renderReticle method

void renderReticle(Canvas canvas, Size viewportSize)

Renders the reticle (crosshair) at screen center with dwell feedback: an accent progress ring, tick marks, and a selection flash.

Implementation

void renderReticle(Canvas canvas, Size viewportSize) {
  final center = Offset(viewportSize.width / 2, viewportSize.height / 2);
  const baseRadius = 4.0;
  final dwellRadius = baseRadius + dwellProgress * 8;
  final hasTarget = _gazeTargetId != null;

  // Outer ring (dwell progress) with color ramp white -> accent.
  if (dwellProgress > 0) {
    final ringColor = Color.lerp(
      const Color(0xFFFFFFFF),
      const Color(0xFF2E90FA),
      dwellProgress,
    )!;
    canvas.drawArc(
      Rect.fromCircle(center: center, radius: dwellRadius),
      -1.5708, // Start at top
      dwellProgress * 6.2832, // Full circle
      false,
      Paint()
        ..color = ringColor
        ..style = PaintingStyle.stroke
        ..strokeWidth = 2,
    );

    // Tick marks at quarter positions for readable progress.
    final tickPaint = Paint()
      ..color = ringColor.withValues(alpha: 0.7)
      ..strokeWidth = 1.5;
    for (var i = 0; i < 4; i++) {
      final angle = -1.5708 + i * 1.5708;
      final inner = Offset(
        center.dx + (dwellRadius - 3) * math.cos(angle),
        center.dy + (dwellRadius - 3) * math.sin(angle),
      );
      final outer = Offset(
        center.dx + (dwellRadius + 3) * math.cos(angle),
        center.dy + (dwellRadius + 3) * math.sin(angle),
      );
      canvas.drawLine(inner, outer, tickPaint);
    }
  }

  // Selection flash: expanding ring fading out right after dwell-select.
  if (_selected) {
    canvas.drawCircle(
      center,
      dwellRadius + 4,
      Paint()
        ..color = const Color(0x662E90FA)
        ..style = PaintingStyle.stroke
        ..strokeWidth = 3,
    );
  }

  // Hover halo when a target is gazed but dwell has not started.
  if (hasTarget && dwellProgress == 0) {
    canvas.drawCircle(
      center,
      baseRadius + 4,
      Paint()
        ..color = const Color(0x40FFFFFF)
        ..style = PaintingStyle.stroke
        ..strokeWidth = 1,
    );
  }

  // Center dot
  canvas.drawCircle(
    center,
    hasTarget ? 3 : 2,
    Paint()..color = const Color(0xCCFFFFFF),
  );
}