depthcharge was: Ignoring pdftex primitives

[Robert Howlett]

Taco Hoekwater wrote:
> 
> David Carlisle wrote:
> 
> It's so much fun ;-)
> For the original author:
> 
>         \pdfimage depth 15pt \noex..... etc
> 
> also works, but
> 
>         \pdfimage depth 15pt\noex....
> 
> doesn't, because the scanner eats one of the \noexpands when trying to
> find the space after "pt"
> 
>         \pdfimage depth 15pt\relax\noex....
> 
> does not work because once again this sets the filename to "", and
> 
>         \pdfimage depth 15pt\noexpand\noex...
> 
> is also OK.
> 
> For David:
> 
> you need three \noexpands because TeX is looking for three keywords in
> a loop that does not end until all three keyword searches return
> "false". You won't need more \noexpands until TeX can do typesetting
> in 3-d or colored rules, I guess. But for other images you need less:
> 
> "widthcharge.png" needs only 1 \noexpand, "heightcharge.png" needs 2
> (but more \noexpands don't do any harm).

\pdfimage \noexpand\noexpand\noexpand\noexpand\empty anything.png

is no good, presumably since after three times through its loop TeX has
decided
there is no width height or depth, and it expects the next thing to be
the
file name.

I've checked that ordinary TeX complains when it encounters
abc \vrule \noexpand\empty height xyz
but not when it encounters
abc \vrule \noexpand\empty width xyz

Surely this can only be interpreted as a bug in TeX!

Bob