Make chart mouse hover feel responsive

[ubershmekel]

100 ms causes a 10 fps performance which feels like it's lagging behind your cursor. 30 ms feels too fast and noisy, 50 ms feels snappy yet stable.

#503

[etpinard]

Thanks for the PR 🍻

We'll need some sort of consensus before merging it though.

@alexcjohnson @mdtusz @monfera thoughts?

[monfera]

This looks like good, reasonable fine/tuning, I'm fine with this PR. I do NOT suggest the below, much more heavyweight options for now because any of them is best done as part of a major polish/usability improvement effort.

In the future, we might think of:

• debounce: not showing details when the mouse is in motion
• fade in / fade out: nice thing about it is that a fading trail gives a sense of the data volatility but it's not good for numbers/text that would overlap
• easing: for example, a tooltip box doesn't have to jump to the next point, it may be animated (for which the usual transition time is 50-200ms) - most often, the noise comes not from quickly changing numbers, but changing location as a non-smooth or discontinuous function over time
• motion blur (had to include this one): for example, http://nbremer.github.io/openvis2016/slides/#/fuzzy-code

I think that easing is the easiest of these esp. with D3 but again, this PR is fine as it is.

[mdtusz]

BIG fan of this PR. @monfera - you're right that in the future we should a "softer" visual transition, but this definitely improves the feel of plots.

🍻 @ubershmekel! 💃 from me.

[alexcjohnson]

@ubershmekel 💃 - nice optimization.

@monfera I'm all for enhancements that make it easier to understand the data, or improve aesthetics without compromising understanding. I like the idea of debounce; fade out, when we're not going to show another tooltip; fade in maybe if it's very quick. But I have to say that tooltips easing from one data point to another have always grated on me when I've seen that done in other libraries. Animation has its place in object constancy but elsewhere I feel it impedes understanding the data.

[etpinard]

@ubershmekel Nicely done. You win the PR of the week 🏆

[monfera]

Linking a relating article: http://valhead.com/2016/05/05/how-fast-should-your-ui-animations-be/