CODEWITHSUNDEEP
xsltxslt-2.0xsl-foapache-fop
Jhakkaassh
Jhakkaassh

Reputation: 1

Check if <fo:page-number> is even or not using XSLT 2.0

How to check the <fo:page-number> is even or odd using xslt 2.0 Is there any way to use <fo:page-number> inside <xsl:if test="fo:page-number mod 2 = 0">

Upvotes: 0

Views: 678

Answers (2)

Kevin Brown
Kevin Brown

Reputation: 8877

What you ask for cannot be done with a true batch formatter in a single pass. It requires "human" intervention to mark only those places where the break needs to occur and not others.

Also, there is no guarantee that one XSL FO formatter might yield different results than another. Because of the complexities in the way some formatters handle "line tightness" (which is very small squeezing of spaces and characters together to fit text within a line) as well as some supporting kerning and others not as well as many other factors, it is not possible to "pre-predict" whether some paragraph will appear/start on a page or not.

Formatting text in true typography is not merely word-space-word-space ... there are many other factors involved that could change the number of lines in a paragraph between one formatter and another which can easily ripple to a known paragraph existing on an even page in one formatter, yet an odd page in a different formatter.

Then you also need other rules like what if your paragraph using your formatter of choice is the first one on your page in which you wish to break. Do you want a blank page? Maybe, who knows?

The only way to accomplish your task is through a multipass approach that could be implemented such that it is generic to any formatter. You would need to format a whole document (or if you are chunking that document with page masters) at least a chunk that starts and ends in page boundaries. Format it, test your condition on the first paragraph. If it passes (meaning if a break is needed), go back to original content (or modify the XSL FO) and mark some attribute that would result in break-before="page" on that structure. Then repeat the process until you reach the end of the document. Some formatters can provide you the area tree and markers you can put in that tree so that you could do this programmatically and not by eye).

If your document is long and in one page-sequence (say like 3000 pages when formatted) and your break condition is frequent, you may have to repeat the process 700+ times.

As stated, some formatters through their API may allow you to control this programmatically. You can examine the area tree, look for your marker and keep count of pages. You may even be able to start formatting again at the break condition and not start over, but you need to program such things.

Upvotes: 0

Tony Graham
Tony Graham

Reputation: 8068

The XSLT stage generates the XSL-FO that the formatter then makes into pages. So, no, you can't get the current page number when you are generating the XSL-FO.

What do you want to change if it is an even-numbered page?

With XSL-FO, you can set up different page masters for odd and even pages (and more besides). The different page masters can have different margins, and you can set things up so that the formatter will direct different content to headers and footers on even pages than is used on odd pages.

See the 'Page Region and Structure' PDF and FO files in the 'XSL-FO Samples Collection' at https://www.antennahouse.com/xsl-fo-samples#structure

Upvotes: 1

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