GCC has some optimization for the inclusion guard, but they only work if
the check is the outermost one.
We're fairly inconsistent because of historical reasons, so we should
ensure that we follow the same pattern in every public header.
PanAction is a GestureAction-subclass that implements the panning
concept for scrollable actors, with the ability to emit interpolated
signals to emulate the kinetic inertia of the panning. PanAction provides:
• pan signal, notifying users of the panning gesture status;
• pan-stopped signal, emitted at the end of the interpolated phase
of the panning gesture, if enabled;
• pan-axis property, to allow constraining the dragging to a specific
axis;
• interpolated property, to enable or disable the inertial behaviour;
• deceleration property, to customize the rate at which the momentum
of the panning will be slowed down;
• acceleration-factor property, applied to the inertial momentum when
starting the interpolated sequence.
An interactive test is also provided.
https://bugzilla.gnome.org/show_bug.cgi?id=681648
