drawTriangle function
Draw the Triangle shape marker
Implementation
void drawTriangle(Path path, double x, double y, double width, double height) {
path.moveTo(x - width / 2, y + height / 2);
path.lineTo(x + width / 2, y + height / 2);
path.lineTo(x, y - height / 2);
path.lineTo(x - width / 2, y + height / 2);
path.close();
}