Add font metrics API for CoreText, and stub one out for FreeType

src/servo/text/font.rs

@@ -1,4 +1,4 @@
-export Font, test_font_bin, create_test_font;
+export Font, FontMetrics, test_font_bin, create_test_font;
 
 use glyph::GlyphIndex;
 use vec_to_ptr = vec::raw::to_ptr;
@@ -16,6 +16,7 @@ struct Font {
     lib: @FontLibrary,
     fontbuf: @~[u8],
     native_font: NativeFont,
+    metrics: FontMetrics
 }
 
 impl Font {
@@ -35,14 +36,27 @@ impl Font {
     }
 }
 
-fn Font(lib: @FontLibrary, fontbuf: @~[u8], +native_font: NativeFont) -> Font {
+fn Font(lib: @FontLibrary, fontbuf: @~[u8], +native_font: NativeFont, +metrics: FontMetrics) -> Font {
     Font {
         lib: lib,
         fontbuf : fontbuf,
         native_font : move native_font,
+        metrics: move metrics
     }
 }
 
+struct FontMetrics {
+    underline_size:   float,
+    underline_offset: float,
+    leading:          float,
+    x_height:         float,
+
+    em_height:        float,
+    em_ascent:        float,
+    em_descent:       float,
+    max_advance:      float
+}
+
 const TEST_FONT: [u8 * 33004] = #include_bin("JosefinSans-SemiBold.ttf");
 
 fn test_font_bin() -> ~[u8] {

src/servo/text/font_library.rs

@@ -46,7 +46,8 @@ fn create_font(lib: @FontLibrary, native_lib: &native::NativeFontLibrary) -> Res
     } else {
         return Err(native_font.get_err());
     };
-    return Ok(@Font(lib, font_bin, native_font));
+    let metrics = native_font.get_metrics();
+    return Ok(@Font(lib, font_bin, native_font, metrics));
 }
 
 #[cfg(target_os = "linux")]

src/servo/text/native_font/ft_native_font.rs

@@ -4,6 +4,7 @@ use vec_as_buf = vec::as_imm_buf;
 use ptr::{addr_of, null};
 use unsafe::reinterpret_cast;
 use glyph::GlyphIndex;
+use font::FontMetrics;
 use azure::freetype;
 use freetype::{ FT_Error, FT_Library, FT_Face, FT_Long, FT_ULong, FT_UInt, FT_GlyphSlot };
 use freetype::bindgen::{
@@ -67,6 +68,20 @@ impl FreeTypeNativeFont {
             return None;
         }
     }
+
+    fn get_metrics() -> FontMetrics {
+        /* TODO: complete me (Issue #76) */
+        return FontMetrics {
+            underline_size:   0.0,
+            underline_offset: 0.0,
+            leading:          0.0,
+            x_height:         0.0,
+            em_ascent:        0.0,
+            em_descent:       0.0,
+            em_height:        0.0,
+            max_advance:      0.0
+        }
+    }
 }
 
 fn create(lib: &FT_Library, buf: @~[u8]) -> Result<FreeTypeNativeFont, ()> {

src/servo/text/native_font/quartz_native_font.rs

@@ -2,6 +2,8 @@ extern mod cocoa;
 
 export QuartzNativeFont, with_test_native_font, create;
 
+use font::FontMetrics;
+
 use libc::size_t;
 use ptr::null;
 use glyph::GlyphIndex;
@@ -38,6 +40,16 @@ mod coretext {
         height: CGFloat,
     }
 
+    struct CGPoint {
+        x: CGFloat,
+        y: CGFloat,
+    }
+
+    struct CGRect {
+        origin: CGPoint,
+        size: CGSize
+    }
+
     type CGAffineTransform = ();
     type CTFontDescriptorRef = *u8;
 
@@ -47,6 +59,17 @@ mod coretext {
         fn CTFontCreateWithGraphicsFont(graphicsFont: CGFontRef, size: CGFloat, matrix: *CGAffineTransform, attributes: CTFontDescriptorRef) -> CTFontRef;
         fn CTFontGetGlyphsForCharacters(font: CTFontRef, characters: *UniChar, glyphs: *CGGlyph, count: CFIndex) -> bool;
         fn CTFontGetAdvancesForGlyphs(font: CTFontRef, orientation: CTFontOrientation, glyphs: *CGGlyph, advances: *CGSize, count: CFIndex) -> libc::c_double;
+
+        /* metrics API */
+        fn CTFontGetAscent(font: CTFontRef) -> libc::c_float;
+        fn CTFontGetDescent(font: CTFontRef) -> libc::c_float;
+        fn CTFontGetLeading(font: CTFontRef) -> libc::c_float;
+        fn CTFontGetUnitsPerEm(font: CTFontRef) -> libc::c_uint;
+        fn CTFontGetUnderlinePosition(font: CTFontRef) -> libc::c_float;
+        fn CTFontGetUnderlineThickness(font: CTFontRef) -> libc::c_float;
+        fn CTFontGetXHeight(font: CTFontRef) -> libc::c_float;
+        fn CTFontGetBoundingBox(font: CTFontRef) -> CGRect;
+            
         fn CFRelease(font: CTFontRef);
     }
 }
@@ -120,6 +143,30 @@ impl QuartzNativeFont {
 
         return Some(advance as int);
     }
+
+    fn get_metrics() -> FontMetrics {
+        use coretext::CGRect;
+        use coretext::coretext::*;
+
+        let ctfont = self.ctfont;
+        assert ctfont.is_not_null();
+
+        let convFactor : float = 1.0 / (CTFontGetUnitsPerEm(ctfont) as float);
+        let bounding_rect: CGRect = CTFontGetBoundingBox(ctfont);
+        let em_ascent = CTFontGetAscent(ctfont) as float * convFactor;
+        let em_descent = CTFontGetDescent(ctfont) as float * convFactor;
+
+        return FontMetrics {
+            underline_size:   CTFontGetUnderlineThickness(ctfont) as float * convFactor,
+            underline_offset: CTFontGetUnderlinePosition(ctfont) as float * convFactor,
+            leading:          CTFontGetLeading(ctfont) as float * convFactor,
+            x_height:         CTFontGetXHeight(ctfont) as float * convFactor,
+            em_ascent:        CTFontGetAscent(ctfont) as float * convFactor,
+            em_descent:       CTFontGetDescent(ctfont) as float * convFactor,
+            em_height:        em_ascent + em_descent,
+            max_advance:      bounding_rect.size.width as float * convFactor,
+        }
+    }
 }
 
 fn ctfont_from_cgfont(cgfont: CGFontRef) -> coretext::CTFontRef {