modifying Z-order of slide images at runtime

[David McFarlane]

I got curious, so I took a quick look into this.  Short story:  No 
streamlined way to modify Slide sub-object z-order at run time, 
although one might do this with some careful coding.  Details...

I fired up good old EP1 to make a simple test program and look at the 
generated source code.  I added a Slide, then added a SlideText and a 
SlideImage object to the Slide, with the SlideImage in *front* of the 
SlideText.  The relevant lines in the generated source code (under 
InitObjects) go

     Slide1.States.Item("Default").Objects.Add Slide1_SlideImage, "Image1"
     ...
     Slide1.States.Item("Default").Objects.Add Slide1_SlideText, "Text1"

I then moved the SlideImage *behind* the SlideText, then the relevant 
lines of code went

     Slide1.States.Item("Default").Objects.Add Slide1_SlideText, "Text1"
     ...
     Slide1.States.Item("Default").Objects.Add Slide1_SlideImage, "Image1"

Based on this, it looks like the z-order from front to back 
corresponds to the order of objects in the associated 
SlideStimCollection object.  (IOW, if you think about it, E-Prime 
draws Slide sub-objects in reverse order of their position in the 
SlideStimCollection.)  I did not verify this any further, I leave 
that to others.

If this is correct, then one might modify the z-order at run time by 
using inline code to directly manipulate the objects in the 
SlideStimCollection.  I leave this as an exercise (and if anyone does 
this, please post back with your results!).

As a workaround, if one has to consider only a few z-orders, then one 
might make several SlideStates on the Slide, one SlideState for each 
different z-order.  One could then use an attribute reference to 
select the SlideState with the desired z-order at run time, possibly 
with no code at all.  It might be hard, however, to maintain the 
parallel but independent SlideStates during development.

-----
David McFarlane
E-Prime training 
online:  http://psychology.msu.edu/Workshops_Courses/eprime.aspx
Twitter:  @EPrimeMaster (https://twitter.com/EPrimeMaster )

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At 1/16/2014 11:32 AM Thursday, JACanterbury wrote:
>Hi Alon,
>
>Hopefully you found out how to do this. If so, could you post the answer?
>
>Thanks,
>
>John

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