expo: Add width and height to objects

At present objects only have a position so it is not possible to determine
the amount of space they take up on the display.

Add width and height properties, using a struct to keep all the dimensions
together.

For now this is not used. Future work will set up these new properties.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/include/expo.h b/include/expo.h
index b8f5327..5135954 100644
--- a/include/expo.h
+++ b/include/expo.h
@@ -123,14 +123,28 @@
 };
 
 /**
+ * struct scene_dim - Dimensions of an object
+ *
+ * @x: x position, in pixels from left side
+ * @y: y position, in pixels from top
+ * @w: width, in pixels
+ * @h: height, in pixels
+ */
+struct scene_dim {
+	int x;
+	int y;
+	int w;
+	int h;
+};
+
+/**
  * struct scene_obj - information about an object in a scene
  *
  * @scene: Scene that this object relates to
  * @name: Name of the object (allocated)
  * @id: ID number of the object
  * @type: Type of this object
- * @x: x position, in pixels from left side
- * @y: y position, in pixels from top
+ * @dim: Dimensions for this object
  * @hide: true if the object should be hidden
  * @sibling: Node to link this object to its siblings
  */
@@ -139,8 +153,7 @@
 	char *name;
 	uint id;
 	enum scene_obj_t type;
-	int x;
-	int y;
+	struct scene_dim dim;
 	bool hide;
 	struct list_head sibling;
 };