QSGRenderLoop: Remove the exhaust delay timer.

This was replaced by a proper requestUpdate mechanism at the QWindow level, so
it isn't needed anymore. As we can't remove the QQuickWidget version so easily,
document the exhaust_delay reasoning, as it is not too obvious.

Change-Id: I0a15237bacae47dc87af6b6018a7bc1b47eb8d2d
Reviewed-by: Gunnar Sletta <gunnar@sletta.org>

1 files changed, 8 insertions, 0 deletions

diff --git a/src/quickwidgets/qquickwidget.cpp b/src/quickwidgets/qquickwidget.cpp
index 063386ed8e..6a29dea505 100644
--- a/src/quickwidgets/qquickwidget.cpp
+++ b/src/quickwidgets/qquickwidget.cpp
@@ -1280,6 +1280,14 @@ void QQuickWidget::triggerUpdate()
     Q_D(QQuickWidget);
     d->updatePending = true;
      if (!d->eventPending) {
+        // There's no sense in immediately kicking a render off now, as
+        // there may be a number of triggerUpdate calls to come from a multitude
+        // of different sources (network, touch/mouse/keyboard, timers,
+        // animations, ...), and we want to batch them all into single frames as
+        // much as possible for the sake of interactivity and responsiveness.
+        //
+        // To achieve this, we set a timer and only perform the rendering when
+        // this is complete.
         const int exhaustDelay = 5;
         d->updateTimer.start(exhaustDelay, Qt::PreciseTimer, this);
         d->eventPending = true;