--- /dev/null
+/* 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;
+}