perspective-viewer-d3fc-heatmap shows tooltips for the wrong cell

[thoueland-drw]

Bug Report

Steps to Reproduce:

1. Go to https://perspective.finos.org/ (default SPARKGRID Market Monitor dataset)
2. Switch to the Heatmap
3. Remove the "Order By" clause (not required, but stops the columns from rearranging)
4. Mouse-over the heatmap

Expected Result:

The tooltip should show for the cell the cursor is currently in, i.e. change at the row/cell boundaries.

Actual Result:

The tooltip changes from one cell to another around the center of cells, instead of at the edges.

E.g. it changes from the "Homer" row to the "Lisa" row in the middle of the "Homer" row, rather than at the boundary between the two rows.

Environment:

https://perspective.finos.org/ as of 2023-08-14, so presumably Perspective v2.4.0

Chrome Browser - Version 115.0.5790.170 (Official Build) (arm64)

Additional Context:

It looks like the closest corner to the mouse cursor is used, and then the cell associated with that corner is displayed, rather than the cell the cursor is in.

Happens on any browser and any heatmap.

Also separately reproduced in an internal project, built with dependency versions:

    "@finos/perspective": "^2.3.1",
    "@finos/perspective-viewer": "^2.3.1",
    "@finos/perspective-viewer-d3fc": "^2.3.1",
    "@finos/perspective-viewer-datagrid": "^2.3.1",