Keeping the Cache Directory consistent

First up I'd like to explain when you'll be needing a new printout of a diagram and when you won't. Forcing dvilj to make a new printout is simply a matter of deleting the obsolete printout file by hand. Determining when to do this is basically very simple:

• You need a new printout when you change the diagram's magnification (using the scale command) or change its cropping values (using the crop command). Likewise a new printout is needed if the diagram itself has changed, of course.
• You don't need a new printout if the diagram has merely changed position. It's one of the truly wonderful aspects of PCL that you can place raster graphics anywhere on the page.

dvilj can't know if you've changed a diagram's scale or crop values. If you've done either of these you should delete the diagram's printout from the cache manually to make sure a new printout is created the next time you're printing your document.
Although dvilj compares time stamps this only reliably detects if you've updated a diagram. Copying files usually means that the copy inherits the time stamp of the original, so in case you've replaced a diagram with another you should delete the diagram's printout by hand as well.
If you remember those points you shouldn't have any problems with this cacheing mechanism.