fonts: Instantiate system fonts using system font loaders (#33747)

System fonts used to be instantiated using the system font loader and
this change restores that behavior. In addition, on macOS and FreeType
platforms font data for system fonts is loaded using memory mapping. The
benefit is that system font loaders typically are able to cache fonts in
system memory (using memory mapping, for instance) and we'd like to load
them in a the way most compatible with other applications.

On my Linux system, this manages to get the overhead of loading a very
large font down from 10ms to approximately 1ms. Subsequent runs show
even less overhead. We've measured similar gains on macOS systems.

Currently, system font data must be loaded into memory manually for
canvas and this is unlikely to change even with a switch to `vello`. The
use of explicit memmory mapping should help in this case -- though it
probably won't be possible to use this properly on macOS and Windows if
we ever want to load fonts from TTCs properly.

Signed-off-by: Martin Robinson <mrobinson@igalia.com>
Co-authored-by: Mukilan Thiyagarajan <mukilan@igalia.com>

components/fonts/platform/macos/core_text_font_cache.rs

@@ -17,6 +17,7 @@ use core_text::font_descriptor::kCTFontURLAttribute;
 use parking_lot::RwLock;
 
 use crate::system_font_service::FontIdentifier;
+use crate::FontData;
 
 /// A cache of `CTFont` to avoid having to create `CTFont` instances over and over. It is
 /// always possible to create a `CTFont` using a `FontTemplate` even if it isn't in this
@@ -33,7 +34,7 @@ type CachedCTFont = HashMap<Au, CTFont>;
 impl CoreTextFontCache {
     pub(crate) fn core_text_font(
         font_identifier: FontIdentifier,
-        data: Arc<Vec<u8>>,
+        data: Option<&FontData>,
         pt_size: f64,
     ) -> Option<CTFont> {
         //// If you pass a zero font size to one of the Core Text APIs, it'll replace it with
@@ -86,8 +87,11 @@ impl CoreTextFontCache {
 
                 core_text::font::new_from_descriptor(&descriptor, clamped_pt_size)
             },
-            FontIdentifier::Web(_) | FontIdentifier::Mock(_) => {
-                let provider = CGDataProvider::from_buffer(data);
+            FontIdentifier::Web(_) => {
+                let data = data
+                    .expect("Should always have FontData for web fonts")
+                    .clone();
+                let provider = CGDataProvider::from_buffer(Arc::new(data));
                 let cgfont = CGFont::from_data_provider(provider).ok()?;
                 core_text::font::new_from_CGFont(&cgfont, clamped_pt_size)
             },

components/fonts/platform/macos/font.rs

@@ -4,7 +4,6 @@
 
 use std::cmp::Ordering;
 use std::ops::Range;
-use std::sync::Arc;
 use std::{fmt, ptr};
 
 /// Implementation of Quartz (CoreGraphics) fonts.
@@ -23,8 +22,9 @@ use style::values::computed::font::{FontStretch, FontStyle, FontWeight};
 use webrender_api::FontInstanceFlags;
 
 use super::core_text_font_cache::CoreTextFontCache;
+use super::font_list::LocalFontIdentifier;
 use crate::{
-    map_platform_values_to_style_values, FontIdentifier, FontMetrics, FontTableMethods,
+    map_platform_values_to_style_values, FontData, FontIdentifier, FontMetrics, FontTableMethods,
     FontTableTag, FontTemplateDescriptor, FractionalPixel, GlyphId, PlatformFontMethods, CBDT,
     COLR, KERN, SBIX,
 };
@@ -55,9 +55,6 @@ impl FontTableMethods for FontTable {
 #[derive(Debug)]
 pub struct PlatformFont {
     ctfont: CTFont,
-    /// A reference to this data used to create this [`PlatformFont`], ensuring the
-    /// data stays alive of the lifetime of this struct.
-    _data: Arc<Vec<u8>>,
     h_kern_subtable: Option<CachedKernTable>,
 }
 
@@ -167,31 +164,45 @@ impl fmt::Debug for CachedKernTable {
     }
 }
 
-impl PlatformFontMethods for PlatformFont {
-    fn new_from_data(
+impl PlatformFont {
+    fn new(
         font_identifier: FontIdentifier,
-        data: Arc<Vec<u8>>,
-        _face_index: u32,
-        pt_size: Option<Au>,
+        data: Option<&FontData>,
+        requested_size: Option<Au>,
     ) -> Result<PlatformFont, &'static str> {
-        let size = match pt_size {
+        let size = match requested_size {
             Some(s) => s.to_f64_px(),
             None => 0.0,
         };
-        let Some(core_text_font) =
-            CoreTextFontCache::core_text_font(font_identifier, data.clone(), size)
+        let Some(core_text_font) = CoreTextFontCache::core_text_font(font_identifier, data, size)
         else {
             return Err("Could not generate CTFont for FontTemplateData");
         };
 
         let mut handle = PlatformFont {
-            _data: data,
             ctfont: core_text_font.clone_with_font_size(size),
             h_kern_subtable: None,
         };
         handle.h_kern_subtable = handle.find_h_kern_subtable();
         Ok(handle)
     }
+}
+
+impl PlatformFontMethods for PlatformFont {
+    fn new_from_data(
+        font_identifier: FontIdentifier,
+        data: &FontData,
+        requested_size: Option<Au>,
+    ) -> Result<PlatformFont, &'static str> {
+        Self::new(font_identifier, Some(data), requested_size)
+    }
+
+    fn new_from_local_font_identifier(
+        font_identifier: LocalFontIdentifier,
+        requested_size: Option<Au>,
+    ) -> Result<PlatformFont, &'static str> {
+        Self::new(FontIdentifier::Local(font_identifier), None, requested_size)
+    }
 
     fn descriptor(&self) -> FontTemplateDescriptor {
         let traits = self.ctfont.all_traits();

components/fonts/platform/macos/font_list.rs

@@ -3,12 +3,12 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
 use std::fs::File;
-use std::io::Read;
 use std::path::Path;
 
 use base::text::{unicode_plane, UnicodeBlock, UnicodeBlockMethod};
 use log::debug;
 use malloc_size_of_derive::MallocSizeOf;
+use memmap2::Mmap;
 use serde::{Deserialize, Serialize};
 use style::values::computed::font::GenericFontFamily;
 use style::Atom;
@@ -43,13 +43,16 @@ impl LocalFontIdentifier {
         0
     }
 
-    pub(crate) fn read_data_from_file(&self) -> Vec<u8> {
-        let mut bytes = Vec::new();
-        File::open(Path::new(&*self.path))
-            .expect("Couldn't open font file!")
-            .read_to_end(&mut bytes)
-            .unwrap();
-        bytes
+    pub(crate) fn read_data_from_file(&self) -> Option<Vec<u8>> {
+        // TODO: This is incorrect, if the font file is a TTC (collection) with more than
+        // one font. In that case we either need to reconstruct the pertinent tables into
+        // a bundle of font data (expensive) or make sure that the value returned by
+        // `index()` above is correct. The latter is potentially tricky as macOS might not
+        // do an accurate mapping between the PostScript name that it gives us and what is
+        // listed in the font.
+        let file = File::open(Path::new(&*self.path)).ok()?;
+        let mmap = unsafe { Mmap::map(&file).ok()? };
+        Some((&mmap[..]).to_vec())
     }
 }