Sliders should receive keyboard focus on mouse click

Issue type

UX/Interaction bug (incorrect behaviour)

Description with steps to reproduce

When you click on a slider (or any UI object that accepts input from the arrow keys) it should receive keyboard focus.

1. Click on a note or rest in the score.
2. Open the Mixer and click on a volume slider.
3. Try to move the volume slider with the Left and Right arrow keys.
   • Not the Up and Down arrow keys because these are used for navigation in the Mixer, not to change values.

Expected result: The volume slider should move up and down.

Actual result: Navigation occurs in the score.

• Though changed pitches or shifted texts (tempo) are score-damaging and not mere navigation

What is the latest version of MuseScore Studio where this issue is present?

4.4.2 and latest nightly

Regression

Yes, this used to work in MuseScore 3.

Operating system

Windows 11

Additional context

Objects that do not accept input from the arrow keys (e.g. buttons, checkboxes) should NOT receive focus on click. For example, if you click the 'mute' button in the Mixer, or a duration button in the toolbar, focus should remain in the score.

For objects that DO receive focus on click, when it receives focus this way, the dark focus rectangle should NOT be displayed. This rectangle should ONLY be displayed if the object received focus by pressing a keyboard shortcut such as arrow keys or tab.

For example, consider the input field next to the pan control in the Mixer. The correct states are:

Not focussed	Focussed via mouse	Focussed via keyboard

In the middle image, it still has keyboard focus, but the dark focus rectangle is not displayed. This is the correct behaviour.

Note: When focussed via keyboard the text in the field is selected. This is correct behaviour. When focussed via mouse the text is not selected. This is also correct behaviour. The user can double-click to select the text or press an arrow key to deselect it.