cmd-drag race condition on OSX

[leeavital]

Hi folks,

I think I've found a race condition, or at least a bug with cmd-dragging automation tracks on OSX.
Environment:

• OSX 10.11.5
• Clang
• qt5

Bug: if I open any synth (I tried triple oscillator and organic), and try to cmd+drag one of the knobs onto an automation track.

Some things I tried:

• with some print statement debugging, it seems like we get to
  AutomationTrackView::dragEnterEvent and call acceptProposedAction() on the
  passed event, but even then, AutomationTrackView::dropEvent doesn't get called.
• If I call, dropEvent() directly from dragEnterEvent(), it looks like dropEvent() does what it's supposed to. Qt just isn't calling dropEvent for some reason.
• Now the race condition part: if I step through in lldb and set a breakpoint inside dragEnterEvent, dropEvent somehow starts getting called.

questions:

• is anyone else seeing this? Perhaps on different platforms
• how would one go about debugging this? I know next to nothing about Qt.
• is there another way to create automation tracks like this without click-dragging?

[tresf]

@leeavital yes, we are also experiencing this.

#2890

We were under the belief that it was Qt5 + XCode SDK related. If it is a race condition it will help us fix this. It's a blocker for a Mac Qt5 release.

[leeavital]

I just built this against qt 5.7.x, and cmd-drag is working. I think you're right, this can be chalked up to a bug in QT.