gtk-General: Main loop and Events

Description Methods and Functions Detailed Description User Functions Author(s) References

Description

Library initialization, main event loop, and events

Methods and Functions

gtkGetDefaultLanguage()
gtkInit(args = "R")
gtkExit(error.code)
gtkEventsPending()
gtkMain()
gtkMainLevel()
gtkMainQuit()
gtkMainIteration()
gtkMainIterationDo(blocking = TRUE)
gtkMainDoEvent(event)
gtkTrue()
gtkFalse()
gtkGrabAdd(object)
gtkGrabGetCurrent()
gtkGrabRemove(object)
gtkInitAdd(fun, data = NULL)
gtkQuitAddDestroy(main.level, object)
gtkQuitAdd(main.level, fun, data = NULL)
gtkQuitAddFull(main.level, fun, data = NULL)
gtkQuitRemove(quit.handler.id)
gtkQuitRemoveByData(data)
gtkTimeoutAddFull(interval, fun, data = NULL)
gtkTimeoutAdd(interval, fun, data = NULL)
gtkTimeoutRemove(timeout.handler.id)
gtkIdleAdd(fun, data = NULL)
gtkIdleAddPriority(priority, fun, data = NULL)
gtkIdleAddFull(priority, fun, data = NULL)
gtkIdleRemove(idle.handler.id)
gtkIdleRemoveByData(data)
gtkInputRemove(input.handler.id)
gtkKeySnooperInstall(snooper, func.data = NULL)
gtkKeySnooperRemove(snooper.handler.id)
gtkGetCurrentEvent()
gtkGetCurrentEventTime()
gtkGetCurrentEventState()
gtkGetEventWidget(event)
gtkPropagateEvent(object, event)

Detailed Description

Before using GTK+, you need to initialize it; initialization connects to the window system display, and parses some standard command line arguments. The gtkInit function initializes GTK+. gtkInit exits the application if errors occur; to avoid this, use gtkInitCheck(). gtkInitCheck() allows you to recover from a failed GTK+ initialization - you might start up your application in text mode instead.

Like all GUI toolkits, GTK+ uses an event-driven programming model. When the user is doing nothing, GTK+ sits in the main loop and waits for input. If the user performs some action - say, a mouse click - then the main loop "wakes up" and delivers an event to GTK+. GTK+ forwards the event to one or more widgets.

When widgets receive an event, they frequently emit one or more signals. Signals notify your program that "something interesting happened" by invoking functions you've connected to the signal with gSignalConnect. Functions connected to a signal are often termed callbacks.

When your callbacks are invoked, you would typically take some action - for example, when an Open button is clicked you might display a GtkFileSelectionDialog. After a callback finishes, GTK+ will return to the main loop and await more user input.

Typical main function for a GTK+ application

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int
main (int argc, char **argv)
{
  /* Initialize i18n support */
  gtk_set_locale (    );
  /* Initialize the widget set */
  gtk_init (&argc, &argv);
  /* Create the main window */
  mainwin = gtk_window_new (GTK_WINDOW_TOPLEVEL);
  /* Set up our GUI elements */
  ...
  /* Show the application window */
  gtk_widget_show_all (mainwin);
  /* Enter the main event loop, and wait for user interaction */
  gtk_main (    );
  /* The user lost interest */
  return 0;
}

It's OK to use the GLib main loop directly instead of gtkMain, though it involves slightly more typing. See GMainLoop in the GLib documentation.

User Functions

GtkModuleInitFunc(argc, argv)

Each GTK+ module must have a function gtkModuleInit() with this prototype. This function is called after loading the module with the argc and argv cleaned from any arguments that GTK+ handles itself.

argc

Pointer to the number of arguments remaining after gtkInit.

argv

Points to the argument vector.

GtkModuleDisplayInitFunc()

Since 2.2

GtkKeySnoopFunc(grab.widget, event, func.data)

Key snooper functions are called before normal event delivery. They can be used to implement custom key event handling.

grab.widget

the widget to which the event will be delivered.

event

the key event.

func.data

the func.data supplied to gtkKeySnooperInstall.

Returns: [integer] TRUE to stop further processing of event, FALSE to continue.

Author(s)

Derived by RGtkGen from GTK+ documentation

References

https://developer.gnome.org/gtk2/stable/gtk2-General.html


RGtk2 documentation built on Oct. 14, 2021, 5:08 p.m.

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