QuickTime Layers - Core Animation - page 126

this so that we can encapsulate all our capture functionality in the layer and then reuse
the layer wherever we like in our applications that need capture functionality.

In the Photo Capture sample code, we have created this QTCaptureLayer derived class and
named it simply CaptureLayer . Listing 7-11 shows the init code used to initialize the
layer.

LISTING 7-11 QTCaptureLayer Derived Class Initialization

- ( id )init;
{

self = [super init];
if ( !self ) return nil ;
[ self initCaptureSession];
return self ;

}

As you can see, we have called -initCaptureSession here from Listing 7-10. This way,
when we initialize a new CaptureLayer object, QTCaptureSession is already fired up and
ready to go. Next, add CaptureLayer to the window's root layer tree. You can see how this
code is implemented in the AppDelegate 's -awakeFromNib , as shown in Listing 7-12.

LISTING 7-12 Implementing CaptureLayer in the AppDelegate

-( void )awakeFromNib;
{

[[window contentView ] setWantsLayer: YES ];

captureLayer = [[CaptureLayer alloc ] init ];

// Use the frame from the generic NSView we have
// named captureView
[captureLayer setBounds :
NSRectToCGRect([captureView frame ])];
[captureLayer setPosition :
CGPointMake ([captureView frame ]. size . width /2,
[captureView frame ]. size . height /2)];

[[captureView layer ]
insertSublayer :captureLayer atIndex :0];

[captureLayer starCaptureSession];

}