Add glyph advance cache to enhance speed of layout

src/components/gfx/font.rs

@@ -49,7 +49,7 @@ pub trait FontHandleMethods {
     fn clone_with_style(&self, fctx: &FontContextHandle, style: &UsedFontStyle)
                      -> Result<FontHandle, ()>;
     fn glyph_index(&self, codepoint: char) -> Option<GlyphIndex>;
-    fn glyph_h_advance(&self, GlyphIndex) -> Option<FractionalPixel>;
+    fn glyph_h_advance(&mut self, GlyphIndex) -> Option<FractionalPixel>;
     fn get_metrics(&self) -> FontMetrics;
     fn get_table_for_tag(&self, FontTableTag) -> Option<FontTable>;
 }
@@ -244,6 +244,7 @@ pub struct Font {
     backend: BackendType,
     profiler_chan: ProfilerChan,
     shape_cache: HashCache<~str, Arc<GlyphStore>>,
+    glyph_advance_cache: HashCache<u32, FractionalPixel>,
 }
 
 impl Font {
@@ -272,6 +273,7 @@ impl Font {
             backend: backend,
             profiler_chan: profiler_chan,
             shape_cache: HashCache::new(),
+            glyph_advance_cache: HashCache::new(),
         });
     }
 
@@ -289,6 +291,7 @@ impl Font {
             backend: backend,
             profiler_chan: profiler_chan,
             shape_cache: HashCache::new(),
+            glyph_advance_cache: HashCache::new(),
         }
     }
 
@@ -474,13 +477,15 @@ impl Font {
         self.handle.glyph_index(codepoint)
     }
 
-    pub fn glyph_h_advance(&self, glyph: GlyphIndex) -> FractionalPixel {
+    pub fn glyph_h_advance(&mut self, glyph: GlyphIndex) -> FractionalPixel {
-        match self.handle.glyph_h_advance(glyph) {
+	do self.glyph_advance_cache.find_or_create(&glyph) |glyph| {
+	    match self.handle.glyph_h_advance(*glyph) {
 	        Some(adv) => adv,
 		None => /* FIXME: Need fallback strategy */ 10f as FractionalPixel
 	    }
 	}
     }
+}
 
 /*fn should_destruct_on_fail_without_leaking() {
     #[test];

src/components/gfx/platform/android/font.rs

@@ -198,7 +198,7 @@ impl FontHandleMethods for FontHandle {
     }
 
     #[fixed_stack_segment]
-    fn glyph_h_advance(&self,
+    fn glyph_h_advance(&mut self,
                            glyph: GlyphIndex) -> Option<FractionalPixel> {
         assert!(self.face.is_not_null());
         unsafe {

src/components/gfx/platform/linux/font.rs

@@ -198,7 +198,7 @@ impl FontHandleMethods for FontHandle {
     }
 
     #[fixed_stack_segment]
-    fn glyph_h_advance(&self,
+    fn glyph_h_advance(&mut self,
                            glyph: GlyphIndex) -> Option<FractionalPixel> {
         assert!(self.face.is_not_null());
         unsafe {

src/components/gfx/platform/macos/font.rs

@@ -147,7 +147,7 @@ impl FontHandleMethods for FontHandle {
         return Some(glyphs[0] as GlyphIndex);
     }
 
-    fn glyph_h_advance(&self, glyph: GlyphIndex) -> Option<FractionalPixel> {
+    fn glyph_h_advance(&mut self, glyph: GlyphIndex) -> Option<FractionalPixel> {
         let glyphs = [glyph as CGGlyph];
         let advance = self.ctfont.get_advances_for_glyphs(kCTFontDefaultOrientation,
                                                           &glyphs[0],

src/components/gfx/text/shaping/harfbuzz.rs

@@ -13,6 +13,7 @@ use servo_util::range::Range;
 use text::util::{float_to_fixed, fixed_to_float, fixed_to_rounded_int};
 
 use std::cast::transmute;
+use std::cast;
 use std::char;
 use std::libc::{c_uint, c_int, c_void, c_char};
 use std::ptr;
@@ -509,7 +510,7 @@ extern fn glyph_h_advance_func(_: *hb_font_t,
                                glyph: hb_codepoint_t,
                                _: *c_void)
                             -> hb_position_t {
-    let font: *Font = font_data as *Font;
+    let font: *mut Font = unsafe { cast::transmute(font_data as *Font) };
     assert!(font.is_not_null());
 
     unsafe {