NSString boundingRectWithSize返回不必要的高度 [英] NSString boundingRectWithSize returning unnecessarily tall height

问题描述

当使用 [NSString boundingRectWithSize：options：attributes] 时，返回的rect的大小比我对某些字符串所期望的大。返回的高度似乎表示具有给定属性的字符串的最大可能高度，而不是字符串本身的高度。

When using [NSString boundingRectWithSize:options:attributes] the size of the rect that is returned is taller than I would expect for certain strings. The height returned appears to represent the maximum possible height of a string with the given attributes, rather than the height of the string itself.

假设相同的属性和选项，字符串 cars 返回的高度是返回的字符串ÉTAS-UNIS （注意E上的重音）。

Assuming the same attributes and options, the height returned for the string "cars" is the same height returned for the string "ÉTAS-UNIS" (note the accent on the E).

我本来希望 boundingRectWithSize 只考虑给定字符串中的字符，为字符串 cars 返回较短的高度。

I would have expected boundingRectWithSize to only consider the characters in the given string, which in my opinion would have it return a shorter height for the string "cars".

在附加的屏幕截图中，我填写了 boundingRectWithSize 返回的rect，假设边界矩形应该已经。矩形的宽度是我所期望的，但是高度比我预期的高得多。这是为什么？

In the attached screenshots, I've filled the rect returned from boundingRectWithSize and outlined in red what I would have assumed the bounding rect should have been. The width of the rect is pretty much as I would expect but the height is considerably taller than I would have expected. Why is that?

示例代码：

NSRect boundingRect = NSZeroRect;
NSSize constraintSize = NSMakeSize(CGFLOAT_MAX, 0);

NSString *lowercaseString = @"cars";
NSString *uppercaseString = @"ÉTAS-UNIS";
NSString *capitalizedString = @"Japan";

NSFont *drawingFont = [NSFont fontWithName:@"Georgia" size:24.0];
NSDictionary *attributes = @{NSFontAttributeName : drawingFont, NSForegroundColorAttributeName : [NSColor blackColor]};

boundingRect = [lowercaseString boundingRectWithSize:constraintSize options:0 attributes:attributes];
NSLog(@"Lowercase rect: %@", NSStringFromRect(boundingRect));

boundingRect = [uppercaseString boundingRectWithSize:constraintSize options:0 attributes:attributes];
NSLog(@"Uppercase rect: %@", NSStringFromRect(boundingRect));

boundingRect = [capitalizedString boundingRectWithSize:constraintSize options:0 attributes:attributes];
NSLog(@"Capitalized rect: %@", NSStringFromRect(boundingRect));

输出：

Lowercase rect: {{0, -6}, {43.1953125, 33}}
Uppercase rect: {{0, -6}, {128.44921875, 33}}
Capitalized rect: {{0, -6}, {64.5, 33}}

推荐答案

您可能想在选项中使用 NSStringDrawingUsesDeviceMetrics 。从 docs ：

You might want to use NSStringDrawingUsesDeviceMetrics in the options. From the docs:

NSStringDrawingUsesDeviceMetrics

在计算布局时使用图像字形边界（而不是印刷边界）。

Use the image glyph bounds (instead of the typographic bounds) when computing layout.

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