[Interest] QtQuick - How to move focus away from disabled Item?

[Ola Røer Thorsen]

Hi,

I'm having some trouble making a robust QtQuick 5.4-based application where
I only have 4 cursor keys and a return key available as the input method
for the user.

I have various gui buttons that I can move focus between. I've set this up
using the KeyNavigation.onXXX etc. For a simple static gui, this is fine.

However I get into trouble once some buttons get disabled (enabled-property
set to false). This is done based on external events, so it may happen at
any time.

If a button with active focus is disabled, I'm stuck. The button's focus
property is still true, but it will not receive key events, so I cannot
move focus to the next using the cursor keys. I'd like focus to move on to
some other item automatically anyway.

Have any of you got some recommended way of dealing with situations like
this?

I think I've spent half the development time on this application just
making sure keyboard navigation cannot get stuck.

I did not have such issues when creating similar applications with Qt
Widgets. There the behavior is that focus moves on to another widget
automatically if I call setEnabled(false) on a widget with current active
focus.

I've tried doing something like this in my Button item:

Button {
   id: button
   activeFocusOnTab: true
   function transferFocus() {
      if(!visible || enabled)
         return;
      if(nextItemInFocusChain() === button)
         return;
      if(focus)
         nextItemInFocusChain().focus = true;
   }
   onEnabledChanged: transferFocus()
}

This works OK in a smaller test application, but makes the larger
application hang when  "nextItemInFocusChain" is called for the 20th time
or so.

Cheers,
Ola
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