如何在CALayer上绘制本机外观的状态项背景

Question

实际上，我想在自定义NSStatusItem的CALayer上绘制选定statusItemView的背景。但是因为

- (void)drawStatusBarBackgroundInRect:(NSRect)rect withHighlight:(BOOL)highlight

不工作(?)在图层上，我尝试使用backgroundColor属性来绘制颜色。但是将selectedMenuItemColor转换成RGB并没有多大帮助。没有渐变，它看起来真的很简单。:-/

我使用以下代码将[NSColor selectedMenuItemColor]转换为CGColorRef：

- (CGColorRef)highlightColor {
    static CGColorRef highlight = NULL;
    if(highlight == NULL) {
        CGFloat red, green, blue, alpha;
        NSColor *hlclr = [[NSColor selectedMenuItemColor] colorUsingColorSpace:
                     [NSColorSpace genericRGBColorSpace]];
        [hlclr getRed:&red green:&green blue:&blue alpha:&alpha];
        CGFloat values[4] = {red, green, blue, alpha};
        highlight = CGColorCreate([self genericRGBSpace], values);
    }
    return highlight;
}

你知道如何在CALayer上绘制一个原生的状态项背景吗？

Answer 1

尝试将CALayer子类化并将the drawInContext: method实现为create an NSGraphicsContext for the CGContext、set the NSGraphicsContext as the current context，然后告诉状态项绘制其背景。

Answer 2

NSImage *backgroundImage = [[NSImage alloc] initWithSize:self.frame.size]];
[backgroundImage lockFocus];
[self.statusItem drawStatusBarBackgroundInRect:self.bounds withHighlight:YES];
[backgroundImage unlockFocus];
[self.layer setContents:backgroundImage];
[backgroundImage release];

Answer 3

我在我的层委托中使用了以下代码：

- (void)drawLayer:(CALayer *)layer 
        inContext:(CGContextRef)context {
    NSGraphicsContext* gc = [NSGraphicsContext graphicsContextWithGraphicsPort:context flipped:NO];
    [NSGraphicsContext saveGraphicsState];
    [NSGraphicsContext setCurrentContext:gc];
    [self.statusItem drawStatusBarBackgroundInRect:self.frame 
                                     withHighlight:self.isHighlighted];
    [NSGraphicsContext restoreGraphicsState];
}