The idea that redraw events are dispatched with a specific ordering
that makes it possible to specifically report when we have finished
dispatching redraw events isn't portable and the way in which we
dispatched RedrawEventsCleared was inconsistent across backends.
More generally speaking, there is no inherent relationship between
redrawing and event loop iterations. An event loop may wake up at any
frequency depending on what sources of input events are being listened
to but redrawing is generally throttled and in some way synchronized
with the display frequency.
Similarly there's no inherent relationship between a single event loop
iteration and the dispatching of any specific kind of "main" event.
An event loop wakes up when there are events to read (e.g. input
events or responses from a display server / compositor) and goes back
to waiting when there's nothing else to read.
There isn't really a special kind of "main" event that is dispatched
in order with respect to other events.
What we can do more portably is emit an event when the event loop
is about to block and wait for new events.
In practice this is very similar to how MainEventsCleared was
implemented except it wasn't the very last event previously since
redraw events could be dispatched afterwards.
The main backend where we don't strictly know when we're going to
wait for events is Web (since the real event loop is internal to
the browser). For now we emulate AboutToWait on Web similar to how
MainEventsCleared was dispatched.
In practice most applications almost certainly shouldn't care about
AboutToWait because the frequency of event loop iterations is
essentially arbitrary and usually irrelevant.
This re-works the portable `run()` API that consumes the `EventLoop` and
runs the loop on the calling thread until the app exits.
This can be supported across _all_ platforms and compared to the
previous `run() -> !` API is now able to return a `Result` status on all
platforms except iOS and Web. Fixes: #2709
By moving away from `run() -> !` we stop calling `std::process::exit()`
internally as a means to kill the process without returning which means
it's possible to return an exit status and applications can return from
their `main()` function normally.
This also fixes Android support where an Activity runs in a thread but
we can't assume to have full ownership of the process (other services
could be running in separate threads).
Additionally all examples have generally been updated so that `main()`
returns a `Result` from `run()`
Fixes: #2709
* Improve web example
* Implement basic logger into the example webpage
* Repace bash script with xtask
* replace wasm-bindgen-cli with wasm-bindgen-cli-support
* refactor
* Move logic into external crate.
* Remove CI changes
* Review feedback
* examples: Fix unused `Result` that must be used when initializing console_log
* examples: Fix unused imports
* Fix unread name field warning in linux x11 ime InputMethod struct
* Fix unread name field warning in linux x11 Device struct
* Ignore unread field warning in macos/ios MonitorHandle struct
* ci: Add `--deny warnings` to `RUSTFLAGS`
* Remove support for `stdweb`
* Expunge `stdweb`; make `web-sys` the default
* Mark this change as a breaking change
* Re-insert accidental removal of space
* Use the correct cargo feature syntax
* Re-add some `cfg` attributes
* Remove `web-sys` feature from CI
