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Unify the task source and task canceller API

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I moved away from the `Window` struct all the logic to handle task
sources, into a new struct called `TaskManager`. In a happy world, I'd
be able to just have there two functions, of the types:

```rust
fn task_source<T: TaskSource>(&self, name: TaskSourceName) -> Box<T>
fn task_source_with_canceller<T: TaskSource>(&self, name: TaskSourceName)
  -> (Box<T>, TaskSourceCanceller)
```

And not so much duplicated code. However, because TaskSource can't be a
trait object (because it has generic type parameters), that's not
possible. Instead, I decided to reduce duplicated logic through macros.

For reasons[1], I have to pass both the name of the function with
canceller and the name of the function without, as I'm not able to
concatenate them in the macro itself. I could probably use
`concat_idents` to create both types already defined and reduce the
amount of arguments by one, but that macro is nightly only. At the same
time, not being able to declare macros inside `impl` forces me to pass
`self` as an argument.

All this makes this solution more verbose than it would be ideally. It
does reduce duplication, but it doesn't reduce the size of the file.

[1](https://github.com/rust-lang/rust/issues/29599)
This commit is contained in:
Agustin Chiappe Berrini 2018-09-24 19:31:59 -04:00
parent 14bc8ab754
commit 75eb94afca
26 changed files with 362 additions and 252 deletions
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22
components/script/task_source/history_traversal.rs
View file

@ -2,28 +2,16 @@
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
use crate::script_runtime::{CommonScriptMsg, ScriptThreadEventCategory};
use crate::script_thread::MainThreadScriptMsg;
use crate::task::{TaskCanceller, TaskOnce};
use crate::task_source::{TaskSource, TaskSourceName};
use msg::constellation_msg::PipelineId;
use script_runtime::{CommonScriptMsg, ScriptChan, ScriptThreadEventCategory};
use script_thread::MainThreadScriptMsg;
use servo_channel::Sender;
use task::{TaskCanceller, TaskOnce};
use task_source::{TaskSource, TaskSourceName};
#[derive(JSTraceable)]
#[derive(Clone, JSTraceable)]
pub struct HistoryTraversalTaskSource(pub Sender<MainThreadScriptMsg>, pub PipelineId);
impl ScriptChan for HistoryTraversalTaskSource {
fn send(&self, msg: CommonScriptMsg) -> Result<(), ()> {
self.0
.send(MainThreadScriptMsg::Common(msg))
.map_err(|_| ())
}
fn clone(&self) -> Box<ScriptChan + Send> {
Box::new(HistoryTraversalTaskSource((&self.0).clone(), (&self.1).clone()))
}
}
impl TaskSource for HistoryTraversalTaskSource {
const NAME: TaskSourceName = TaskSourceName::HistoryTraversal;