I really hate to ask this ...

Don't. It's a perfectly fair and reasonable question. Yes, I did miss that section before posting.

Essentially, I wasn't looking for it because I didn't know it existed. The Canvas docs are sufficiently large that I tend to search for stuff (Arc, Oval, Line etc.) rather than scrolling through linearly.

I was looking for wherever Tk_GetGash was documented, as directed by the section of the Canvas docs I was referencing. First I searched the Canvas doc and found half a dozen references, but they are all references to it. None with an explanation.

Then I grepped the docs directories and found all the same ones in the Canvas doc, and one other that was also a reference to, not an explanation of either the information or where to find it.

If all those references to Tk_GetDash were links or references to the "Dash Patterns" section, I wouldn't have had the problem :).