Re[3]: [Gnash-dev] Re: gotoAndPlay bug in Gnash

[Udo Giacomozzi]

Hello Eric,

Wednesday, May 9, 2007, 7:05:22 PM, you wrote:
EH> Rewinding to a previous execution state and going to a particular point of
EH> execution are distinct and very different operations.  gotoAndPlay is of
EH> the latter type.  It is not rewinding to some previous state, merely moving
EH> a current execution point.

Your concept is not exactly clear to me, however we need to jump to a
previous point in the time line.



EH> Wait a minute.  Is anything really restored, by which I mean, reverted to a
EH> previous state?

No ActionScript variables, if that's what you mean. However these
effects are possible:

- instances being constructed / appearing (in case they didn't exist
  at the time of the gotoAndXXXX call)
  
- instances being destroyed / disappearing (the opposite)

- instance matrix being modified (assuming the instance already
  existed)
  
- instance color xform being modified (dito)

Don't know about sounds, but I don't see any other effect.
ActionScript is not directly involved except for constructed/destroyed
instances or script code in the target frame.


EH> Or are these instances simply added to the frame as if
EH> GOTO were absent and the frame were duplicated as the next frame?

Nothing is duplicated.


EH> There seems to be an inconsistent story here about what's happening.  When
EH> a GOTO executes, does it restore something (which I would consider 
EH> "something special") or doesn't it ("nothing special")?  I can see that it
EH> might have to display something; fine.  Does this display act like a 
EH> restoration or like an initial display?

Can't follow you, but I think my list above answers your question.


EH> I can understand a desire to avoid recomputation, but _that's_ a caching or
EH> memo issue rather than a behavior-definition one.

Avoiding recomputation is only a side effect. There are too many
special situations we need to keep track. Just look at the updated
wiki page:
http://www.gnashdev.org/wiki/index.php/TimelineControl

Udo