C指针原理(26)-gtk

Posted 2021-01-31

下面演示了如何在窗口中增加一个按钮，示例代码均有注释?

#include?<gtk/gtk.h>

static?void?print_hello?(GtkWidget?*widget,gpointer?data)

{

//这是一个回调函数，这个data表示传给回调函数的参数。

??g_print?("你好，世界
");

}

static?gboolean?on_delete_event?(GtkWidget?*widget,GdkEvent?*event,gpointer?data)

{

//如果返回FALSE在delete_event信号处理中，GTK将发送destroy信号，否则不会，这样窗口就不会关闭。

??g_print?("delete?event?occurred
");

??return?TRUE;

}

int?main?(int?argc,char?*argv[])

{

????????GtkWidget?*window;

????GtkWidget?*button;

????//初始化gtk应用程序

????gtk_init?(&argc,?&argv);

????//创造新的窗口，设置它的标题

????window?=?gtk_window_new?(GTK_WINDOW_TOPLEVEL);

????gtk_window_set_title?(GTK_WINDOW?(window),?"你好");

????//将delete_event信号绑定在on_delte_devent回调函数上，传递的参数为NULL

????????????g_signal_connect?(window,?"delete-event",?G_CALLBACK?(on_delete_event),?NULL);

????//将destroy信号绑定在gtk_main_quit回调函数上，传递的参数为NULL

????????????g_signal_connect?(window,?"destroy",?G_CALLBACK?(gtk_main_quit),?NULL);

????//设置窗口的边框宽度

????????????gtk_container_set_border_width?(GTK_CONTAINER?(window),?10);

????//创建一个新的标签?

??? ?????button?=?gtk_button_new_with_label?("Hello?World");

?????//处理按钮的clicked信号

????g_signal_connect?(button,?"clicked",?G_CALLBACK?(print_hello),?NULL);

????????????//g_signal_connect_swapped将clicked信号连接到window窗口的gtk_widget_destroy事件中。

????????????g_signal_connect_swapped?(button,?"clicked",?G_CALLBACK?(gtk_widget_destroy),?window);

????????????//将按钮加入到容器中

????????????gtk_container_add?(GTK_CONTAINER?(window),?button);

????//显示这个按钮

????????????gtk_widget_show?(button);

???????????//显示窗口

????gtk_widget_show?(window);

????//开始GTK的主循环

????????????gtk_main?();

????????????return?0;

}

在XMANGER下用VIM编写好后，编译运行

#include <gtk/gtk.h>

/* Surface to store current scribbles */
static cairo_surface_t *surface = NULL;

static void
clear_surface (void)
{
  cairo_t *cr;

  cr = cairo_create (surface);

  cairo_set_source_rgb (cr, 1, 1, 1);
  cairo_paint (cr);

  cairo_destroy (cr);
}

/* Create a new surface of the appropriate size to store our scribbles */
static gboolean
configure_event_cb (GtkWidget         *widget,
                    GdkEventConfigure *event,
                    gpointer           data)
{
  if (surface)
    cairo_surface_destroy (surface);

  surface = gdk_window_create_similar_surface (gtk_widget_get_window (widget),
                                               CAIRO_CONTENT_COLOR,
                                               gtk_widget_get_allocated_width (widget),
                                               gtk_widget_get_allocated_height (widget));

  /* Initialize the surface to white */
  clear_surface ();

  /* We‘ve handled the configure event, no need for further processing. */
  return TRUE;
}

/* Redraw the screen from the surface. Note that the ::draw
 * signal receives a ready-to-be-used cairo_t that is already
 * clipped to only draw the exposed areas of the widget
 */
static gboolean
draw_cb (GtkWidget *widget,
         cairo_t   *cr,
         gpointer   data)
{
  cairo_set_source_surface (cr, surface, 0, 0);
  cairo_paint (cr);

  return FALSE;
}

/* Draw a rectangle on the surface at the given position */
static void
draw_brush (GtkWidget *widget,
            gdouble    x,
            gdouble    y)
{
  cairo_t *cr;

