Remove all the old 2.x and 3.x version annotations.
GTK+ 4 is a new start, and from the perspective of a
GTK+ 4 developer all these APIs have been around since
the beginning.
Those are now needless and wrong, as we get guarantees that handled
events will contain widget-relative coordinates. A side effect is
that these events are very possibly not explicitly sent to the
GdkWindow that implementations expect, any extra checks performed
through gtk_gesture_set_window() will be wrong, so the function has
been dropped entirely.
Event controllers now auto-attach, and the GtkCapturePhase only determines
when are events dispatched, but all controllers are managed by the widget wrt
grabs.
All callers have been updated.
The propagation phase property/methods in GtkEventController are gone,
This is now set directly on the GtkWidget add/remove controller API,
which has been made private.
The only public bit now are the new functions gtk_gesture_attach() and
gtk_gesture_detach() that will use the private API underneath.
All callers have been updated.
This API eliminates the need for overriding
GtkWidget::sequence-state-changed virtually everywhere. Grouped
gestures share common states for a same GdkEventSequence, so the
state of sequences stay in sync across those.
The policy of sequence states has been made tighter on GtkGesture,
so gestures can never return to a "none" state, nor get out of a
"denied" state, a "claimed" sequence can go "denied" though.
The helper API at the widget level will first emit
GtkWidget::sequence-state-changed on the called widget, and then
notify through the same signal to every other widget in the captured
event chain. So the effect of that signal is twofold, on one hand
it lets the original widget set the state on its attached controllers,
and on the other hand it lets the other widgets freely adapt to the
sequence state changing elsewhere in the event widget chain.
By default, that signal updates every controller on the first usecase,
and propagates the default gesture policy to every other widget in the
chain on the second. This means that, by default:
1) Sequences start out on the "none" state, and get propagated through
all the event widget chain.
2) If a widget in the chain denies the sequence, all other widgets are
unaffected.
3) If a widget in the chain claims the sequence, then:
3.1) Every widget below the claiming widget (ie. towards the event widget)
will get the sequence cancelled.
3.2) Every widget above the claiming widget that had the sequence as "none"
will remain as such, if it was claimed it will go denied, but that should
rarely happen.
This behavior can be tweaked through the GtkWidget::sequence-state-changed and
GtkGesture::event-handled vmethods, although this should be very rarely done.
