SUMMARY So, if you double-click (or click quickly after another click) on the play/pause button, only the first click is registered. SOFTWARE/OS VERSIONS KDE Frameworks Version: 5.68 Qt Version: 5.15.0 Beta
Fixed in the 5.19 visual refresh!
This still happens exactly as described, it's not fixed.
The button is not doing anything nonstandard, so the issue must be in PlasmaComponents.ToolButton itself.
*** Bug 443665 has been marked as a duplicate of this bug. ***
I did a simple test and I changed onClicked event to onReleased event and was launched properly. Also I reviewed the source code for PlasmaComponents.ToolButton and it seems fine. So, I think that this bug would involved to the original Qt object. Would be just a different behaviour for the onClicked events when a double click arrives?
It's quite possible this is an upstream bug in how double-click events are handled. However this control doesn't have an onDoubleClicked: handler, so that would be inappropriate behavior to invoke. Would you be interested in taking a look upstream in Qt?