  /* Paint to the surface, where we store our state */
  cr = cairo_create (surface);

  cairo_rectangle (cr, x - 3, y - 3, 6, 6);
  cairo_fill (cr);

  cairo_destroy (cr);

  /* Now invalidate the affected region of the drawing area. */
  gtk_widget_queue_draw_area (widget, x - 3, y - 3, 6, 6);
}

/* Handle button press events by either drawing a rectangle
 * or clearing the surface, depending on which button was pressed.
 * The ::button-press signal handler receives a GdkEventButton
 * struct which contains this information.
 */
static gboolean
button_press_event_cb (GtkWidget      *widget,
                       GdkEventButton *event,
                       gpointer        data)
{
  /* paranoia check, in case we haven‘t gotten a configure event */
  if (surface == NULL)
    return FALSE;

  if (event->button == 1)
    {
      draw_brush (widget, event->x, event->y);
    }
  else if (event->button == 3)
    {
      clear_surface ();
      gtk_widget_queue_draw (widget);
    }

  /* We‘ve handled the event, stop processing */
  return TRUE;
}

/* Handle motion events by continuing to draw if button 1 is
 * still held down. The ::motion-notify signal handler receives
 * a GdkEventMotion struct which contains this information.
 */
static gboolean
motion_notify_event_cb (GtkWidget      *widget,
                        GdkEventMotion *event,
                        gpointer        data)
{
  int x, y;
  GdkModifierType state;

  /* paranoia check, in case we haven‘t gotten a configure event */
  if (surface == NULL)
    return FALSE;

  /* This call is very important; it requests the next motion event.
   * If you don‘t call gdk_window_get_pointer() you‘ll only get
   * a single motion event. The reason is that we specified
   * GDK_POINTER_MOTION_HINT_MASK to gtk_widget_set_events().
   * If we hadn‘t specified that, we could just use event->x, event->y
   * as the pointer location. But we‘d also get deluged in events.
   * By requesting the next event as we handle the current one,
   * we avoid getting a huge number of events faster than we
   * can cope.
   */
  gdk_window_get_pointer (event->window, &x, &y, &state);

  if (state & GDK_BUTTON1_MASK)
    draw_brush (widget, x, y);

  /* We‘ve handled it, stop processing */
  return TRUE;
}

static void
close_window (void)
{
  if (surface)
    cairo_surface_destroy (surface);

  gtk_main_quit ();
}

int
main (int   argc,
      char *argv[])
{
  GtkWidget *window;
  GtkWidget *frame;
  GtkWidget *da;

  gtk_init (&argc, &argv);

  window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
  gtk_window_set_title (GTK_WINDOW (window), "Drawing Area");

  g_signal_connect (window, "destroy", G_CALLBACK (close_window), NULL);

  gtk_container_set_border_width (GTK_CONTAINER (window), 8);

  frame = gtk_frame_new (NULL);
  gtk_frame_set_shadow_type (GTK_FRAME (frame), GTK_SHADOW_IN);
  gtk_container_add (GTK_CONTAINER (window), frame);

  da = gtk_drawing_area_new ();
  /* set a minimum size */
  gtk_widget_set_size_request (da, 100, 100);

  gtk_container_add (GTK_CONTAINER (frame), da);

  /* Signals used to handle the backing surface */
  g_signal_connect (da, "draw",
                    G_CALLBACK (draw_cb), NULL);
  g_signal_connect (da,"configure-event",
                    G_CALLBACK (configure_event_cb), NULL);

  /* Event signals */
  g_signal_connect (da, "motion-notify-event",
                    G_CALLBACK (motion_notify_event_cb), NULL);
  g_signal_connect (da, "button-press-event",
                    G_CALLBACK (button_press_event_cb), NULL);

  /* Ask to receive events the drawing area doesn‘t normally
   * subscribe to. In particular, we need to ask for the
   * button press and motion notify events that want to handle.
   */
  gtk_widget_set_events (da, gtk_widget_get_events (da)
                             | GDK_BUTTON_PRESS_MASK
                             | GDK_POINTER_MOTION_MASK
                             | GDK_POINTER_MOTION_HINT_MASK);

  gtk_widget_show_all (window);

  gtk_main ();

  return 0;
}