标签(Labels)是 GTK 中最常用的控件，实际上它很简单。因为没有相关联的 X 窗口，标签不能引发信号。如果需要获取或引发信号，可以将它放在一个事件盒中，或放在按钮控件里面。

用以下函数创建一个新标签：

GtkWidget *gtk_label_new( const char *str );

GtkWidget *gtk_label_new_with_mnemonic( const char *str ); 

唯一的参数是要由标签显示的字符串。

创建标签后，要改变标签你的文本，用以下函数：

void gtk_label_set_text( GtkLabel   *label,
                         const char *str ); 

第一参数是前面创建的标签(用 GTK_LABEL() 宏转换)，第二个参数是新的字符串。

如果需要，新字符串需要的空间会做自动调整。在字符串中放置换行符，可以创建多行标签。

用以下函数取得标签的当前文本：

const gchar* gtk_label_get_text( GtkLabel  *label );

不要释放返回的字符串，因为 GTK 内部要使用它。

标签的文本可以用以下函数设置对齐方式：

void gtk_label_set_justify( GtkLabel         *label,
                            GtkJustification  jtype ); 

jtype 的值可以是：

  GTK_JUSTIFY_LEFT  左对齐
  GTK_JUSTIFY_RIGHT  右对齐
  GTK_JUSTIFY_CENTER  居中对齐(默认)
  GTK_JUSTIFY_FILL  充满 

标签控件的文本会自动换行。用以下函数激活“自动换行”：

void gtk_label_set_line_wrap (GtkLabel *label,
                              gboolean  wrap); 

wrap参数可取 TRUE 或 FALSE。

如果想要使标签加下划线，可以在标签中设置显示模式：

void       gtk_label_set_pattern   (GtkLabel          *label,
                                    const gchar       *pattern); 

pattern 参数指定下划线的外观。它由一串下划线和空格组成。下划线指示标签的相应字符应该加一个下划线。例如,”__ __” 将在标签的第1、第2个字符和第8、第9个字符加下划线。

Note 如果你只是想创建一个用下划线代表快捷键(“mnemonic”)的标签，你应该用 gtk_label_new_with_mnemonic() 或 gtk_label_set_text_with_mnemonic()，而不是用 gtk_label_set_pattern()。

下面是一个说明这些函数的短示例。这个示例用框架控件(Frame widget)能更好地示范标签的风格。现在你不用理会这点,框架控件以后再作介绍。

在 GTK+ 2.0 里，标签文本里能包含改变字体等文本属性的标记,并且标签能设置为可以被选择(用来复制-粘贴)。这些高级特性在这里并不介绍。

#include <gtk/gtk.h>

int main( int   argc,
          char *argv[] )
{
  static GtkWidget *window = NULL;
  GtkWidget *hbox;
  GtkWidget *vbox;
  GtkWidget *frame;
  GtkWidget *label;

  /* 初始化 */
  gtk_init (&argc, &argv);

  window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
  g_signal_connect (G_OBJECT (window), "destroy",
            G_CALLBACK (gtk_main_quit),
            NULL);

  gtk_window_set_title (GTK_WINDOW (window), "Label");
  vbox = gtk_vbox_new (FALSE, 5);
  hbox = gtk_hbox_new (FALSE, 5);
  gtk_container_add (GTK_CONTAINER (window), hbox);
  gtk_box_pack_start (GTK_BOX (hbox), vbox, FALSE, FALSE, 0);
  gtk_container_set_border_width (GTK_CONTAINER (window), 5);

  frame = gtk_frame_new ("Normal Label");
  label = gtk_label_new ("This is a Normal label");
  gtk_container_add (GTK_CONTAINER (frame), label);
  gtk_box_pack_start (GTK_BOX (vbox), frame, FALSE, FALSE, 0);

  frame = gtk_frame_new ("Multi-line Label");
  label = gtk_label_new ("This is a Multi-line label.\nSecond line\n" \
             "Third line");
  gtk_container_add (GTK_CONTAINER (frame), label);
  gtk_box_pack_start (GTK_BOX (vbox), frame, FALSE, FALSE, 0);

  frame = gtk_frame_new ("Left Justified Label");
  label = gtk_label_new ("This is a Left-Justified\n" \
             "Multi-line label.\nThird      line");
  gtk_label_set_justify (GTK_LABEL (label), GTK_JUSTIFY_LEFT);
  gtk_container_add (GTK_CONTAINER (frame), label);
  gtk_box_pack_start (GTK_BOX (vbox), frame, FALSE, FALSE, 0);

  frame = gtk_frame_new ("Right Justified Label");
  label = gtk_label_new ("This is a Right-Justified\nMulti-line label.\n" \
             "Fourth line, (j/k)");
  gtk_label_set_justify (GTK_LABEL (label), GTK_JUSTIFY_RIGHT);
  gtk_container_add (GTK_CONTAINER (frame), label);
  gtk_box_pack_start (GTK_BOX (vbox), frame, FALSE, FALSE, 0);

  vbox = gtk_vbox_new (FALSE, 5);
  gtk_box_pack_start (GTK_BOX (hbox), vbox, FALSE, FALSE, 0);
  frame = gtk_frame_new ("Line wrapped label");
  label = gtk_label_new ("This is an example of a line-wrapped label.  It " \
             "should not be taking up the entire             " /* 用一段较长的空白字符来测试空白的自动排列 */\
             "width allocated to it, but automatically " \
             "wraps the words to fit.  " \
             "The time has come, for all good men, to come to " \
             "the aid of their party.  " \
             "The sixth sheik's six sheep's sick.\n" \
             "     It supports multiple paragraphs correctly, " \
             "and  correctly   adds "\
             "many          extra  spaces. ");
  gtk_label_set_line_wrap (GTK_LABEL (label), TRUE);
  gtk_container_add (GTK_CONTAINER (frame), label);
  gtk_box_pack_start (GTK_BOX (vbox), frame, FALSE, FALSE, 0);

  frame = gtk_frame_new ("Filled, wrapped label");
  label = gtk_label_new ("This is an example of a line-wrapped, filled label.  " \
             "It should be taking "\
             "up the entire              width allocated to it.  " \
             "Here is a sentence to prove "\
             "my point.  Here is another sentence. "\
             "Here comes the sun, do de do de do.\n"\
             "    This is a new paragraph.\n"\
             "    This is another newer, longer, better " \
             "paragraph.  It is coming to an end, "\
             "unfortunately.");
  gtk_label_set_justify (GTK_LABEL (label), GTK_JUSTIFY_FILL);
  gtk_label_set_line_wrap (GTK_LABEL (label), TRUE);
  gtk_container_add (GTK_CONTAINER (frame), label);
  gtk_box_pack_start (GTK_BOX (vbox), frame, FALSE, FALSE, 0);

  frame = gtk_frame_new ("Underlined label");
  label = gtk_label_new ("This label is underlined!\n"
             "This one is underlined in quite a funky fashion");
  gtk_label_set_justify (GTK_LABEL (label), GTK_JUSTIFY_LEFT);
  gtk_label_set_pattern (GTK_LABEL (label),
             "_________________________ _ _________ _ ______     __ _______ ___");
  gtk_container_add (GTK_CONTAINER (frame), label);
  gtk_box_pack_start (GTK_BOX (vbox), frame, FALSE, FALSE, 0);

  gtk_widget_show_all (window);

  gtk_main ();

  return 0;
}