GtkEventControllerScroll
GtkEventControllerScroll — Event controller for scroll events
Functions
Properties
| GtkEventControllerScrollFlags | flags | Read / Write |
Signals
| void | decelerate | Run First |
| gboolean | scroll | Run Last |
| void | scroll-begin | Run First |
| void | scroll-end | Run First |
Types and Values
Object Hierarchy
GObject
╰── GtkEventController
╰── GtkEventControllerScroll
Includes
#include <gtk/gtk.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_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 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.
Functions
gtk_event_controller_scroll_new ()
GtkEventController *
gtk_event_controller_scroll_new (GtkEventControllerScrollFlags flags); Creates a new event controller that will handle scroll events.
Parameters
flags | behavior flags |
Returns
a new GtkEventControllerScroll
gtk_event_controller_scroll_set_flags ()
void gtk_event_controller_scroll_set_flags (GtkEventControllerScroll *scroll,GtkEventControllerScrollFlags flags);
Sets the flags conditioning scroll controller behavior.
Parameters
scroll | ||
flags | behavior flags |
gtk_event_controller_scroll_get_flags ()
GtkEventControllerScrollFlags
gtk_event_controller_scroll_get_flags (GtkEventControllerScroll *scroll); Gets the flags conditioning the scroll controller behavior.
Parameters
scroll |
Returns
the controller flags.
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. |
Property Details
The “flags” property
“flags” GtkEventControllerScrollFlags
The flags affecting event controller behavior
Owner: GtkEventControllerScroll
Flags: Read / Write
Signal Details
The “decelerate” signal
void user_function (GtkEventControllerScroll *controller, double vel_x, double 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
gboolean user_function (GtkEventControllerScroll *controller, double dx, double 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. |
Returns
TRUE if the scroll event was handled, FALSE otherwise.
Flags: Run Last
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
© 2005–2020 The GNOME Project
Licensed under the GNU Lesser General Public License version 2.1 or later.
https://developer.gnome.org/gtk4/4.0/GtkEventControllerScroll.html