Camera is reset when graph is updated

[jacomyal]

When a new graph prop value is given to some SigmaContainer instance, the camera is reset. I was expecting the camera to remain the same.

The reason is visible here:

react-sigma/project/packages/core/src/components/SigmaContainer.tsx

Lines 82 to 86 in 9b55729

	if (containerRef.current !== null) {
	const sigGraph = graph ? (typeof graph === "function" ? new graph() : graph) : new Graph();
	instance = new Sigma(sigGraph, containerRef.current, { allowInvalidContainer: true, ...sigmaSettings.current });
	}
	setSigma(instance);

The fix would be to copy the camera state if an instance exists already, and set it to the new instance's camera right after it's created. Something like:

const cameraState = instance ? instance.getCamera().getState() : null;

// [...] existing code that remounts the instance

if (cameraState) instance.getCamera().setState(cameraState);