[Development] WindowSystemEvent accepted status

Sorvig Morten Morten.Sorvig at digia.com
Wed Mar 20 14:31:39 CET 2013


There are cases where the platform plugin needs to block and check if Qt accepts an event or not:

-  ShortcutOverride:  tryHandleShortcutEvent is synchronous (uses QGuiApplicationPrivate:: shortcutMap directly) and returns a bool.

- CloseEvent: The platform needs to know if Qt cancels the close.

- The general "embedded Qt" case: Qt is a view embedded in an application. Key and mouse events should be propagated to the the application if Qt does not accept them.

We can already flush the event queue by calling flushWindowSystemEvents(), but getting the accepted status is not possible.

Proposal: (for dev/5.2)
- Add "bool accepted" to WindowSystemEvent.
- Make all QWindowSystemInterface::handleFooEvent functions return a WindowSystemEvent pointer.
- The returned WindowSystemEvent is owned by QWindowSystemInterface and will be deleted "later".
- Make all QGuiApplicationPrivate::processFooEvent functions set the accepted status.
- All events should go through QWindowSystemInterfacePrivate::handleWindowSystemEvent. Don't call QGuiApplication directly.

The pattern for getting the accepted status then becomes:

QWindowSystemInterface::WindowSystemEvent *event = QWindowSystemInterface::handleFooEvent(…)
QWindowSystemInterface::flushWindowSystemEvents();
// use event->accepted immediately after calling flushWindowSystemEvents();

Morten




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