[xep-support] Scaling of images

[G. Ken Holman]

At 2007-10-17 02:42 -0400, Daragh Pender wrote:
>I seem to have found a solution with:
>
><fo:external-graphic src="url({$href})" content-width="scale-to-fit"
>content-height="100%" width="100%" scaling="uniform"/>
>
>it is very particular about quotes and/or double-quotes !!

I'm not sure what you are referring to when you say "it".  There are 
rules for XML that have to be followed.  I note that you didn't 
follow my recommendation for the encoding of the src= attribute and 
I'm not sure why.

You changed the reference from @src to $href and it works ... that's 
based on stylesheet code that you did not include in your original 
post ... but there is one thing remaining that should be left in the 
archive for readers to know.

Changing the reference to the new one you've used, I suggested in my 
earlier post that you use:

     src='url("{$href}")'

IETF RFC 2396 specifically allows left and right parentheses and 
single quotes in URI strings.  As a stylesheet writer one does not 
have control over the URI strings that are being written by the 
authors of the XML.  Therefore stylesheet writers have to protect 
their stylesheets from "breaking" when their users use an arbitrary 
URI sequence.

So, I tell my students the safest way to write the stylesheet is to 
enclose the URI in double quotes because a double quote is not 
allowed in URI syntax according to IETF RFC 2396.  By using double 
quotes, there is no way the stylesheet will choke on a valid URI 
string written by the XML author.

Given that the attribute has to contain double quotes, there are two 
ways this can be specified in XML.  The easiest is above, where the 
attribute delimiters are single quotes.

If you feel compelled to use double quotes for your attribute 
delimiters (and there are some who do and don't like using single 
quote delimiters), then you need to escape the double quotes that 
I've shown above are essential to protect your stylesheet:

    src="url(&quot;{$href}&quot;)"

I think this is a good example of why on the XML committee it was 
decided to build in the &quot; and &apos; entity references for 
well-formed files.

>...there is probably a better way of implementing this -

I had suggested one, yes.  I think readers of the archive should know 
that the one I suggested is safer than the one you used.

>but I can find very little instruction available on the web.

Which parts were you missing?  When you tried "@src" and it didn't 
work, but "$href" did work, I don't think there is anything that 
would have helped ... that decision is based on the structure of your 
input XML vocabulary and your stylesheet use of variables.

I hope this helps!  (And I'm trying very careful not to be accused of 
being grumpy again ... was I gentle enough?  I'm only trying to 
ensure the long-term archive accurately reflects what stylesheet 
writers need to know)

. . . . . . . . . . . . Ken

--
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