Drawing text with CGContextShowGlyphsAtPoint - how to get font dimensions?

Question

Hoping this is fairly simple. Basically, I'm drawing some text onto an NSView and need to know the "physical" height and width of the glyphs being drawn.

The font is fixed-width so I don't need to worry about kerning, all I need to do is ensure each glyph is centred horizontally and vertically within its "space"

This isn't the actual code but I've re-written it in a way that should make it easier to understand what I'm trying to achieve.

CGFontRef myFontRef = CGFontCreateWithDataProvider(myFontDataProvider);
CGContextSetFont(thisContext, myFontRef);
CGFloat fontSize = 1.0; //will be changeable later
CGContextSetFontSize(thisContext, fontSize);
CGRect charBounds = CGRectMake(x, y, widthPerChar, heightPerChar);
//paint charBounds with background colour
CGFloat textX = x + 2;
CGFloat textY = y + 5;
CGContextShowGlyphsAtPoint(thisContext, textX, textY, (CGGlyph *)displayedString, 1);

If I was able to calculate the width of the displayed glyph it would be easy to work out what textX and textY should be.

Thanks in advance to anybody willing to assist.

Answer 1

Partly worked it out from this code - here's what I came up with:

CGContextSetTextDrawingMode(thisContext, kCGTextInvisible);            
CGContextShowGlyphsAtPoint(thisContext, 1, 1, (const CGGlyph *)"x", 1);
CGPoint postPosition = CGContextGetTextPosition(thisContext);
CGFloat textOffsetX = ((postPosition.x - 1) / 2);
CGFloat textOffsetY = (fontSize * 5);
CGContextSetTextDrawingMode(thisContext, kCGTextFillStroke);

Not a huge fan of doing it like this but it's working for now. At least it can be calculated once for each window resize which isn't too bad.

Thanks for the help though!