Next stage of refactoring font system. This commit introduces

the font cache task, and adapts client code to use it. It also
cleans up some existing code paths.

- Fonts are only read once from disk while in use (they
  are discarded if the reference count reaches zero, however).
  This saves memory and prevents unnecessary reading from disk.
- It will be easier to add web font support, as all fonts
  are created and managed in a single place and the entire
  pipeline ensures that only one in-memory copy of font data
  is required.

An overview of how the pieces fit together:

FontTemplate - A structure containing everything that
is required to create (and select) font handles. This
structure is shared among all matching font handles
(via Arc).

FontTemplateData - A platform specific structure that
contains the actual font data inside a template (this is
a byte array on Linux/Android, CTFont on Mac).

FontHandle - An opaque, platform specific handle to
a font instance. Each FontHandle contains an Arc<>
reference to the FontTemplate it was created from.

FontCache - This is a separate task, that is responsible
for loading and caching FontTemplate structures. There
is one FontCache per constellation. It is only ever accessed
via the FontContext described below.

FontContext - This is the public interface to the FontCache
and is used by the layout and render code to create font
handles. These must *not* be shared between threads. There
is typically one FontContext per thread/task.

1 files changed, 7 insertions, 0 deletions

diff --git a/src/components/compositing/pipeline.rs b/src/components/compositing/pipeline.rs
index cabf2984b15..dbd054feb55 100644
--- a/src/components/compositing/pipeline.rs
+++ b/src/components/compositing/pipeline.rs
@@ -14,6 +14,7 @@ use script::script_task;
 use servo_msg::constellation_msg::{ConstellationChan, Failure, PipelineId, SubpageId};
 use servo_msg::constellation_msg::WindowSizeData;
 use servo_net::image_cache_task::ImageCacheTask;
+use gfx::font_cache_task::FontCacheTask;
 use servo_net::resource_task::ResourceTask;
 use servo_util::opts::Opts;
 use servo_util::time::TimeProfilerChan;
@@ -49,6 +50,7 @@ impl Pipeline {
                        constellation_chan: ConstellationChan,
                        compositor_chan: CompositorChan,
                        image_cache_task: ImageCacheTask,
+                       font_cache_task: FontCacheTask,
                        time_profiler_chan: TimeProfilerChan,
                        opts: Opts,
                        script_pipeline: Rc<Pipeline>,
@@ -68,6 +70,7 @@ impl Pipeline {
                            render_port,
                            compositor_chan.clone(),
                            constellation_chan.clone(),
+                           font_cache_task.clone(),
                            failure.clone(),
                            opts.clone(),
                            time_profiler_chan.clone(),
@@ -81,6 +84,7 @@ impl Pipeline {
                            script_pipeline.script_chan.clone(),
                            render_chan.clone(),
                            image_cache_task.clone(),
+                           font_cache_task.clone(),
                            opts.clone(),
                            time_profiler_chan,
                            layout_shutdown_chan);
@@ -110,6 +114,7 @@ impl Pipeline {
                   constellation_chan: ConstellationChan,
                   compositor_chan: CompositorChan,
                   image_cache_task: ImageCacheTask,
+                  font_cache_task: FontCacheTask,
                   resource_task: ResourceTask,
                   time_profiler_chan: TimeProfilerChan,
                   window_size: WindowSizeData,
@@ -150,6 +155,7 @@ impl Pipeline {
                            render_port,
                            compositor_chan.clone(),
                            constellation_chan.clone(),
+                           font_cache_task.clone(),
                            failure.clone(),
                            opts.clone(),
                            time_profiler_chan.clone(),
@@ -163,6 +169,7 @@ impl Pipeline {
                            script_chan.clone(),
                            render_chan.clone(),
                            image_cache_task,
+                           font_cache_task,
                            opts.clone(),
                            time_profiler_chan,
                            layout_shutdown_chan);