CGContextSelectFont equivalent

Question

In iOS7 CGContextSelectFont is deprecated. Deprecation message says that I have to use Core Text, but I don't know which is the exact equivalent of this piece of code:

CGContextSelectFont(context, "Helvetica", kBarLabelSize, kCGEncodingMacRoman);
CGContextSetTextDrawingMode(context, kCGTextFill);
CGContextSetRGBFillColor(context, 0, 0, 0, 1.0);
CGContextSetTextMatrix (context, CGAffineTransformMake(1.0, 0.0, 0.0, -1.0, 0.0, 0.0));
CGContextShowTextAtPoint(context, barX, barY, [@"Some text" cStringUsingEncoding:NSUTF8StringEncoding], [barValue length]);

I've been able to create the font with this code:

CFMutableAttributedStringRef attrStr = CFAttributedStringCreateMutable(kCFAllocatorDefault, 0);
CTFontRef font = CTFontCreateWithName(CFSTR("Helvetica"), kBarLabelSize, NULL);
CFAttributedStringSetAttribute(attrStr, CFRangeMake(0, CFAttributedStringGetLength(attrStr)), kCTFontAttributeName, font);

But now haw can I "draw" a text with this font into the context?

Solution 1

As best I can understand from your code, the exact equivalent is:

CGContextSetTextDrawingMode(context, kCGTextFill); // This is the default
[[UIColor blackColor] setFill]; // This is the default
[@"Some text" drawAtPoint:CGPointMake(barX, barY)
           withAttributes:@{NSFontAttributeName:[UIFont fontWithName:@"Helvetica"
                                                                size:kBarLabelSize]
                            }];

Note that your calls to CGContextSetTextDrawingMode and CGContextSetRGBFillColor are setting the values to the defaults. Your call to CGContextSetTextMatrix is not needed when using UIKit drawing like this.

I have no idea what [barValue length] is here, however. I'm assuming that you simply incorrectly used this for the length of @"Some text". (length is not the number of bytes which is what you need. What you probably meant was [barValue lengthOfBytesUsingEncoding:NSUTF8StringEncoding]).

Note that UIKit string drawing (seen here) wraps Core Text.

Solution 2

I have found, at least in my case, the problem with the new NSString.drawAtPoint interface is that it may draw upside down, depending on how you are using the context.

An alternate is to use the Core Text methods, specifically the CTLine interface thusly:

NSDictionary *attribs = @{NSFontAttributeName:[UIFont fontWithName:@"Helvetica" size:14.0]};

NSAttributedString *fontStr = [[NSAttributedString alloc] initWithString:@"some text" attributes:attribs];

CTLineRef displayLine = CTLineCreateWithAttributedString( (__bridge CFAttributedStringRef)fontStr );
CGContextSetTextPosition( ctx, xPosition, yPosition );
CTLineDraw( displayLine, ctx );
CFRelease( displayLine );

Comments

[Rob Napier]

This is not compatible with CGContextShowTextAtPoint (which is also deprecated anyway)

[rai212]

I can't test it until now... and it works!. And yes, [barValue length] refers to @"Some text" length and yes, it was incorrectly used, I should use lengthOfBytes, but due to this works I don't realize it was wrong. Thank you very much

[Dan Rosenstark]

Amazing and useful answer. However: the setFill is being ignored. Any hints?

[Dan Rosenstark]

You can't use setFill, in my experience. I'm using this guy: NSDictionary *fontAsAttributes = @{NSFontAttributeName:font, NSForegroundColorAttributeName:textColor};

[fishinear]

How do you tell drawAtPoint:withAttributes: to use the given context? It looks like it uses the default one, which would likely be incorrect.

[Rob Napier]

@fishinear Why would the default one likely be incorrect? In most cases it's exactly what you want. If you want to change the current context, use the UIGraphics functions to set the context (UIGraphicsPushContext, UIGraphicsBeginImageContext, UIGraphicsBeginPDFContext...)

[fishinear]

Ah, cool, UIGraphicsPushContext was what I was looking for. Thanks.