Add keyboard shortcut to start/stop drawing annotation

[mvandenburgh]

Pressing n will

• Open the New Annotation dialog if no annotations are selected
• Put the user into or cancel "draw mode" for the current annotation if one is selected

Fixes in part #145

[mvandenburgh]

@manthey coverage is failing - do you usually have tests for things like keyboard shortcuts?

[manthey]

This starts drawing a line. Were you thinking of adding additional keyboard bindings for the other shapes? Or should we have a concept of a recent shape and choose that? And, if so, then we might want another key to cycle through the shapes.

[manthey]

We do test some keyboard shortcuts (e.g., https://github.com/DigitalSlideArchive/HistomicsUI/blob/master/tests/web_client_specs/annotationSpec.js#L327).

[mvandenburgh]

This starts drawing a line. Were you thinking of adding additional keyboard bindings for the other shapes? Or should we have a concept of a recent shape and choose that? And, if so, then we might want another key to cycle through the shapes.

Additional keyboard bindings for each shape would be easiest to implement code-wise and UX-wise, I think. (just adding keyboard shortcuts to each of the shapes' tooltips seems easier than trying to communicate what the recent shape is to the user). I'll try that.

We do test some keyboard shortcuts (e.g., https://github.com/DigitalSlideArchive/HistomicsUI/blob/master/tests/web_client_specs/annotationSpec.js#L327).

Thanks, I'll take a look at those and write some tests for the new shortcuts.

[manthey]

I think using letters that are somehow associated with the shape will be more memorable than using the top right six letters (but I'm willing to be argued out of it). Maybe:
o point
r rectangle
l ellipse
c circle
p polygon
n line

[mvandenburgh]

I think using letters that are somehow associated with the shape will be more memorable than using the top right six letters (but I'm willing to be argued out of it). Maybe: o point r rectangle l ellipse c circle p polygon n line

I don't have a strong preference, but I can see it being easier to remember if they are associated with a letter. I'll change it to those

[mvandenburgh]

I added tests for the new shortcuts. Looks like CI is happy with coverage now.