Re: CATextLayer question
Re: CATextLayer question
- Subject: Re: CATextLayer question
- From: John Clayton <email@hidden>
- Date: Wed, 14 Nov 2007 07:39:59 +0100
Actually, I'm going to back on up a wee bit.
I am writing an app that composes various bits of media together using
the CAnim system to store the composition model. The CA system has a
really nice fit for this, i.e. layering, beginTime, duration, super/
child relationships, layout mgrs, child positioning relative to parent
- all the kind of stuff that makes modelling media in space *and* time
relatively easy.
For this app, I need to be able to describe my model (i.e. a piece of
text that has a duration of 10 seconds), and then to be able to place
that text into the root CALayer instance with a beginTime of Z (which
is arbitrary).
I'm then using a custom rendering solution that renders a single frame
of any arbitrary CALayer at any given point in time to pick out an
image (based on CALayerRenderer).
Does this mean I'd have to set my root layer beginTime to the
following (note the minus):
( - CACurrentMediaTime() + aTimeThatIWantToRenderAt )
in order to see the frame? Seems so... because the internal
CACurrentMediaTime() is ticking away quite happily in the background,
whereas I want to render at a given point in time, regardless of what
the CACurrentMediaTime() value is.
I will try this out anyway...
--
John Clayton
On 14/11/2007, at 7:13 AM, John Clayton wrote:
Correct, thanks. I modified the program to include a button that
reset the beginTime to the CACurrentMediaTime() value, and then when
I type something into the duration (like 4) the text appears, and
after 4 seconds, fades out.
Thanks for the tip.
--
John Clayton
http://www.coderage-software.com/
On 13/11/2007, at 11:45 PM, David Duncan wrote:
On Nov 13, 2007, at 1:41 PM, John Clayton wrote:
I have an issue with CATextLayer that I'd like to explore. The
basic question is this: why does a CATextLayer that has a
'duration' specified for it, not draw anything?
Because the beginTime attribute is sometime in the past, likely the
distant past. Since the sum of the beginTime and your duration says
that the animation has expired, the layer is hidden. Generally, if
you want to set a layer's duration, you should also set its
beginTime.
--
David Duncan
Apple DTS Animation and Printing
email@hidden
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