Task-number: QTBUG-34806
Change-Id: I5013baaff0ca86357292474976944c1a3056f219
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
Reviewed-by: Laszlo Agocs <laszlo.agocs@digia.com>

This API is primarily a hook which is needed by the Qt WebEngine to
set up sharing with the scene graph's OpenGL contexts.

Change-Id: I5bb03abd9ab99f502db8e413fe838a8b30365b8d
Reviewed-by: Jocelyn Turcotte <jocelyn.turcotte@digia.com>

See the task for the full reasoning behind this patch.

The threaded renderloop has been refactored to have one window per
thread. This is mostly a simplification of the current code path where
for loops over multiple windows are turned into if (window).

The QSGContext has been split into two classes, QSGRenderContext
for which there is one per OpenGLContext.

The rest of the patch is name changes and a couple of cleanups
in the hopes of simplifying this change.

Task-number: QTBUG-33993

Change-Id: I31c81f9694d7da7474a72333169be38de62613c4
Reviewed-by: Sean Harmer <sean.harmer@kdab.com>

Change-Id: I3750c47640bf21c3567c5fa1c4667e3e2552942e
Reviewed-by: Lars Knoll <lars.knoll@digia.com>

This was the one convenience that was lost when transitioning templates
from QQuickView + Item{} to QQmlApplicationEngine + Window{}.

As the default window incubation controller was tied to the first
window's frameSwapped, we could easily run into a situation where
a secondary window required incubation while the first window
was idle. This would then starve the incubation controller. Instead
make it so that the renderloop emits "timeToIncubate" once it
is done with a renderpass over all windows, so the incubator
gets to run once and exactly once per vsync when animating.

The incubator logic was also flawed in that it could post
a lot of events to itself as a result of incubatingObjectCountChanged
and thus starve system events while processing incubation requests.
Now we start a timer and don't start it again until we have
completed an incubation pass.

Task-number: QTBUG-31203
Change-Id: Iea9e2c81efb46bb7875c70ccda0cdc4b3b3e58e7
Reviewed-by: Alan Alpert <aalpert@blackberry.com>
Reviewed-by: Gunnar Sletta <gunnar.sletta@digia.com>

Change-Id: Ide71b330b13fc3816ed191bd9af84e0fce0d9587
Reviewed-by: Kai Koehne <kai.koehne@digia.com>

The normal GUI thread render loop has several problems on windows.
It does not do vsync animations and on some hardware, where the
vsync delta is higher than the time it takes to fire a 16ms timer,
the eventloop will always contain at least one event and we never
return to processing non-client area events, like resize.

Also, threaded OpenGL seems rather unstable, so the threaded renderer
is not a stable option.

So we introduce a windows based renderloop. It is fully cross platform
but written to make the most out of the limitations which exist.

The overall goal is:
  - vsync animations when allowed by the system. We get this by
    using an animation driver and advancing in sync with rendering
  - Keep system load low and allow for NC processing. The maybeUpdate
    function will start a short timer which will let the renderloop
    idle for few ms, allowing the eventloop to pick up system events.
    (this is similar to what the threaded renderer also does, btw)

Change-Id: Ic192fd0ed7d5ecdaa2c887c08cbeb42c5de6b8a8
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
Reviewed-by: Samuel Rødal <samuel.rodal@digia.com>