wlr_keyboard manages the xkb-common state of the compositor.
It used to update the state, update the modifiers, then notify the
compositor.
When [Shift_L] was pressed and released, this resulted in an event chain:
Modifiers: Shift
Key: Shift_L (Pressed)
Modifiers:
Key: Shift_L (Release)
The xkb-docs state that the state should be updated *after* the key was
handled [1], to prevent the new state from influencing the actual key
generated.
To achieve this, the event to the compositor is emitted, *before*
wlroots handles the xkb and internal keyboard state.
With this patch applied, the emitted events ill be:
Modifiers:
Key: Shift_L (Pressed)
Modifiers: Shift
Key: Shift_L (Release)
[1] https://xkbcommon.org/doc/current/group__state.html#gac554aa20743a621692c1a744a05e06ce
c8ccb1bef3