Introduction
This article carries strong personal sentiment. If you feel uncomfortable reading it, please close it as soon as possible. This article is only used as a personal learning record, and you are also welcome to reprint or share it within the scope of the license agreement. Please respect the copyright and keep the original link. Thank you for your understanding and cooperation. If you think this site is helpful to you, you can subscribe to it via RSS. Thanks for your support!
The main idea is to use CTFramesetterSuggestFrameSizeWithConstraints to calculate the height and width of the text. Remember to set the related properties (line spacing and automatic line wrapping) for the CTFramesetterRef. The following is an Objective-C code example that uses CoreText to draw text and calculate its height:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
- (void)calculatedHeight:(CGSize)bounds
{
NSString *text = @"This\nis\nsome\nmulti-line\nsample\ntext.";
UIFont *uiFont = [UIFont fontWithName:@"Helvetica" size:17.0];
CTFontRef ctFont = CTFontCreateWithName((CFStringRef) uiFont.fontName, uiFont.pointSize, NULL);
// Set line spacing
CGFloat leading = uiFont.lineHeight - uiFont.ascender + uiFont.descender;
CTParagraphStyleSetting LineSpacing;
LineSpacing.spec = kCTParagraphStyleSpecifierLineSpacingAdjustment;
LineSpacing.value = &leading;
LineSpacing.valueSize = sizeof(CGFloat);
// Set line break mode
CTParagraphStyleSetting lineBreakMode;
CTLineBreakMode lineBreak = kCTLineBreakByCharWrapping;
lineBreakMode.spec = kCTParagraphStyleSpecifierLineBreakMode;
lineBreakMode.value = &lineBreak;
lineBreakMode.valueSize = sizeof(CTLineBreakMode);
CTParagraphStyleSetting paragraphSettings[] = {lineBreakMode,LineSpacing};
CTParagraphStyleRef paragraphStyle = CTParagraphStyleCreate(paragraphSettings, 2);
CFRange textRange = CFRangeMake(0, text.length);
CFMutableAttributedStringRef string = CFAttributedStringCreateMutable(kCFAllocatorDefault, text.length);
CFAttributedStringReplaceString(string, CFRangeMake(0, 0), (CFStringRef) text);
// Set font line spacing and size
CFAttributedStringSetAttribute(string, textRange, kCTFontAttributeName, ctFont);
CFAttributedStringSetAttribute(string, textRange, kCTParagraphStyleAttributeName, paragraphStyle);
CTFramesetterRef framesetter = CTFramesetterCreateWithAttributedString(string);
CFRange fitRange;
// Calculate the height needed by the text
CGSize frameSize = CTFramesetterSuggestFrameSizeWithConstraints(framesetter, textRange, NULL, bounds, &fitRange);
CFRelease(framesetter);
CFRelease(string);
}
Summary
Recording some easily forgotten code