add_movie corrupts powerpoint file when a non-openxml feature is used in animations

[flavianh]

When a non-openxml feature is used in animations, Powerpoint wraps the <p:timing> element in a <mc:AlternateContent>.
For example, setting Bounce end to true:

(see enclosed file: file_with_bounce.pptx )

However, python-pptx assumes that <p:timing> is at the root of <p:sld> and creates a new <p:timing>.

This results in a powerpoint file that has the form:

<p:sld>
  ...
  <mc:AlternateContent>
    <mc:Choice>
       <p:timing>
         ... (timing without video)
       </p:timing>
    </mc:Choice>
    ...
  </mc:AlternateContent>
     <p:timing>
       ... (video timing)
     </p:timing>
</p:sld>

The file is then detected as corrupt and deleted.

I can make the fix, but I would need to know where I can find a standard way to account for AlternateContent in the lib?

Thanks

[MartinPacker]

I added mine to the slide.element in md2pptx. If you search for the definition and use of the function addSlideTransition in my code you'll see what I mean.

However, I also would like to understand what would be closer to the heart of python-pptx in this matter.

(Very secondarily, extensions to that code's capability are something I'd contemplate. But I don't actually use transitions in my day job, though I built md2pptx (and mdpre) for my daily needs.)

[flavianh]

@MartinPacker the animation is added externally through Powerpoint in my case, and this is intentional in my workflow. I think this is different from slide transitions too, because slide transitions are transitions between slides, and animations are within the slide itself. I don't know the office open xml spec very well, but animations are specified in a single <p:timing> element (or multiple, when using features out of the standard).