GtkEventControllerScroll: GTK+ 3 Reference Manual

## GtkEventControllerScroll GtkEventControllerScroll — Event controller for scroll events |

## Functions

GtkEventController * | gtk_event_controller_scroll_new ()
void | gtk_event_controller_scroll_set_flags ()
GtkEventControllerScrollFlags | gtk_event_controller_scroll_get_flags ()

## Properties

GtkEventControllerScrollFlags | flags | Read / Write

## Signals

void | decelerate | Run First
void | scroll | Run First
void | scroll-begin | Run First
void | scroll-end | Run First

## Types and Values

| GtkEventControllerScroll
enum | GtkEventControllerScrollFlags

## 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

scroll | a GtkEventControllerScroll |

#### 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

## See Also

GtkEventController