Refactoring/Enhancements/Fixes

Breaking Changes:
- Removed the `api` parameter; callbacks no longer need to be in a specific class.
- Topbar callbacks now take a chart as an argument (see updated callback examples)
- Removed the `topbar` parameter from chart declaration. The Topbar will be automatically created upon declaration of a topbar widget.
- Removed the `searchbox` parameter from charts. It will be created upon subscribing to it in `chart.events`.
- Removed `dynamic_loading`.
- Removed ‘volume_enabled’ parameter. Volume will be enabled if the volumn column is present in the dataframe.
- Widgets’ `func` parameter is now declared last.
- Switchers take a tuple of options rather than a variable number of arguments.
- `add_hotkey` renamed to `hotkey`
- Horizontal lines now take a `func` argument rather than `interactive`. This event will emit the Line object that was moved.
- Removed the `name` parameter from `line.set`. Line object names are now declared upon creation.

Enhancements:
- Added the `button` widget to the Topbar.
- Added the color picker to the drawing context menu.
- Charts now have a `candle_data` method, which returns the current data displayed on the chart as a DataFrame.
- Fixed callbacks are now located in the `chart.events` object:
    - search (e.g `chart.events.search += on_search`)
    - new_bar
    - range_change
- Added volume to the legend
- Drawings can now be accessed through `chart.toolbox.drawings`
- added the `style` and `name` parameters to `create_line`

Bug Fixes:
- Fixed a bug causing new charts not to load after `exit` was called.
- Refactored rayline placement to ensure they do not move the visible range.
- Fixed a bug causing the visible range to shift when trendlines are moved past the final candlestick.
- Fixed a bug preventing trendlines and raylines on irregular timeframes.
- Fixed a bug causing the legend to prevent mouse input into the chart.

examples/6_callbacks/callbacks.py

@@ -9,39 +9,38 @@ def get_bar_data(symbol, timeframe):
     return pd.read_csv(f'bar_data/{symbol}_{timeframe}.csv')
 
 
-class API:
-    def __init__(self):
-        self.chart: Chart = None  # Changes after each callback.
+def on_search(chart, searched_string):  # Called when the user searches.
+    new_data = get_bar_data(searched_string, chart.topbar['timeframe'].value)
+    if new_data.empty:
+        return
+    chart.topbar['symbol'].set(searched_string)
+    chart.set(new_data)
 
-    def on_search(self, searched_string):  # Called when the user searches.
-        new_data = get_bar_data(searched_string, self.chart.topbar['timeframe'].value)
-        if new_data.empty:
-            return
-        self.chart.topbar['symbol'].set(searched_string)
-        self.chart.set(new_data)
 
-    def on_timeframe_selection(self):  # Called when the user changes the timeframe.
-        new_data = get_bar_data(self.chart.topbar['symbol'].value, self.chart.topbar['timeframe'].value)
-        if new_data.empty:
-            return
-        self.chart.set(new_data, True)
+def on_timeframe_selection(chart):  # Called when the user changes the timeframe.
+    new_data = get_bar_data(chart.topbar['symbol'].value, chart.topbar['timeframe'].value)
+    if new_data.empty:
+        return
+    chart.set(new_data, True)
 
-    def on_horizontal_line_move(self, line_id, price):
-        print(f'Horizontal line moved to: {price}')
+
+def on_horizontal_line_move(chart, line):
+    print(f'Horizontal line moved to: {line.price}')
 
 
 if __name__ == '__main__':
-    api = API()
-
-    chart = Chart(api=api, topbar=True, searchbox=True, toolbox=True)
+    chart = Chart(toolbox=True)
     chart.legend(True)
 
+    chart.events.search += on_search
+
     chart.topbar.textbox('symbol', 'TSLA')
-    chart.topbar.switcher('timeframe', api.on_timeframe_selection, '1min', '5min', '30min', default='5min')
+    chart.topbar.switcher('timeframe', ('1min', '5min', '30min'), default='5min',
+                          func=on_timeframe_selection)
 
     df = get_bar_data('TSLA', '5min')
     chart.set(df)
 
-    chart.horizontal_line(200, interactive=True)
+    chart.horizontal_line(200, func=on_horizontal_line_move)
 
-    chart.show(block=True)
+    chart.show(block=True)