Re: NSAffineTransform on iOS
On Mon, 09 Apr 2012 15:55:45 +0100, Pascal Harris 45rpmli...@googlemail.com said: And are there any books that you'd recommend that cover these kind of issues, books to assist a Mac OS X developer write for iOS? Yes, see my .sig below for one. :) Since I too came to iOS programming from Mac OS X programming, certain key differences jumped out at me, and are often explicitly noted in the text. m. -- matt neuburg, phd = m...@tidbits.com, http://www.apeth.net/matt/ A fool + a tool + an autorelease pool = cool! Programming iOS 5! http://shop.oreilly.com/product/0636920023562.do ___ 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
NSAffineTransform on iOS
I'm trying to write some code for iOS and Wow! I didn't expect it to be so unfamiliar. Kind of like walking into a familiar city, like London, and discovering that everyone is speaking Dutch and no one speaks English. Weird. I'm slowly getting to grips with the differences and similarities - but I'm a bit perplexed by transforms. As I say, I'm writing a tile based game and the following code works very nicely in Mac OS X: NSGraphicsContext *context = [NSGraphicsContext currentContext]; [context saveGraphicsState]; id transform = [NSAffineTransform transform]; [transform translateXBy:NSMidX(tileFrame) yBy:NSMidY(tileFrame)]; [transform concat]; [self drawTile:tileFrame]; [context restoreGraphicsState]; Unfortunately, my iOS version doesn't work. That isn't to say that it crashes - it just doesn't produce the expected output. CGContextRef context = UIGraphicsGetCurrentContext(); CGContextSaveGState(context); CGAffineTransform transform; CGAffineTransformTranslate(transform, CGRectGetMidX(tileFrame), CGRectGetMidY(tileFrame)); CGContextConcatCTM(context, transform); [self drawTile:tileFrame]; CGContextRestoreGState(context); I'm sure that my error will be obvious to anyone who isn't a complete newb, but I am - so it isn't obvious to me! And are there any books that you'd recommend that cover these kind of issues, books to assist a Mac OS X developer write for iOS? ___ 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
Re: NSAffineTransform on iOS
I think the major source of confusion is that NSAffineTransform is an object, and CGAffineTransform is not; it's a struct. This is really important. :) CGAffineTransform transform; CGAffineTransformTranslate(transform, CGRectGetMidX(tileFrame), CGRectGetMidY(tileFrame)); The first line declares a CGAffineTransform struct, but doesn't initialize it, which means it contains garbage values. The second line takes a garbage affine transform, attempts to translate it, and then ignores the return value. The result is that your call to CGContextConcatCTM is being passed a garbage CGAffineTransform. What you're probably look for is this: CGAffineTransform transform = CGAffineTransformIdentity; transform = CGAffineTransformTranslate(transform, CGRectGetMidX(tileFrame), CGRectGetMidY(tileFrame)); Or more tersely: CGAffineTransform transform = CGAffineTransformMakeTranslation(CGRectGetMidX(tileFrame), CGRectGetMidY(tileFrame)); HTH, Dave On Apr 9, 2012, at 7:55 AM, Pascal Harris wrote: I'm trying to write some code for iOS and Wow! I didn't expect it to be so unfamiliar. Kind of like walking into a familiar city, like London, and discovering that everyone is speaking Dutch and no one speaks English. Weird. I'm slowly getting to grips with the differences and similarities - but I'm a bit perplexed by transforms. As I say, I'm writing a tile based game and the following code works very nicely in Mac OS X: NSGraphicsContext *context = [NSGraphicsContext currentContext]; [context saveGraphicsState]; id transform = [NSAffineTransform transform]; [transform translateXBy:NSMidX(tileFrame) yBy:NSMidY(tileFrame)]; [transform concat]; [self drawTile:tileFrame]; [context restoreGraphicsState]; Unfortunately, my iOS version doesn't work. That isn't to say that it crashes - it just doesn't produce the expected output. CGContextRef context = UIGraphicsGetCurrentContext(); CGContextSaveGState(context); CGAffineTransform transform; CGAffineTransformTranslate(transform, CGRectGetMidX(tileFrame), CGRectGetMidY(tileFrame)); CGContextConcatCTM(context, transform); [self drawTile:tileFrame]; CGContextRestoreGState(context); I'm sure that my error will be obvious to anyone who isn't a complete newb, but I am - so it isn't obvious to me! And are there any books that you'd recommend that cover these kind of issues, books to assist a Mac OS X developer write for iOS? ___ 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/davedelong%40me.com This email sent to davedel...@me.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
Re: NSAffineTransform on iOS
Also keep in mind that iOS defaults to a flipped (or what non-Cocoa people would call normal) coordinate system, with (0,0) at the top left and the Y axis increasing downward. —Jens smime.p7s Description: S/MIME cryptographic signature ___ 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
