Add CoordSysLassoSelector for free-form, even-odd coord-space selection

[Copilot]

This PR adds a new interaction primitive for CoordSysRenderer: drag-to-draw free-form lasso selection in coord space, finalized on mouse release and non-editable thereafter. The selected region is represented as Path2D with WIND_EVEN_ODD so self-intersections resolve by boundary parity (contains(...) behaves correctly for odd-crossing interior).

• New selector class

  • Introduces CoordSysLassoSelector in hageldave.jplotter.interaction.kml.
  • Class hierarchy: CoordSysLassoSelector extends CoordSysViewSelector implements KeyListener.
  • Default key mask is VK_L (customizable via constructor KeyMaskListener).

• Selection lifecycle + rendering

  • Keymask + press inside coord area starts a new lasso and clears prior finalized selection.
  • Drag appends points in coord space and renders live outline with a provisional close segment.
  • Release finalizes the closed outline, marks selection as persistent/non-editable, and emits areaSelected(Path2D).
  • Degenerate lassos (<3 points) are discarded.

• Input handling details

  • Right-click clears via clearLasso().
  • ESC clears via dedicated escListener registered in register() / removed in deRegister().
  • Cursor is coordinated via CursorCoordinator only:
    • keymask + selection: HAND_CURSOR
    • keymask + no selection: CROSSHAIR_CURSOR
    • otherwise: release cursor request

• Path semantics + drag decimation

  • Final path construction uses Path2D.Double(Path2D.WIND_EVEN_ODD) and closePath().
  • Drag point decimation applies a >2px AWT-distance threshold to reduce near-duplicate samples.
  • clearLasso() fully resets overlay/render/state and triggers areaCleared().

new CoordSysLassoSelector(canvas, coordsys) {
    @Override
    public void areaSelected(Path2D selectedArea) {
        // selectedArea uses WIND_EVEN_ODD
        // selectedArea.contains(x, y) handles self-intersections by odd crossing rule
    }
}.register();

Original prompt

Overview

Implement a new CoordSysLassoSelector class in hageldave.jplotter.interaction.kml that provides free-form lasso selection for the coordinate view of CoordSysRenderer. The user drags the mouse to draw an arbitrary closed shape; on mouse release the shape is finalised and not editable.

File to create

jplotter/src/main/java/hageldave/jplotter/interaction/kml/CoordSysLassoSelector.java

Class hierarchy

CoordSysLassoSelector extends CoordSysViewSelector implements KeyListener

CoordSysViewSelector is in the same package and provides: canvas, jPlotterCanvas, coordsys, overlay (CompleteRenderer), areaBorder (Lines), keyMaskListener, register(), deRegister().

Interaction model

User action	Effect
Key mask + press mouse button inside coordsys area	Clears any previous lasso; starts recording lasso points
Key mask + drag	Continuously appends cursor position (coord-space) to the lasso path; renders live outline with a provisional "close" segment back to start
Release mouse button	Closes path; fires areaSelected(Path2D); shape is final
Right-click	Clears lasso (clearLasso())
ESC	Clears lasso (clearLasso()) via a KeyAdapter escListener registered in register()

Key implementation details

State fields

protected boolean isDragging = false;
protected boolean hasSelection = false;
protected final List<Point2D.Double> lassoPoints = new ArrayList<>();
protected final Lines lassoLines = new Lines();
protected boolean isLassoInOverlay = false;

Point decimation in mouseDragged

Only append a new point if its AWT pixel distance from the previously recorded point is > 2px. This avoids thousands of near-duplicate points during slow/still drags.

Path construction — WIND_EVEN_ODD

private Path2D calculateSelectedArea() {
    Path2D path = new Path2D.Double(Path2D.WIND_EVEN_ODD);
    path.moveTo(lassoPoints.get(0).x, lassoPoints.get(0).y);
    for (int i = 1; i < lassoPoints.size(); i++)
        path.lineTo(lassoPoints.get(i).x, lassoPoints.get(i).y);
    path.closePath();  // automatically closes back to start
    return path;
}

Using WIND_EVEN_ODD means self-intersecting shapes are handled correctly: path.contains(x, y) returns true only if a ray from the point crosses the boundary an odd number of times.

mousePressed

• Guard: keyMaskListener.areKeysPressed() AND click is inside coordsys.getCoordSysArea().
• If right-click OR hasSelection is true: call clearLasso() and return.
• Otherwise: set isDragging = true, clear lassoPoints, add first coord-space point, add lassoLines to overlay if not already there.

mouseDragged

• Guard: isDragging must be true.
• Clamp the AWT point to coordsys.getCoordSysArea() (same clamping logic as CoordSysViewSelector).
• Transform clamped AWT point → coord-space via coordsys.transformAWT2CoordSys.
• Decimation check: only add if AWT distance from last recorded AWT point > 2px.
• Rebuild lassoLines: clear all segments, add segments for consecutive lassoPoints, add one preview-close segment from last point back to lassoPoints.get(0) using colorScheme.getColor2() or a distinct color.
• Call areaSelectedOnGoing(calculateSelectedArea()) and jPlotterCanvas.scheduleRepaint().

mouseReleased

• Guard: isDragging must be true.
• Set isDragging = false.
• If lassoPoints.size() < 3: call clearLasso() and return (degenerate selection).
• Rebuild lassoLines final outline (solid close segment, same color as rest of outline).
• Set hasSelection = true.
• Call areaSelected(calculateSelectedArea()) and jPlotterCanvas.scheduleRepaint().

clearLasso()

public void clearLasso() {
    lassoLines.removeAllSegments();
    if (isLassoInOverlay) {
        overlay.lines.removeItemToRender(lassoLines);
        isLassoInOverlay = false;
    }
    lassoPoints.clear();
    isDragging = false;
    hasSelection = false;
    CursorCoordinator.get(canvas).requestCursor(null, this);
    jPlotterCanvas.scheduleRepaint();
    areaCleared();
}

Cursor

• mouseMoved: if key mask pressed + hasSelection → HAND_CURSOR; if key mask pressed + no selection → CROSSHAIR_CURSOR; else release cursor via CursorCoordinator.get(canvas).requestCursor(null, this).
• Also implement keyPressed / keyReleased from KeyListener to call the same cursor-update logic.
• Use CursorCoordinator.get(canvas).requestCursor(...) throughout (never set cursor directly on canvas).

register() / deRegister()

• register(): call super.register(), then add escListener and this (as KeyListener) to canvas if not already present.
• deRegister(): call super.deRegister(), then remove escListener and this.
• escListener is a KeyAdapter field: VK_ESCAPE → clearLasso().

Abstract / overridable callbacks

// Final closed path; WIND_EVEN_ODD. path.contains(x,y) handles self-...

</details>



<!-- START COPILOT CODING AGENT SUFFIX -->

*This pull request was created from Copilot chat.*
>