NSView draw permanently to background

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:

enter image description here

call [view setNeedsDisplay] after the other UI elements are dismissed and you need to redraw the background — Jack
Hi, thanks for your answer. But this "solution" is insane. It causes a very ugly flickering and it's very inconvenient, because I have a) create for every element an IBAction and b) I have to put this line into this action. — Lupurus
Can you post some images of your exact problem and maybe we can find a better solution — Jack
What relation do the coordinates in your NSRectFill() call have to your view's bounds? Why are they not in fact computed from the bounds (e.g. with offsets or whatever)? — Ken Thomases

El Tomato El Tomato · Accepted Answer · 2014-02-13T23:14:16

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 //

NSView draw permanently to background

1 Answers