Snaplines in OpenOffice Impress

Joe Gregorio

I give a lot of presentations and Slide:ology is one of the best books I've read on the subject. One of the things that I learned was setting up a grid system in your presentation software using snap lines, which not only gives you a much cleaner layout on the page but it also ensures that the elements you place on the slides are consistent from page to page, which is less distracting for the audience. Slide:ology covers two variations on such grids, the simple rectangle and a Fibonacci based grid.

And now we run headlong into the software problem; my presentation software of choice, OpenOffice, has made the decision to store snapline information with each individual presentation. Not only that but there is no way to import or export a snapline configuration. Which means that adding snaplines to an already built presentation, or changing the grid layout on a presentation, requires manually placing each snapline, along with using a calculator to determine positions, which is incredibly tedious. Until today.

Laziness, impatient and hubris are the three great virtues of a programmer, and I'm way too lazy and impatient to fiddle with snaplines more than a couple times, so I wrote a Python script ( to add snaplines to an OpenOffice Impress presentation. The source is located here on Google code hosting.

$ python --help
Usage: [options] 

Adds grid lines of various geometries to OpenOffice Impress 
Presenations. Always creates a new file with the grid lines, never
overwrites the original file.

  -h, --help            show this help message and exit
  -f MxN, --fibonacci=MxN
                        Fibonnaci grid of MxN cells
  -r MxN, --rectangular=MxN
                        Rectangular grid of MxN cells
  -m MARGIN, --margin=MARGIN
                        Margin, in units of inches NNin or centimeters NNcm
 is very careful to not modify your original file. If you run:

$ python --fibonacci=5x5 --margin=0.25in MyPreso.odp

It will create a copy of the presentation, grid-MyPreso.odp, that has the specified snaplines.

This was bit more tedious to write than I expected, first because the snaplines locations don't seem to be part of the Impress format that got standardized, so there was a tiny bit of discovery involved in how they are specified. I then had to go through the same discovery process to figure out the dimensions of the master page which you need to calculate the correct location for the grid lines. Finally I had to deal with OpenOffices file format. While OpenOffice serializes its data into a format that can be consumed by an XML parser, OpenOffice itself does not use XML. Merely opening an XML file, modifying it, and then serializing it back to XML isn't guaranteed to make it consumable by OpenOffice. I'm not sure if it was unhappy about changing the namespace prefixes, or if it was a QName problem, but Python's minidom was the only XML library that I found that could placate OpenOffice.

Last note, the code is hosted in, which is just a project of small scripts of mine that to are too small to require their own standalone project. I got the idea from someone, but for the life of me I can't remember who, but thanks to them for the idea.

Update: First patch.

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