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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+ FAQ: Development with GTK+: widget specific questions </TITLE> <LINK HREF="gtkfaq-7.html" REL=next> <LINK HREF="gtkfaq-5.html" REL=previous> <LINK HREF="gtkfaq.html#toc6" REL=contents></HEAD><BODY BGCOLOR="#FFFFFF"><A HREF="gtkfaq-7.html">Next</A><A HREF="gtkfaq-5.html">Previous</A><A HREF="gtkfaq.html#toc6">Contents</A><HR NOSHADE><H2><A NAME="s6">6. Development with GTK+: widget specific questions </A></H2><H2><A NAME="ss6.1">6.1 How do I find out about the selection of a GtkList?</A></H2><P>Get the selection something like this:<BLOCKQUOTE><CODE><PRE>GList *sel;sel = GTK_LIST(list)->selection;</PRE></CODE></BLOCKQUOTE><P>This is how GList is defined (quoting glist.h):<BLOCKQUOTE><CODE><PRE>typedef struct _GList GList;struct _GList{ gpointer data; GList *next; GList *prev;};</PRE></CODE></BLOCKQUOTE><P>A GList structure is just a simple structure for doubly linked lists.there exist several g_list_*() functions to modify a linked list inglib.h. However the GTK_LIST(MyGtkList)->selection is maintainedby the gtk_list_*() functions and should not be modified.<P>The selection_mode of the GtkList determines the selectionfacilities of a GtkList and therefore the contentsof GTK_LIST(AnyGtkList)->selection:<P><PRE>selection_mode GTK_LIST()->selection contents------------------------------------------------------GTK_SELECTION_SINGLE) selection is either NULL or contains a GList* pointer for a single selected item.GTK_SELECTION_BROWSE) selection is NULL if the list contains no widgets, otherwise it contains a GList* pointer for one GList structure.GTK_SELECTION_MULTIPLE) selection is NULL if no listitems are selected or a a GList* pointer for the first selected item. that in turn points to a GList structure for the second selected item and so onGTK_SELECTION_EXTENDED) selection is NULL.</PRE><P>The data field of the GList structure GTK_LIST(MyGtkList)->selection pointsto the first GtkListItem that is selected. So if you would like to determine which listitems are selected you should go like this:<P>Upon Initialization:<BLOCKQUOTE><CODE><PRE>{ gchar *list_items[]={ "Item0", "Item1", "foo", "last Item", }; guint nlist_items=sizeof(list_items)/sizeof(list_items[0]); GtkWidget *list_item; guint i; list=gtk_list_new(); gtk_list_set_selection_mode(GTK_LIST(list), GTK_SELECTION_MULTIPLE); gtk_container_add(GTK_CONTAINER(AnyGtkContainer), list); gtk_widget_show (list); for (i = 0; i < nlist_items; i++) { list_item=gtk_list_item_new_with_label(list_items[i]); gtk_object_set_user_data(GTK_OBJECT(list_item), (gpointer)i); gtk_container_add(GTK_CONTAINER(list), list_item); gtk_widget_show(list_item); }}</PRE></CODE></BLOCKQUOTE><P>To get known about the selection:<BLOCKQUOTE><CODE><PRE>{ GList *items; items=GTK_LIST(list)->selection; printf("Selected Items: "); while (items) { if (GTK_IS_LIST_ITEM(items->data)) printf("%d ", (guint) gtk_object_get_user_data(items->data)); items=items->next; } printf("\n");}</PRE></CODE></BLOCKQUOTE><P><P><H2><A NAME="ss6.2">6.2 I don't want the user of my applications to enter text into a GtkCombo. Any idea?</A></H2><P>A GtkCombo has an associated entry which can be accessed using thefollowing expression:<P><BLOCKQUOTE><CODE><PRE> GTK_COMBO(combo_widget)->entry</PRE></CODE></BLOCKQUOTE><P>If you don't want the user to be able to modify the content of thisentry, you can use the gtk_entry_set_editable() function:<P><BLOCKQUOTE><CODE><PRE> void gtk_entry_set_editable(GtkEntry *entry, gboolean editable);</PRE></CODE></BLOCKQUOTE><P>Set the editable parameter to FALSE to disable typing into the entry.<P><H2><A NAME="ss6.3">6.3 How do I catch a combo box change?