javascript - 在 Canvas 边界限制内移动对象

Question

我试图限制 Canvas 内的移动对象，但是在顶部和左侧的限制区域中移动对象时遇到了一些困难，当我将对象缩放得更大时，我也无法限制左侧的移动对象和 Canvas 的顶部

canvas.observe("object:moving", function(e) {
  var obj = e.target;
  // if object is too big ignore
  if(obj.currentHeight > obj.canvas.height || obj.currentWidth > obj.canvas.width) {
    return;
  }

  var halfw = obj.currentWidth/2;
  var halfh = obj.currentHeight/2;
  var bounds = {
    tl: {x: halfw, y:halfh},
    br: {x: obj.canvas.width-halfw, y: obj.canvas.height-halfh}
  };

  // top-left  corner
  if(obj.top < bounds.tl.y || obj.left < bounds.tl.x) {
    obj.top = Math.max(obj.top, bounds.tl.y);
    obj.left = Math.max(obj.left, bounds.tl.x )
  }
        
  // bot-right corner
  if(obj.top > bounds.br.y || obj.left > bounds.br.x) {
    obj.top = Math.min(obj.top, bounds.br.y);
    obj.left = Math.min(obj.left, bounds.br.x)
  }
});

Answer 1

canvas.on('object:moving', function (e) {
  var obj = e.target;
  // if object is too big ignore
  if(obj.currentHeight > obj.canvas.height || obj.currentWidth > obj.canvas.width){
    return;
  }
  obj.setCoords();
  // top-left  corner
  if(obj.getBoundingRect().top < 0 || obj.getBoundingRect().left < 0){
    obj.top = Math.max(obj.top, obj.top-obj.getBoundingRect().top);
    obj.left = Math.max(obj.left, obj.left-obj.getBoundingRect().left);
  }
  // bot-right corner
  if(obj.getBoundingRect().top+obj.getBoundingRect().height  > obj.canvas.height || obj.getBoundingRect().left+obj.getBoundingRect().width  > obj.canvas.width){
    obj.top = Math.min(obj.top, obj.canvas.height-obj.getBoundingRect().height+obj.top-obj.getBoundingRect().top);
    obj.left = Math.min(obj.left, obj.canvas.width-obj.getBoundingRect().width+obj.left-obj.getBoundingRect().left);
  }
});