Add support for manually closing PopupWindows

[tronical]

This patch adds a close() function that can be called to close a popup window, and a close-to-click boolean that can be set to false to disable the default behavior.

[tronical]

I'd like to see if this is acceptable. If it is, then I can try to add a test for it to get at least code coverage for the generators. I tested it locally :-)

[ogoffart]

I wonder if we should still close the popup when clicking outside of the popup or not?
Maybe there should be several flags, or some enum?

If we don't close the popup when clicking outside, how can a user do that if they want to?

[tronical]

I wonder if we should still close the popup when clicking outside of the popup or not? Maybe there should be several flags, or some enum?

If we don't close the popup when clicking outside, how can a user do that if they want to?

To me that's starting to sound like a Window item feature, not a popup anymore though. A popup to me is something that is frameless and goes away when pressing escape or clicking outside of it.

But we can extend Window in the future with more sophisticated ways - in a way perhaps PopupWindow should become a special version of Window in the future.

[flukejones]

I wonder if we should still close the popup when clicking outside of the popup or not? Maybe there should be several flags, or some enum?

If we don't close the popup when clicking outside, how can a user do that if they want to?

It should be up to the developer to determine what the UX should be. In my case I would rather have a TouchArea and a callback to close (or a big red button) so I can be sure that a user explicitly closed a popup instead of a possible accidental touch.

The HMI I am working on is going to be made available on tens of thousands of welding machines over time and these machines are going in to workshops where there is a combination of user types from tech-savy to computer illiterate. So with PopupWindow I have two usecases for it - a big notification, and a dropdown menu.

For the big notification I could have a callback to the main window to show a Rectangle with text or similar, but I may also need to show widgets - and I'm unsure how to do that with callbacks since I can't pass widgets in a function. Whereas with a PopupWindow I have a bit more freedom to show some complex stuff when required.

However for PopupWindow to be suitable as a dropdown I still need #1691 so that I can prevent clipping offscreen.

I'm certainly open to alternative ideas on how to achieve these things.

Thanks for adding this capability BTW, it solves the issue I had with Flickable in a PopupWindow closing on click release.