Ruler annotations disappear when cycling through tools

If annotations are drawn with the ruler, then the tool is changed using "\", the annotations disappear until the tool is cycled back for to the ruler.

This also holds true for ruler workflows ( #102 ). That is, if a ruler step is specified for part of a workflow, subsequent steps wont have the ruler annotations.

Reproduce the issue by drawing ruler annotations, changing tools with "\\", and checking whether the annotations return only after cycling back to the ruler. Compare this with the ruler workflow described in issue #102; done means annotations remain visible after tool changes and through subsequent workflow steps.

Written by the indexing model from the issue text.