Hi,

I plot a time serie, along with a WheelZoomTool to zoom in & out (on the x_axis).

I’m trying to auto scale the y_range based on the line plot displayed.

```
import bokeh
import numpy as np
import pandas as pd
import bokeh.plotting
time_series = pd.Series(np.random.random(1000) - .49).cumsum().to_frame('data').rename_axis('ts').reset_index()
source_ref = bokeh.plotting.ColumnDataSource(data=time_series)
source_disp = bokeh.plotting.ColumnDataSource(data=time_series)
""" Define tools """
pan = bokeh.models.PanTool(dimensions='width')
wheel = bokeh.models.WheelZoomTool(dimensions='width', maintain_focus=True)
figure = bokeh.plotting.figure(title='Performance Report',
x_range=bokeh.models.Range1d(time_series.index[0], time_series.index[-1],
min_interval=15,
bounds=(time_series.index[0], # set limit to range
time_series.index[-1])),
tools=[pan, wheel],
active_drag=pan,
active_scroll=wheel,
y_axis_label='Plot',
x_axis_label='Time')
figure.line(x='index', y='data', source=source_disp)
figure.x_range.js_on_change('end',
bokeh.models.CustomJS(args={
# 'figure': figure,
'y_range': figure.y_range,
'source': source_ref,
'source_disp': source_disp},
code=
"""
let i = Math.max(Math.floor(cb_obj.start), 0);
let j = Math.min(Math.ceil(cb_obj.end), source.data['data'].length);
let max = Math.max.apply(null, source.data['data'].slice(i, j));
const ref = source.data;
const data = source_disp.data;
data["index"] = ref["index"].slice(i, j);
data["ts"] = ref["ts"].slice(i, j);
data["data"] = ref["data"].slice(i, j);
source_disp.change.emit();
console.log("y_range end" + y_range.end);
y_range.end = max;
y_range.change.emit();
console.log("y_range end" + y_range.end);
console.log("end callback");
"""
))
bokeh.plotting.show(figure,
filename=filepath)
```

Here we can see that when I zoom in, the y_range scale does not adjust accordingly