Summary

• Fixes chart tooltips being slow to appear or never showing
• Root cause: tooltips used Euclidean pixel distance (50px radius), requiring the mouse to be very close to actual data point markers. With sparse time-series data (points every 15 mins), there are large gaps between markers where no tooltip appears
• Fix: use X-axis (time) proximity as primary filter (80px horizontal threshold), Y-axis distance as tiebreaker for multi-series charts
• Tooltips now appear reliably when hovering at any Y position near a data point's time — standard behavior for time-series charts
• Added try-catch for robustness, reduced throttle from 50ms to 30ms

Test plan

• Launch Dashboard, hover over any chart with data
• Verify tooltips appear promptly and consistently
• Verify tooltips show the correct series name, value, and time
• Test with multi-series charts (e.g., CPU chart with SQL vs Other)
• Verify tooltip disappears when leaving the chart area

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