On Sep 22, 2013, at 4:20 AM, Dave <[email protected]> wrote: > > >> On 21 Sep 2013, at 21:38, Markus Spoettl <[email protected]> wrote: >> >> Hi, >> >> I have a UIView on iOS that shares (a lot of) code with an NSView I have on >> OSX. That code relies on a LLO (lower left origin) coordinate system and >> it's not an option to change that. > > I'm in a similar position, in fact I have a lot of code that is ULO based and > a lot of code that is LLO based. If I has only a single wish that would > enable me to change something about Cocoa it would be that it always ULO or > as a second wish that iOS used LLO as well. > > I'd really like to know why LLO was chosen for the Mac in the first place, > and, why in iOS they chose to do the opposite?
Because OS X is derived from NEXTSTEP, which used Display PostScript as its windowing system. PostScript has a lower-left origin because that's how Cartesian coordinate systems are often defined, including those used on plotters. > > Anyone understand why/how this happened? > > Also, given that you have code what is written for both systems, how have > people dealt with this? If you're just drawing using Core Graphics, you can flip the CTM and get the right results. But if you have subviews or sublayers, you're hosed. Just so you know, OS X supports both origins. AppKit exposes -[NSGraphicsContext isFlipped] and -[NSView isFlipped], so coordinate-space agnostic code does a lot of `y = [self isFlipped] ? CGRectGetMinY(…) : CGRectGetMaxY(…)`. --Kyle Sluder _______________________________________________ Cocoa-dev mailing list ([email protected]) 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 [email protected]
