[gtk+] gtk-demo: Add test of transparent GdkWindows

[Alexander Larsson <alexl src gnome org>]

commit 4962167864921ff372dc4d01d197b892cc37f473
Author: Alexander Larsson <alexl redhat com>
Date:   Tue Dec 6 00:23:18 2011 +0100

    gtk-demo: Add test of transparent GdkWindows
    
    This shows a semi-transparent shadow from a GtkOverlay window

 demos/gtk-demo/Makefile.am   |    1 +
 demos/gtk-demo/transparent.c |  248 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 249 insertions(+), 0 deletions(-)
---
diff --git a/demos/gtk-demo/Makefile.am b/demos/gtk-demo/Makefile.am
index 2dac9ec..e15a8c6 100644
--- a/demos/gtk-demo/Makefile.am
+++ b/demos/gtk-demo/Makefile.am
@@ -43,6 +43,7 @@ demos =						\
 	textview.c				\
 	textscroll.c				\
 	toolpalette.c				\
+	transparent.c				\
 	tree_store.c				\
 	ui_manager.c
 
diff --git a/demos/gtk-demo/transparent.c b/demos/gtk-demo/transparent.c
new file mode 100644
index 0000000..d1b2cb4
--- /dev/null
+++ b/demos/gtk-demo/transparent.c
@@ -0,0 +1,248 @@
+/* Transparent
+ *
+ * Use transparent background on GdkWindows to create a shadow effect on a GtkOverlay widget.
+ */
+
+#include <gtk/gtk.h>
+
+#define SHADOW_OFFSET_X 7
+#define SHADOW_OFFSET_Y 7
+#define SHADOW_RADIUS 5
+
+static void
+draw_shadow_box (cairo_t   *cr,
+		 GdkRectangle rect,
+		 double radius,
+		 double transparency)
+{
+  cairo_pattern_t *pattern;
+  double x0, x1, x2, x3;
+  double y0, y1, y2, y3;
+
+  x0 = rect.x;
+  x1 = rect.x + radius;
+  x2 = rect.x + rect.width - radius;
+  x3 = rect.x + rect.width;
+  
+  y0 = rect.y;
+  y1 = rect.y + radius;
+  y2 = rect.y + rect.height - radius;
+  y3 = rect.y + rect.height;
+  
+   /* Fill non-border part */
+  cairo_set_source_rgba (cr, 0, 0, 0, transparency);
+  cairo_rectangle (cr,
+		   x1, y1, x2 - x1, y2 - y1);
+  cairo_fill (cr);
+
+  /* Upper border */
+
+  pattern = cairo_pattern_create_linear (0, y0, 0, y1);
+  
+  cairo_pattern_add_color_stop_rgba (pattern, 0.0, 0.0, 0, 0, 0.0);
+  cairo_pattern_add_color_stop_rgba (pattern, 1.0, 0.0, 0, 0, transparency);
+  
+  cairo_set_source (cr, pattern);
+  cairo_pattern_destroy (pattern);
+  
+  cairo_rectangle (cr,
+		   x1, y0,
+		   x2 - x1, y1 - y0);
+  cairo_fill (cr);
+
+  /* Bottom border */
+
+  pattern = cairo_pattern_create_linear (0, y2, 0, y3);
+  
+  cairo_pattern_add_color_stop_rgba (pattern, 0.0, 0.0, 0, 0, transparency);
+  cairo_pattern_add_color_stop_rgba (pattern, 1.0, 0.0, 0, 0, 0.0);
+  
+  cairo_set_source (cr, pattern);
+  cairo_pattern_destroy (pattern);
+  
+  cairo_rectangle (cr,
+		   x1, y2,
+		   x2 - x1, y3 - y2);
+  cairo_fill (cr);
+  
+  /* Left border */
+
+  pattern = cairo_pattern_create_linear (x0, 0, x1, 0);
+  
+  cairo_pattern_add_color_stop_rgba (pattern, 0.0, 0.0, 0, 0, 0.0);
+  cairo_pattern_add_color_stop_rgba (pattern, 1.0, 0.0, 0, 0, transparency);
+  
+  cairo_set_source (cr, pattern);
+  cairo_pattern_destroy (pattern);
+  
+  cairo_rectangle (cr,
+		   x0, y1,
+		   x1 - x0, y2 - y1);
+  cairo_fill (cr);
+
+  /* Right border */
+
+  pattern = cairo_pattern_create_linear (x2, 0, x3, 0);
+  
+  cairo_pattern_add_color_stop_rgba (pattern, 0.0, 0.0, 0, 0, transparency);
+  cairo_pattern_add_color_stop_rgba (pattern, 1.0, 0.0, 0, 0, 0.0);
+  
+  cairo_set_source (cr, pattern);
+  cairo_pattern_destroy (pattern);
+  
+  cairo_rectangle (cr,
+		   x2, y1,
+		   x3 - x2, y2 - y1);
+  cairo_fill (cr);
+
+  /* NW corner */
+  
+  pattern = cairo_pattern_create_radial (x1, y1, 0,
+					 x1, y1, radius);
+
+  cairo_pattern_add_color_stop_rgba (pattern, 0.0, 0.0, 0, 0, transparency);
+  cairo_pattern_add_color_stop_rgba (pattern, 1.0, 0.0, 0, 0, 0.0);
+  
+  cairo_set_source (cr, pattern);
+  cairo_pattern_destroy (pattern);
+  
+  cairo_rectangle (cr,
+		   x0, y0,
+		   x1 - x0, y1 - y0);
