I was thinking to myself that it could be handy to be able to control the location of a Marker on the timeline with an expression . That marker could be set to be a trigger for an animation, like Dan shows in his great blog.
is such a "reverse engineering" even possible?
if no, is there another way to trigger an animation with a "checkbox"? instead of a marker?
Expressions can't move anything in the time line. You could certainly use checkbox keyframes (any keyframes actually) as triggers, and the code is very similar to the way you use markers. With checkboxes, it depends on whether you want to use both the "On" and "Off" states as triggers and if you want them to both trigger the same action. I'm not sure what advantage they would have over markers though.
The main reason is that I if I build a Controller Layer/panel, which in I contain all the animation controls I need for a certain comp, then it's comfortable (in my mind anyhow) if I would have also control over the timing of certain animation from the same panel.
regarding what you said, I guess I can use a Checkbox which in the "On" phase is the beginning of the animation. At the same time I can also use a slider control to decide on the exact frame in which I want the animation to start.
if you have a spare moment I will be happy if you could revise your code to achieve the same result but using a checkbox/slider instead.
(I tried myself and failed...)