comments on the graphLayout hack

Author: alexcjohnson

dash-renderer/src/components/error/CallbackGraph/CallbackGraphContainer.react.js

@@ -195,6 +195,13 @@ function CallbackGraph() {
         cy.nodes().each(n => {
             positions[n.id()] = n.position();
         });
+
+        // Hack! We're mutating the redux store directly here, rather than
+        // dispatching an action, because we don't want this to trigger a
+        // rerender, we just want the layout to persist when the callback graph
+        // is rerendered - either because there's new profile information to
+        // display or because the graph was closed and reopened. The latter is
+        // the reason we're not using component state to store the layout.
         profile.graphLayout = {
             name: 'preset',
             fit: false,

dash-renderer/src/reducers/profile.js

@@ -38,6 +38,9 @@ const profile = (state = defaultState, action) => {
             updated: [id],
             resources: state.resources,
             callbacks: state.callbacks,
+            // graphLayout is never passed in via actions, because we don't
+            // want it to trigger a rerender of the callback graph.
+            // See CallbackGraphContainer.react
             graphLayout: state.graphLayout
         };