Buffer mark line and line-height info?

[cornell@unix1.cs.umass.edu (Matthew Cornell)]

I need the line height of a fred-dialog-item given a buffer mark but I
can find no functions for returning it. (Is this due to fixed lines
going away in a future release?) So I thought I could compute it by
using fred-line-vpos and using the mark's line and the preceding line
but I cannot find any functions that return a mark's line! I thought
these would be common needs but the documentation doesn't acknowledge
them. I expected to find MARK->LINE-NUMBER and
LINE-NUMBER->LINE-HEIGHT functions. I'd appreciate any help on this.

matt

(Inspecting fred-items I see FRECs (fred records, I expect) and
fr.lineht "fields" but I don't know how to access them. Of course
using these data structures violates modularity.)