Add some RAII and black magic to let harfbuzz determine font table blob lifetimes.

src/servo-gfx/font.rs

@@ -35,7 +35,7 @@ pub trait FontHandleMethods {
     fn glyph_index(codepoint: char) -> Option<GlyphIndex>;
     fn glyph_h_advance(GlyphIndex) -> Option<FractionalPixel>;
     fn get_metrics() -> FontMetrics;
-    fn get_table_for_tag(FontTableTag) -> Option<~[u8]>;
+    fn get_table_for_tag(FontTableTag) -> Option<FontTable>;
 }
 
 // TODO(Issue #163): this is a workaround for static methods and
@@ -74,6 +74,16 @@ impl FontTableTag : FontTableTagConversions {
     }
 }
 
+#[cfg(target_os = "macos")]
+pub type FontTable/& = quartz::font::QuartzFontTable;
+
+#[cfg(target_os = "linux")]
+pub type FontTable/& = freetype::font::FreeTypeFontTable;
+
+trait FontTableMethods {
+    fn with_buffer(fn&(*u8, uint));
+}
+
 struct FontMetrics {
     underline_size:   Au,
     underline_offset: Au,
@@ -311,7 +321,7 @@ impl Font {
         shaper
     }
 
-    fn get_table_for_tag(tag: FontTableTag) -> Option<~[u8]> {
+    fn get_table_for_tag(tag: FontTableTag) -> Option<FontTable> {
         let result = self.handle.get_table_for_tag(tag);
         let status = if result.is_some() { "Found" } else { "Didn't find" };
 

src/servo-gfx/quartz/font.rs

@@ -2,12 +2,35 @@ extern mod core_foundation;
 extern mod core_graphics;
 extern mod core_text;
 
+use cf = core_foundation;
+use cf::base::{
+    CFIndex,
+    CFRelease,
+    CFTypeOps,
+    CFTypeRef,
+};
+use cf::data::{CFData, CFDataRef};
+use cf::string::UniChar;
+use cg = core_graphics;
+
+use cg::base::{CGFloat, CGAffineTransform};
+use cg::data_provider::{CGDataProviderRef, CGDataProvider};
+use cg::font::{CGFontCreateWithDataProvider, CGFontRef, CGFontRelease, CGGlyph};
+use cg::geometry::CGRect;
+
+use ct = core_text;
+use ct::font::CTFont;
+use ct::font_descriptor::{kCTFontDefaultOrientation, CTFontSymbolicTraits};
+use ct::font_descriptor::{SymbolicTraitAccessors};
+
 use font_context::QuartzFontContextHandle;
 use geometry::Au;
 use gfx_font::{
     CSSFontWeight,
     FontHandleMethods,
     FontMetrics,
+    FontTable,
+    FontTableMethods,
     FontTableTag,
     FontWeight100,
     FontWeight200,
@@ -23,24 +46,25 @@ use gfx_font::{
 };
 use text::glyph::GlyphIndex;
 
-use cf = core_foundation;
-use cf::base::{
-    CFIndex,
-    CFRelease,
-    CFTypeRef
-};
-use cf::data::CFData;
-use cf::string::UniChar;
-use cg = core_graphics;
-use cg::base::{CGFloat, CGAffineTransform};
-use cg::data_provider::{CGDataProviderRef, CGDataProvider};
-use cg::font::{CGFontCreateWithDataProvider, CGFontRef, CGFontRelease, CGGlyph};
-use cg::geometry::CGRect;
 use core::libc::size_t;
-use ct = core_text;
-use ct::font::CTFont;
-use ct::font_descriptor::{kCTFontDefaultOrientation, CTFontSymbolicTraits};
-use ct::font_descriptor::{SymbolicTraitAccessors};
+
+struct QuartzFontTable {
+    data: CFData,
+
+    drop {  }
+}
+
+pub impl QuartzFontTable {
+    static fn wrap(data: CFData) -> QuartzFontTable {
+        QuartzFontTable { data: move data }
+    }
+}
+
+pub impl QuartzFontTable : FontTableMethods {
+    fn with_buffer(blk: fn&(*u8, uint)) {
+        blk(self.data.bytes(), self.data.len());
+    }
+}
 
 pub struct QuartzFontHandle {
     priv mut cgfont: Option<CGFontRef>,
@@ -182,10 +206,10 @@ pub impl QuartzFontHandle : FontHandleMethods {
         return metrics;
     }
 
-    fn get_table_for_tag(tag: FontTableTag) -> Option<~[u8]> {
-        let result = self.ctfont.get_font_table(tag);
+    fn get_table_for_tag(tag: FontTableTag) -> Option<FontTable> {
+        let result : Option<CFData> = self.ctfont.get_font_table(tag);
         return option::chain(move result, |data| {
-            Some(data.copy_to_buf())
+            Some(QuartzFontTable::wrap(move data))
         });
     }
 

src/servo-gfx/text/harfbuzz/shaper.rs

@@ -7,6 +7,7 @@ use au::Au;
 
 use font::{
     Font,
+    FontTable,
     FontTableTag,
 };
 
@@ -191,16 +192,31 @@ extern fn get_font_table_func(_face: *hb_face_t, tag: hb_tag_t, user_data: *c_vo
     let font: *Font = user_data as *Font;
     assert font.is_not_null();
 
-    // TODO(Issue #197): reuse font table data, which will change return type here.
-    // it will also require us to provide deletion callbacks to hb_blob_create, so
-    // that refcounts of shared blobs can be managed.
+    // TODO(Issue #197): reuse font table data, which will change the unsound trickery here.
     match (*font).get_table_for_tag(tag as FontTableTag) {
         None => return ptr::null(),
-        Some(table_buffer) => {
-            let blob: *hb_blob_t = vec::as_imm_buf(table_buffer, |buf: *u8, len: uint| {
-                hb_blob_create(buf as *c_char, len as c_uint, HB_MEMORY_MODE_READONLY, null(), null())
+        Some(ref font_table) => {
+            let skinny_font_table = ~font_table;
+            let skinny_font_table_ptr = ptr::to_unsafe_ptr(skinny_font_table);
+            let mut blob: *hb_blob_t = ptr::null();
+            (*skinny_font_table_ptr).with_buffer(|buf: *u8, len: uint| {
+                blob = hb_blob_create(buf as *c_char,
+                                      len as c_uint,
+                                      HB_MEMORY_MODE_READONLY,
+                                      cast::transmute(skinny_font_table_ptr), // private context for below.
+                                      destroy_blob_func); // HarfBuzz calls this when blob not needed.
             });
+            assert blob.is_not_null();
             return blob;
         }
     }
-}
+}
+
+// TODO(Issue #197): reuse font table data, which will change the unsound trickery here.
+// In particular, we'll need to cast to a boxed, rather than owned, FontTable.
+
+// even better, should cache the harfbuzz blobs directly instead of recreating a lot.
+extern fn destroy_blob_func(user_data: *c_void) unsafe {
+    // this will cause drop to run.
+    let _wrapper : &~FontTable = cast::transmute(user_data);
+}