For example:
gtk_signal_connect( GTK_OBJECT(button), "clicked",
GTK_SIGNAL_FUNC(callback_function), callback_data);
|
This casts the button into an object, and provides a cast for the function pointer to the callback.
Many widgets are also containers. If you look in the class hierarchy below, you'll notice that many widgets derive from the Container class. Any one of these widgets may be used with the GTK_CONTAINER macro to pass them to functions that ask for containers.
Unfortunately, these macros are not extensively covered in the tutorial, but I recommend taking a look through the GTK header files. It can be very educational. In fact, it's not difficult to learn how a widget works just by looking at the function declarations.
5.2 Widget Hierarchy
For your reference, here is the class hierarchy tree used to implement widgets.
GtkObject
+GtkWidget
| +GtkMisc
| | +GtkLabel
| | | +GtkAccelLabel
| | | `GtkTipsQuery
| | +GtkArrow
| | +GtkImage
| | `GtkPixmap
| +GtkContainer
| | +GtkBin
| | | +GtkAlignment
| | | +GtkFrame
| | | | `GtkAspectFrame
| | | +GtkButton
| | | | +GtkToggleButton
| | | | | `GtkCheckButton
| | | | | `GtkRadioButton
| | | | `GtkOptionMenu
| | | +GtkItem
| | | | +GtkMenuItem
| | | | | +GtkCheckMenuItem
| | | | | | `GtkRadioMenuItem
| | | | | `GtkTearoffMenuItem
| | | | +GtkListItem
| | | | `GtkTreeItem
| | | +GtkWindow
| | | | +GtkColorSelectionDialog
| | | | +GtkDialog
| | | | | `GtkInputDialog
| | | | +GtkDrawWindow
| | | | +GtkFileSelection
| | | | +GtkFontSelectionDialog
| | | | `GtkPlug
| | | +GtkEventBox
| | | +GtkHandleBox
| | | +GtkScrolledWindow
| | | `GtkViewport
| | +GtkBox
| | | +GtkButtonBox
| | | | +GtkHButtonBox
| | | | `GtkVButtonBox
| | | +GtkVBox
| | | | +GtkColorSelection
| | | | `GtkGammaCurve
| | | `GtkHBox
| | | +GtkCombo
| | | `GtkStatusbar
| | +GtkCList
| | | `GtkCTree
| | +GtkFixed
| | +GtkNotebook
| | | `GtkFontSelection
| | +GtkPaned
| | | +GtkHPaned
| | | `GtkVPaned
| | +GtkLayout
| | +GtkList
| | +GtkMenuShell
| | | +GtkMenuBar
| | | `GtkMenu
| | +GtkPacker
| | +GtkSocket
| | +GtkTable
| | +GtkToolbar
| | `GtkTree
| +GtkCalendar
| +GtkDrawingArea
| | `GtkCurve
| +GtkEditable
| | +GtkEntry
| | | `GtkSpinButton
| | `GtkText
| +GtkRuler
| | +GtkHRuler
| | `GtkVRuler
| +GtkRange
| | +GtkScale
| | | +GtkHScale
| | | `GtkVScale
| | `GtkScrollbar
| | +GtkHScrollbar
| | `GtkVScrollbar
| +GtkSeparator
| | +GtkHSeparator
| | `GtkVSeparator
| +GtkPreview
| `GtkProgress
| `GtkProgressBar
+GtkData
| +GtkAdjustment
| `GtkTooltips
`GtkItemFactory
|
5.3 Widgets Without Windows
The following widgets do not have an associated window. If you want to capture events, you'll have to use the EventBox. See the section on the EventBox widget.
GtkAlignment
GtkArrow
GtkBin
GtkBox
GtkImage
GtkItem
GtkLabel
GtkPixmap
GtkScrolledWindow
GtkSeparator
GtkTable
GtkAspectFrame
GtkFrame
GtkVBox
GtkHBox
GtkVSeparator
GtkHSeparator
|
We'll further our exploration of GTK by examining each widget in turn, creating a few simple functions to display them. Another good source is the testgtk.c program that comes with GTK. It can be found in gtk/testgtk.c.
