[xep-support] Behavior of xml:base in font configuration file (3.77)

[Alexander Peshkov]

Hello Eliot,

Currently relative URLs in the xml:base property used in font
configuration file are resolved with respect to location specified by
METRICS property. By default METRICS is set to 'afm' subdirectory of
XEP root. That's why you have such a result. I agree that this
behavior is somewhat awkward and we will change it in the next major
release. In the meantime you can work around this problem by setting
METRICS to the path where fonts.xml is found. In general for font
configuration in XEP 3.x it is recommended to set METRICS to the root
fonts catalogue and then address all font file in fonts.xml by
relative paths.
Actually we have never advertised use of xml:base in fonts.xml :-)

Best regards,
Alexander Peshkov                             mailto:peshkov at renderx.com
RenderX

WEK> I think the behavior of xml:base in font configuration files is 
WEK> incorrect. At a minimum it's both different from what I expected and not 
WEK> useful as currently implemented (in that it doesn't help to make the 
WEK> font configuration file transportable).

WEK> What I need to be able to do is create a font configuration file that 
WEK> can be deployed without knowledge of where either the file itself is put 
WEK> or where it is relative to the XEP installation. In this scenario both 
WEK> the font configuration file and the fonts it references are in 
WEK> consistent locations relative to each other.

WEK> Here's what I have in my font configuration file:

WEK> <fonts xml:base="../lib/fonts/">

WEK> Where the font file is in a directory that is a sibling of the lib/ 
WEK> directory, e.g.:

WEK> dist/config/xep-fonts.xml
WEK> dist/lib/fonts/someefont.ttf
WEK> dist/lib/fonts/afm/Helvetica-BoldOblique.afm

WEK> A typical font specification is:

WEK>     <font name="Helvetica-BoldOblique"
WEK>           afm="afm/Helvetica-BoldOblique.afm"
WEK>           embed="false">
WEK>        <alias name="Helv-BoldOblique"/>
WEK>        <alias name="Swiss-BoldOblique"/>
WEK>     </font>

WEK> I am calling XEP with the FONTLIST set to the location of the 
WEK> xep-fonts.xml file, e.g.:

WEK> XSLDriver -DXEP_HOME=$XEP_HOME
WEK>    -DFONTLIST=/user/local/dist/config/xep-fonts.xml
WEK>    myfile.fo

WEK> When I make the xml:base value an absolute path ending in "lib/fonts" 
WEK> then this font is resolved.

WEK> If I use the above relative xml:base, then I get a failure message like 
WEK> this:

WEK> [error] java.io.FileNotFound exception: 
WEK> /home/xml/XEP/fonts/afm/Helvetica.afm (No such file or directory)

WEK> This suggests that XEP is using the location of the Java JAR file, not 
WEK> the location of the xep-fonts.xml file, as the base for constructing an 
WEK> absolute URL from the relative xml:base value.

WEK> My reading of both the XML Base specs and RFC 2396, on which it depends, 
WEK> suggest that in a case like this the location of the document should be 
WEK> used as the base for resolving relative URIs.

WEK> This is with version 3.77.

WEK> Cheers,

WEK> Eliot


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