text_box_info.run.advance_for_range(&left_range);
-                    let height = self.border_box.size.height;
-                    let size = Size2D(width, height);
-                    Some(self.transform(size, ScannedTextBox(new_text_box_info)))
-                } else {
+                let left_is_some = left_range.length() > CharIndex(0);
+
+                if (pieces_processed_count == 1 || !left_is_some) && !starts_line {
                     None
-                };
-
-                let right_box = right_range.map_or(None, |right_range: Range<CharIndex>| {
-                    let new_text_box_info = ScannedTextBoxInfo::new(text_box_info.run.clone(), right_range);
-                    let width = new_text_box_info.run.advance_for_range(&right_range);
-                    let height = self.border_box.size.height;
-                    let size = Size2D(width, height);
-                    Some(self.transform(size, ScannedTextBox(new_text_box_info)))
-                });
-
-                if pieces_processed_count == 1 || left_box.is_none() {
-                    SplitDidNotFit(left_box, right_box)
                 } else {
-                    SplitDidFit(left_box, right_box)
+                    let left_box = if left_is_some {
+                        let new_text_box_info = ScannedTextBoxInfo::new(text_box_info.run.clone(), left_range);
+                        let width = new_text_box_info.run.advance_for_range(&left_range);
+                        let height = self.border_box.size.height;
+                        let size = Size2D(width, height);
+                        Some(self.transform(size, ScannedTextBox(new_text_box_info)))
+                    } else {
+                        None
+                    };
+
+                    let right_box = right_range.map(|right_range| {
+                        let new_text_box_info = ScannedTextBoxInfo::new(text_box_info.run.clone(), right_range);
+                        let width = new_text_box_info.run.advance_for_range(&right_range);
+                        let height = self.border_box.size.height;
+                        let size = Size2D(width, height);
+                        (self.transform(size, ScannedTextBox(new_text_box_info)))
+                    });
+
+                    Some((left_box, right_box))
                 }
             }
         }

src/components/main/layout/inline.rs

@@ -3,7 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use css::node_style::StyledNode;
-use layout::box_::{Box, CannotSplit, SplitDidFit, SplitDidNotFit};
+use layout::box_::Box;
 use layout::context::LayoutContext;
 use layout::floats::{FloatLeft, Floats, PlacementInfo};
 use layout::flow::{BaseFlow, FlowClass, Flow, InlineFlowClass};
@@ -425,19 +425,16 @@ impl LineboxScanner {
         } else {
             // In case of box includes new-line character
             match in_box.split_by_new_line() {
-                SplitDidFit(left, right) => {
-                    match (left, right) {
-                        (Some(left_box), Some(right_box)) => {
-                            self.push_box_to_line(left_box);
-                            self.work_list.push_front(right_box);
-                        }
-                        (Some(left_box), None) => {
-                            self.push_box_to_line(left_box);
-                        }
-                        _ => error!("LineboxScanner: This split case makes no sense!"),
-                    }
-                }
-                _ => {}
+                Some((left_box, Some(right_box))) => {
+                    self.push_box_to_line(left_box);
+                    self.work_list.push_front(right_box);
+                },
+                Some((left_box, None)) => {
+                    self.push_box_to_line(left_box);
+                },
+                None => {
+                    error!("LineboxScanner: This split case makes no sense!")
+                },
             }
             false
         }
@@ -495,46 +492,35 @@ impl LineboxScanner {
         }
 
