style: Add a "start_end()" method to LogicalMargin

Add a `LogicalMargin::start_end()` method that receives a `Direction'
parameter. This is useful for some layout that is symmetric in inline
and block directions, like flexbox.

components/layout/construct.rs

@@ -34,7 +34,6 @@ use inline::{FIRST_FRAGMENT_OF_ELEMENT, InlineFlow};
 use inline::{InlineFragmentNodeInfo, LAST_FRAGMENT_OF_ELEMENT};
 use linked_list::prepend_from;
 use list_item::{ListItemFlow, ListStyleTypeContent};
-use model::Direction;
 use multicol::{MulticolColumnFlow, MulticolFlow};
 use parallel;
 use script_layout_interface::{LayoutElementType, LayoutNodeType, is_image_data};
@@ -49,6 +48,7 @@ use style::computed_values::{caption_side, display, empty_cells, float, list_sty
 use style::computed_values::content::ContentItem;
 use style::computed_values::position;
 use style::context::SharedStyleContext;
+use style::logical_geometry::Direction;
 use style::properties::{self, ServoComputedValues};
 use style::selector_impl::{PseudoElement, RestyleDamage};
 use style::selector_matching::Stylist;

components/layout/flex.rs

@@ -19,7 +19,7 @@ use fragment::{Fragment, FragmentBorderBoxIterator, Overflow};
 use gfx::display_list::StackingContext;
 use gfx_traits::ScrollRootId;
 use layout_debug;
-use model::{Direction, IntrinsicISizes, MaybeAuto, MinMaxConstraint};
+use model::{IntrinsicISizes, MaybeAuto, MinMaxConstraint};
 use model::{specified, specified_or_none};
 use std::cmp::{max, min};
 use std::ops::Range;
@@ -27,7 +27,7 @@ use std::sync::Arc;
 use style::computed_values::{align_content, align_self, flex_direction, flex_wrap, justify_content};
 use style::computed_values::border_collapse;
 use style::context::{SharedStyleContext, StyleContext};
-use style::logical_geometry::LogicalSize;
+use style::logical_geometry::{Direction, LogicalSize};
 use style::properties::ServoComputedValues;
 use style::servo::restyle_damage::{REFLOW, REFLOW_OUT_OF_FLOW};
 use style::values::computed::{LengthOrPercentage, LengthOrPercentageOrAuto};

components/layout/fragment.rs

@@ -23,7 +23,7 @@ use inline::{InlineMetrics, LAST_FRAGMENT_OF_ELEMENT, LineMetrics};
 use ipc_channel::ipc::IpcSender;
 #[cfg(debug_assertions)]
 use layout_debug;
-use model::{self, Direction, IntrinsicISizes, IntrinsicISizesContribution, MaybeAuto};
+use model::{self, IntrinsicISizes, IntrinsicISizesContribution, MaybeAuto};
 use msg::constellation_msg::PipelineId;
 use net_traits::image::base::{Image, ImageMetadata};
 use net_traits::image_cache_thread::{ImageOrMetadataAvailable, UsePlaceholder};
@@ -44,7 +44,7 @@ use style::computed_values::{transform_style, vertical_align, white_space, word_
 use style::computed_values::content::ContentItem;
 use style::context::SharedStyleContext;
 use style::dom::TRestyleDamage;
-use style::logical_geometry::{LogicalMargin, LogicalRect, LogicalSize, WritingMode};
+use style::logical_geometry::{Direction, LogicalMargin, LogicalRect, LogicalSize, WritingMode};
 use style::properties::ServoComputedValues;
 use style::selector_impl::RestyleDamage;
 use style::servo::restyle_damage::RECONSTRUCT_FLOW;

components/layout/model.rs

@@ -504,13 +504,6 @@ impl ToGfxMatrix for ComputedMatrix {
     }
 }
 
-// Used to specify the logical direction.
-#[derive(Debug, Clone, Copy, PartialEq)]
-pub enum Direction {
-    Inline,
-    Block
-}
-
 // https://drafts.csswg.org/css2/visudet.html#min-max-widths
 // https://drafts.csswg.org/css2/visudet.html#min-max-heights
 /// A min or max constraint

components/style/logical_geometry.rs

@@ -213,6 +213,13 @@ impl Debug for DebugWritingMode {
 }
 
 
+// Used to specify the logical direction.
+#[derive(Debug, Clone, Copy, PartialEq)]
+pub enum Direction {
+    Inline,
+    Block
+}
+
 /// A 2D size in flow-relative dimensions
 #[derive(PartialEq, Eq, Clone, Copy)]
 #[cfg_attr(feature = "servo", derive(Serialize))]
@@ -763,6 +770,16 @@ impl<T: Copy + Add<T, Output=T>> LogicalMargin<T> {
         self.block_start + self.block_end
     }
 
+    #[inline]
+    pub fn start_end(&self, direction: Direction) -> T {
+        match direction {
+            Direction::Inline =>
+                self.inline_start + self.inline_end,
+            Direction::Block =>
+                self.block_start + self.block_end
+        }
+    }
+
     #[inline]
     pub fn top_bottom(&self, mode: WritingMode) -> T {
         self.debug_writing_mode.check(mode);