I am using Apache FOP version 0.95. Furthermore I am using xsl-fo to
generate pdf out of Matlab (matlab generates an xml-file and I use a
xsl-fo file as style sheet)

I don't know how to adjust the width of a next block to the previous
block. I have an external graphic in a block and want the next block
to have the same size as the block containing the external graphic.

There are no such semantics in XSL-FO 1.1 that I
can think of.  And there is no feedback loop to
your transformation to tell you what the width is.

The only time I've seen a width change based on
content is with a side float, and even then
putting more text than the width of the graphic
would simply widen the float area.

Some XSL-FO tools have an intermediate format
that you might be able to exploit to determine
and massage the values needed.  But nothing I
know of is standardized in this regard.

If your graphic's intrinsic size is maintained as
metadata somewhere you could use that information
to establish the width of the block, but there
are no facilities in XSLT with which to do this with the actual image file.

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