app: allow depth chart zoom up to +/- 100%

[buck54321]

Zoom was constrained to +/- 50% of the mid-gap rate, but could accommodate double that width without major changes to other parts.

Allowing more is possible, but there are tradeoffs for > 100%, as either a) the charts will need to be reconfigured to allow an off-center mid-gap, or b) the chart will expose a negative scale on the left.

For now, I'm hoping this is an improvement and enough to resolve #553.

[chappjc]

Sort of fixes it. I can zoom out more, (but not all the way to get very high/low orders for the reasons you mentioned), but it zooms back in a bit automatically after a moment.

moments later:

Unlike with the previous random zoom changes, this does not seem to coincide with epoch notes.

[JoeGruffins]

In my opinion the zoom is enough.

I'm not by any means a good trader, and I don't spend much time looking at charts. Just a normal user. And the exchange I normally use is Binance. I almost exclusively use their mobile app, and their depth map does not zoom very much at all. It really isn't a problem for me.

It would be nice to have the candlesticks graph though, which is probably much more useful for traders to see trends.

However, the zoom does pop back automatically for me too, which is jarring.

[buck54321]

Should be good now. You'll still see the zoom level change ever so slightly if you're at 200% and the mid gap price changes, forcing a re-centering, but that's different. The bug you were seeing is fixed.