Bokeh background rectangle that covers an entire plot including panable area

bokeh_datetime_axis.py

def d64(start, end):
    """ find the midpoints of two dates and return as numpy int64"""
    midpoint = start + (end-start)/2
    print(start, end, midpoint)
    return np.datetime64(midpoint).astype('datetime64[ms]').view(np.int64)
    
xrange = Range1d(q.start_dt,q.end_dt)
plot = figure(plot_width=850, plot_height=100, x_range=xrange)
plot.xaxis[0].ticker = DatetimeTicker()

mini, maxi = df.start.min(), df.finish.max()

plot.rect(
    x = d64(mini, maxi), 
    y = plot_height/2,
    width=(maxi-mini).total_seconds()*1000,
    height = plot_height,
    color = '#%02x%02x%02x' % (r, g, b),
)