gtk_tut-6.html
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"><HTML><HEAD> <META NAME="GENERATOR" CONTENT="SGML-Tools 1.0.9"> <TITLE>GTK v1.2 Tutorial: The Button Widget</TITLE> <LINK HREF="gtk_tut-7.html" REL=next> <LINK HREF="gtk_tut-5.html" REL=previous> <LINK HREF="gtk_tut.html#toc6" REL=contents></HEAD><BODY TEXT="#CCCCCC" BGCOLOR="#000000" LINK="#33cc00" VLINK="#009900" ALINK="#FF0000"><A HREF="gtk_tut-7.html">Next</A><A HREF="gtk_tut-5.html">Previous</A><A HREF="gtk_tut.html#toc6">Contents</A><HR><H2><A NAME="s6">6. The Button Widget</A></H2><H2><A NAME="ss6.1">6.1 Normal Buttons</A></H2><P>We've almost seen all there is to see of the button widget. It'spretty simple. There are however two ways to create a button. You canuse 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 youto pack a label or pixmap into this new button. To do this, create anew box, and then pack your objects into this box using the usualgtk_box_pack_start, and then use gtk_container_add to pack the boxinto the button.<P>Here's an example of using gtk_button_new to create a button with apicture and a label in it. I've broken up the code to create a boxfrom the rest so you can use it in your programs. There are furtherexamples of using pixmaps later in the tutorial.<P><BLOCKQUOTE><CODE><PRE>/* 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\n", (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 */</PRE></CODE></BLOCKQUOTE><P>The xpm_label_box function could be used to pack xpm's and labels intoany widget that can be a container.<P>Notice in <CODE>xpm_label_box</CODE> how there is a call to<CODE>gtk_widget_get_style</CODE>. Every widget has a "style", consisting offoreground and background colors for a variety of situations, fontselection, and other graphics data relevant to a widget. These stylevalues are defaulted in each widget, and are required by many GDKfunction calls, such as <CODE>gdk_pixmap_create_from_xpm</CODE>, which here isgiven the "normal" background color. The style data of widgets maybe customized, using <A HREF="gtk_tut-21.html#sec_gtkrc_files">GTK's rc files</A>.<P>Also notice the call to <CODE>gtk_widget_realize</CODE> after setting thewindow's border width. This function uses GDK to create the Xwindows related to the widget. The function is automatically calledwhen you invoke <CODE>gtk_widget_show</CODE> for a widget, and so has not beenshown in earlier examples. But the call to<CODE>gdk_pixmap_create_from_xpm</CODE> requires that its <CODE>window</CODE> argumentrefer to a real X window, so it is necessary to realize the widgetbefore this GDK call.<P>The Button widget has the following signals:<P><UL><LI><CODE>pressed</CODE> - emitted when pointer button is pressed withinButton widget</LI><LI><CODE>released</CODE> - emitted when pointer button is released withinButton widget</LI><LI><CODE>clicked</CODE> - emitted when pointer button is pressed and thenreleased within Button widget</LI><LI><CODE>enter</CODE> - emitted when pointer enters Button widget</LI><LI><CODE>leave</CODE> - emitted when pointer leaves Button widget</LI></UL><P><H2><A NAME="ss6.2">6.2 Toggle Buttons</A></H2><P>Toggle buttons are derived from normal buttons and are very similar,except they will always be in one of two states, alternated by aclick. They may be depressed, and when you click again, they will popback up. Click again, and they will pop back down.<P>Toggle buttons are the basis for check buttons and radio buttons, assuch, many of the calls used for toggle buttons are inherited by radioand check buttons. I will point these out when we come to them.