Re: Scrolling Text Algorithm for a Screen Saver
Re: Scrolling Text Algorithm for a Screen Saver
- Subject: Re: Scrolling Text Algorithm for a Screen Saver
- From: Alastair Houghton <email@hidden>
- Date: Mon, 30 Oct 2006 12:26:54 +0000
On 30 Oct 2006, at 09:34, Doug Fort wrote:
Hi,
I'm working on a screen saver. It involves scrolling text across the
screen. I'm using the simplest algorithm I could think of: calls to
NSString drawAtPoint:withAttributes: with the point moving a fixed
offset at each call to animateOneFrame. This works Ok at low scrolling
speeds, but at higher speeds (i.e. a larger offset), the motion
appears jerky.
I'm working on improving my code to minimize the amount of computation
in animateOneFrame. However, if anyone can suggest a better algorithm
for scrolling text, I'd appreciate it.
Using NSString's drawing methods will be inefficient because it will
re-do the text layout every time. You should probably look at using
the Cocoa Text system's NSLayoutManager object to do the layout once
and then you can render the string over and over again with much
lower overhead.
An alternative to that might be to render it once into a bitmap, and
scroll the bitmap across the display instead. That approach would
also mean you could use OpenGL if you wanted rather than Quartz.
Kind regards,
Alastair.
--
http://alastairs-place.net
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