Simple line graph function

[PartialVolume]

@AndreRenaud

Hi, hope all's well with you.

I'm thinking about a new piece of information I'd like to add to the ShredOS PDF reports. Basically a plot of disk throughput in MB/s over time as shown in the example below.

In your opinion, is this something that's doable as a function in PdfGen.

I've not spent any time yet looking at your code but just wondered whether you think it's possible.

Although I write a lot of code for nwipe so am familiar with C I would need to spend some time understanding your code and how it generates varies objects etc if I was going to add such a function.

[AndreRenaud]

All the primitive aspects of that are present I think. But PDFGen doesn't really have support for these higher-level concepts. I think a graph function wouldn't be a good fit inside PDFGen itself, it feels too high level for such a low level library. But it should be possible to build a function that sites on top of it.

Dashed lines aren't supported at the moment, but that could be added.

[PartialVolume]

Yes, I see what you mean, basically it should be possible to write a function that uses all the available existing primitive, basically line drawing and vertical and horizontal text for the axis. Like you say the only thing missing is the dashed lines.

I'm also considering using something like gnuplot to create the graph as a PNG or jpg and insert that as an alternative method. It would be a lot less work, however it would be yet another dependency on nwipe which I'm trying to avoid.

I like the idea of a higher level C function.

Is the dashed line something you would be able to add to pdfGen sometime in the future? If not, would you accept a PR.

BTW, I'm in no hurry, it's just something I'd like to add maybe later in the year. Just in an early planning stage.

[AndreRenaud]

Adding dashed/dotted liens should be doable inside PDFGen. I'm ok to accept a patch, or have a look at that myself. I believe the pdf standard supports specifying a line pattern that it repeats, (as opposed to a dashed line being manually calculated and drawn as a series of separate short lines).

[AndreRenaud]

Yep, line patterns were basically almost already supported. I've added a new generic pdf_add_line_pattern - #174

[PartialVolume]

Wow, that was quick, thanks for adding that. That's really useful, I'll start with the graph function for nwipe and let you know what it looks like in due course.

[PartialVolume]

@AndreRenaud Thanks Andre, that's much appreciated. I put together a function to be included in nwipe that creates a suitable throughput graph using PDFGen and shows the typical saw tooth speed change as the heads move from outer to inner cylinders. The example test data simulates a disc drastically slowing down on a specific cyclinder but only the verification read pass. I've more work to do on integrating it into the nwipe PDF code but this solves a big chunk of it.

Once again, thank you for you help and quick response.

nwipe_report.pdf

[AndreRenaud]

That looks really good. Nicely done.

[PartialVolume]

Thanks 👍