<P>Creating a new toggle button:<P><BLOCKQUOTE><CODE><PRE>GtkWidget *gtk_toggle_button_new( void );GtkWidget *gtk_toggle_button_new_with_label( gchar *label );</PRE></CODE></BLOCKQUOTE><P>As you can imagine, these work identically to the normal button widgetcalls. The first creates a blank toggle button, and the second, abutton with a label widget already packed into it.<P>To retrieve the state of the toggle widget, including radio and checkbuttons, we use a construct as shown in our example below. This teststhe state of the toggle, by accessing the <CODE>active</CODE> field of thetoggle widget's structure, after first using the<CODE>GTK_TOGGLE_BUTTON</CODE> macro to cast the widget pointer into a togglewidget pointer. The signal of interest to us emitted by togglebuttons (the toggle button, check button, and radio button widgets) isthe "toggled" signal. To check the state of these buttons, set up asignal handler to catch the toggled signal, and access the structureto determine its state. The callback will look something like:<P><BLOCKQUOTE><CODE><PRE>void toggle_button_callback (GtkWidget *widget, gpointer data){ if (GTK_TOGGLE_BUTTON (widget)->active) { /* If control reaches here, the toggle button is down */ } else { /* If control reaches here, the toggle button is up */ }}</PRE></CODE></BLOCKQUOTE><P>To force the state of a toggle button, and its children, the radio andcheck buttons, use this function:<P><BLOCKQUOTE><CODE><PRE>void gtk_toggle_button_set_active( GtkToggleButton *toggle_button, gint state );</PRE></CODE></BLOCKQUOTE><P>The above call can be used to set the state of the toggle button, andits children the radio and check buttons. Passing in your createdbutton as the first argument, and a TRUE or FALSE for the second stateargument to specify whether it should be down (depressed) or up(released). Default is up, or FALSE.<P>Note that when you use the gtk_toggle_button_set_active() function, andthe state is actually changed, it causes the "clicked" signal to beemitted from the button.<P><BLOCKQUOTE><CODE><PRE>void gtk_toggle_button_toggled (GtkToggleButton *toggle_button);</PRE></CODE></BLOCKQUOTE><P>This simply toggles the button, and emits the "toggled" signal.<P><H2><A NAME="ss6.3">6.3 Check Buttons</A></H2><P>Check buttons inherit many properties and functions from the thetoggle buttons above, but look a little different. Rather than beingbuttons with text inside them, they are small squares with the text tothe right of them. These are often used for toggling options on andoff in applications.<P>The two creation functions are similar to those of the normal button.<P><BLOCKQUOTE><CODE><PRE>GtkWidget *gtk_check_button_new( void );GtkWidget *gtk_check_button_new_with_label ( gchar *label );</PRE></CODE></BLOCKQUOTE><P>The new_with_label function creates a check button with a label besideit.<P>Checking the state of the check button is identical to that of thetoggle button.<P><H2><A NAME="sec_Radio_Buttons"></A> <A NAME="ss6.4">6.4 Radio Buttons </A></H2><P>Radio buttons are similar to check buttons except they are grouped sothat only one may be selected/depressed at a time. This is good forplaces in your application where you need to select from a short listof options.<P>Creating a new radio button is done with one of these calls:<P><BLOCKQUOTE><CODE><PRE>GtkWidget *gtk_radio_button_new( GSList *group );GtkWidget *gtk_radio_button_new_with_label( GSList *group, gchar *label );</PRE></CODE></BLOCKQUOTE><P>You'll notice the extra argument to these calls. They require a groupto perform their duty properly. The first call togtk_radio_button_new_with_label or gtk_radio_button_new_with_labelshould pass NULL as the first argument. Then create a group using:<P><BLOCKQUOTE><CODE><PRE>GSList *gtk_radio_button_group( GtkRadioButton *radio_button );</PRE></CODE></BLOCKQUOTE><P>The important thing to remember is that gtk_radio_button_group must becalled for each new button added to the group, with the previousbutton passed in as an argument. The result is then passed into thenext call to gtk_radio_button_new orgtk_radio_button_new_with_label. This allows a chain of buttons to beestablished. The example below should make this clear.