How do I know if I won't receive a FileOpen event?

Kerndog73

I have an application that edits files. When the user double clicks on a file, my application is launched and the FileOpen event is received. When my application is launched directly by the user, a dialog window for creating a new file is shown.

The problem that I'm having is that I don't know if I'm not going to receive the FileOpen event. When my application launches, I show the file creation dialog window. Then when I receive the FileOpen event, I close the dialog window and open the file. The result is that the dialog window flashes on the screen for a moment.

FileOpen is received after ApplicationStateChange which means I can't wait until ApplicationStateChange and then show the dialog only if FileOpen wasn't received.

Should I set a timer to show the dialog after 500ms if FileOpen wasn't received? That seems kind of hacky to me. I don't really want to sacrifice launch time to get this to work. Is there another way of getting this information other than through events?

Kerndog73

I've just discovered some shocking news. The FileOpen event is only supported by macOS.

Seriously? Why? I'm genuinely shocked.

jsulm

@Kerndog73 said in How do I know if I won't receive a FileOpen event?:

Why?

That you should ask Qt developers on their mailing list

Kerndog73

@jsulm Nah, I won't bother them with my nonsense.

jsulm

@Kerndog73 Well, I don't know why it is only supported on MacOS. You can take a look at the source code, maybe you will find out why.

Kerndog73

My solution for the moment is to set a timer for 100ms. I consistently have about 20-30ms to spare so this seems to be a good time. The big problem with this is that I'm setting a timer for 100ms! This just feels so wrong. There has to be a better way.

This is just as bad as those ancient video games that depend on the clock speed of the machine they're running on.

jsulm

@Kerndog73 I'm not sure, but don't you get the file name user double clicked, as a parameter to your app (I mean argc/argv)? If this is the case you don't need that event and can easily check whether you should show file open dialog or not.

Kerndog73

@jsulm That doesn't seem to be the case, unfortunately. The only command line argument I get is -psn_0_29527079. I've got no idea what that means!

SGaist

Hi,

There's nothing specially shocking, it just means that there was no other OS providing a similar event as macOS does.

Kerndog73

@SGaist But Windows supports this feature, doesn't it? I mean, when you double click on a .docx file, MS Word is asked to open it, right?

SGaist

I don't know how that part is currently done on Windows. It could be just that a parameter is passed to the executable or something completely different.

wrosecrans

I don't know OS-X guts well enough to give a precise answer, but in the underlying Cocoa API's, it's possible to decide you aren't getting on initial openFile event as soon as you get the applicationDidFinishLaunching event. I dunno if that's actually plumbed through to Qt in any obvious way, or if it's easy to check by dropping to some native code in a way that doesn't break Qt.

https://developer.apple.com/documentation/appkit/nsapplicationdelegate/1428612-application?language=objc

Maybe it's enough to set a 0ms timer rather than 100ms? I don't have a Mac to test with, but perhaps the timeout of a 0ms timer won't actually be serviced until after the application has "finished launching" ?

Kerndog73

@wrosecrans A 0ms timer seems to have solved the problem! The timer only times out after the application is fully initialised. This kind of makes sense because a 0ms timer is the “right solution” to some other problems too.