GtkEventControllerScroll

GtkEventControllerScroll — Event controller for scroll events

Properties

Object Hierarchy

    GObject
    ╰── GtkEventController
        ╰── GtkEventControllerScroll

Includes

#include <gtk/gtkunixprint.h>

Description

GtkEventControllerScroll 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, GtkEventControllerScroll 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 gtk_event_controller_scroll_set_flags() (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 GTK_EVENT_CONTROLLER_SCROLL_VERTICAL, GTK_EVENT_CONTROLLER_SCROLL_HORIZONTAL and GTK_EVENT_CONTROLLER_SCROLL_BOTH. 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 GTK_EVENT_CONTROLLER_SCROLL_DISCRETE. This can be used to implement discrete actions triggered through scroll events (e.g. switching across combobox options).

The GTK_EVENT_CONTROLLER_SCROLL_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.

Functions

gtk_event_controller_scroll_new ()

GtkEventController *
gtk_event_controller_scroll_new (GtkWidget *widget,
                                 GtkEventControllerScrollFlags flags);

Creates a new event controller that will handle scroll events for the given widget .

Parameters

widget

a GtkWidget

 

flags

behavior flags

 

Returns

a new GtkEventControllerScroll

Since: 3.24


gtk_event_controller_scroll_set_flags ()

void
gtk_event_controller_scroll_set_flags (GtkEventControllerScroll *controller,
                                       GtkEventControllerScrollFlags flags);

Sets the flags conditioning scroll controller behavior.

Parameters

scroll

a GtkEventControllerScroll

 

flags

behavior flags

 

Since: 3.24


gtk_event_controller_scroll_get_flags ()

GtkEventControllerScrollFlags
gtk_event_controller_scroll_get_flags (GtkEventControllerScroll *controller);

Gets the flags conditioning the scroll controller behavior.

Parameters

Returns

the controller flags.

Since: 3.24

Types and Values

GtkEventControllerScroll

typedef struct _GtkEventControllerScroll GtkEventControllerScroll;

enum GtkEventControllerScrollFlags

Describes the behavior of a GtkEventControllerScroll.

Members

GTK_EVENT_CONTROLLER_SCROLL_NONE

Don't emit scroll.

 

GTK_EVENT_CONTROLLER_SCROLL_VERTICAL

Emit scroll with vertical deltas.

 

GTK_EVENT_CONTROLLER_SCROLL_HORIZONTAL

Emit scroll with horizontal deltas.

 

GTK_EVENT_CONTROLLER_SCROLL_DISCRETE

Only emit deltas that are multiples of 1.

 

GTK_EVENT_CONTROLLER_SCROLL_KINETIC

Emit “decelerate” after continuous scroll finishes.

 

GTK_EVENT_CONTROLLER_SCROLL_BOTH_AXES

Emit scroll on both axes.

 

Since: 3.24

Property Details

The “flags” property

  “flags”                    GtkEventControllerScrollFlags

The flags affecting event controller behavior

Flags: Read / Write

Since: 3.24

Signal Details

The “decelerate” signal

void
user_function (GtkEventControllerScroll *controller,
               gdouble                   vel_x,
               gdouble                   vel_y,
               gpointer                  user_data)

Emitted after scroll is finished if the GTK_EVENT_CONTROLLER_SCROLL_KINETIC flag is set. vel_x and vel_y express the initial velocity that was imprinted by the scroll events. vel_x and vel_y are expressed in pixels/ms.

Parameters

controller

The object that received the signal

 

vel_x

X velocity

 

vel_y

Y velocity

 

user_data

user data set when the signal handler was connected.

 

Flags: Run First


The “scroll” signal

void
user_function (GtkEventControllerScroll *controller,
               gdouble                   dx,
               gdouble                   dy,
               gpointer                  user_data)

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

Parameters

controller

The object that received the signal

 

dx

X delta

 

dy

Y delta

 

user_data

user data set when the signal handler was connected.

 

Flags: Run First


The “scroll-begin” signal

void
user_function (GtkEventControllerScroll *controller,
               gpointer                  user_data)

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

Parameters

controller

The object that received the signal

 

user_data

user data set when the signal handler was connected.

 

Flags: Run First


The “scroll-end” signal

void
user_function (GtkEventControllerScroll *controller,
               gpointer                  user_data)

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

Parameters

controller

The object that received the signal

 

user_data

user data set when the signal handler was connected.

 

Flags: Run First