Test that assigning colors works:
* Test the implicit `Brush(const Color &)` C++ constructor
* Add derive_more::From to allow convenient conversion in Rust
* When assigning to brush properties in JavaScript, try at least to see if it's a color string (could be extended in the future)
Return an iterator when querying the properties. This requires a
one-time copy of the property declarations out of the compiler data
structure, which is read-only.
* sixtyfps_timer_start needs to *take* the timer id out of the Rust
timer to avoid that the subsequent drop stops the timer again
* For the Qt event loop, call `timer_event()` once before entering
QCoreApplication::exec(), to schedule any timers that were started
beforehand.
* Added a way to quit the event loop gently, in order to use that
from the C++ unit test.
Similar to the window properties, use a property tracker with a change
handler in window to issue redraw requests. This allows eliminating the
forced repaints in the event loop after event processing and ensures
that the UI is repainted when programmatically setting a property, for
example.
Synchronize title/background/etc. once when the window is mapped and
afterwards lazily when the corresponding property tracker notifies us.
Since that callback can happen at any point in time and to also capture
potentially multiple changes, this first triggers a wakeup of the event
loop, when the actual application of properties happens.
A Property tracker can now be constructed with a callback that's invoked
when a property accessed during evaluate is changed.
The callback is guarded to be called only once until the tracker has
been evaluated. This is implemented by passing the information about
whether the property/tracker was already dirty before through the
mark_dirty() vtable call.
By default PropertyTracker::evaluate() registers the currently
evaluating binding/tracker as a dependency. This should help with
repeaters and other scenarios where in the run-time we use property
trackers but want to track the overall "dirtyness" in the window with
regards to whether a redraw is needed or not.
The new evaluate_as_dependency_root() function allows skipping this
mechanism and is used for the two trackers in the window.
The alignment and sizes are different for some of the enums, so their opaque counterparts need
to be defined accordingly in order for the assertions in ffi.rs to pass.
