Major The attribute draw:enhanced-path (19.145) defines the drawing, which the element <draw:custom-shapes> shows.
Such enhanced-path can have several sets. A new set starts after the command N (endpath). A set ends when there are no more commands or it ends with a command N.
Each set consists of sub-paths. A sub-path starts with an explicit command M (moveTo) or with command B, U or V (diverse arcs), which have an implicit moveTo. A sub-path ends with the start of the next sub-path or when the set ends.
There exists a command Z (closepath). It does, "Close the current sub-path by drawing a straight line from the current point to current sub-path's initial point."
The line style for the shape can specify draw markers. That are attributes draw:marker-end (20.143) and draw:marker-start (20.146).
ODF 1.3 does not specify which of the lines in an enhanced-path gets a marker.
Problems:
1.
If an enhanced-path consists of several sets, is then each set handled separately in regard of markers or not? [The sets are handled separately in regard to stroke and fill, so that a set is drawn in front of previous sets and covers those.] Examples: E,F,G,H
2.
If a set consists of several sub-paths, does each of the sub-paths get both marker-start and marker-end? Or does only the first sub-path gets a marker-start and the last sub-path gets a marker-end? Examples: C,D,E
3.
If a sub-path is "closed" by a command Z and it is the only sub-path in the set, does it get a marker-start? Does it get a marker-end, and if yes, on which point? Examples: A,F,G
4.
If a sub-path is "closed" by a command Z and there exists further segments after the "closed" one, does the last of those segments get a marker-end? Does the "closed" sub-path gets marker? Examples: C,H
5.
If one set has a sub-path which is "closed" by command Z and another set has no "closed" sub-path, is then the behavior for the "closed" one different from cases 3 and 4? Examples F,G,H
6.
Is the behavior for cases with "first point of sub-path = last point of sub-path" different from "closed" sub-path? Examples A versus B, C versus D
PowerPoint cannot use marker declarations but uses a default arrow head. Therefore I have made different shapes for marker-start and marker-end. Otherwise they cannot be distinguished in PowerPoint.