关于半透明窗口的设置

Question

从网上找了个例子：

#include <gtk/gtk.h>

  

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

{

   GtkWidget *window = NULL;

  

   gtk_init(&argc, &argv);

  

   window = gtk_window_new(GTK_WINDOW_TOPLEVEL);

   gtk_window_set_opacity(GTK_WINDOW(window), 0.7);       // 设置透明度函数

  

   gtk_widget_show_all(window);

   gtk_main();

   return TRUE;

}

但是还是实现不了半透明。据说“gtk_window_set_opacity 函数只能在 gtk-2.12 以上版本中使用 ”
但是我的GTK是2.20.1，也没有问题啊。

还是说还有别的地方需要设置？

Answer 1

需要底层的窗口管理器支持。gtk只是尽量和wm沟通。lz可以试试composite功能的 wm

Answer 2

composite.
gdk_window_set_composited(GDK_WINDOW(widget), TRUE);

这里的参数widget是gdkwindow类型的。
我没有找到gtkwindow与gdkwindow的联系，总感觉是两个不同的东西。

另外在devhelp中有个例子：
#include <gtk/gtk.h>
/* The expose event handler for the event box.
*
* This function simply draws a transparency onto a widget on the area
* for which it receives expose events.  This is intended to give the
* event box a "transparent" background.
*
* In order for this to work properly, the widget must have an RGBA
* colourmap.  The widget should also be set as app-paintable since it
* doesn't make sense for GTK+ to draw a background if we are drawing it
* (and because GTK+ might actually replace our transparency with its
* default background colour).
*/
static gboolean
transparent_expose (GtkWidget      *widget,
                    GdkEventExpose *event)
{
  cairo_t *cr;
  g_print("entry transparent_expose\n");
  cr = gdk_cairo_create (widget->window);
  cairo_set_operator (cr, CAIRO_OPERATOR_CLEAR);
  gdk_cairo_region (cr, event->region);
  cairo_fill (cr);
  cairo_destroy (cr);
  return FALSE;
}
/* The expose event handler for the window.
*
* This function performs the actual compositing of the event box onto
* the already-existing background of the window at 50% normal opacity.
*
* In this case we do not want app-paintable to be set on the widget
* since we want it to draw its own (red) background. Because of this,
* however, we must ensure that we use g_signal_connect_after so that
* this handler is called after the red has been drawn. If it was
* called before then GTK would just blindly paint over our work.
*
* Note: if the child window has children, then you need a cairo 1.6
* feature to make this work correctly.
*/
static gboolean
window_expose_event (GtkWidget      *widget,
                     GdkEventExpose *event)
{
  GdkRegion *region;
  GtkWidget *child;
  cairo_t *cr;
  g_print("entry window_expose_event\n");
  /* get our child (in this case, the event box) */
  child = gtk_bin_get_child (GTK_BIN (widget));
  /* create a cairo context to draw to the window */
  cr = gdk_cairo_create (widget->window);
  /* the source data is the (composited) event box */
  gdk_cairo_set_source_pixmap (cr, child->window,
                               child->allocation.x,
                               child->allocation.y);
  /* draw no more than our expose event intersects our child */
  region = gdk_region_rectangle (&child->allocation);
  gdk_region_intersect (region, event->region);
  gdk_cairo_region (cr, region);
  cairo_clip (cr);
  /* composite, with a 50% opacity */
  cairo_set_operator (cr, CAIRO_OPERATOR_OVER);
  cairo_paint_with_alpha (cr, 0.5);
  /* we're done */
  cairo_destroy (cr);
  return FALSE;
}
int
main (int argc, char **argv)
{
  GtkWidget *window, *event, *button;
  GdkScreen *screen;
  GdkColormap *rgba;
  GdkColor red;
  gtk_init (&argc, &argv);
  /* Make the widgets */
  button = gtk_button_new_with_label ("A Button");
  event = gtk_event_box_new ();
  window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
  /* Put a red background on the window */
  gdk_color_parse ("green", &red);
  gtk_widget_modify_bg (window, GTK_STATE_NORMAL, &red);
  /* Set the colourmap for the event box.
   * Must be done before the event box is realised.
   */
  screen = gtk_widget_get_screen (event);
  rgba = gdk_screen_get_rgba_colormap (screen);
  gtk_widget_set_colormap (event, rgba);
  /* Set our event box to have a fully-transparent background
   * drawn on it. Currently there is no way to simply tell GTK+
   * that "transparency" is the background colour for a widget.
   */
  gtk_widget_set_app_paintable (GTK_WIDGET (event), TRUE);
  g_signal_connect (event, "expose-event",
                    G_CALLBACK (transparent_expose), NULL);
  /* Put them inside one another */
  gtk_container_set_border_width (GTK_CONTAINER (window), 10);
  gtk_container_add (GTK_CONTAINER (window), event);
  gtk_container_add (GTK_CONTAINER (event), button);
  /* Realise and show everything */
  gtk_widget_show_all (window);
  /* Set the event box GdkWindow to be composited.
   * Obviously must be performed after event box is realised.
   */
  gdk_window_set_composited (event->window, TRUE);
  /* Set up the compositing handler.
   * Note that we do _after_ so that the normal (red) background is drawn
   * by gtk before our compositing occurs.
   */
  g_signal_connect_after (window, "expose-event",
                          G_CALLBACK (window_expose_event), NULL);
  gtk_main ();
  return 0;
}
将button的背景变成半透明。用了gdk_window_set_composited函数将eventbox复合在window内，而产生的。
但是我需要让窗口变成半透明。
这里该怎么做呢？

Answer 3

需要底层的窗口管理器支持。
你用的啥桌面环境？

Answer 4

用Ubuntu 10.04
难道要修改rc文件么？