cookbook: Added example for pointer cross recipe

Code example demonstrates detecting pointers entering/leaving
an actor by implementing a (very) simple button with hover
effect.

doc/cookbook/examples/Makefile.am

@@ -11,6 +11,7 @@ noinst_PROGRAMS = \
 	layouts-stacking \
 	layouts-stacking-diff-sized-actors	\
 	events-mouse-scroll \
+	events-pointer-cross \
 	$(NULL)
 
 INCLUDES = \
@@ -40,5 +41,6 @@ textures_sub_texture_SOURCES               = textures-sub-texture.c
 layouts_stacking_SOURCES                   = layouts-stacking.c
 layouts_stacking_diff_sized_actors_SOURCES = layouts-stacking-diff-sized-actors.c
 events_mouse_scroll_SOURCES                = events-mouse-scroll.c
+events_pointer_cross_SOURCES               = events-pointer-cross.c
 
 -include $(top_srcdir)/build/autotools/Makefile.am.gitignore

doc/cookbook/examples/events-pointer-cross.c

@@ -0,0 +1,113 @@
+#include <clutter/clutter.h>
+
+static const ClutterColor stage_color = { 0x33, 0x33, 0x55, 0xff };
+static const ClutterColor yellow = { 0xaa, 0x99, 0x00, 0xff };
+static const ClutterColor white = { 0xff, 0xff, 0xff, 0xff };
+
+static gboolean
+_on_enter_cb (ClutterActor *actor,
+              ClutterEvent *event,
+              gpointer      user_data)
+{
+  ClutterState *transitions = CLUTTER_STATE (user_data);
+  clutter_state_set_state (transitions, "fade-in");
+  return TRUE;
+}
+
+static gboolean
+_on_leave_cb (ClutterActor *actor,
+              ClutterEvent *event,
+              gpointer      user_data)
+{
+  ClutterState *transitions = CLUTTER_STATE (user_data);
+  clutter_state_set_state (transitions, "fade-out");
+  return TRUE;
+}
+
+int
+main (int argc, char *argv[])
+{
+  ClutterActor *stage;
+  ClutterLayoutManager *layout;
+  ClutterActor *box;
+  ClutterActor *rect;
+  ClutterActor *text;
+  ClutterState *transitions;
+
+  clutter_init (&argc, &argv);
+
+  stage = clutter_stage_get_default ();
+  clutter_stage_set_color (CLUTTER_STAGE (stage), &stage_color);
+  clutter_stage_set_title (CLUTTER_STAGE (stage), "btn");
+
+  layout = clutter_bin_layout_new (CLUTTER_BIN_ALIGNMENT_FILL,
+                                   CLUTTER_BIN_ALIGNMENT_FILL);
+
+  box = clutter_box_new (layout);
+  clutter_actor_set_position (box, 25, 25);
+  clutter_actor_set_reactive (box, TRUE);
+  clutter_actor_set_size (box, 100, 30);
+
+  /* background for the button */
+  rect = clutter_rectangle_new_with_color (&yellow);
+  clutter_container_add_actor (CLUTTER_CONTAINER (box), rect);
+
+  /* text for the button */
+  text = clutter_text_new_full ("Sans 10pt", "Hover me", &white);
+  clutter_text_set_line_alignment (CLUTTER_TEXT (text), PANGO_ALIGN_CENTER);
+
+  /*
+   * NB don't set the height, so the actor assumes the height of the text;
+   * then when added to the bin layout, it gets centred on it;
+   * also if you don't set the width, the layout goes gets really wide;
+   * the 10pt text fits inside the 30px height of the rectangle
+   */
+  clutter_actor_set_width (text, 100);
+  clutter_bin_layout_add (CLUTTER_BIN_LAYOUT (layout),
+                          text,
+                          CLUTTER_BIN_ALIGNMENT_CENTER,
+                          CLUTTER_BIN_ALIGNMENT_CENTER);
+
+  /* animations */
+  transitions = clutter_state_new ();
+  clutter_state_set (transitions, NULL, "fade-out",
+                     box, "opacity", CLUTTER_LINEAR, 180,
+                     NULL);
+
+ /*
+  * NB you can't use an easing mode where alpha > 1.0 if you're
+  * animating to a value of 255, as the value you're animating
+  * to will possibly go > 255
+  */
+  clutter_state_set (transitions, NULL, "fade-in",
+                     box, "opacity", CLUTTER_LINEAR, 255,
+                     NULL);
+
+  clutter_state_set_duration (transitions, NULL, NULL, 50);
+
+  clutter_state_warp_to_state (transitions, "fade-out");
+
+  g_signal_connect (box,
+                    "enter-event",
+                    G_CALLBACK (_on_enter_cb),
+                    transitions);
+
+  g_signal_connect (box,
+                    "leave-event",
+                    G_CALLBACK (_on_leave_cb),
+                    transitions);
+
+  /* bind the stage size to the box size + 50px in each axis */
+  clutter_actor_add_constraint (stage, clutter_bind_constraint_new (box, CLUTTER_BIND_HEIGHT, 50.0));
+  clutter_actor_add_constraint (stage, clutter_bind_constraint_new (box, CLUTTER_BIND_WIDTH, 50.0));
+
+  clutter_container_add_actor (CLUTTER_CONTAINER (stage), box);
+
+  clutter_actor_show (stage);
+
+  clutter_main ();
+
+  g_object_unref (transitions);
+
+  return 0;
+}