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iosobjective-ccore-text

Why is my text drawing from the bottom up?


In my custom view, I have the following code:

-(void) drawRect:(CGRect) rect
{
    // Drawing code   
    CGContextRef context = UIGraphicsGetCurrentContext();

    ![NSString *myString = @"Hello World, This is for\nhttp://www.stackoverflow.com";
    // Prepare font
    CTFontRef font = CTFontCreateWithName(CFSTR("Times"), 12, NULL);

    // Create an attributed string
    CFStringRef keys[] = { kCTFontAttributeName };
    CFTypeRef values[] = { font };
    CFDictionaryRef attr = CFDictionaryCreate(NULL, (const void **)&keys, (const void **)&values,
                                              sizeof(keys) / sizeof(keys[0]), &kCFTypeDictionaryKeyCallBacks, &kCFTypeDictionaryValueCallBacks);
    CFAttributedStringRef attrString = CFAttributedStringCreate(NULL, (CFStringRef)myString, attr);
    CFRelease(attr);

    // Draw the string
    //CTLineRef line = CTLineCreateWithAttributedString(attrString);
    CTFramesetterRef framesetter = CTFramesetterCreateWithAttributedString(attrString);
    CGMutablePathRef path = CGPathCreateMutable();
    CGPathAddRect(path, NULL, self.frame);
    CTFrameRef frame = CTFramesetterCreateFrame(framesetter, CFRangeMake(0, 0), path, NULL);
    //CGContextSetTextMatrix(context, CGAffineTransformIdentity); // this line is wrong,  use the below line
    CGContextSetTextMatrix(context, CGAffineTransformMakeScale(1.0, -1.0)); 
    CGContextSetTextPosition(context, 20, 12);
    CTFrameDraw(frame, context);

    // Clean up
    CFRelease(path);
    CFRelease(frame);
    CFRelease(attrString);
    CFRelease(font);
}

However, that looks like this:

https://i.sstatic.net/iGonN.png

How can I make the text go down, and also start from the top left?


Solution

  • Here's the copy & paste of one of my drawRect: methods, which does work perfectly.

    CGContextRef ctx = UIGraphicsGetCurrentContext();
    CGContextSaveGState( ctx );
    
    CGContextSetTextMatrix( ctx, CGAffineTransformIdentity );
    
    CGContextTranslateCTM( ctx, rect.origin.x, rect.origin.y );
    CGContextScaleCTM( ctx, 1.0f, -1.0f );
    CGContextTranslateCTM( ctx, rect.origin.x, - ( rect.origin.y + rect.size.height ) );
    
    CGMutablePathRef path = CGPathCreateMutable();
    CGPathAddRect( path, NULL, rect );
    
    CTFramesetterRef framesetter = CTFramesetterCreateWithAttributedString( __labelData.attributedString );  
    CTFrameRef frame = CTFramesetterCreateFrame( framesetter, CFRangeMake( 0, 0 ), path, NULL );    
    
    CTFrameDraw( frame, ctx );
    
    CGPathRelease( path );  
    CFRelease( frame );
    CFRelease( framesetter );
    
    CGContextRestoreGState( ctx );  
    

    Just replace __labelData.attributedString with your attributed string.