This idiom has been dying out in new Rust code; it's especially
confusing for layers because there is a higher chance of making the
mistaken assumption that the iteration is occurring over multiple
layers.
Rename find_child_with_layer_and_pipeline_id to
find_child_with_pipeline_and_layer_id so that it matches both the
logical and actual parameter ordering.
Using {:?} prints a debugging representation such as
collections::string::String{
vec: collections::vec::Vec<u8>{
len: 4u,
cap: 4u,
ptr: (0x7f75670285d8 as *mut ())
}
}
which is not very helpful.
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.
Currently the compositor tracks its state in the processing of shutting
down with two boolean instance variables `shutting_down` and `done`, but
these two variables really implement a three-state abstraction.
The Scene::set_transform method was only introduced because of an old
rustc bug around mutating properties across crates. Now that the rustc
bug is fixed, we can stop calling this method.
