Root task to improve the overall behavior of KWin's virtual keyboard (vk).
* Support [[ https://github.com/wayland-project/wayland-protocols/blob/master/unstable/text-input/text-input-unstable-v3.xml | text_input_unstable_v3 ]] protocol: D16735
* Support future [[ https://lists.freedesktop.org/archives/wayland-devel/2018-August/039255.html | zwp-input-method-v2 ]] protocol.
* Define virtual keyboard visibility modes (auto/always/disabled):
* auto: only show when no physical keyboard attached
* always: show always when text input is expected, maybe additionally only if last pointer interaction was with touch.
* disabled: do not show vk.
* Visibility change logic on touch/click: Currently when enabled the vk shows directly when focus goes to a text input field. But it makes more sense to only show it when a touch point was registered in the text input field This probably needs to be solved on application level.
* Adjust window positioning to virtual keyboard being visible:
* Adjust height of clients temporarily so that vk does not cover them.
* What to do with Plasma applets with text input and transients?
* Xwayland support.