         let available_width = green_zone.width - self.pending_line.bounds.size.width;
-        let split = in_box.split_to_width(available_width, line_is_empty);
-        let (left, right) = match (split, line_is_empty) {
-            (CannotSplit, _) => {
-                debug!("LineboxScanner: Tried to split unsplittable render box! {}",
-                        in_box);
+        match in_box.split_to_width(available_width, line_is_empty) {
+            None => {
+                debug!("LineboxScanner: Tried to split unsplittable render box! Deferring to next \
+                       line. {}", in_box);
                 self.work_list.push_front(in_box);
-                return false
-            }
-            (SplitDidNotFit(_, _), false) => {
-                debug!("LineboxScanner: case=split box didn't fit, not appending and deferring \
-                        original box.");
-                self.work_list.push_front(in_box);
-                return false
-            }
-            (SplitDidFit(left, right), _) => {
-                debug!("LineboxScanner: case=split box did fit; deferring remainder box.");
-                (left, right)
-                // Fall through to push boxes to the line.
-            }
-            (SplitDidNotFit(left, right), true) => {
-                // TODO(eatkinson, issue #224): Signal that horizontal overflow happened?
-                debug!("LineboxScanner: case=split box didn't fit and line {:u} is empty, so \
-                        overflowing and deferring remainder box.",
-                        self.lines.len());
-                (left, right)
-                // Fall though to push boxes to the line.
-            }
-        };
-
-        match (left, right) {
-            (Some(left_box), Some(right_box)) => {
+                false
+            },
+            Some((Some(left_box), Some(right_box))) => {
+                debug!("LineboxScanner: Line break found! Pushing left box to line and deferring \
+                       right box to next line.");
                 self.push_box_to_line(left_box);
                 self.work_list.push_front(right_box);
-            }
-            (Some(left_box), None) => self.push_box_to_line(left_box),
-            (None, Some(right_box)) => self.push_box_to_line(right_box),
-            (None, None) => error!("LineboxScanner: This split case makes no sense!"),
+                true
+            },
+            Some((Some(left_box), None)) => {
+                debug!("LineboxScanner: Pushing left box to line.");
+                self.push_box_to_line(left_box);
+                true
+            },
+            Some((None, Some(right_box))) => {
+                debug!("LineboxScanner: Pushing right box to line.");
+                self.push_box_to_line(right_box);
+                true
+            },
+            Some((None, None)) => {
+                error!("LineboxScanner: This split case makes no sense!");
+                true
+            },
         }
-
-        true
     }
 
     // An unconditional push

src/test/ref/basic.list

@@ -73,3 +73,4 @@
 == setattribute_id_restyle_a.html setattribute_id_restyle_b.html
 == pseudo_element_a.html pseudo_element_b.html
 == linebreak_simple_a.html linebreak_simple_b.html
+== linebreak_inline_span_a.html linebreak_inline_span_b.html

src/test/ref/linebreak_inline_span_a.html

@@ -0,0 +1,24 @@
+<html>
+<head>
+<style type="text/css">
+* {
+	margin: 0px;
+	padding: 0px;
+}
+</style>
+</head>
+<body>
+<blockquote>
+    The <span>most terrifying</span> fact about the universe <span>is not that
+    it is hostile but that it is indifferent;</span> but if we can come to terms
+    with this indifference and accept the<span> challenges</span> of <span>life
+    <span>within</span></span> the boundaries of death - <span>however</span>
+    mutable man may be able to make them - our existence as a species can have
+    genuine meaning and fulfillment. However vast the darkness, we must supply
+    our own light.
+    <footer>
+        <cite>Stanley Kubrick</cite>
+    </footer>
+</blockquote>
+</body>
+</html>

src/test/ref/linebreak_inline_span_b.html

@@ -0,0 +1,23 @@
+<html>
+<head>
+<style type="text/css">
+* {
+	margin: 0px;
+	padding: 0px;
+}
+</style>
+</head>
+<body>
+<blockquote>
+    The most terrifying fact about the universe is not that it is hostile but
+    that it is indifferent; but if we can come to terms with this indifference
+    and accept the challenges of life within the boundaries of death - however
+    mutable man may be able to make them - our existence as a species can have
+    genuine meaning and fulfillment. However vast the darkness, we must supply
+    our own light.
+    <footer>
+        <cite>Stanley Kubrick</cite>
+    </footer>
+</blockquote>
+</body>
+</html>