Mac Developer (Australia): Mac Example -- Drawing Strings with Cocoa

Source code

A source code example of how to use Cocoa to to draw strings using 4 different methods. This is a very simple application of the string class, attributed string class, glyph class and text layout manager..

An XCode project implementing this algorithm can be downloaded here...

Theory

No theory!

The source code that implements this follows:

/*
 ----------------------------------------------------
 The drawing is done here when requested by the
 Cocoa framework. 
 */
- (void)drawRect:(NSRect)rect
{
  NSString* label = NULL;
  NSPoint labelLocation;
  
  NSRect bounds = [self bounds];
  labelLocation.x = bounds.size.width/2;
  labelLocation.y = bounds.size.height/2;
  
  switch(mLayoutMode)
  {
    case eBezierPathCharacterMode:
    {
      // Begin: USE_BEZIER_PATHS
      label = @"Bezier Path Character Mode";
      // Get a font
      //NSFont* font = [NSFont boldSystemFontOfSize: 12];
      // Get a Bezier path
      NSBezierPath* glyphPath = [NSBezierPath bezierPath];
      NSFont *font = [NSFont fontWithName:@"Helvetica" size:100.0];
      NSGlyph glyph = [font glyphWithName: [label substringToIndex: 1]];
      [glyphPath moveToPoint: labelLocation];
      [glyphPath appendBezierPathWithGlyph: glyph inFont: font];
      [glyphPath stroke];
      // End: USE_BEZIER_PATHS
      break;
    }
    case eBezierPathStringMode:
    {
      // Begin: USE_BEZIER_PATHS
      label = @"Bezier Path String Mode";
      // Get a font
      //NSFont* font = [NSFont boldSystemFontOfSize: 12];
      // Get a Bezier path
      NSBezierPath* glyphPath = [NSBezierPath bezierPath];
      NSFont *font = [NSFont fontWithName:@"Helvetica" size:100.0];
      [glyphPath moveToPoint: labelLocation];
      // Build glypth array
      int stringCount = [label length];
      NSGlyph* glyphs = NULL;
      glyphs = (NSGlyph*)malloc(sizeof(NSGlyph)*stringCount);
      int stringIndex = 0;
      for(stringIndex = 0; stringIndex < stringCount; stringIndex++)
      {
        NSString* singleCharacter = [label 
		           substringWithRange: NSMakeRange(stringIndex, 1)];
        glyphs[stringIndex] = [font glyphWithName: singleCharacter];
      }
      // Add glyphs to path
      [glyphPath appendBezierPathWithGlyphs: glyphs 
	                               count: stringCount inFont: font];
      [glyphPath stroke];
      free(glyphs);
      // End: USE_BEZIER_PATHS
      break;
    }
    case eStringDrawingMode:
    {
      // Begin: USE_STRING_METHOD
      label = @"String Drawing Mode";
      // Draw a string
      [label drawAtPoint: labelLocation withAttributes:NULL];
      // End: USE_STRING_METHOD 
      break;
    }
    case eCentredStringDrawingMode:
    {
      // Begin: USE_ATTRIBUTED_STRING_METHOD
      label = @"Centred String Drawing Mode";
      NSAttributedString* aLabel = [[NSAttributedString alloc] 
	               initWithString: label];
      NSSize textBox = [aLabel size];
      labelLocation.x -= textBox.width/2;
      labelLocation.y += textBox.height/2;
      // Draw a string
      // Note 1: for a string use 
	  // (but the size message used above does not work)
      //[label drawAtPoint: labelLocation withAttributes:NULL];
      //[label drawInRect: bounds withAttributes:NULL];
      // Note 2: for an attributed string
      [aLabel drawAtPoint: labelLocation];
      //[aLabel drawInRect: labelLocation];
      [aLabel release];
      // End: USE_ATTRIBUTED_STRING_METHOD 
      break;
    }
    case eLayoutManagerMode:
    {
      // Begin: USE_LAYOUT_MANAGER
      label = @"Layout Manager Mode";
      // Initialise NSLayoutManager for drawing glyphs
      NSTextStorage* textStorage = [[NSTextStorage alloc] initWithString: label];
      NSLayoutManager* layoutManager = [[NSLayoutManager alloc] init];
      NSTextContainer* textContainer = [[NSTextContainer alloc] init];
      [layoutManager addTextContainer: textContainer];
      [textContainer release];
      [textStorage addLayoutManager: layoutManager];
      [layoutManager release];
      // End: USE_LAYOUT_MANAGER

      // Draw glyphs
      #define DRAW_ENTIRE_STRING
      #ifdef DRAW_ENTIRE_STRING
        // To draw entire string
        NSRange glyphRange = [layoutManager 
		         glyphRangeForTextContainer: textContainer];
      #else // DRAW_ENTIRE_STRING
        // To draw just a string range
        NSRange charRange;
        NSRange actualCharRange;
        charRange.location = 0;
        charRange.length = 1;
        NSRange glyphRange = [mLayoutManager 
		       glyphRangeForCharacterRange: charRange 
			   actualCharacterRange: &actualCharRange];
      #endif // DRAW_ENTIRE_STRING
      [self lockFocus];
      [layoutManager drawGlyphsForGlyphRange: glyphRange atPoint: bounds.origin];
      [self unlockFocus];
      // End: USE_LAYOUT_MANAGER
      break;
    }
  }
}
/*
 ----------------------------------------------------
 */
	  

Comments or corrections welcome. Send an email to farad'aty'farad.com.au.

An XCode project implementing this algorithm can be downloaded here...