Access shadowCanvas from outside

[lansheng8929]

The ForceGraph instance internally maintains a shadowCanvas for hidden color mapping.
Currently, it’s not possible to access this canvas or its context from outside the library.
Exposing it would allow developers to read pixel data for advanced interaction features.

likeconst shadowCanvas = fg.getShadowCanvas(); const shadowCtx = shadowCanvas.getContext('2d');

[vasturiano]

@lansheng8929 thank for reaching out.

The shadow canvas is really meant to be an internal part of the module so I'm not sure about the usefulness of exposing it externally. Though actually currently you can access it as a work around if you hook into the nodePointerAreaPaint since that provides the shadow canvas context in its callback parameters.

But in any case, can you describe an interaction feature that would require access to this internal element? Perhaps there's another way to achieve it.

[lansheng8929]

I register color codes for nodes manually, like this:

const colorTracker = new ColorTracker() // my new colorTracker
const shadowColor = colorTracker.register({ type: "Plus", d: node });
if (!shadowColor) return;

Then, on mouse move, I need to detect the object using:

const indexColor = shadowCtx.getImageData(mousePos.x, mousePos.y, 1, 1).data;
const obj = colorTracker.lookup(indexColor);

But without access to inner shadowCtx, this is seem not possible.
I could create a separate shadowCtx myself, but that would be redundant and out of sync with the library’s internal rendering flow.

[vasturiano]

@lansheng8929 the library is already doing all of this for you, and making available when objects are moused over via .onNodeHover and onLinkHover methods for instance. So the part I'm missing is why you'd have to re-do this externally.

In any case, if indeed needed it is possible to gain access to the shadow canvas context via the nodePointerAreaPaint method, as mentioned earlier.