JavaScript Custom Cursor Chart

This example serves as an example for creating a custom cursor for XY charts.

Custom cursors can be required for different purposes - like major structural changes or very application specific styling requirements.

Custom cursors are most importantly based on LCJS methods that allow solving nearest data points in series from any supplied location.
Custom user interactions and data point solving require solid understanding of different coordinate systems in web and LCJS, which is the primary reason this example exists;

// Add custom action when user moves mouse over series area.
chart.onSeriesBackgroundMouseMove((_, event) => {
  // `event` is a native JavaScript event, which packs the active mouse location in `clientX` and `clientY` properties.
  const mouseLocationClient = { x: event.clientX, y: event.clientY };

  // Before using client coordinates with LCJS, the coordinates have to be translated relative to the LCJS engine.
  const mouseLocationEngine = chart.engine.clientLocation2Engine(
    mouseLocationClient.x,
    mouseLocationClient.y
  );

  // Now that the coordinates are in the correct coordinate system, they can be used
  // to solve data points, or further translated to any Axis.

  // (1) Translate mouse location an Axis.
  const mouseLocationAxis = translatePoint(
    mouseLocationEngine,
    // Source coordinate system.
    chart.engine.scale,
    // Target coordinate system.
    series[0].scale
  );

  // (2) Solve nearest data point from a series to the mouse.
  const nearestDataPoint = series.solveNearestFromScreen(mouseLocationEngine);
  // `nearestDataPoint` is either `undefined`, or an object 
  // which contains a collection of information about the solved data point.
});

In this example, the custom cursor visual is created with internal LCJS user interface components, showcasing a multi-cursor which displays one X coordinate and several Y coordinates at once.

The result table is created by combining LCJS layout elements with UITextBox elements - this allows any kind of value grid to be created.

More custom cursor examples can be found by looking for "cursor" tag in the Interactive Examples gallery - for example, using HTML & CSS for an animated result table or connecting to an UI framework.