WIP: Allow for persistence in Cytoscape component.

demos/usage-persistence.py

@@ -0,0 +1,47 @@
+"""
+An example to show how to use persistence. After loading data, refreshing
+the page should not loose the cytoscape data nor the selection of nodes/edges.
+Persistence should be set to:
+- local
+- session
+- memory
+Read more about persistence here: https://dash.plotly.com/persistence
+"""
+import dash
+from dash.dependencies import Input, Output
+from dash.exceptions import PreventUpdate
+import dash_cytoscape as cyto
+import dash_html_components as html
+
+
+elements = [
+    {'data': {'id': 'one', 'label': 'Node 1'}, 'position': {'x': 50, 'y': 50}},
+    {'data': {'id': 'two', 'label': 'Node 2'}, 'position': {'x': 200, 'y': 200}},
+    {'data': {'source': 'one', 'target': 'two', 'label': 'Node 1 to 2'}}
+]
+
+layout = {'name': 'grid'}
+
+app = dash.Dash(__name__)
+app.layout =  html.Div([
+    html.Button('Load data', id='bt-load'),
+    cyto.Cytoscape(
+        id='cytoscape',
+        layout=layout,
+        # persistence=True
+    ),
+])
+
+@app.callback(
+    Output('cytoscape', 'elements'),
+    [Input('bt-load', 'n_clicks')]
+)
+def load_elements(_):
+    ctx = dash.callback_context
+
+    if not ctx.triggered:
+        raise PreventUpdate
+    return elements
+
+if __name__ == '__main__':
+    app.run_server(debug=True)