Displaying distances, angles from measure tool

It occurred to me that it would be quite a nice feature if, when atoms are selected using the measure tool, the distance, angle, or dihedral concerned are displayed on the molecule as a dotted line or curve, with the relevant value as an annotation, rather than in the corner as currently.

I found this issue which is similar but seems more geared towards permanent labelling rather than just temporary display.

If the measure tool renders measurements on-molecule, perhaps then some shortcut like double clicking or Ctrl+LClick could be the way to make those labels persist.

This is functionality I have actually used myself in Mercury which could be very useful to have eventually (>2.0).

@matterhorn103 Perhaps with a toggle between to use either Angstroms (the more traditional unit) and pm (seems to be more frequently used in biochem, a hunch) when displaying distances, as e.g. in Jmol?

Though speaking of such, somewhere in QIII/QIV 2023 Jmol got an optional scale (adjustable in appearance and unit) which obviously is more suitable in the non-perspective projection (both Jmol and Avogadro allow to use). To replicate the illustration below, launch it, and issue on its proper command line (File → Console)

load $pyridine;
color scale white;
scale angstroms;

Instead of scale angstroms; one equally may issue scale pm; or (large proteins in mind) scale nm;. One can reposition the scale along abscissa and ordinate (e.g., scale angstroms 0% 40%), too.

I had a student play around with scale bars a while ago. It works okay for your benzene case, but didn’t seem to work so well in more general cases. No matter the perspective / projection, it’s misleading for parts of the molecule far from the camera.

There’s already some code support in the bond-centric tool for displaying temporary captions on the molecule. It’s worth trying.

Yes. That request is more for the label render code to enable more general annotations (e.g., not just atoms and residues). I’ve added some code for bond labels internally.

I agree, a choice between Angstrom and picometres is definitely something we should put in the planned settings menu.