+  cairo_fill (cr);
+
+  /* NE corner */
+  
+  pattern = cairo_pattern_create_radial (x2, y1, 0,
+					 x2, y1, radius);
+
+  cairo_pattern_add_color_stop_rgba (pattern, 0.0, 0.0, 0, 0, transparency);
+  cairo_pattern_add_color_stop_rgba (pattern, 1.0, 0.0, 0, 0, 0.0);
+  
+  cairo_set_source (cr, pattern);
+  cairo_pattern_destroy (pattern);
+  
+  cairo_rectangle (cr,
+		   x2, y0,
+		   x3 - x2, y1 - y0);
+  cairo_fill (cr);
+
+  /* SW corner */
+  
+  pattern = cairo_pattern_create_radial (x1, y2, 0,
+					 x1, y2, radius);
+
+  cairo_pattern_add_color_stop_rgba (pattern, 0.0, 0.0, 0, 0, transparency);
+  cairo_pattern_add_color_stop_rgba (pattern, 1.0, 0.0, 0, 0, 0.0);
+  
+  cairo_set_source (cr, pattern);
+  cairo_pattern_destroy (pattern);
+  
+  cairo_rectangle (cr,
+		   x0, y2,
+		   x1 - x0, y3 - y2);
+  cairo_fill (cr);
+
+  /* SE corner */
+  
+  pattern = cairo_pattern_create_radial (x2, y2, 0,
+					 x2, y2, radius);
+
+  cairo_pattern_add_color_stop_rgba (pattern, 0.0, 0.0, 0, 0, transparency);
+  cairo_pattern_add_color_stop_rgba (pattern, 1.0, 0.0, 0, 0, 0.0);
+  
+  cairo_set_source (cr, pattern);
+  cairo_pattern_destroy (pattern);
+  
+  cairo_rectangle (cr,
+		   x2, y2,
+		   x3 - x2, y3 - y2);
+  cairo_fill (cr);
+}
+
+static gboolean
+draw_callback (GtkWidget *widget,
+               cairo_t   *cr,
+               gpointer   data)
+{
+  GdkRectangle rect;
+
+  gtk_widget_get_allocation (widget, &rect);
+  rect.x += SHADOW_OFFSET_X;
+  rect.y += SHADOW_OFFSET_Y;
+  rect.width -= SHADOW_OFFSET_X;
+  rect.height -= SHADOW_OFFSET_Y;
+
+  draw_shadow_box (cr,
+		   rect, SHADOW_RADIUS, 0.4);
+  
+  return FALSE;
+}
+
+GtkWidget *
+do_transparent (GtkWidget *do_widget)
+{
+  static GtkWidget *window = NULL;
+
+  if (!window)
+    {
+      GtkWidget *view;
+      GtkWidget *sw;
+      GtkWidget *overlay;
+      GtkWidget *align;
+      GtkWidget *entry;
+      GdkRGBA transparent = {0.1, 0, 0, 0};
+
+      window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
+      gtk_window_set_screen (GTK_WINDOW (window),
+                             gtk_widget_get_screen (do_widget));
+      gtk_window_set_default_size (GTK_WINDOW (window),
+                                   450, 450);
+
+      g_signal_connect (window, "destroy",
+                        G_CALLBACK (gtk_widget_destroyed), &window);
+
+      gtk_window_set_title (GTK_WINDOW (window), "Transparent");
+      gtk_container_set_border_width (GTK_CONTAINER (window), 0);
+
+      view = gtk_text_view_new ();
+
+      sw = gtk_scrolled_window_new (NULL, NULL);
+      gtk_scrolled_window_set_policy (GTK_SCROLLED_WINDOW (sw),
+                                      GTK_POLICY_AUTOMATIC,
+                                      GTK_POLICY_AUTOMATIC);
+      gtk_container_add (GTK_CONTAINER (sw), view);
+
+      overlay = gtk_overlay_new ();
+      gtk_container_add (GTK_CONTAINER (overlay), sw);
+      gtk_container_add (GTK_CONTAINER (window), overlay);
+
+      gtk_widget_override_background_color (overlay, 0, &transparent);
+
+      align = gtk_alignment_new (0.0, 0.0, 0.0, 0.0);
+      gtk_alignment_set_padding (GTK_ALIGNMENT (align),
+				 0, SHADOW_OFFSET_Y, 0, SHADOW_OFFSET_X);
+      g_signal_connect (align, "draw", G_CALLBACK (draw_callback), NULL);
+      
+      entry = gtk_entry_new ();
+      gtk_container_add (GTK_CONTAINER (align), entry);
+      
+      gtk_overlay_add_overlay (GTK_OVERLAY (overlay), align);
+      gtk_widget_set_halign (align, GTK_ALIGN_CENTER);
+      gtk_widget_set_valign (align, GTK_ALIGN_START);
+
+      gtk_widget_show_all (overlay);
+    }
+
+  if (!gtk_widget_get_visible (window))
+    {
+      gtk_widget_show (window);
+    }
+  else
+    {
+      gtk_widget_destroy (window);
+      window = NULL;
+    }
+
+  return window;
+}