CATextLayer不会绘制NSAttributedString背景色 [英] CATextLayer doesn't draw NSAttributedString background color

问题描述

我有CATextLayer，想将背景颜色设置为字符串的一部分。但是，将背景颜色设置为属性字符串（NSBackgroundColorAttributeName）无效。正确应用了其他属性，例如前景色。

I have CATextLayer and want to set background color to part of the string. But setting background color to attributed string (NSBackgroundColorAttributeName) doesn't have any effect. Other attributes, such as foreground color, are applied correctly.

NSMutableAttributedString *str = [[[NSMutableAttributedString alloc] initWithString:@"Some Text"] autorelease];
NSDictionary *attributes = [NSDictionary dictionaryWithObjectsAndKeys:
                            [NSColor yellowColor], NSForegroundColorAttributeName,
                            [NSColor redColor], NSBackgroundColorAttributeName, nil];

[str setAttributes:attributes range:NSMakeRange(0, 3)];

textLayer.string = str;

前三个符号以黄色绘制，但背景不会改变。有什么想法吗？

First three symbols are drawn in yellow color, but background won't change. Any ideas?

推荐答案

我认为 CATextLayer 类使用 CoreText API进行渲染。 CoreText API是非常底层的，仅支持 NSAttributedString 属性的子集。不幸的是， NSBackgroundColorAttributeName 并不是其中之一。您必须手动处理它（请参见此SO条目）。

I think that the CATextLayer class uses the CoreText API for its rendering. The CoreText API are very low-level and only support a subset of the NSAttributedString attributes. Unfortunately, the NSBackgroundColorAttributeName is not one of those. You have to deal with it manually (see this SO entry).

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