#358 Make the whole menu system be controlable through the keyboard

[Jean-Philippe Meuret]

Because for now, you can't do without the mouse in many menus :

• the normal binding of the up/down arrow keys (Focus previous / Focus next) is sometimes overridden by menu-level shortcuts),
• some of our widgets can never get the focus (like Label controls), which makes the pseudo-combo-boxes not focusable,
• some other have a broken / weak focus management (like Combo-boxes),
• there's no decent API for excluding widgets from the navigation path.

And we should probably also move to the widely spread Tab / Shift-Tab navigation scheme, as it would then free the arrow keys in favor of other uses (more user friendly).

Note: This would then make the long awaited "joystick/joypad button"-only navigation quite straightforward to implement (just before the PS3 port ;-).

[Jean-Philippe Meuret]

r3424 does some progress on the combo-box side, by hiding their composite behavior in order to get a focus management that is consistent with much of the other (legacy) controls : the whole combo-box now gets / looses the focus at once (no more sub-control by sub-control), which enables up/down arrow key navigation in the menus.

Note : Many hand-made combo-boxes still exist in the menu (explicit creation of 3 separate controls : 2 graphical buttons + 1 label) : we need to move them to real "monolithic" combo-box controls.

[beaglejoe]

Most menus can be made navigable via up/down errors by adding a call to:
GfuiMenuDefaultKeysAdd()