2010-02-05

# Updating graffle-export to work with OmniGraffle 5

I recently upgraded to OmniGraffle 5, which caused my graffle-export script to break:

\$ graffle.sh ~/git/cwa/figures/analyst.graffle foo.pdf
OmniGraffle Professional 5
/Users/dcreager/git/cwa/figures/analyst.graffle
./graffle.scpt: execution error: OmniGraffle Professional 5 got an error: The document cannot be exported to the "pdf" format. (-50)


(This was first reported to me by Nima Talebi as a ticket on graffle-export’s Github page.)

Before we can understand what error we’re seeing, a little explanation is in order. The core logic of the OmniGraffle exporter is an AppleScript. Unfortunately, AppleScripts are stored in a binary format, so if you go to the Github page, you can’t easily view the contents of the file. The important line of the script is:

save doc as format in file output


This saves an OmniGraffle document (which an earlier part of the script makes sure is open) into a new output file. The output variable is the name of the desired output file, and is taken directly from the graffle.sh command line.

The format variable is what’s causing us problems. This parameter to the save command tells OmniGraffle what format to use for the file it’s about to save. This is how we get our export functionality; we just give it the name of one of the export formats that it supports. The value of our format variable comes from the optional first parameter to the graffle.sh script. Previously, if no value was specified, I used “pdf” as a default.

Now, there’s no real documentation that I’ve been able to find out what values are allowed for this parameter. I came across pdf simply by trial and error. “PDF” also seems to work, as does “PDF vector image”, which is the text that appears in the Format entry of OmniGraffle’s Export dialog box.

Or, to be more accurate, I should say that these values all work in OmniGraffle 4. Once you upgrade to version 5, these values no longer seem to be valid choices for that parameter of the save command — hence the error message. A quick, non-exhaustive test shows that none of these variations work for EPS or SVG, either. The only one that seems to still work is PNG.

So, what are we to do? After looking at several other related AppleScripts on the web, it seems that the as parameter of the save command is optional. After some experimentation, it turns out that if you leave out this parameter, OmniGraffle tries to deduce the correct output format based on the extension of your output filename. So, we change our save command to the following:

if format = "" then
save doc in file output
else
save doc as format in file output
end if


(We also have to modify the graffle.sh wrapper script to not use pdf as a default, but you can see that change on Github.) This lets us export a PDF version of a .graffle file by giving an output filename ending in .pdf, and leaving out the format parameter.

I still have my old copy of OmniGraffle 4, and it looks like this trick works with that version as well. So, this is now the default behavior, regardless of which version you have installed.

It would be nice if there was an accurate list of what values were allowed for the as parameter, but we do have a working solution, at least. The only problem is if you want to export a PDF with a different extension; with this solution, you’d have to export to a .pdf file and then rename it to your new extension. But then again, why would you want to do that?