Add `tabletToolEvent()` to DecorationEventFilter class so it can handle
tablet events.
Add `tabletToolEvent()` to MoveResizeFilter class to avoid incorrect
titlebar highlight after a window is resized by using a stylus.
Add `tabletToolEvent()` to WindowActionInputFilter class so window focus
can be changed by clicking on the window content area when using a stylus.
Add `update()` to `TabletInputRedirection::tabletToolEvent()` to enable
switching window focus by using a stylus.
BUG: 432104
The main motivation behind this change is to prepare input abstractions
for virtual input devices so the wl_seat can properly advertise caps or
the cursor getting properly mapped/unmapped when a fake pointer is
added/removed on a system without a hardware mouse connected.
With this, there are three abstractions - InputDevice, InputBackend, and
InputRedirection.
An InputDevice represents an input device such as a mouse, a keyboard, a
tablet, etc. The InputBackend class notifies the InputRedirection about
(dis-)connected devices. The InputRedirection manages the input devices.
Such design allows to unify the event flow for real and virtual input
devices.
There can be several input backends active. For example, the libinput
backend and an input backend that provides virtual input devices, e.g.
libeis or org_kde_kwin_fake_input.
Once in a while, we receive complaints from other fellow KDE developers
about the file organization of kwin. This change addresses some of those
complaints by moving all of source code in a separate directory, src/,
thus making the project structure more traditional. Things such as tests
are kept in their own toplevel directories.
This change may wreak havoc on merge requests that add new files to kwin,
but if a patch modifies an already existing file, git should be smart
enough to figure out that the file has been relocated.
We may potentially split the src/ directory further to make navigating
the source code easier, but hopefully this is good enough already.
