CALayer not showing - objective-c

Question

In trying to make a draggable sort of CALayer ( Question on Stack Overflow here ) I tried creating a window through code and adding a CALayer to it, but I don't get why it's not showing.
NSRect rect = NSZeroRect;
rect.size = NSMakeSize( SSRandomFloatBetween( 300.0, 200.0 ), SSRandomFloatBetween( 300.0, 200.0 ));
NSWindow *newWin = [[NSWindow alloc] initWithContentRect:rect styleMask:NSBorderlessWindowMask backing:NSWindowBackingLocationDefault defer:YES];
[newWin setBackgroundColor: [NSColor clearColor]];
[newWin setOpaque:NO];
[newWin setIgnoresMouseEvents:NO];
[newWin setMovableByWindowBackground:YES];
[newWin makeKeyAndOrderFront:self];
[[newWin contentView] setWantsLayer:YES];
NSRect contentFrame = [[newWin contentView] frame];
CALayer *newWinLayer = [CALayer layer];
newWinLayer.frame = NSRectToCGRect(contentFrame);
layer.backgroundColor=CGColorCreateGenericGray(0.0f, 0.5f);
layer.borderColor=CGColorCreateGenericGray(0.756f, 0.5f);
layer.borderWidth=5.0;
// Calculate random origin point
rect.origin = SSRandomPointForSizeWithinRect( rect.size, [window frame] );
// Set the layer frame to our random rectangle.
layer.frame = NSRectToCGRect(rect);
layer.cornerRadius = 25.0f;
[newWinLayer addSublayer:layer];
"Window" is linked to a big window, with a semi-transparent (black filled) window that is resized to fill the screen.
I've made the window draggable, but why isn't the CALayer in the window showing?

Answer 1

NSRect rect = NSZeroRect;
rect.size = NSMakeSize( SSRandomFloatBetween( 300.0, 200.0 ),
SSRandomFloatBetween( 300.0, 200.0 ));
NSWindow *newWin = [[NSWindow alloc] initWithContentRect:rect
styleMask:NSBorderlessWindowMask
backing:NSWindowBackingLocationDefault defer:YES];
[newWin setBackgroundColor:[NSColor clearColor]];
[newWin setOpaque:NO];
[newWin setIgnoresMouseEvents:NO];
[newWin setMovableByWindowBackground:YES];
[newWin makeKeyAndOrderFront:self];
// you don't want to do this yet
// [[newWin contentView] setWantsLayer:YES];
NSRect contentFrame = [[newWin contentView] frame];
CALayer *newWinLayer = [CALayer layer];
newWinLayer.frame = NSRectToCGRect(contentFrame);
Line break, also a memory-managment issue:
// NOTE: remember that the following 2 *Create* methods return
// results that need to be released, unless you're using Garbage-Collection
// Also, I'm guessing that `layer` is created somewhere?
CALayer *layer = [CALayer layer];
CGColorRef backgroundCol = CGColorCreateGenericGray(0.0f, 0.5f);
CGColorRef borderCol = CGColorCreateGenericGray(0.756f, 0.5f);
layer.backgroundColor=backgroundCol;
layer.borderColor=borderCol;
CGColorRelease(backgroundCol); CGColorRelease(borderCol);
layer.borderWidth=5.0;
// Calculate random origin point
rect.origin = SSRandomPointForSizeWithinRect( rect.size, [window frame] );
// Set the layer frame to our random rectangle.
layer.frame = NSRectToCGRect(rect);
layer.cornerRadius = 25.0f;
[newWinLayer addSublayer:layer];
NSView *view = [newWin contentView];
// the order of the following 2 methods is critical:
[view setLayer:newWinLayer];
[view setWantsLayer:YES];
See NSView's documentation for setWantsLayer:
Discussion
The order that
setWantsLayer: and setLayer: are
called is important, it makes the
distinction between a layer-backed
view, and a layer-hosting view.
A layer-backed view is a view that is
backed by a Core Animation layer. Any
drawing done by the view is the cached
in the backing layer. You configured a
layer-backed view by simply invoking
setWantsLayer: with a value of YES.
The view class will automatically
create the a backing layer for you,
and you use the view class’s drawing
mechanisms. When using layer-backed
views you should never interact
directly with the layer.
A layer-hosting view is a view that
contains a Core Animation layer that
you intend to manipulate directly. You
create a layer-hosting view by
instantiating an instance of a Core
Animation layer class and setting that
layer using the view’s setLayer:
method. After doing so, you then
invoke setWantsLayer: with a value of
YES. When using a layer-hosting view
you should not rely on the view for
drawing, nor should you add subviews
to the layer-hosting view.
I believe the way you were doing it would be trying to create a layer-backed view, where you shouldn't be trying to interact with the view's underlying layer like you were. What you want is the layer-hosting variety.