</A></H2><P>The entry which is associated to your GtkCombo send a "changed" signal when:<UL><LI>some text is typed in</LI><LI>the selection of the combo box is changed</LI></UL><P>To catch any combo box change, simply connect your signal handler with<P><BLOCKQUOTE><CODE><PRE> gtk_signal_connect(GTK_COMBO(cb)->entry, "changed", GTK_SIGNAL_FUNC(my_cb_change_handler), NULL);</PRE></CODE></BLOCKQUOTE><P><H2><A NAME="ss6.4">6.4 How can I define a separation line in a menu? </A></H2><P>See the <A HREF="http://www.gtk.org/tutorial/">Tutorial</A> for information on how to create menus.However, to create a separation line in a menu, just insert anempty menu item:<P><BLOCKQUOTE><CODE><PRE>menuitem = gtk_menu_item_new();gtk_menu_append(GTK_MENU(menu), menuitem);gtk_widget_show(menuitem);</PRE></CODE></BLOCKQUOTE><P><H2><A NAME="ss6.5">6.5 How can I right justify a menu, such as Help? </A></H2><P>Depending on if you use the MenuFactory or not, there are two ways to proceed.With the MenuFactory, use something like the following:<P><BLOCKQUOTE><CODE><PRE>menu_path = gtk_menu_factory_find (factory, "<MyApp>/Help");gtk_menu_item_right_justify(menu_path->widget);</PRE></CODE></BLOCKQUOTE><P>If you do not use the MenuFactory, you should simply use:<P><BLOCKQUOTE><CODE><PRE>gtk_menu_item_right_justify(my_menu_item);</PRE></CODE></BLOCKQUOTE><P><H2><A NAME="ss6.6">6.6 How do I add some underlined accelerators to menu items?</A></H2><P>Damon Chaplin, the technical force behind the Glade project, provided thefollowing code sample (this code is an output from Glade). It creates asmall <CODE>File</CODE> menu item with only one child (<CODE>New</CODE>). The F in <CODE>File</CODE> and the N in <CODE>New</CODE> are underlined, and the relevant accelerators are created.<P><BLOCKQUOTE><CODE><PRE> menubar1 = gtk_menu_bar_new (); gtk_object_set_data (GTK_OBJECT (window1), "menubar1", menubar1); gtk_widget_show (menubar1); gtk_box_pack_start (GTK_BOX (vbox1), menubar1, FALSE, FALSE, 0); file1 = gtk_menu_item_new_with_label (""); tmp_key = gtk_label_parse_uline (GTK_LABEL (GTK_BIN (file1)->child), _("_File")); gtk_widget_add_accelerator (file1, "activate_item", accel_group, tmp_key, GDK_MOD1_MASK, 0); gtk_object_set_data (GTK_OBJECT (window1), "file1", file1); gtk_widget_show (file1); gtk_container_add (GTK_CONTAINER (menubar1), file1); file1_menu = gtk_menu_new (); file1_menu_accels = gtk_menu_ensure_uline_accel_group (GTK_MENU (file1_menu)); gtk_object_set_data (GTK_OBJECT (window1), "file1_menu", file1_menu); gtk_menu_item_set_submenu (GTK_MENU_ITEM (file1), file1_menu); new1 = gtk_menu_item_new_with_label (""); tmp_key = gtk_label_parse_uline (GTK_LABEL (GTK_BIN (new1)->child), _("_New")); gtk_widget_add_accelerator (new1, "activate_item", file1_menu_accels, tmp_key, 0, 0); gtk_object_set_data (GTK_OBJECT (window1), "new1", new1); gtk_widget_show (new1); gtk_container_add (GTK_CONTAINER (file1_menu), new1);</PRE></CODE></BLOCKQUOTE><P><H2><A NAME="ss6.7">6.7 How do I right (or otherwise) justify a GtkLabel?</A></H2><P>Are you sure you want to <EM>justify</EM> the labels? The label class contains the <CODE>gtk_label_set_justify()</CODE> function that is used to control the justification of a multi-line label.<P>What you probably want is to set the <EM>alignment</EM> of the label, ie right align it, center it or left align it. If you want to do this, you should use:<P><BLOCKQUOTE><CODE><PRE>void gtk_misc_set_alignment (GtkMisc *misc, gfloat xalign, gfloat yalign);</PRE></CODE></BLOCKQUOTE><P>where the <CODE>xalign</CODE> and <CODE>yalign</CODE> values are floats in [0.00;1.00].<P><BLOCKQUOTE><CODE><PRE>GtkWidget *label;/* horizontal : left align, vertical : top */gtk_misc_set_alignment(GTK_MISK(label), 0.0f, 0.0f);/* horizontal : centered, vertical : centered */gtk_misc_set_alignment(GTK_MISK(label), 0.5f, 0.5f);/* horizontal : right align, vertical : bottom */gtk_misc_set_alignment(GTK_MISK(label), 1.0f, 1.0f);</PRE></CODE></BLOCKQUOTE><P><H2><A NAME="ss6.8">6.8 How do I set the color and font of a GtkLabel using a Resource File?</A></H2><P>The widget name path constructed for a Label consists of the widgetnames of its object hierarchy as well, e.g.<P><PRE>window (name: humphrey) hbox label (name: mylabel)</PRE><P>The widget path your pattern needs to match would be:<CODE>humphrey.GtkHBox.mylabel</CODE><P>The resource file may look something like:<P><PRE>style "title"{ fg[NORMAL] = {1.0, 0.0, 0.0} font = "-adobe-helvetica-bold-r-normal--*-140-*-*-*-*-*-*"}widget "*mylabel" style "title"</PRE><P>In your program, you would also need to give a name to the Labelwidget, which can be done using:<PRE> label = gtk_label_new("Some Label Text"); gtk_widget_set_name(label, "mylabel"); gtk_widget_show(label);</PRE><P><H2><A NAME="ss6.9">6.9 How do I configure Tooltips in a Resource File?