Auto-scale Y-axis for indicators when zooming kernc#356

Author: zlpatel

backtesting/_plotting.py

@@ -523,6 +523,12 @@ def __eq__(self, other):
             colors = colors and cycle(_as_list(colors)) or (
                 cycle([next(ohlc_colors)]) if is_overlay else colorgen())
             legend_label = LegendStr(value.name)
+            
+            indicator_max=value.df.max(axis='columns')
+            indicator_min=value.df.min(axis='columns')
+            source.add(indicator_max, f'indicator_{j}_range_max')
+            source.add(indicator_min,f'indicator_{j}_range_min')
+            
             for j, arr in enumerate(value, 1):
                 color = next(colors)
                 source_name = f'{legend_label}_{i}_{j}'
@@ -609,6 +615,12 @@ def __eq__(self, other):
                           source=source)
     if plot_volume:
         custom_js_args.update(volume_range=fig_volume.y_range)
+    
+    indicator_ranges = {}
+    for idx,indicator in enumerate(indicator_figs):
+        indicator_range_key = f'indicator_{idx}_range'
+        indicator_ranges.update({indicator_range_key:indicator.y_range})
+    custom_js_args.update({'indicator_ranges':indicator_ranges})
 
     fig_ohlc.x_range.js_on_change('end', CustomJS(args=custom_js_args,
                                                   code=_AUTOSCALE_JS_CALLBACK))