qmarker open|solid|brush +|x|-|||o|s|d|<|>|^|v|p|h size
selects a marker. An "open" mark is outlined with the current pen
and filled with white; a "solid" mark is outlined with the current pen
and filled with its color; a "brush" mark is outlined with the current
pen and filled with the current brush (which may be "none").
Marks are: o: circle/disk
+ x: horizontal+vertical or diagonal crosses
- |: horizontal or vertical lines
s d p h: square, diamond, pentagon, or hexagon
< > ^ v: left / right / up / down pointing triangles
The fill style has no effect on +|x|-|| marks.