gtk:event-controller, gobject:object, common-lisp:standard-object, common-lisp:t

None

The gtk:event-controller-scroll object is an event controller meant to handle scroll events from mice and touchpads. It is capable of handling both discrete and continuous scroll events, abstracting them both on the "scroll" signal. Deltas in the discrete case are multiples of 1.

In the case of continuous scroll events, the gtk:event-controller-scroll object encloses all "scroll" events between two "scroll-begin" and "scroll-end" signals.

The behavior of the event controller can be modified by the flags given at creation time, or modified at a later point through the gtk:event-controller-scroll-flags function, e.g. because the scrolling conditions of the widget changed.

The controller can be set up to emit motion for either/both vertical and horizontal scroll events through :vertical, :horizontal and :both-axes. If any axis is disabled, the respective "scroll" delta will be 0. Vertical scroll events will be translated to horizontal motion for the devices incapable of horizontal scrolling.

The event controller can also be forced to emit discrete events on all devices through :discrete. This can be used to implement discrete actions triggered through scroll events, e.g. switching across combobox options.

The :kinetic flag toggles the emission of the "decelerate" signal, emitted at the end of scrolling with two X/Y velocity arguments that are consistent with the motion that was received.

This object was added in 3.24.

The "decelerate" signal

lambda (controller xvel yvel)    :run-first      

Emitted after scroll is finished if the :kinetic flag is set. xvel and yvel express the initial velocity that was imprinted by the scroll events. xvel and yvel are expressed in pixels/ms.

controller

The gtk:event-controller-scroll object that received the signal.

xvel

a double float with the x velocity

yvel

a double float with the y velocity

The "scroll" signal

lambda (controller dx dy)    :run-first      

Signals that the widget should scroll by the amount specified by dx and dy.

controller

The gtk:event-controller-scroll object that received the signal.

dx

a double float with the x delta

dy

a double float with the y delta

The "scroll-begin" signal

lambda (controller)    :run-first      

Signals that a new scrolling operation has begun. It will only be emitted on devices capable of it.

controller

The gtk:event-controller-scroll object that received the signal.

The "scroll-end" signal

lambda (controller)    :run-first      

Signals that a new scrolling operation has finished. It will only be emitted on devices capable of it.

controller

The gtk:event-controller-scroll object that received the signal.