On 30/04/2010, at 9:08 PM, steven Hooley wrote: >> From your later response it seems like your question is really > regarding drawing strikethroughs and underlines. If so, the strike > through and underline are not part of the glyph or font - they are > just a line drawn from the start point of a range of glyphs to the end > point of a range of glyphs. You cannot draw them piecemeal, a glyph at > a time, and expect them to perfectly match up without overlap or > underlap (apologies for making up a word), as the amount that any 2 > glyphs overlap is particular to those 2 glyhps. ie. The strikethrough > of an 'A' followed by a 'V' would need to be a different length than > that of an 'A' followed by a 'j'.
Not that this will tell you anything about what Cocoa does, but when I had to implement underlines and strikethroughs for text-on-path in DrawKit, I did so by working a line at a time and knocking out any places where descenders would hit the line. For text-on-path, drawing a line per glyph looks absolutely terrible, being straight and not curved, and having gaps where the character curves away from its neighbour. I would imagine that for performance reasons as well as aesthetic, Cocoa draws whole lines for strikethroughs and underlines as well. I did also discover that relying on the values exactly returned by a font didn't always give similar results to Cocoa's underline positioning - I never did quite work out its metrics but arrived at certain fudge factors empirically that gave almost identical results with most fonts. --Graham _______________________________________________ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
