Refactor font metric calculation

This splits out the advance calculation and makes it more declarative

2 files changed, 21 insertions, 13 deletions

diff --git a/src/components/gfx/text/glyph.rs b/src/components/gfx/text/glyph.rs
index 09e4c773d00..1ae767f1d06 100644
--- a/src/components/gfx/text/glyph.rs
+++ b/src/components/gfx/text/glyph.rs
@@ -640,6 +640,12 @@ impl<'a> GlyphStore {
         }
     }
 
+    #[inline]
+    pub fn advance_for_char_range(&self, rang: &Range<CharIndex>) -> Au {
+        self.iter_glyphs_for_char_range(rang)
+            .fold(Au(0), |advance, (_, glyph)| advance + glyph.advance())
+    }
+
     // getter methods
     pub fn char_is_space(&self, i: CharIndex) -> bool {
         assert!(i < CharIndex(self.entry_buffer.len() as int));
diff --git a/src/components/gfx/text/text_run.rs b/src/components/gfx/text/text_run.rs
index a61769cdacf..cbea5fbd90e 100644
--- a/src/components/gfx/text/text_run.rs
+++ b/src/components/gfx/text/text_run.rs
@@ -183,25 +183,27 @@ impl<'a> TextRun {
         true
     }
 
-    pub fn metrics_for_range(&self, range: &Range<CharIndex>) -> RunMetrics {
+    pub fn advance_for_range(&self, range: &Range<CharIndex>) -> Au {
         // TODO(Issue #199): alter advance direction for RTL
         // TODO(Issue #98): using inter-char and inter-word spacing settings  when measuring text
-        let mut advance = Au(0);
-        for (glyphs, _offset, slice_range) in self.iter_slices_for_range(range) {
-            for (_i, glyph) in glyphs.iter_glyphs_for_char_range(&slice_range) {
-                advance = advance + glyph.advance();
-            }
-        }
-        RunMetrics::new(advance, self.font_metrics.ascent, self.font_metrics.descent)
+        self.iter_slices_for_range(range)
+            .fold(Au(0), |advance, (glyphs, _, slice_range)| {
+                advance + glyphs.advance_for_char_range(&slice_range)
+            })
+    }
+
+    pub fn metrics_for_range(&self, range: &Range<CharIndex>) -> RunMetrics {
+        RunMetrics::new(self.advance_for_range(range),
+                        self.font_metrics.ascent,
+                        self.font_metrics.descent)
     }
 
     pub fn metrics_for_slice(&self, glyphs: &GlyphStore, slice_range: &Range<CharIndex>) -> RunMetrics {
-        let mut advance = Au(0);
-        for (_i, glyph) in glyphs.iter_glyphs_for_char_range(slice_range) {
-            advance = advance + glyph.advance();
-        }
-        RunMetrics::new(advance, self.font_metrics.ascent, self.font_metrics.descent)
+        RunMetrics::new(glyphs.advance_for_char_range(slice_range),
+                        self.font_metrics.ascent,
+                        self.font_metrics.descent)
     }
+
     pub fn min_width_for_range(&self, range: &Range<CharIndex>) -> Au {
         let mut max_piece_width = Au(0);
         debug!("iterating outer range {:?}", range);