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

None

The gtk:event-controller-scroll object is an event controller is an event controller that handles scroll events. It is capable of handling both discrete and continuous scroll events, abstracting them both with 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, for example, 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 the :discrete flag. This can be used to implement discrete actions triggered through scroll events, for example, 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.

The "decelerate" signal

lambda (controller xvel yvel)    :run-first      

controller

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

xvel

The double float with the x velocity

yvel

The double float with the y velocity

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

The "scroll" signal

lambda (controller dx dy)    :run-first      

controller

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

dx

The double float with the x delta

dy

The double float with the y delta

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

The "scroll-begin" signal

lambda (controller)    :run-first      

controller

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

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

The "scroll-end" signal

lambda (controller)    :run-first      

controller

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

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