Actionscript Cookbook

7.12. Getting a Movie Clip’s Boundaries

Problem

You want to know the minimum and maximum x and y coordinates that determine the edges of a movie clip (its bounding box).

Solution

Use the getBounds( ) method.

Discussion

You can determine the left, right, top, and bottom coordinates of a movie clip within its parent movie clip using a combination of the _x, _y, _width, and _height properties:

left   = myMovieClip._x;
right  = left + myMovieClip._width;
top    = myMovieClip._y;
bottom = top + myMovieClip._height;

While this technique works, it is rather intensive and inefficient when compared to the getBounds( ) method. The getBounds( ) method returns an object with four properties:

xMin

The leftmost x coordinate of the movie clip

xMax

The rightmost x coordinate of the movie clip

yMin

The topmost y coordinate of the movie clip

yMax

The bottommost y coordinate of the movie clip

The four properties define the bounding box of the visible content within the movie clip. (Note that y coordinates increase as you move down the screen, which is the opposite of the Cartesian coordinate system.) When you call getBounds( ) without parameters, it returns an object with values relative to the movie clip’s coordinate system. You can also pass the method a reference to a target coordinate system (another movie clip) for which you want the returned object’s values to be given:

// Include DrawingMethods.as from Chapter 4 for its drawCircle(  ) method. #include "DrawingMethods.as" // Create a new movie clip and draw ...