Summary

This PR addresses issue #12179: "Charts with a large number of hidden datasets perform poorly".

When many datasets are present and most are hidden, Chart.js was still performing expensive parsing, stacking, and min/max calculations for hidden datasets. This caused noticeable lag in scenarios like time-tracking charts with 50+ datasets.

Changes

• _resyncElements now skips processing for datasets where meta.hidden === true.
• getMinMax returns { min: Infinity, max: -Infinity } for hidden datasets, avoiding unnecessary calculations.
• Minor refactoring to ensure that hidden datasets do not affect stacks or parsing loops.

Benefits

• Significant performance improvement for charts with many datasets where only a subset is visible.
• Reduces CPU usage and lag in common use cases such as toggling dataset visibility.
• Maintains correct functionality for visible datasets and stacked charts.

Test

• Verified charts with multiple hidden datasets no longer experience lag on updates.
• All existing unit tests pass, and no visual regressions observed.

Issue

Closes #12179