On Sep 28, 2007, at 11:27 AM, Scott Thompson wrote:
On Sep 28, 2007, at 12:53 PM, Wade Tregaskis wrote:
I suppose should be no problem to letting the size of the view
grow to infinity - as long as I'm not drawing any more of it. I
guess I just have to get over the mental hurdle.
Note that there is a practical limit to the size of an NSView,
beyond which all sorts of funkiness occurs (visible as drawing
artefacts) as a consequence of CoreGraphics using floats, and
thus having very much finite precision. It depends on your
particular code as to when exactly you'll see problems, but I
wouldn't let any view (inside a scrollview) get more than
10,000,000 pixels in any dimension.
(I know that sounds huge, but it's pretty easy to naively hit if
you're not careful)
Are you sure about the magnitude of your dimension there? I was
under the impression (potentially mistaken) that the problems
started around 10,000 (ten thousand) instead of 10,000,000 (10
million).
Nope, it's somewhat less than 10 million but much much larger than
10 thousand. That's about the point where the "float" type no
longer has enough precision to represent individual pixels.
An IEEE binary float has 1 bit of sign, 8 bits of exponent, and 23
bits of fractional value. Which means you should be able to
exactly represent pixel values between +8,388,608 and -8,388,608.
(2^23)
Oops! My mistake. I forgot that the first bit of the fractional value
is assumed and is always 1. So you can actually accurately represent
individual pixels up to 2^24: 16.7 million.
