Re: How can I implement labels without the overhead of an NSTextField?

FROM : Henry McGilton
DATE : Mon Dec 13 19:09:17 2004

On Dec 13, 2004, at 9:21 AM, Guy English wrote:

> On Mon, 13 Dec 2004 08:35:55 -0800, Henry McGilton
> <<email_removed>> wrote:

>> I just performed a simple experiment . . .

> Cool, I was going to try it out myself this evening. :)
>
> I think it can still be improved a little though ...
>
> I think you can eliminate the background buffer:
>
> In the init:
> Load the original background, make a copy.
> (if you need the original you can keep it otherwise release it)
> Generate all the strings. I'd use NSAttributedStrings, and draw those
> directly into the copy.
> Lock the image once, draw all your strings, then unlock it.
> In your NIB you would have a scroll view with an NSImageView inside it.
> Set the imageView size to the size of your background.
> Set the imageView image to the image you've just generated.
> You're all done.
>
> I think this will be a little faster because it eliminates an extra
> copy during scrolling. (you don't need to copy from the backbuffer, to
> the view, then to the screen)
> It also moves the initial rendering hit to the init method and, by
> locking only once, and using the attributed strings directly, I think
> it'll be a little faster.


Yes, very good.  If the original person's requirements are as
you described, this would be a much better way to go about it.
As I said, my code was flanged up quickly just as a proof of
concept.

As another demonstration of buffering, one of my Protractors
applications
in one of its view modes, draws 160 string labels around the periphery
of a circle.  So not only are the labels being drawn at specific points,
but the label origins are being translated and rotated as well.  The
double buffering makes any redrawing un-noticeable.

>
> I think this method does fall apart at some point - I seem to remember
> there is a cap on the usable size of an NSImage. It's big but it is
> there.


You are correct, but I could not figire out (even via Google
and Mamasam) what the limits are.  There are some image cache
limitations I believe.  Windows appear to limit sizes to around
16,000 pixels on a side.  A full-colour view of this size would
be around 128 megabytes.

    Cheers,
       ........  Henry


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  Henry McGilton, Boulevardier |    Trilithon Software
    Objective-C/Java Composer  |    Seroia Research
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