Add beforeFrameBegin() and afterFrameEnd() to QQuickWindow

New additions to the QQuickWindow signal family. Out of the three stages
of the (modern) frame generation process, only two are covered by the
existing beforeRendering, beforeRenderPassRecording -
afterRenderPassRecording, afterRendering pairs.

With the new ones, the rendering of a simple Qt Quick scene looks like
the following:

  emit beforeFrameBegin
QRhi::beginFrame()
  emit beforeRendering
... (additional render passes targeting textures when layers or View3D are involved)
QRhi::beginPass()
  emit beforeRenderPassRecording
  ...
  emit afterRenderPassRecording
QRhi::endPass()
  emit afterRendering
QRhi::endFrame()
  emit afterFrameEnd

This fits very well the revised QQuickRenderControl API, which has
explicit beginFrame-endFrame points as well. So now we can make both
QQuickRenderControl and the render loops to emit these signals at the
appropriate points.

Task-number: QTBUG-83883
Change-Id: Ib385b29393f3b39b0700432d14ea3976cf337fa0
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>
Reviewed-by: Andy Nichols <andy.nichols@qt.io>

1 files changed, 3 insertions, 0 deletions

diff --git a/src/quick/items/qquickwindow.h b/src/quick/items/qquickwindow.h
index a2278a8df0..deb57376ab 100644
--- a/src/quick/items/qquickwindow.h
+++ b/src/quick/items/qquickwindow.h
@@ -236,6 +236,9 @@ Q_SIGNALS:
     Q_REVISION(6, 0) void paletteChanged();
     Q_REVISION(6, 0) void paletteCreated();
 
+    Q_REVISION(6, 0) void beforeFrameBegin();
+    Q_REVISION(6, 0) void afterFrameEnd();
+
 public Q_SLOTS:
     void update();
     void releaseResources();