69 lines
2.2 KiB
Markdown
69 lines
2.2 KiB
Markdown
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Title: Initializing GTK
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## Library initialization and main loop
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Before using GTK, you need to initialize it using [func@Gtk.init]; this
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connects to the windowing system, sets up the locale and performs other
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initialization tasks. [func@Gtk.init] exits the application if errors occur;
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to avoid this, you can use [func@Gtk.init_check], which allows you to recover
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from a failed GTK initialization; for instance, you might start up your
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application in text mode instead.
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Like most GUI toolkits, GTK uses an event-driven programming model. When the
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application is doing nothing, GTK sits in the “main loop” and waits for input.
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If the user performs some action - say, a mouse click - then the main loop
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“wakes up” and delivers an event to GTK. GTK forwards the event to one or
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more widgets.
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When widgets receive an event, they frequently emit one or more “signals”.
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Signals notify your program that "something interesting happened" by invoking
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functions you’ve connected to the signal with `g_signal_connect()`. Functions
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connected to a signal are often called “callbacks”.
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When your callbacks are invoked, you would typically take some action - for
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example, when an Open button is clicked you might display a [class@Gtk.FileChooserDialog].
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After a callback finishes, GTK will return to the main loop and await more
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user input.
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### The `main()` function for a simple GTK application
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```c
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int
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main (int argc, char **argv)
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{
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GtkWidget *window;
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// Initialize i18n support with bindtextdomain(), etc.
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// ...
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// Initialize the widget set
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gtk_init ();
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// Create the main window
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window = gtk_window_new ();
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// Set up our GUI elements
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// ...
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// Show the application window
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gtk_window_present (GTK_WINDOW (window));
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// Enter the main event loop, and wait for user interaction
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while (!done)
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g_main_context_iteration (NULL, TRUE);
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// The user lost interest
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return 0;
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}
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```
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It's important to note that if you use [class@Gtk.Application], the
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application class will take care of initializing GTK for you, as well
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as spinning the main loop.
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### See also
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- the GLib manual, especially `GMainLoop`
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- signal-related functions, such as `g_signal_connect()` in GObject
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