[Cocoa]_[中级]_[在指定区域绘制文本的drawrect实现]

场景

1. Cocoa开发时, 往往需要在某个区域绘制文本, 但是文本的长度不是固定的, 所以有可能很长的时候需要自动换行. NSTextField的[NSCell setWraps]可以做到, 但是如果不能添加NSTextField,只能通过绘制的方式？如何做.NSAttributeString的size只是单行的, 没什么用.

2. 宽度固定时, Windows开发时我们可以通过DT_CALCRECT来计算高度, Cocoa开发有没有相应的方法？

说明

Cocoa也有相应的计算当宽度固定时区域文字高度的方法, 是通过NSLayoutManager来实现的.

+(float) heightForStringDrawing:(NSString *)myString withFont:(NSFont *)myFont
                      withWidth:(float) myWidth
{
    NSTextStorage *textStorage = [[[NSTextStorage alloc] initWithString:myString] autorelease];
    NSTextContainer *textContainer = [[[NSTextContainer alloc]initWithContainerSize: NSMakeSize(myWidth, FLT_MAX)] autorelease];
    NSLayoutManager *layoutManager = [[[NSLayoutManager alloc] init] autorelease];
    [layoutManager addTextContainer:textContainer];
    [textStorage addLayoutManager:layoutManager];
    
    [textStorage addAttribute:NSFontAttributeName value:myFont range:NSMakeRange(0, [textStorage length])];
    [textContainer setLineFragmentPadding:0.0];
    (void) [layoutManager glyphRangeForTextContainer:textContainer];
    return [layoutManager usedRectForTextContainer:textContainer].size.height;
}

// 在指定区域绘制文本, 需要自动换行.
+(void) drawStringInView:(NSString*)myString withFont:(NSFont *)myFont withRect:(NSRect)rect withColor:(NSColor*)color withAlign:(NSInteger)align
{
    NSTextStorage *textStorage = [[NSTextStorage alloc]
                                  initWithString:myString];
    
    NSLayoutManager *layoutManager = [[NSLayoutManager alloc] init];
    NSTextContainer *textContainer = [[NSTextContainer alloc]initWithContainerSize: NSMakeSize(rect.size.width, FLT_MAX)];
    
    [layoutManager addTextContainer:textContainer];
    [textContainer release];
    [textStorage addLayoutManager:layoutManager];
    NSRange range = NSMakeRange(0, [textStorage length]);
    [textStorage addAttribute:NSFontAttributeName value:myFont range:range];
    [textStorage addAttribute:NSForegroundColorAttributeName value:color range:range];
    
    NSMutableParagraphStyle* style = [[NSMutableParagraphStyle alloc] init];
    [style setAlignment:align];
    [textStorage addAttribute:NSParagraphStyleAttributeName value:style range:range];
    
    [layoutManager release];
    
    NSRange glyphRange = [layoutManager
                          glyphRangeForTextContainer:textContainer];
    float height = [layoutManager usedRectForTextContainer:textContainer].size.height;
    [layoutManager drawGlyphsForGlyphRange: glyphRange atPoint: rect.origin];
    [textStorage release];
//    [style release];
}


// 调用方式
// [UiUtil drawStringInView:str_startup_tip_ withFont:font_15_bold_
//                                    withRect:rect_startup_tip_ withColor:[NSColor blackColor] withAlign:NSCenterTextAlignment];

其他

Windows GDI GDIPlus编程时计算文字高度的方法.

// GDI
int height = dc.DrawText(str_message_.c_str(),str_message_.size(), &rect_message_,  DT_TOP| DT_WORDBREAK|DT_EDITCONTROL | DT_LEFT | DT_NOPREFIX|DT_CALCRECT);

// GDI+
graphics.MeasureString(str_desc.c_str(),str_desc.size(),&font_normal_bold_,
		rectf_desc_temp,&rectf_desc);

参考

Calculating Text Height