Drawing tabs in an NSView

Question

I am working on implementing tabs for my application. Everything is working well except I can't figure out how to draw the tabs in a lighter shade of gray when the window resigns main status. I am successfully receiving a NSWindowDidBecomeMainNotification and redrawing the tab bar but I am not sure how to calculate the new gray color for the tabs. I am currently using images for all drawing. I tried drawing a semi-transparent layer above to the entire tab bar to make it lighter but it didn't seem to work. I could probably set an opacity value for each image that I use but that seems less than ideal. I also couldn't find any information in the Apple docs about this. What is the best practice in this case?

Answer 1

The way I do inactive controls is to render an inactive state version of the same graphic in my graphics program (Photoshop or Illustrator) and draw the inactive version when needed. If you draw a 50% transparent version of the active image, you need to erase with the background color first.

Answer 2

What you could do is make the tabs draw in code, and then simply not draw a background. Let the window's background, active or inactive, show through.

You might also consider switching to PSMTabBarControl, a reusable tab bar class that's already written and in use in several apps. (And I assume that you've dismissed NSTabView as not the look you're going for.)

Answer 3

You can try drawing the images using a semi-transparent mask. The code I generally use simply draws an image and then uses Quartz's Transparency Layer feature to fill a rect over the image's actual bounds. I do this as a category on NSImage:

@implementation NSImage (ShadedImageAddition)
- (void)drawAtPoint:(NSPoint)point shadeWithColor:(NSColor *)color intensity:(CGFloat)alpha
{
    NSRect imageRect;
    CGContextRef context = (CGContextRef)[[NSGraphicsContext currentContext] graphicsPort];

    imageRect.origin = point;
    imageRect.size = [self size];

    CGContextBeginTransparencyLayerWithRect(context, NSRectToCGRect(imageRect), NULL);

    [self drawInRect:imageRect fromRect:NSZeroRect operation:NSCompositeSourceOver fraction:1.0];
    [[color colorWithAlphaComponent:alpha] setFill];
    NSRectFillUsingOperation(imageRect, NSCompositeSourceAtop);

    CGContextEndTransparencyLayer(context);
}
@end

Then when the image is to be drawn in a non-key window, I generally draw a white mask over it at 50%. Of course you'll have to choose a color and alpha value that looks good with your bitmaps.

[myImage drawAtPoint:NSZeroPoint shadeWithColor:[NSColor whiteColor] intensity:0.50];