[Tex/LaTex] How to make beamer’s alert work in \multiinclude[]

animationsbeamer

Beamer user guide says at p140:

Example: For a more interesting usage
of the ⟨default overlay
specification⟩, consider the following
usage: 

\multiinclude[<alert@+|> +->]{gra}

This will always paint the most recently added part of the
graphic in red (assuming you do not
use special colors in the graphic
itself).

However, a simple test with gra.pdf files (saved from inkscape) doesn't seem to be rendered red at each overlay. The pdf files contain only black lines. No matter what I try, seems every color is a "special color", and beamer does not correctly alert/highlight elements in the pdfs, like in this (correct) example using xfig:

http://p3f.gmxhome.de/fig2mpdf/fig2mpdf.html

What's your experience on this issue? Can I correctly alert pdfs produced by tools like inkscape?

I do not have a minimal example right now, but may supply one a while later. Thanks for any help/hint!

Best Answer

I think that the beamer manual is probably in need of revision here. The \multiinclude macro wraps up the highlighted input using \begin{alertenv} ... \end{aletrenv} (which is how \alert is implemented). Thus the colour only applies to things which LaTeX can make coloured, i.e. where

\begingroup
  \color{red}
   <thing>
\endgroup

works as expected. This is not the case for PDF graphics: I suspect that Till Tantau was thinking of 'graphics' generated by Tikz when he wrote the documentation, where LaTeX can colour the material.

So the bottom line is that you'll have to colour the graphics yourself if they are generated externally.

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