6. The Button Widget
6.1 Normal Buttons
We've almost seen all there is to see of the button widget. It's pretty simple. There are however two ways to create a button. You can use the gtk_button_new_with_label() to create a button with a label, or use gtk_button_new() to create a blank button. It's then up to you to pack a label or pixmap into this new button. To do this, create a new box, and then pack your objects into this box using the usual gtk_box_pack_start, and then use gtk_container_add to pack the box into the button.
Here's an example of using gtk_button_new to create a button with a picture and a label in it. I've broken up the code to create a box from the rest so you can use it in your programs. There are further examples of using pixmaps later in the tutorial.
/* example-start buttons buttons.c */
#include <gtk/gtk.h>
/* Create a new hbox with an image and a label packed into it
* and return the box. */
GtkWidget *xpm_label_box( GtkWidget *parent,
gchar *xpm_filename,
gchar *label_text )
{
GtkWidget *box1;
GtkWidget *label;
GtkWidget *pixmapwid;
GdkPixmap *pixmap;
GdkBitmap *mask;
GtkStyle *style;
/* Create box for xpm and label */
box1 = gtk_hbox_new (FALSE, 0);
gtk_container_set_border_width (GTK_CONTAINER (box1), 2);
/* Get the style of the button to get the
* background color. */
style = gtk_widget_get_style(parent);
/* Now on to the xpm stuff */
pixmap = gdk_pixmap_create_from_xpm (parent->window, &mask,
&style->bg[GTK_STATE_NORMAL],
xpm_filename);
pixmapwid = gtk_pixmap_new (pixmap, mask);
/* Create a label for the button */
label = gtk_label_new (label_text);
/* Pack the pixmap and label into the box */
gtk_box_pack_start (GTK_BOX (box1),
pixmapwid, FALSE, FALSE, 3);
gtk_box_pack_start (GTK_BOX (box1), label, FALSE, FALSE, 3);
gtk_widget_show(pixmapwid);
gtk_widget_show(label);
return(box1);
}
/* Our usual callback function */
void callback( GtkWidget *widget,
gpointer data )
{
g_print ("Hello again - %s was pressed
", (char *) data);
}
int main( int argc,
char *argv[] )
{
/* GtkWidget is the storage type for widgets */
GtkWidget *window;
GtkWidget *button;
GtkWidget *box1;
gtk_init (&argc, &argv);
/* Create a new window */
window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
gtk_window_set_title (GTK_WINDOW (window), "Pixmap'd Buttons!");
/* It's a good idea to do this for all windows. */
gtk_signal_connect (GTK_OBJECT (window), "destroy",
GTK_SIGNAL_FUNC (gtk_exit), NULL);
gtk_signal_connect (GTK_OBJECT (window), "delete_event",
GTK_SIGNAL_FUNC (gtk_exit), NULL);
/* Sets the border width of the window. */
gtk_container_set_border_width (GTK_CONTAINER (window), 10);
gtk_widget_realize(window);
/* Create a new button */
button = gtk_button_new ();
/* Connect the "clicked" signal of the button to our callback */
gtk_signal_connect (GTK_OBJECT (button), "clicked",
GTK_SIGNAL_FUNC (callback), (gpointer) "cool button");
/* This calls our box creating function */
box1 = xpm_label_box(window, "info.xpm", "cool button");
/* Pack and show all our widgets */
gtk_widget_show(box1);
gtk_container_add (GTK_CONTAINER (button), box1);
gtk_widget_show(button);
gtk_container_add (GTK_CONTAINER (window), button);
gtk_widget_show (window);
/* Rest in gtk_main and wait for the fun to begin! */
gtk_main ();
return(0);
}
/* example-end */
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