gnome-devel-docs r602 - in trunk/gtk-drawing: . C examples

[davyd svn gnome org]

Author: davyd
Date: Mon Oct  6 09:06:12 2008
New Revision: 602
URL: http://svn.gnome.org/viewvc/gnome-devel-docs?rev=602&view=rev

Log:
2008-10-06  Davyd Madeley  <davyd fugro-fsi com au>

        * C/gtkdrawingarea.xml:
        * examples/example.gtkdrawingarea.animate.c:
        - small updates


Added:
   trunk/gtk-drawing/examples/example.gtkdrawingarea.animate.c
Modified:
   trunk/gtk-drawing/C/gtkdrawingarea.xml
   trunk/gtk-drawing/ChangeLog

Modified: trunk/gtk-drawing/C/gtkdrawingarea.xml
==============================================================================
--- trunk/gtk-drawing/C/gtkdrawingarea.xml	(original)
+++ trunk/gtk-drawing/C/gtkdrawingarea.xml	Mon Oct  6 09:06:12 2008
@@ -183,6 +183,44 @@
 
  <sect1 id="sect.gtkdrawingarea.updating">
   <title>Updating and Animating the Area</title>
+
+  <para>
+   Updates of the drawing area should always be done via the
+   <function>expose-event</function> handler.
+  </para>
+  <para>
+   To re-expose a rectangular area
+   use <function>gdk_window_invalidate_rect</function>
+   (<xref linkend="example.gtkdrawingarea.update"/>).
+   These functions don't trigger
+   an expose immediately, but queue the redraw for when your program
+   returns to the main loop (i.e. is idle). To process all pending redraw
+   operations for a <classname>GdkWindow</classname> use
+   <function>gdk_window_process_updates</function>.
+  </para>
+
+  <example id="example.gtkdrawingarea.update">
+   <title>Updating a GtkDrawingArea</title>
+   <programlisting>
+<![CDATA[/* queue update for the whole window */
+gdk_window_invalidate_rect (da->window, NULL, FALSE);
+
+/* update just a rectangle */
+GdkRectangle rect;
+rect.x = ...;
+rect.y = ...;
+rect.width = ...;
+rect.height = ...;
+gdk_window_invalidate_rect (da->window, &rect, FALSE);]]></programlisting>
+  </example>
+
+  <sect2 id="sect.gtkdrawingarea.animation">
+   <title>Animation</title>
+   <para>
+    Simple animation can be achieved by repeatedly requeuing the window for
+    redraw on every screen refresh using <function>g_timeout_add</function>.
+   </para>
+  </sect2>
  </sect1>
 
  <sect1 id="sect.gtkdrawingarea.caching">

Added: trunk/gtk-drawing/examples/example.gtkdrawingarea.animate.c
==============================================================================
--- (empty file)
+++ trunk/gtk-drawing/examples/example.gtkdrawingarea.animate.c	Mon Oct  6 09:06:12 2008
@@ -0,0 +1,102 @@
+#include <math.h>
+#include <gtk/gtk.h>
+
+#define SLICE_WIDTH 6
+#define RADIUS 30
+
+static gboolean
+expose_callback (GtkWidget *da, GdkEventExpose *event, gpointer user_data)
+{
+	cairo_t *cr = gdk_cairo_create (event->window);
+	int *alpha = (int *) user_data;
+
+	cairo_translate (cr, da->allocation.width / 2,
+			     da->allocation.height / 2);
+
+	cairo_save (cr); /* pie slice */
+
+	cairo_rotate (cr, M_PI / SLICE_WIDTH * *alpha);
+	cairo_set_source_rgb (cr, 0.5, 0.5, 1.0);
+
+	cairo_move_to (cr, 0, 0);
+	cairo_arc (cr, 0, 0, RADIUS, 0, M_PI / SLICE_WIDTH);
+	cairo_close_path (cr);
+	cairo_fill (cr);
+
+	cairo_restore (cr); /* pie slice */
+	
+	cairo_arc (cr, 0, 0, RADIUS, -M_PI, M_PI);
+	cairo_stroke (cr);
+
+	cairo_destroy (cr);
+
+	return TRUE;
+}
+
+static gboolean
+animate_cb (gpointer user_data)
+{
+	GtkWidget *da = GTK_WIDGET (((GtkWidget **) user_data)[1]);
+	int *alpha = ((int **) user_data)[2];
+
+	*alpha = (*alpha + 1) % (SLICE_WIDTH * 2);
+
+	gdk_window_invalidate_rect (da->window, NULL, FALSE);
+
+	return TRUE;
+}
+
+static void
+animate_toggled (GtkToggleButton *toggle, gpointer user_data)
+{
+	guint *source = ((guint **) user_data)[0];
+
+	if (gtk_toggle_button_get_active (toggle))
+	{
+		/* animate */
+		*source = g_timeout_add (1000 / 30, animate_cb, user_data);
+	}
+	else
+	{
+		/* cancel animation */
+		g_source_remove (*source);
+		*source = 0;
+	}
+}
+
+int
+main (int argc, char **argv)
+{
+	gtk_init (&argc, &argv);
+
+	GtkWidget *window = gtk_window_new (GTK_WINDOW_TOPLEVEL);
+	GtkWidget *vbox = gtk_vbox_new (FALSE, 6);
+	GtkWidget *toggle = gtk_toggle_button_new_with_label ("Animate");
+	GtkWidget *da = gtk_drawing_area_new ();
+
+	gtk_container_add (GTK_CONTAINER (window), vbox);
+	gtk_box_pack_start (GTK_BOX (vbox), toggle, FALSE, FALSE, 0);
+	gtk_box_pack_start (GTK_BOX (vbox), da, TRUE, TRUE, 0);
+
+	/* prepare the user_data - in a real program, this would probably
+	 * be a struct */
+	gpointer user_data[3];
+	guint timeout_source;
+	int alpha = 0;
+	user_data[0] = &timeout_source;
+	user_data[1] = da;
+	user_data[2] = &alpha;
+
+	g_signal_connect (toggle, "toggled",
+			G_CALLBACK (animate_toggled), user_data);
+
+	g_signal_connect_swapped (window, "delete-event",
+			G_CALLBACK (gtk_main_quit), NULL);
+	g_signal_connect (da, "expose-event",
+			G_CALLBACK (expose_callback), &alpha);
+
+	gtk_window_set_default_size (GTK_WINDOW (window), 200, 200);
+	gtk_widget_show_all (window);
+
+	gtk_main ();
+}