On 29.08.2016 at 17:46 Ken Thomases wrote: > On Aug 29, 2016, at 9:55 AM, Andreas Falkenhahn <andr...@falkenhahn.com> > wrote:
>> I'm migrating some code from ATSUI to Core Text. It's pretty raw stuff, i.e. >> it does >> all the layouting itself and only uses ATSUI/Core Text to draw single lines >> of text to >> raw pixel buffers and obtain measurements. >> The raw pixel data emitted by ATSUDrawText() and CTLineDraw() seems to match >> exactly. >> Also, the measurements returned by ATSUI/Core Text seem to match most of the >> time. Thus, >> it's usually the case that the pixels in text generated using ATSUI match >> exactly the >> text pixels generated by Core Text. >> That's nice to see and I didn't expect that but it activated a perfectionist >> tendency >> in me so that I ran some hardcore tests with lots of different texts printed >> in different >> sizes and layouts to see if I could find a deviation between ATSUI and Core >> Text. And I >> did ;) It happens only in very rare cases but sometimes the cursor advance >> returned by >> ATSUI is a pixel off from the cursor advance returned by Core Text. But only >> very >> seldomly. However, in complex layouts this can then accumulate and lead to >> an entirely >> different layout if wordwrapping is involved. > First, this has nothing to do with Cocoa and so isn't appropriate for > Cocoa-Dev. Oops, sorry, I didn't know that there was a separate mailing list for Core Text. I'll ask again over there if we don't manage to solve it here. > That said, when drawing strings, there are the functions > CGContextSetShouldSubpixelPositionFonts() and > CGContextSetAllowsFontSubpixelPositioning(). Those can be used to > turn off sub-pixel positioning of glyphs. It may be that ATSUI > wasn't capable of that and so turning it off gets you the same positioning as > ATSUI. > There doesn't seem to be a direct way to ask Core Text for the > measurements corresponding to that drawing mode. So, you may need > to ask your CTLine for its CTRuns and then ask the CTRun for the > individual glyph advances. Hmm, I don't understand. The only CTRun APIs that take a CGContextRef are CTRunGetImageBounds() and CTRunDraw(). I'd have to use CTRunGetAdvances(), though, but this function doesn't accept a CGContextRef so I don't see how I should implement your suggestions... -- Best regards, Andreas Falkenhahn mailto:andr...@falkenhahn.com _______________________________________________ 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: https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
