cookbook: Example of using button press and release events

A longer example of using button press and release events
to draw rectangles with random colors.

doc/cookbook/examples/Makefile.am

@@ -30,6 +30,7 @@ noinst_PROGRAMS = \
 	script-signals	\
 	events-buttons	\
 	events-buttons-click	\
+	events-buttons-lasso	\
 	$(NULL)
 
 INCLUDES = \
@@ -80,5 +81,6 @@ script_ui_SOURCES                          = script-ui.c
 script_signals_SOURCES                     = script-signals.c
 events_buttons_SOURCES                     = events-buttons.c
 events_buttons_click_SOURCES               = events-buttons-click.c
+events_buttons_lasso_SOURCES               = events-buttons-lasso.c
 
 -include $(top_srcdir)/build/autotools/Makefile.am.gitignore

doc/cookbook/examples/events-buttons-lasso.c

@@ -0,0 +1,154 @@
+/* Simple rectangle drawing using button and pointer events;
+ * click, drag and release a mouse button to draw a rectangle
+ */
+#include <stdlib.h>
+#include <clutter/clutter.h>
+
+static const ClutterColor stage_color = { 0x33, 0x33, 0x55, 0xff };
+static const ClutterColor lasso_color = { 0xaa, 0xaa, 0xaa, 0x33 };
+
+typedef struct
+{
+  ClutterActor *actor;
+  gfloat        x;
+  gfloat        y;
+} Lasso;
+
+static guint
+random_color_component ()
+{
+  return (guint) (155 + (100.0 * rand () / (RAND_MAX + 1.0)));
+}
+
+static gboolean
+button_pressed_cb (ClutterActor *actor,
+                   ClutterEvent *event,
+                   gpointer      user_data)
+{
+  Lasso *lasso = (Lasso *) user_data;
+
+  /* start drawing the lasso actor */
+  lasso->actor = clutter_rectangle_new_with_color (&lasso_color);
+
+  /* store lasso's start coordinates */
+  clutter_event_get_coords (event, &(lasso->x), &(lasso->y));
+
+  clutter_container_add_actor (CLUTTER_CONTAINER (actor), lasso->actor);
+
+  return TRUE;
+}
+
+static gboolean
+button_released_cb (ClutterActor *stage,
+                    ClutterEvent *event,
+                    gpointer      user_data)
+{
+  Lasso *lasso = (Lasso *) user_data;
+  ClutterActor *rectangle;
+  ClutterColor *random_color;
+  gfloat x;
+  gfloat y;
+  gfloat width;
+  gfloat height;
+
+  if (lasso->actor == NULL)
+    return TRUE;
+
+  /* create a new rectangle */
+  random_color = clutter_color_new (random_color_component (),
+                                    random_color_component (),
+                                    random_color_component (),
+                                    random_color_component ());
+  rectangle = clutter_rectangle_new_with_color (random_color);
+
+  /* set the rectangle to the same size and shape as the lasso */
+  clutter_actor_get_position (lasso->actor, &x, &y);
+  clutter_actor_get_size (lasso->actor, &width, &height);
+
+  clutter_actor_set_position (rectangle, x, y);
+  clutter_actor_set_size (rectangle, width, height);
+
+  clutter_container_add_actor (CLUTTER_CONTAINER (stage), rectangle);
+
+  /* clear up the lasso actor */
+  clutter_actor_destroy (lasso->actor);
+  lasso->actor = NULL;
+
+  clutter_actor_queue_redraw (stage);
+
+  return TRUE;
+
+}
+
+static gboolean
+pointer_motion_cb (ClutterActor *stage,
+                   ClutterEvent *event,
+                   gpointer      user_data)
+{
+  gfloat pointer_x;
+  gfloat pointer_y;
+  gfloat new_x;
+  gfloat new_y;
+  gfloat width;
+  gfloat height;
+
+  Lasso *lasso = (Lasso *) user_data;
+
+  if (lasso->actor == NULL)
+    return TRUE;
+
+  /* redraw the lasso actor */
+  clutter_event_get_coords (event, &pointer_x, &pointer_y);
+
+  new_x = MIN (pointer_x, lasso->x);
+  new_y = MIN (pointer_y, lasso->y);
+  width = MAX (pointer_x, lasso->x) - new_x;
+  height = MAX (pointer_y, lasso->y) - new_y;
+
+  clutter_actor_set_position (lasso->actor, new_x, new_y);
+  clutter_actor_set_size (lasso->actor, width, height);
+
+  return TRUE;
+}
+
+int
+main (int   argc,
+      char *argv[])
+{
+  /* seed random number generator */
+  srand ((unsigned int) time (NULL));
+
+  Lasso *lasso = g_new0 (Lasso, 1);
+
+  ClutterActor *stage;
+
+  clutter_init (&argc, &argv);
+
+  stage = clutter_stage_get_default ();
+  clutter_actor_set_size (stage, 320, 240);
+  clutter_stage_set_color (CLUTTER_STAGE (stage), &stage_color);
+  g_signal_connect (stage, "destroy", G_CALLBACK (clutter_main_quit), NULL);
+
+  g_signal_connect (stage,
+                    "button-press-event",
+                    G_CALLBACK (button_pressed_cb),
+                    lasso);
+
+  g_signal_connect (stage,
+                    "button-release-event",
+                    G_CALLBACK (button_released_cb),
+                    lasso);
+
+  g_signal_connect (stage,
+                    "motion-event",
+                    G_CALLBACK (pointer_motion_cb),
+                    lasso);
+
+  clutter_actor_show (stage);
+
+  clutter_main ();
+
+  g_free (lasso);
+
+  return EXIT_SUCCESS;
+}