GtkOverlay test

#include <stdbool.h>
#include <gtk/gtk.h>

static void close_window (void);

static cairo_surface_t *surface1 = NULL;
static cairo_surface_t *surface2 = NULL;

static gboolean darea1_draw_cb (GtkWidget *widget,
                                cairo_t   *cr,
                                gpointer   data);

static gboolean darea2_draw_cb (GtkWidget *widget,
                                cairo_t   *cr,
                                gpointer   data);

static gboolean darea1_configure_event_cb (GtkWidget         *widget,
                                           GdkEventConfigure *event,
                                           gpointer           data);

static gboolean darea2_configure_event_cb (GtkWidget         *widget,
                                           GdkEventConfigure *event,
                                           gpointer           data);

int
main (int argc, char *argv[])
{
    GtkWidget *window;
    GtkWidget *viewport;
    GtkWidget *scrolled;
    GtkWidget *overlay;
    GtkWidget *darea;
///    GtkSettings *settings;

    gtk_init (&argc, &argv);

    /* setup window */
    window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
    gtk_window_set_default_size (GTK_WINDOW (window), 800, 600);
    gtk_window_set_title (GTK_WINDOW (window), "Overlay");
    gtk_container_set_border_width (GTK_CONTAINER (window), 0);

    g_signal_connect (window, "delete-event", G_CALLBACK (gtk_main_quit), NULL);
    g_signal_connect (window, "destroy", G_CALLBACK (close_window), &window);

///    settings = gtk_settings_get_default ();
///    g_object_set (G_OBJECT (settings), "gtk-application-prefer-dark-theme", true, NULL);

    /* setup alignment */
    viewport = gtk_viewport_new (NULL, NULL);

    /* setup scrolled window */
    scrolled = gtk_scrolled_window_new (NULL, NULL);
    gtk_scrolled_window_set_policy (GTK_SCROLLED_WINDOW (scrolled),
                                    GTK_POLICY_AUTOMATIC,
                                    GTK_POLICY_AUTOMATIC);
    gtk_container_add (GTK_CONTAINER (viewport), scrolled);

    /* setup the overlay */
    overlay = gtk_overlay_new ();
    gtk_container_add (GTK_CONTAINER (overlay), viewport);
    gtk_container_add (GTK_CONTAINER (window), overlay);

    /* finally setup the widgets to place inside of the overlay */
    darea = gtk_drawing_area_new ();
    gtk_widget_set_size_request (darea, 200, 200);
    gtk_widget_set_app_paintable (darea, true);
    gtk_overlay_add_overlay (GTK_OVERLAY (overlay), darea);
    gtk_widget_set_halign (darea, GTK_ALIGN_START);
    gtk_widget_set_valign (darea, GTK_ALIGN_START);
    gtk_widget_set_margin_left (darea, 10);
    gtk_widget_set_margin_right (darea, 10);
    gtk_widget_set_margin_top (darea, 10);
    gtk_widget_set_margin_bottom (darea, 10);

    g_signal_connect (darea, "draw", G_CALLBACK (darea1_draw_cb), NULL);
    g_signal_connect (darea, "configure-event", G_CALLBACK (darea1_configure_event_cb), NULL);

    darea = gtk_drawing_area_new ();
    gtk_widget_set_size_request (darea, 300, 300);
    gtk_widget_set_app_paintable (darea, true);
    gtk_overlay_add_overlay (GTK_OVERLAY (overlay), darea);
    gtk_widget_set_halign (darea, GTK_ALIGN_END);
    gtk_widget_set_valign (darea, GTK_ALIGN_END);
    gtk_widget_set_margin_left (darea, 20);
    gtk_widget_set_margin_right (darea, 20);
    gtk_widget_set_margin_top (darea, 20);
    gtk_widget_set_margin_bottom (darea, 20);

    g_signal_connect (darea, "draw", G_CALLBACK (darea2_draw_cb), NULL);
    g_signal_connect (darea, "configure-event", G_CALLBACK (darea2_configure_event_cb), NULL);

    gtk_widget_show_all (window);

    gtk_main ();

    return 0;
}

static void
close_window (void)
{
    if (surface1)
        cairo_surface_destroy (surface1);
    surface1 = NULL;

    if (surface2)
        cairo_surface_destroy (surface2);
    surface2 = NULL;
}

static gboolean
darea1_draw_cb (GtkWidget *widget,
                cairo_t   *cr,
                gpointer   data)
{
    g_debug ("Draw: drawing area 1");

    cairo_set_source_surface (cr, surface1, 0, 0);

    cairo_set_source_rgba (cr, 0.6, 0.2, 0.2, 0.5);
    cairo_rectangle (cr, 10, 10, 150, 150);
    cairo_fill (cr);

    cairo_paint (cr);

    return false;
}

static gboolean
darea2_draw_cb (GtkWidget *widget,
                cairo_t   *cr,
                gpointer   data)
{
    g_debug ("Draw: drawing area 2");

    cairo_set_source_surface (cr, surface2, 0, 0);

    cairo_set_source_rgba (cr, 0.4, 0.8, 0.4, 0.5);
    cairo_rectangle (cr, 10, 10, 100, 100);
    cairo_fill (cr);

    cairo_paint (cr);

    return false;
}

static gboolean
darea1_configure_event_cb (GtkWidget         *widget,
                           GdkEventConfigure *event,
                           gpointer           data)
{
    GtkAllocation allocation;
    cairo_t *cr;

    g_debug ("Configure: drawing area 1");

    if (surface1)
        cairo_surface_destroy (surface1);

    gtk_widget_get_allocation (widget, &allocation);
    surface1 = gdk_window_create_similar_surface (gtk_widget_get_window (widget),
                                                  CAIRO_CONTENT_COLOR,
                                                  allocation.width,
                                                  allocation.height);

    /* initialize the surface to white */
    cr = cairo_create (surface1);

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

    cairo_destroy (cr);

    return true;
}

static gboolean
darea2_configure_event_cb (GtkWidget         *widget,
                           GdkEventConfigure *event,
                           gpointer           data)
{
    GtkAllocation allocation;
    cairo_t *cr;

    g_debug ("Configure: drawing area 2");

    if (surface2)
        cairo_surface_destroy (surface2);

    gtk_widget_get_allocation (widget, &allocation);
    surface2 = gdk_window_create_similar_surface (gtk_widget_get_window (widget),
                                                  CAIRO_CONTENT_COLOR,
                                                  allocation.width,
                                                  allocation.height);

    /* initialize the surface to white */
    cr = cairo_create (surface2);

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

    cairo_destroy (cr);

    return true;
}