Make Edit the default interaction mode.

[allemangD]

Working through #178 highlighted some unintuitive behavior behind the Explore and Edit modes. I'm opening this issue for some discussion about changing the default behavior when opening the app.

I also saw some similar confusion from Rusty during his demo regarding #182; he aligned the view to the specimen, but that work was undone once he clicked "Edit". That is similar #178, but has a different root cause. Personally, I've also made the same mistake while debugging.

The orientation of the slice is stored within the annotation; this is how multiple annotations may be on different slices within the same file. When you enter Edit mode, the displayed slice is updated to match the annotation orientation.

In Explore mode the annotation orientation cannot be updated; all annotations are read-only. You can still move the displayed slice, but that is not stored anywhere. Thus when you switch back to Edit mode, the displayed slice is updated to match the (unaltered) orientation of the annotation.

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I think it would be more intuitive to change the default mode to Edit, and remove the default annotation. This way the more intuitive workflow would succeed, without needing to worry about a hidden, default, read-only state.

• Open the program
  • (Scene is empty)
• Add an annotation
  • (Implicitly enter edit mode)
• Align the view
• Place the annotation

Since it seems pretty common to forget to switch the mode before aligning; I expect it might also be common to forget to add an annotation before editing the view. New annotations are already oriented to match the displayed slice, so we would get the inverted workflow for free.

• Open the program
  • (Scene is empty)
• Align the view
• Add an annotation
  • (Implicitly enter edit mode)
  • (Use the displayed orientation)
• Place the annotation

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To do this, I would suggest implementing these changes:

• (1) If any annotation is selected in the sidebar, enter Edit mode for that annotation.
• (2) When an annotation is added, select that annotation and enter Edit mode for it.
• (3) When Explore mode is active, deselect annotations in the sidebar.
• (4) Remove the default annotation from startup; the user must add the desired annotation and implicitly enter edit mode by (2)