与画布上的上一个笔画不同

Question

下面的代码没有画出一个圆，并且再画了一下（当我从HTML页面按run时），它将先前绘制的函数绘制为红色，并且仍然没有按预期显示该圆。

我提到了this question，但仍然无法解决我的问题。

var canvas = document.getElementById("mycanvas");
var c = canvas.getContext("2d");
var c1 = canvas.getContext("2d");
canvas.height = $canvasDiv.innerHeight();
canvas.width = $canvasDiv.innerWidth();

function crtanjeGrede(l)
{
  var oslonac1 = parseInt(l) + 30;

  c.beginPath();
  c.fillRect(30, 30, l, 5);

  c.beginPath();
  c.moveTo(oslonac1, 35);
  c.lineTo(oslonac1 + 25, 45);
  c.lineTo(oslonac1 - 25, 45);
  c.lineTo(oslonac1, 35);
  c.moveTo(oslonac1 + 25, 50);
  c.lineTo(oslonac1 - 25, 50);
  c.stroke();
	
  c.beginPath();
  c.moveTo(30, 35);
  c.stroke();
  c.lineTo(55, 45);
  c.stroke();
  c.lineTo(5, 45);
  c.stroke();
  c.lineTo(30, 35);
  c.stroke();
	
  c.moveTo(30, 55);
  c.lineTo(30, 400);
  c.moveTo(oslonac1, 55);
  c.lineTo(oslonac1, 400);
  c.closePath();
  c.stroke();
}

function crtanjeGerbera1(q){
  var gerber1 = parseInt(q) + 30;
  c1.beginPath();
  c1.arc(q, 32, 44, 0, 2 * Math.PI); // length is inserted by user (variable q) and
  // the starting point Y has to be directly on rectangle (has to be lined over the
  // previous maded rectangle, that's why I wrote 32)
  c1.fillStyle = 'red';
  c1.fill();
  c1.lineWidth = 1;
  c1.strokeStyle = 'red';
  c1.stroke();
  c1.closePath();
}

crtanjeGrede(duzina);
crtanjeGerbera1();