I have created a table in xsl-fo like this:
<fo:block margin-top="0.4cm">
<fo:table border-collapse="collapse">
<fo:table-column column-width="15%"
column-number="1" />
<fo:table-column column-width="16%"
column-number="2" />
<fo:table-column column-width="53%"
column-number="3" />
<fo:table-column column-width="16%"
column-number="4" />
<fo:table-header>
<fo:table-row>
<fo:table-cell padding="2px" font-size="7px">
<fo:block text-align="center" font-weight="bold">Column1
</fo:block>
</fo:table-cell>
<fo:table-cell padding="2px" font-size="7px">
<fo:block text-align="center" font-weight="bold">Column2
</fo:block>
</fo:table-cell>
<fo:table-cell padding="2px" font-size="7px">
<fo:block text-align="left" font-weight="bold">Column3
</fo:block>
</fo:table-cell>
<fo:table-cell padding="2px" font-size="7px">
<fo:block text-align="center" font-weight="bold">Column4
</fo:block>
</fo:table-cell>
</fo:table-row>
</fo:table-header>
<fo:table-body font-size="9px">
<fo:table-row>
<fo:table-cell padding="2px" border="0.5pt solid #cfcfcf">
<fo:block text-align="center">
12345678910111213
</fo:block>
</fo:table-cell>
<fo:table-cell padding="2px" border="0.5pt solid #cfcfcf">
<fo:block text-align="center">
some text
</fo:block>
</fo:table-cell>
<fo:table-cell padding="2px" border="0.5pt solid #cfcfcf">
<fo:block text-align="left">
some text
</fo:block>
</fo:table-cell>
<fo:table-cell padding="2px" border="0.5pt solid #cfcfcf">
<fo:block text-align="right">
some text
</fo:block>
</fo:table-cell>
</fo:table-row>
</xsl:for-each>
</fo:table-body>
</fo:table>
</fo:block>
<fo:block padding-top="40px">
some text
</fo:block>
</fo:block>
The String "12345678910111213" in Column1 is written over the borders of its table-cell.
How can I force a line break in the table-cells of this column after a specific number of characters in the String?
By injecting a zero-width space ​ at the desired location.
This technique is very useful for indicating multiple possible break locations for a contiguous string, even if the room is big enough to accommodate the entire string, because the zero-width spaces are invisible. If, however, a break is needed, the rendering knows to break the string at a space, and a zero-width space is treated as a space.
In the classroom I use the example of a URI string, where adding a zero-width space after every / will render as a regular URI (without visible spaces) and yet will break at the desired points if necessary.