cookbook: Add example of scaling a texture

Added a simple application for scaling a
texture while keeping the mouse pointer over
the same coordinates on its surface.

doc/cookbook/examples/Makefile.am

@@ -13,6 +13,7 @@ noinst_PROGRAMS = \
 	animations-reuse	\
 	animations-rotating	\
 	animations-scaling	\
+	animations-scaling-zoom	\
 	text-shadow		\
 	textures-reflection	\
 	textures-split-go	\
@@ -68,6 +69,7 @@ animations_moving_state_SOURCES            = animations-moving-state.c
 animations_reuse_SOURCES                   = animations-reuse.c
 animations_rotating_SOURCES                = animations-rotating.c
 animations_scaling_SOURCES                 = animations-scaling.c
+animations_scaling_zoom_SOURCES            = animations-scaling-zoom.c
 text_shadow_SOURCES                        = text-shadow.c
 textures_reflection_SOURCES                = textures-reflection.c
 textures_split_go_SOURCES                  = textures-split-go.c

doc/cookbook/examples/animations-scaling-zoom.c

@@ -0,0 +1,155 @@
+/*
+ * Load an image into a texture, which can then be zoomed in/out
+ * (double click on button 1, double click on button 3 respectively);
+ * also resets the texture to the stage center when a key is pressed
+ * (better would be to prevent drags taking the actor off-stage,
+ * but the implementation is much more complicated)
+ */
+#include <stdlib.h>
+#include <clutter/clutter.h>
+
+#define STAGE_SIDE 400.0
+
+static const ClutterColor stage_color = { 0x33, 0x33, 0x55, 0xff };
+
+/* on key press, center the actor on the stage;
+ * useful if you drag it off-stage accidentally
+ */
+static gboolean
+key_press_cb (ClutterActor *actor,
+              ClutterEvent *event,
+              gpointer      user_data)
+{
+  gfloat width, height;
+
+  clutter_actor_get_size (actor, &width, &height);
+
+  clutter_actor_set_anchor_point (actor, width / 2, height / 2);
+
+  clutter_actor_set_position (actor,
+                              STAGE_SIDE / 2,
+                              STAGE_SIDE / 2);
+
+  return TRUE;
+}
+
+/* on double click, zoom in on the clicked point;
+ * also keeps scale in the range 0.1 to 20
+ */
+static gboolean
+clicked_cb (ClutterActor *actor,
+            ClutterEvent *event,
+            gpointer      user_data)
+{
+  gdouble scale;
+  gfloat click_x, click_y;
+  gfloat click_target_x, click_target_y;
+  guint32 button;
+
+  /* don't do anything unless there was a double click */
+  if (clutter_event_get_click_count (event) < 2)
+    return TRUE;
+
+  /* work out new scale */
+  button = clutter_event_get_button (event);
+
+  clutter_actor_get_scale (actor, &scale, NULL);
+
+  if (button == 1)
+    scale *= 1.2;
+  else if (button == 3)
+    scale /= 1.2;
+
+  /* don't do anything if scale is outside bounds */
+  if (scale < 0.1 || scale > 20.0)
+    return TRUE;
+
+  /* get the location of the click on the scaled actor */
+  clutter_event_get_coords (event, &click_x, &click_y);
+  clutter_actor_transform_stage_point (actor,
+                                       click_x, click_y,
+                                       &click_target_x, &click_target_y);
+
+  /* anchor the actor on the clicked point on its surface */
+  clutter_actor_set_anchor_point (actor, click_target_x, click_target_y);
+
+  /* set the actor's position to the click coords: it won't move,
+   * because the anchor point is already there; but
+   * the scale will now be centered on these coords (as the
+   * scale center defaults to the anchor point); so the anchor point
+   * on the actor won't move from under the pointer
+   */
+  clutter_actor_set_position (actor, click_x, click_y);
+
+  clutter_actor_animate (actor, CLUTTER_LINEAR, 500,
+                         "scale-x", scale,
+                         "scale-y", scale,
+                         NULL);
+
+  return TRUE;
+}
+
+int
+main (int   argc,
+      char *argv[])
+{
+  ClutterActor *stage;
+  ClutterActor *texture;
+  gchar *image_path;
+  GError *error = NULL;
+
+  if (argc < 2)
+    {
+      g_print ("Usage: %s <path to image file>\n", argv[0]);
+      exit (EXIT_FAILURE);
+    }
+
+  image_path = argv[1];
+
+  clutter_init (&argc, &argv);
+
+  stage = clutter_stage_get_default ();
+  clutter_actor_set_size (stage, STAGE_SIDE, STAGE_SIDE);
+  clutter_stage_set_color (CLUTTER_STAGE (stage), &stage_color);
+  g_signal_connect (stage, "destroy", G_CALLBACK (clutter_main_quit), NULL);
+
+  texture = clutter_texture_new ();
+  clutter_actor_set_reactive (texture, TRUE);
+  clutter_actor_set_width (texture, STAGE_SIDE);
+  clutter_texture_set_keep_aspect_ratio (CLUTTER_TEXTURE (texture), TRUE);
+
+  clutter_actor_add_action (texture, clutter_drag_action_new ());
+
+  g_object_set (G_OBJECT (texture),
+                "scale-gravity", CLUTTER_GRAVITY_NORTH_WEST,
+                NULL);
+
+  clutter_texture_set_from_file (CLUTTER_TEXTURE (texture), image_path, &error);
+
+  if (error != NULL)
+    {
+      g_warning ("Error loading %s\n%s", image_path, error->message);
+      g_error_free (error);
+      exit (EXIT_FAILURE);
+    }
+
+  clutter_actor_set_y (texture, (STAGE_SIDE - clutter_actor_get_height (texture)) * 0.5);
+
+  g_signal_connect (texture,
+                    "button-release-event",
+                    G_CALLBACK (clicked_cb),
+                    NULL);
+
+  g_signal_connect_swapped (stage,
+                            "key-press-event",
+                            G_CALLBACK (key_press_cb),
+                            texture);
+
+  clutter_container_add_actor (CLUTTER_CONTAINER (stage), texture);
+
+  clutter_actor_show (stage);
+
+  clutter_main ();
+
+  return EXIT_SUCCESS;
+}