<P>You can shorten this slightly by using the following syntax, whichremoves the need for a variable to hold the list of buttons. This formis used in the example to create the third button:<P><BLOCKQUOTE><CODE><PRE> button2 = gtk_radio_button_new_with_label( gtk_radio_button_group (GTK_RADIO_BUTTON (button1)), "button2");</PRE></CODE></BLOCKQUOTE><P>It is also a good idea to explicitly set which button should be thedefault depressed button with:<P><BLOCKQUOTE><CODE><PRE>void gtk_toggle_button_set_active( GtkToggleButton *toggle_button, gint state );</PRE></CODE></BLOCKQUOTE><P>This is described in the section on toggle buttons, and works inexactly the same way. Once the radio buttons are grouped together,only one of the group may be active at a time. If the user clicks onone radio button, and then on another, the first radio button willfirst emit a "toggled" signal (to report becoming inactive), and thenthe second will emit its "toggled" signal (to report becoming active).<P>The following example creates a radio button group with three buttons.<P><BLOCKQUOTE><CODE><PRE>/* example-start radiobuttons radiobuttons.c */#include <gtk/gtk.h>#include <glib.h>gint close_application( GtkWidget *widget, GdkEvent *event, gpointer data ){ gtk_main_quit(); return(FALSE);}int main( int argc, char *argv[] ){ GtkWidget *window = NULL; GtkWidget *box1; GtkWidget *box2; GtkWidget *button; GtkWidget *separator; GSList *group; gtk_init(&argc,&argv); window = gtk_window_new (GTK_WINDOW_TOPLEVEL); gtk_signal_connect (GTK_OBJECT (window), "delete_event", GTK_SIGNAL_FUNC(close_application), NULL); gtk_window_set_title (GTK_WINDOW (window), "radio buttons"); gtk_container_set_border_width (GTK_CONTAINER (window), 0); box1 = gtk_vbox_new (FALSE, 0); gtk_container_add (GTK_CONTAINER (window), box1); gtk_widget_show (box1); box2 = gtk_vbox_new (FALSE, 10); gtk_container_set_border_width (GTK_CONTAINER (box2), 10); gtk_box_pack_start (GTK_BOX (box1), box2, TRUE, TRUE, 0); gtk_widget_show (box2); button = gtk_radio_button_new_with_label (NULL, "button1"); gtk_box_pack_start (GTK_BOX (box2), button, TRUE, TRUE, 0); gtk_widget_show (button); group = gtk_radio_button_group (GTK_RADIO_BUTTON (button)); button = gtk_radio_button_new_with_label(group, "button2"); gtk_toggle_button_set_active (GTK_TOGGLE_BUTTON (button), TRUE); gtk_box_pack_start (GTK_BOX (box2), button, TRUE, TRUE, 0); gtk_widget_show (button); button = gtk_radio_button_new_with_label( gtk_radio_button_group (GTK_RADIO_BUTTON (button)), "button3"); gtk_box_pack_start (GTK_BOX (box2), button, TRUE, TRUE, 0); gtk_widget_show (button); separator = gtk_hseparator_new (); gtk_box_pack_start (GTK_BOX (box1), separator, FALSE, TRUE, 0); gtk_widget_show (separator); box2 = gtk_vbox_new (FALSE, 10); gtk_container_set_border_width (GTK_CONTAINER (box2), 10); gtk_box_pack_start (GTK_BOX (box1), box2, FALSE, TRUE, 0); gtk_widget_show (box2); button = gtk_button_new_with_label ("close"); gtk_signal_connect_object (GTK_OBJECT (button), "clicked", GTK_SIGNAL_FUNC(close_application), GTK_OBJECT (window)); gtk_box_pack_start (GTK_BOX (box2), button, TRUE, TRUE, 0); GTK_WIDGET_SET_FLAGS (button, GTK_CAN_DEFAULT); gtk_widget_grab_default (button); gtk_widget_show (button); gtk_widget_show (window); gtk_main(); return(0);}/* example-end */</PRE></CODE></BLOCKQUOTE><P><P><HR><A HREF="gtk_tut-7.html">Next</A><A HREF="gtk_tut-5.html">Previous</A><A HREF="gtk_tut.html#toc6">Contents</A></BODY></HTML>⌨️ 快捷键说明
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