ToolButtons and focus

[Frederik Gladhorn]

Hello,

I just looked at the screen locker from an accessibility point of view (it's 
kinda' buggersome when there's no way to get back into a session after it has 
been locked) and with a bit of nudging (see review request) I can use it 
nicely. Not perfect, but good enough to get back to work.

Now the ToolButton.qml that plasma components ship is by default not 
"tabbable" - pressing tab you'll never land on one of these. For the lock 
screen I think the situation is simple, it should be tab-able, so I added the 
good old activeFocusOnTab property (sidenote: I recommend reading its 
implementation, it's beautiful graph traversal).

That made me wonder if Tool Buttons shouldn't receive the tab focus by 
default. I'm not 100% sure, but my gut-feeling says that might be a good idea. 
Currently that's intentionally not the case - aligning well with QWidgets. I 
wonder though if the plasma use of tool buttons is not quite often a different 
one, more like normal small buttons...

Greetings,
Frederik

PS: please let your tool buttons and other icon-only things have tooltips 
and/or set the Accessible.name. That will make my life as grumpy old man much 
more pleasant. Thanks.