javascript - fabric.js - 在鼠标移动时结束自由绘图模式

Question

我有一个应用程序允许用户在有限的时间内在织物 Canvas 中绘图。时间结束后，我想结束绘图模式，将画好的图保存为图片。

我的问题是，如果用户仍在绘图(拖动鼠标)时时间结束，则绘图将消失(再次单击 Canvas 后)。

下面的 fiddle 示例显示了我制作的应用程序，产生问题的步骤是:

1. 运行 fiddle，立即开始绘图。
2. 3 秒后超时事件发生，自由绘图模式结束。绘图将停止。
3. 再次单击 Canvas 并拖动鼠标。
4. 绘图将消失。

代码示例:

var canvas = new fabric.Canvas("c",{backgroundColor : "#fff"});
canvas.isDrawingMode = true;
canvas.freeDrawingBrush.color = "green";
canvas.freeDrawingBrush.width = 4;

setTimeout(stop_drawing, 3000);

function stop_drawing() {
    canvas.isDrawingMode = false;
}

fiddle 示例:

https://jsfiddle.net/usaadi/808x5d20/1/

Answer 1

您可以模拟 library 中发生的事情:

_onMouseUpInDrawingMode: function(e) {
  this._isCurrentlyDrawing = false;
  if (this.clipTo) {
    this.contextTop.restore();
  }
  this.freeDrawingBrush.onMouseUp();
  this._handleEvent(e, 'up');
},

在您的情况下，您只需触发 onMouseUp 事件，因此您的函数 stop_drawing 将是:

function stop_drawing() {
  canvas.isDrawingMode = false;
  canvas.freeDrawingBrush.onMouseUp();

}

在我们的案例中 onMouseUp将是:

/**
* Invoked on mouse up
*/
onMouseUp: function() {
  this._finalizeAndAddPath();
},

让我们看看它是如何工作的_finalizeAndAddPath :

     /**
     * On mouseup after drawing the path on contextTop canvas
     * we use the points captured to create an new fabric path object
     * and add it to the fabric canvas.
     */
    _finalizeAndAddPath: function() {
      var ctx = this.canvas.contextTop;
      ctx.closePath();

      var pathData = this.convertPointsToSVGPath(this._points).join('');
      if (pathData === 'M 0 0 Q 0 0 0 0 L 0 0') {
        // do not create 0 width/height paths, as they are
        // rendered inconsistently across browsers
        // Firefox 4, for example, renders a dot,
        // whereas Chrome 10 renders nothing
        this.canvas.renderAll();
        return;
      }

      var path = this.createPath(pathData);

      this.canvas.add(path);
      path.setCoords();

      this.canvas.clearContext(this.canvas.contextTop);
      this._resetShadow();
      this.canvas.renderAll();

      // fire event 'path' created
      this.canvas.fire('path:created', { path: path });
    }

此时绘制的路径已经添加到 Canvas 中。

我已经更新了您的代码段 here如果你想看看下面的代码......

一切顺利

var canvas = new fabric.Canvas("c", {
  backgroundColor: "#fff"
});
canvas.isDrawingMode = true;
canvas.freeDrawingBrush.color = "green";
canvas.freeDrawingBrush.width = 4;

setTimeout(stop_drawing, 3000);

function stop_drawing() {
  canvas.isDrawingMode = false;
  canvas.freeDrawingBrush.onMouseUp();

}

<script src="https://rawgit.com/kangax/fabric.js/master/dist/fabric.js"></script>
<canvas id="c" width="500" height="500" style="border:1px solid #ccc"></canvas>