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Re: How to properly flip a UIView's coordinate system
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Re: How to properly flip a UIView's coordinate system


  • Subject: Re: How to properly flip a UIView's coordinate system
  • From: Dave <email@hidden>
  • Date: Mon, 23 Sep 2013 12:52:26 +0100

On 22 Sep 2013, at 16:18, David Rowland <email@hidden> wrote:

>
> On Sep 22, 2013, at 4:20 AM, Dave <email@hidden> wrote:
>
>>
>> On 21 Sep 2013, at 21:38, Markus Spoettl <email@hidden> 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?
>>
>> Anyone understand why/how this happened?
>
> The earliest interface was the Teletype machine. It used a roll of low-grade paper and could print 80 characters on one line. Carriage return moved the print head to the first column, line feed moved the paper up one line.
>
> The first electronic terminals were often "glass teletypes" with 80 columns and 24 rows. The cursor could be placed anywhere, and the convention was line 1 at the top and line 24 at the bottom. I believe that is where the inverted coordinates began. Bitmapped screens mimicked the TTY. Later creations like OpenGL respected the older, mathematical model, and we are now caught between.

No, I worked on these early teletype emulators, they had 0,0 (e.g. VT100 and friends) as top left on the ones that could address the cursor!.

Dave


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References: 
 >How to properly flip a UIView's coordinate system (From: Markus Spoettl <email@hidden>)
 >Re: How to properly flip a UIView's coordinate system (From: Dave <email@hidden>)
 >Re: How to properly flip a UIView's coordinate system (From: David Rowland <email@hidden>)

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