The interaction is fine for me, just not very discoverable. We will have to document it somehow.

Anyway, nobody raised the issue about the exact value in the tooltip (except me) so another sensible alternative is to do nothing.

But since we have to possibility to do something, even not ideal, that is better than nothing 😉

+1 even if the interaction is not discoverable.

Okay, so I've had another look at the implementation, and I have concerns with:

• the arbitrary middle-click interaction interfering with other interactions (we don't currently allow panning with middle click in @h5web/lib, but we might in the future, for instance, or consumers might choose to develop their own custom middle-click interaction)
• the tight coupling with TooltipMesh, which makes customising the interaction (button, modifier key, etc.) and persisting the setting between dataset/visualisation challenging.

Here is another approach that consists in simply adding a toggle to the line and heatmap toolbars (and their equivalents for complex numbers):

I'm not super psyched about adding a control to the toolbar, but at least we get persistence and discoverability out of the box, and no risk of conflicting interactions.

Not sure it's easy to grasp what the "exact" button does since there is no immediate visible feedback.

What about showing the exact value after a delay without mouse move (like for help tooltips)?
No need for an extra button nor to use a mouse interaction.

That's a nice idea as well, though it might be a bit tricky to find a timing that feels reasonable while not being too distracting. There's also the idea of showing the exact value in a status bar of sorts, but this would reduce the space available for the visualization.

As discussed offline, it appears that none of the ideas explored so far are 100% conclusive, so the decision is to remain with the status quo for the time being. I'm going to close this PR, as well as #1646, since we did implement exact notation in the Matrix vis, which was the core request of the issue.