[gtkmm] fenetre transparence

Bonjour,

voici un code qui fonctionne :

Code:

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#include <gtk/gtk.h>
#include <gdk/gdkscreen.h>
#include <cairo.h>
 
gboolean supports_alpha = FALSE;
 
static void screen_changed (GtkWidget *widget, GdkScreen *old_screen,
                            gpointer userdata)
{
  GdkScreen *screen = NULL;
  GdkColormap *colormap = NULL;
 
  screen = gtk_widget_get_screen (widget);
  colormap = gdk_screen_get_rgba_colormap (screen);
  if (colormap == NULL)
  {
    g_message ("Your screen does not support alpha channels!\n");
    colormap = gdk_screen_get_rgb_colormap(screen);
    supports_alpha = FALSE;
  }
  else
  {
    g_message ("Your screen supports alpha channels!\n");
    supports_alpha = TRUE;
  }
 
  gtk_widget_set_colormap (widget, colormap);
}
 
static gboolean expose (GtkWidget *widget, GdkEventExpose *event,
                        gpointer userdata)
{
  gint width;
  gint height;
  cairo_t *cr = NULL;
 
  cr = gdk_cairo_create(widget->window);
  if (supports_alpha)
  {
    cairo_set_source_rgba (cr, 1.0, 1.0, 1.0, 0.0);
  }
  else
  {
    cairo_set_source_rgb (cr, 1.0, 1.0, 1.0);
  }
 
  cairo_set_operator (cr, CAIRO_OPERATOR_SOURCE);
  cairo_paint (cr);
 
  gtk_window_get_size (GTK_WINDOW (widget), &width, &height);
 
  cairo_set_source_rgba (cr, 1, 0.2, 0.2, 0.6);
  cairo_arc (cr, width / 2, height / 2,
             (width < height ? width : height) / 2 - 8 , 0, 2 * 3.14);
  cairo_fill (cr);
  cairo_stroke (cr);
 
  cairo_destroy (cr);
  return FALSE;
}
 
int main (int argc, char **argv)
{
  GtkWidget *window = NULL;
 
  gtk_init(&argc, &argv);
 
  window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
  gtk_window_set_title (GTK_WINDOW(window), "Alpha Demo");
  g_signal_connect (G_OBJECT(window), "delete-event", gtk_main_quit, NULL);
 
 
  gtk_widget_set_app_paintable (window, TRUE);
 
  g_signal_connect (G_OBJECT (window), "expose-event", G_CALLBACK (expose),
                    NULL);
  g_signal_connect (G_OBJECT (window), "screen-changed",
                    G_CALLBACK (screen_changed), NULL);
 
  screen_changed (window, NULL, NULL);
 
  gtk_widget_show_all (window);
  gtk_main();
 
  return 0;
}

Essaye le en C pour commencer pour voir si ton système supporte la transparence et ensuite tu pourras le transformer en C++.

Voici le résultat attendu :
http://gtk.developpez.com/faq/images/transparent.png