</A></H2><P>The tooltip's window is named "gtk-tooltips", GtkTooltips in itself is nota GtkWidget (though a GtkObject) and as such is not attempted to match anywidget styles.<P>So, you resource file should look something like:<PRE> style "postie"{ bg[NORMAL] = {1.0, 1.0, 0.0}}widget "gtk-tooltips*" style "postie"</PRE><H2><A NAME="ss6.10">6.10 How do I use horizontal scrollbars with a GtkText widget?</A></H2><P>The short answer is that you can't. The current version of the GtkTextwidget does not support horizontal scrolling. There is an intention tocompletely rewrite the GtkText widget, at which time this limitationwill be removed.<P><H2><A NAME="ss6.11">6.11 I can't add more than (something like) 2000 chars in a GtkEntry. What's wrong?</A></H2><P>There is now a known problem in the GtkEntry widget. In the<CODE>gtk_entry_insert_text()</CODE> function, the following lines limitthe number of chars in the entry to 2047.<P><BLOCKQUOTE><CODE><PRE> /* The algorithms here will work as long as, the text size (a * multiple of 2), fits into a guint16 but we specify a shorter * maximum length so that if the user pastes a very long text, there * is not a long hang from the slow X_LOCALE functions. */ if (entry->text_max_length == 0) max_length = 2047; else max_length = MIN (2047, entry->text_max_length);</PRE></CODE></BLOCKQUOTE><P><H2><A NAME="ss6.12">6.12 How do I change the font of a GtkText widget?</A></H2><P>There are a couple of ways of doing this. As GTK+ allows theappearance of applications to be changed at run time using resourcesyou can use something like the following in the appropriatefile:<P><BLOCKQUOTE><CODE><PRE>style "text"{ font = "-adobe-helvetica-medium-r-normal--*-100-*-*-*-*-*-*"}</PRE></CODE></BLOCKQUOTE><P>Another way to do this is to load a font within your program, and thenuse this in the functions for adding text to the text widget. You canload a font using, for example:<P><BLOCKQUOTE><CODE><PRE> GdkFont *font; font = gdk_font_load("-adobe-helvetica-medium-r-normal--*-140-*-*-*-*-*-*");</PRE></CODE></BLOCKQUOTE><P><H2><A NAME="ss6.13">6.13 How do I set the cursor position in a GtkText object?</A></H2><P>Notice that the response is valid for any object that inherits from the GtkEditable class.<P>Are you sure that you want to move the cursor position? Most of the time,while the cursor position is good, the insertion point does not match thecursor position. If this apply to what you really want, then you should usethe <CODE>gtk_text_set_point()</CODE> function. If you want to set the insertion pointat the current cursor position, use the following:<P><BLOCKQUOTE><CODE><PRE> gtk_text_set_point(GTK_TEXT(text), gtk_editable_get_position(GTK_EDITABLE(text)));</PRE></CODE></BLOCKQUOTE><P>If you want the insertion point to follow the cursor at all time, youshould probably catch the button press event, and then move theinsertion point. Be careful : you'll have to catch it after the widget has changed the cursor position though. Thomas Mailund Jensen proposed thefollowing code:<P><BLOCKQUOTE><CODE><PRE>static voidinsert_bar (GtkWidget *text){ /* jump to cursor mark */ gtk_text_set_point (GTK_TEXT (text), gtk_editable_get_position (GTK_EDITABLE (text))); gtk_text_insert (GTK_TEXT (text), NULL, NULL, NULL, "bar", strlen ("bar"));}intmain (int argc, char *argv[]){ GtkWidget *window, *text; gtk_init (&argc, &argv); window = gtk_window_new (GTK_WINDOW_TOPLEVEL); text = gtk_text_new (NULL, NULL); gtk_text_set_editable (GTK_TEXT (text), TRUE); gtk_container_add (GTK_CONTAINER (window), text); /* connect after everything else */ gtk_signal_connect_after (GTK_OBJECT(text), "button_press_event", GTK_SIGNAL_FUNC (insert_bar), NULL); gtk_widget_show_all(window); gtk_main(); return 0;}</PRE></CODE></BLOCKQUOTE><P>Now, if you really want to change the cursor position, you should use the<CODE>gtk_editable_set_position()</CODE> function.<P><HR NOSHADE><A HREF="gtkfaq-7.html">Next</A><A HREF="gtkfaq-5.html">Previous</A><A HREF="gtkfaq.html#toc6">Contents</A></BODY></HTML>⌨️ 快捷键说明
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