ENH: Link hover crosshairs across plots

Fixes #133

Author: kernc

backtesting/_plotting.py

@@ -15,6 +15,7 @@
 )
 from bokeh.plotting import figure as _figure
 from bokeh.models import (
+    CrosshairTool,
     CustomJS,
     ColumnDataSource,
     NumeralTickFormatter,
@@ -192,7 +193,7 @@ def plot(*, results: pd.Series,
         x_axis_type='linear',
         plot_width=plot_width,
         plot_height=400,
-        tools="xpan,xwheel_zoom,box_zoom,undo,redo,reset,crosshair,save",
+        tools="xpan,xwheel_zoom,box_zoom,undo,redo,reset,save",
         active_drag='xpan',
         active_scroll='xwheel_zoom')
 
@@ -600,6 +601,8 @@ def __eq__(self, other):
                                                   code=_AUTOSCALE_JS_CALLBACK))
 
     plots = figs_above_ohlc + [fig_ohlc] + figs_below_ohlc
+    linked_crosshair = CrosshairTool(dimensions='both')
+
     for f in plots:
         if f.legend:
             f.legend.location = 'top_left' if show_legend else None
@@ -616,6 +619,7 @@ def __eq__(self, other):
         f.min_border_right = 10
         f.outline_line_color = '#666666'
 
+        f.add_tools(linked_crosshair)
         wheelzoom_tool = next(wz for wz in f.tools if isinstance(wz, WheelZoomTool))
         wheelzoom_tool.maintain_focus = False