Simple Canvas Example: GooCanvas Reference Manual

## Simple Canvas Example Simple Canvas Example — how to create a simple canvas. |

## Simple Canvas Example

Here's a complete example application that creates a GooCanvas with a rectangle and a text item in it:

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    #include <stdlib.h>
    #include <goocanvas.h>

    static gboolean on_rect_button_press (GooCanvasItem  *view,
                                          GooCanvasItem  *target,
                                          GdkEventButton *event,
                                          gpointer        data);

    static gboolean on_delete_event      (GtkWidget      *window,
                                          GdkEvent       *event,
                                          gpointer        unused_data);

    int
    main (int argc, char *argv[])
    {
      GtkWidget *window, *scrolled_win, *canvas;
      GooCanvasItem *root, *rect_item, *text_item;

      /* Initialize GTK+. */
      gtk_init (&argc, &argv);

      /* Create the window and widgets. */
      window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
      gtk_window_set_default_size (GTK_WINDOW (window), 640, 600);
      gtk_widget_show (window);
      g_signal_connect (window, "delete_event", G_CALLBACK (on_delete_event),
                        NULL);

      scrolled_win = gtk_scrolled_window_new (NULL, NULL);
      gtk_scrolled_window_set_shadow_type (GTK_SCROLLED_WINDOW (scrolled_win),
                                           GTK_SHADOW_IN);
      gtk_widget_show (scrolled_win);
      gtk_container_add (GTK_CONTAINER (window), scrolled_win);

      canvas = goo_canvas_new ();
      gtk_widget_set_size_request (canvas, 600, 450);
      goo_canvas_set_bounds (GOO_CANVAS (canvas), 0, 0, 1000, 1000);
      gtk_widget_show (canvas);
      gtk_container_add (GTK_CONTAINER (scrolled_win), canvas);

      root = goo_canvas_get_root_item (GOO_CANVAS (canvas));

      /* Add a few simple items. */
      rect_item = goo_canvas_rect_new (root, 100, 100, 400, 400,
                                       "line-width", 10.0,
                                       "radius-top-left-x", 10.0,
                                       "radius-top-left-y", 10.0,
                                       "radius-top-right-x", 60.0,
                                       "radius-top-right-y", 60.0,
                                       "radius-bottom-right-x", 30.0,
                                       "radius-bottom-right-y", 30.0,
                                       "radius-bottom-left-x", 15.0,
                                       "radius-bottom-left-y", 15.0,
                                       "stroke-color", "yellow",
                                       "fill-color", "red",
                                       NULL);

      text_item = goo_canvas_text_new (root, "Hello World", 300, 300, -1,
                                       GOO_CANVAS_ANCHOR_CENTER,
                                       "font", "Sans 24",
                                       NULL);
      goo_canvas_item_rotate (text_item, 45, 300, 300);

      /* Connect a signal handler for the rectangle item. */
      g_signal_connect (rect_item, "button_press_event",
                        G_CALLBACK (on_rect_button_press), NULL);

      /* Pass control to the GTK+ main event loop. */
      gtk_main ();

      return 0;
    }

    /* This handles button presses in item views. We simply output a message to
       the console. */
    static gboolean
    on_rect_button_press (GooCanvasItem  *item,
                          GooCanvasItem  *target,
                          GdkEventButton *event,
                          gpointer        data)
    {
      g_print ("rect item received button press event\n");
      return TRUE;
    }

    /* This is our handler for the "delete-event" signal of the window, which
       is emitted when the 'x' close button is clicked. We just exit here. */
    static gboolean
    on_delete_event (GtkWidget *window,
                     GdkEvent  *event,
                     gpointer   unused_data)
    {
      exit (0);
    }