Loader / onFirstRender callback for GraphCanvas

[Edouard-Tby]

When integrating GraphCanvas into React/Next.js applications, there can be a noticeable delay between the component mounting and the graph being fully rendered. This can lead to a poor user experience, particularly in SSR/Next.js apps, where users may see a blank area before the graph appears.

Currently, there is no documented or reliable way to detect when the graph has finished its initial render.

Proposed Solution:
Providing an official callback or loader API would allow developers to display a loading state until the graph is fully rendered, avoiding visual glitches and improving perceived performance.

For example, a new prop could be added:

<GraphCanvas
  ...
  onFirstRender={() => setGraphReady(true)}
/>

This would signal when the graph has completed its first render, enabling developers to conditionally show a loader or perform other actions.

Any thoughts on this? Would love to hear if the team thinks this would be a useful addition.

[amcdnl]

Happy to accept this PR.