drawArrow function
Draws a line with an arrowhead on top of it.
This function is used to draw a line from the specified start
point to the
end
point using the provided painter
, and it also adds an arrowhead at
the end
point.
canvas
: The canvas on which to draw the arrow.start
: The starting point of the line.end
: The ending point of the line and the location of the arrowhead.painter
: The paint object specifying the line's color, width, and style.
Implementation
void drawArrow(Canvas canvas, Offset start, Offset end, Paint painter) {
final arrowPainter = Paint()
..color = painter.color
..strokeWidth = painter.strokeWidth
..style = PaintingStyle.stroke;
// Draw the line.
canvas.drawLine(start, end, painter);
// Calculate the path for the arrowhead.
final pathOffset = painter.strokeWidth / 15;
final path = Path()
..lineTo(-15 * pathOffset, 10 * pathOffset)
..lineTo(-15 * pathOffset, -10 * pathOffset)
..close();
// Save the canvas state, translate it to the end point, rotate it to match
// the direction of the line, and then draw the arrowhead.
canvas.save();
canvas.translate(end.dx, end.dy);
canvas.rotate((end - start).direction);
canvas.drawPath(path, arrowPainter);
canvas.restore();
}