Fix infinite polling for usb devices after the "add to whitelist" dia…

[amaiorano]

…log has been opened once

Problem is that USBDeviceAddToWhitelistDialog starts a timer once created to poll for devices every second. In Qt, closing a dialog doesn't delete it, so it keeps on polling. The fix is to tell QT to delete this dialog on close, so that the timer gets destroyed with it.

[amaiorano]

Addresses: https://bugs.dolphin-emu.org/issues/11126

@Zexaron

[ghost]

Tested, works fine.

[Antidote]

Does that dialog really need to be allocated on the heap? It's a modal dialog box, so it blocks input to other windows until it's closed. Making it a stack variable would have the same effect as setting that attribute.

@Zexaron @amaiorano

[amaiorano]

Does that dialog really need to be allocated on the heap? It's a modal dialog box, so it blocks input to other windows until it's closed. Making it a stack variable would have the same effect as setting that attribute.

@Zexaron @amaiorano

(Edit: @Zexaron) @Antidote is right; however, there are two ways to run a modal dialog in Qt. One way is to call setModal(true) + show(), which the code currently does, but this doesn't block. So in this case, we cannot allocate the dialog on the stack. The other way is to call exec(), which is a blocking call, and more common, actually. (See the section entitled "Modal Dialogs" in the Qt docs here). I'm not sure why the code used the less common approach; but I tried with exec(), and it seems to work just fine. This way, we don't need to set the WA_DeleteOnClose attribute. I've rewritten by commit with this new solution.

[Antidote]

I was referring to it being a blocking call for the user, I forgot that show wasn't a blocking call for the application itself.

[amaiorano]

I know you probably hadn't realized that show wasn't application blocking, but it's possible to make it so using exec, so that's what I did. Unless there's a good reason not to, should we go ahead with this version? Or go back to my first solution?

[Antidote]

I think using exec was the proper solution from the start, dunno why show was used instead.

[amaiorano]

If we're happy with this, can someone from Dolphin team approve this PR?