It's something that could be automated, easier or harder depending on the
tools and processes you use for maintaining your graphics. However, I can
understand the desire to avoid this type of solution, regardless. So, some
alternatives...
Do you have control of the DTD? If so, you could add an attribute to
control the width and use a variant of Suzanne's approach to have the FOSI
fill it in when it is empty and you're in screen mode (leaving it as-is for
print). If you want to avoid your authors messing with the attribute,
there are ways of hiding it, or you could add a completely separate
element, also configured as a graphic element in the DCF, which you can
hide from element lists so only the FOSI uses it.
If you don't have control of the DTD, you might be able to do the above
with a FOSI pseudo-element, though I don't know if the DCF will let you set
that up or not. Alternatively, you could maintain a separate version of
the DTD that is only used during authoring. This version would be the same
except it would add the width attribute and provide a default value
appropriate for screen display.
-Brandon 🙂
