draw method

void draw(Canvas canvas, Size size, Graph graph)

Draws the graph of the function on the given canvas with the provided size and graph settings.

Implementation

void draw(Canvas canvas, Size size, Graph graph) {
  // Pre-calculate constants
  final double leftLimit =
      -((size.width / 2) - graph.focusPoint.x) / graph.gridStep;
  final double rightLimit =
      ((size.width / 2) + graph.focusPoint.x) / graph.gridStep;
  final double halfHeight = size.height / 2;

  // Pre-compute points
  final List<Offset> precomputedPoints = [];
  for (double i = leftLimit; i < rightLimit; i += 0.005) {
    final double y = function(i) * graph.gridStep;
    precomputedPoints.add(Offset(i * graph.gridStep, -y));
  }

  List<Offset> path = [];
  bool isContinue = false;
  int counter = 1;
  for (var point in precomputedPoints) {
    // Combine checks for visibility
    if (point.dy.abs() < halfHeight) {
      if (!isContinue) {
        // No need to check for negative counter
        path.add(precomputedPoints.elementAt(max(0, counter - 2)));
        isContinue = true;
      }
      path.add(point);
    } else {
      if (isContinue) {
        path.add(point);
        isContinue = false;
        canvas.drawPoints(PointMode.polygon, path, paint);
        path = [];
      }
    }
    counter++;
  }
  // Draw the last path if any
  if (isContinue) {
    canvas.drawPoints(PointMode.polygon, path, paint);
  }
}