Fix missing maximize button for attribute form dialog on Windows

[elpaso]

On windows, the attribute form dialog misses the maximize button which can be very useful with large custom forms.

I've tried all possible combination of flags and even a custom windows API event manager but I couldn't make the maximize button appear when the Qt::Tool flag is set.

[troopa81]

I remember having quite the same issue and ending up with quite the same solution. LGTM

[elpaso]

@troopa81 thanks for reviewing!

I'll wait a few days to merge, maybe someone knows a better way to fix this.

[m-kuhn]

How does it behave if "select feature on canvas" from the relation widget or similar features with map canvas interaction are used from within the attribute form?

Looking at the doc Qt::Tool is a combination of Popup | Dialog. Would it be possible / reasonable to keep one of these. And/or apply the hint "If there isn't a parent, you may consider using Qt::WindowStaysOnTopHint as well."?

[elpaso]

How does it behave if "select feature on canvas" from the relation widget or similar features with map canvas interaction are used from within the attribute form?

Looking at the doc Qt::Tool is a combination of Popup | Dialog. Would it be possible / reasonable to keep one of these. And/or apply the hint "If there isn't a parent, you may consider using Qt::WindowStaysOnTopHint as well."?

Qt::Dialog is already the default for a QDialog, I suspect that it is the Qt::Popup flag which prevents the maximize button to be shown whatever "hint" flag you set.

I will test the various workflows to make sure everything is still working as expected.

[elpaso]

@m-kuhn I tested the last commit with a relation-ref widget with canvas selection and it seems to work just fine.

[m-kuhn]

Thanks @elpaso