Fabricjs Fixed TextBox

Question

How can I fix the size of a textBox in order to prevent it to overflow its size when typing (fixed width and height)?

var canvas = window._canvas = new fabric.Canvas('c');

var text = new fabric.Textbox('MyText', {
    width: 300,
    height: 300,
    top: 5,
    left: 5,
    hasControls: false,
    fontSize: 30,
    fixedWidth: 300,
    fixedFontSize: 30
});
canvas.add(text);

http://jsfiddle.net/643qazk0/2/

Answer 1

You can override insertChars method and check text overflow.

See snippet below.

// Create canvas
const canvas = new fabric.Canvas(document.querySelector('canvas'));

// Define `LimitedTextbox` class which extends `Textbox`
const LimitedTextbox = fabric.util.createClass(fabric.Textbox, {

  // Override `insertChars` method
  insertChars: function(chars) {

    if (this.maxWidth) {
      const textWidthUnderCursor = this._getLineWidth(this.ctx, this.get2DCursorLocation().lineIndex);
      if (textWidthUnderCursor + this.ctx.measureText(chars).width > this.maxWidth) {
        chars = '\n' + chars;
      }
    }

    if (this.maxLines) {
      const newLinesLength = this._wrapText(this.ctx, this.text + chars).length;
      if (newLinesLength > this.maxLines) {
        return;
      }
    }

    // Call parent class method
    this.callSuper('insertChars', chars);
  }

});

// Create limited text box with max width 300px and max 2 lines
canvas.add(
  new LimitedTextbox('text', {
    top: 10,
    left: 10,
    width: 300,
    maxWidth: 300,
    maxLines: 2
  })
);

canvas.renderAll();

.canvas-container {
  border: 1px solid gray;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/fabric.js/1.7.20/fabric.js"></script>

<canvas width="600" height="300"></canvas>

Tested with Fabric 1.7.20

Answer 2

For fixed textbox in fabric js Version 2+, We need to override the onInput function as follows

onInput: function(e) {
    if(this.width > this.maxWidth) {
        return;
    }

    if((this._textLines.length) > this.maxLines) {
        return;
    }

    // Call parent class method
    this.callSuper('onInput', e);
}

Note: maxWidth - to limit width and maxLines - to limit height / lines in text box