I'm converting an OSX application from Qt 4/Carbon to Qt5.11 with the QOpenGLWidget.
I've moved the drawing "calls" to my overridden QOpenGlWidget::paintGL().
The problem is I'm still getting these messages on the console:
QWidget::paintEngine: Should no longer be called
Getting a stack trace, I've discovered that this is being called eventually from QCoreApplication::processEvents, which I'm calling from my own internal event loop.
Here's a stack trace (edited for readability)
QWidget::paintEngine()
frame #1: libQt5Widgets_debug.5.dylibQOpenGLWidget::paintEngine(0)
frame #2: libQt5Gui_debug.5.dylibQPainter::begin()
frame #3: libQt5Gui_debug.5.dylibQPainter::QPainter()
frame #4: libQt5Gui_debug.5.dylibQPainter::QPainter()
frame #5: libQt5Widgets_debug.5.dylibQWidgetPrivate::drawWidget()
frame #6: libQt5Widgets_debug.5.dylibQWidgetPrivate::repaint_sys()
frame #7: libQt5Widgets_debug.5.dylibQWidgetPrivate::syncBackingStore()
frame #8: libQt5Widgets_debug.5.dylibQWidgetWindow::handleExposeEvent()
frame #9: libQt5Widgets_debug.5.dylibQWidgetWindow::event()
frame #10: libQt5Widgets_debug.5.dylibQApplicationPrivate::notify_helper()
frame #11: libQt5Widgets_debug.5.dylibQApplication::notify()
frame #12: libQt5Core_debug.5.dylibQCoreApplication::notifyInternal2()
frame #13: libQt5Gui_debug.5.dylibQCoreApplication::sendSpontaneousEvent()
frame #14: libQt5Gui_debug.5.dylibQGuiApplicationPrivate::processExposeEvent()
frame #15: libQt5Gui_debug.5.dylibQGuiApplicationPrivate::processWindowSystemEvent()
frame #16: libQt5Gui_debug.5.dylibbool QWindowSystemInterfacePrivate::handleWindowSystemEvent<QWindowSystemInterface::SynchronousDelivery>()
frame #17: libQt5Gui_debug.5.dylibvoid QWindowSystemInterface::handleExposeEvent()
frame #18: libqcocoa_debug.dylibQCocoaWindow::handleExposeEvent()
frame #19: libqcocoa_debug.dylib::-[QNSView updateRegion:](self=0x000061200039fc40, _cmd="updateRegion:", dirtyRegion=QRegion @ 0x00007ffeefbf9b18)
frame #20: libqcocoa_debug.dylib::-[QNSView updateLayer](self=0x000061200039fc40, _cmd="updateLayer")
frame #21: AppKit_NSViewUpdateLayer + 45
frame #22: AppKit-[_NSViewBackingLayer display] + 495
frame #23: QuartzCoreCA::Layer::display_if_needed(CA::Transaction*) + 634
frame #24: QuartzCoreCA::Context::commit_transaction(CA::Transaction*) + 319
frame #25: QuartzCoreCA::Transaction::commit() + 576
frame #26: QuartzCoreCA::Transaction::observer_callback(__CFRunLoopObserver*, unsigned long, void*) + 66
frame #27: CoreFoundationCFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION + 23
frame #28: CoreFoundation__CFRunLoopDoObservers + 452
frame #29: CoreFoundationCFRunLoopRunSpecific + 523
frame #30: HIToolboxRunCurrentEventLoopInMode + 293
frame #31: HIToolboxReceiveNextEventCommon + 618
frame #32: HIToolbox_BlockUntilNextEventMatchingListInModeWithFilter + 64
frame #33: AppKit_DPSNextEvent + 997
frame #34: AppKit-[NSApplication(NSEvent) _nextEventMatchingEventMask:untilDate:inMode:dequeue:] + 1362
frame #35: libqcocoa_debug.dylibQCocoaEventDispatcher::processEvents(this=0x00006040000dbdf0, flags=(i = 0)) at qcocoaeventdispatcher.mm:482
frame #36: libQt5Core_debug.5.dylib`QCoreApplication::processEvents(flags=(i = 0)) at qcoreapplication.cpp:1252 The problem is that ::processEvents is eventually calling ::paintEngine for the QOpenGLWidget, OUTSIDE of ::paintGL, but it's totally out of my control.
FWIW, the Event driving this is a QEvent::UpdateRequest.
I tried overriding ::event in my QOpenGLWidget-inheriting class to call QOpenGlWidget::update when it receives a QEvent::UpdateRequest, but that just ended up making the app non-responsive.
How should I handle ::processEvents attempting to draw QOpenGlWidgets?
Thanks!
I fixed this by removing this statement from our QOpenGlWidget subclass:
setAttribute( Qt::WA_PaintOnScreen, true );
Removing this got ride of the paintEngine calls (and solved all kinds of other problems).