NSView draw permanently to background - objective-c

Question

I'm trying to draw some things on the background of my windows. Therefore I subclassed the NSView of the window and added some drawing code like this:
- (void)drawRect:(NSRect)dirtyRect {
float color = 0.95;
[[NSColor colorWithDeviceRed:color green:color blue:color alpha:1.0] set];
NSRectFill(NSMakeRect(320, 0, 220, NSHeight(dirtyRect)-60));
}
This works great, but as soon as I open a NSComboBox or if I activate a checkbox, the background of these elements erases my just drawn rect.
I don't understand this, because checking for example the checkbox causes, that drawRect is called (I added a NSLog). Only resizing the window draws my rect again.
EDIT:
here is a screenshot of the problem:

Answer 1

I sometimes face the same problem. I think the following is what I use.
/// .h
#interface BackgroundView1 : NSView {
NSImage *myImage;
}
// .m
- (void)awakeFromNib {
[self setupBackgroundImage];
}
- (void)setupBackgroundImage {
NSColor *c = [NSColor colorWithDeviceRed:0.0f/255.0f green:55.0f/255.0f blue:150.0f/255.0f alpha:1.0f];
if (myImage == nil)
myImage = [self createColorImage:NSMakeSize(1,1):c];
}
- (void)drawRect:(NSRect)rect {
[myImage drawInRect:NSMakeRect([self bounds].origin.x,[self bounds].origin.y,[self frame].size.width,[self frame].size.height)
fromRect:NSMakeRect(0,0,[myImage size].width, [myImage size].height)
operation:NSCompositeCopy
fraction:1.0];
}
// Start Functions //
- (NSImage *)createColorImage:(NSSize)size :(NSColor *)color {
NSImage *image = [[NSImage alloc] initWithSize:size];
NSBitmapImageRep *rep = [[NSBitmapImageRep alloc]
initWithBitmapDataPlanes:NULL
pixelsWide:size.width
pixelsHigh:size.height
bitsPerSample:8
samplesPerPixel:4
hasAlpha:YES
isPlanar:NO
colorSpaceName:NSCalibratedRGBColorSpace
bytesPerRow:0
bitsPerPixel:0];
[image addRepresentation:rep];
[image lockFocus]; // Lock focus of image, making it a destination for drawing
[color set];
NSRectFill(NSMakeRect(0,0,size.width,size.height));
[image unlockFocus];
return image;
}
// End Functions //