Is possible to lock certain keys in keyboard during input in "edittext" box – Photoshop script CS6?

Consider utilizing the following custom ScriptUI example.

It produces a simple dialogwindow that contains two edittext elements.

1. The first edittext element has restricted input. It permits one comma , character/key to be input, and one or more of the following character keys only:

   0 1 2 3 4 5 6 7 8 9 + -

2. The second edittext element has unrestricted input. It permits any character/key to be input, i.e. it’s as per default functionality.

example.jsx

#target photoshop;

/**
 * @fileoverview Shows how to create a key restricted custom 'edittext' with
 * ScriptUI. This example permits only one comma `,` to be input and one or
 * more of following characters: `[0-9]` `+` `-`
 */

$.level=0;

//------------------------------------------------------------------------------
// Usage
//------------------------------------------------------------------------------

var mainWindow = new Window("dialog");


// 1. Example `edittext` element with restricted key input.
var label = mainWindow.add('statictext', undefined, 'Restricted input:');
label.alignment = 'left';

var edittext = mainWindow.add('edittext', undefined, 0);
edittext.characters = 40;
restrictInputKeys(edittext); //<-- Enable restricted input.


// 2. Example `edittext` element with unrestricted key input.
var label2 = mainWindow.add('statictext', undefined, 'Unrestricted input:')
label2.alignment = 'left';

var edittext2 = mainWindow.add('edittext', undefined, 0);
edittext2.characters = 40;


mainWindow.show();

//------------------------------------------------------------------------------
// Helpers
//------------------------------------------------------------------------------

/**
 * Determines whether an array includes a certain value among its elements.
 * @param {String} valueToFind - The value to search for.
 * @param {Array} arrayToSearch - The array to search in.
 * @returns {Boolean} true if the value valueToFind is found within the array
 */
function inArray(valueToFind, arrayToSearch) {
  for (var i = 0, max = arrayToSearch.length; i < max; i++) {
    if (arrayToSearch[i] === valueToFind) {
      return true;
    }
  }
  return false;
}

/**
 * Restricts the character keys permitted in a `edittext` element.
 * @param {Object} editTextInstance - Reference to `edittext` ScriptUI element.
 */
function restrictInputKeys(editTextInstance) {

  if (editTextInstance.constructor.name !== 'EditText') {
    throw new Error ('Invalid class. Expected `EditText` class.')
  }

  var hasComma = false;

  var permissibleKeys = ['0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
      'Minus', 'Comma', 'Escape', 'Backspace'];
  /*
   * Add a listener to the given `edittext` element to detect `keydown` events.
   * In the bddy of its handler function we detect each key pressed to determine
   * whether the key is permissible or impermissible.
   */
  editTextInstance.addEventListener('keydown', function (key) {
    var keyName = key.keyName;
    var shiftKeyIsDown = key.shiftKey;
    var altKeyIsDown = key.altKey;

    if (shiftKeyIsDown && keyName === 'Equal') {
      return;
    }

    if ((shiftKeyIsDown || altKeyIsDown) && inArray(keyName, permissibleKeys)) {
      key.preventDefault();
      return;
    }

    if (! hasComma && keyName === 'Comma')  {
      hasComma = true;
      return;
    }

    if (hasComma && keyName === 'Comma') {
      key.preventDefault();
      return;
    }

    if (! inArray(keyName, permissibleKeys)) {
      key.preventDefault();
    }
  });

  /*
   * The `onChanging` event is utilized to detect whether a comma already exists.
   * If a comma DOES NOT exist set the `hasComma` variable to `false`.
   */
  editTextInstance.onChanging = function() {
    if (this.text.indexOf(',') === -1) {
      hasComma = false;
    }
  }
}

Explanation:

• This essentially adds an event listener to a given edittext element to detect keydown events.
• In the body of the event listeners handler function we detect each key pressed and determine whether the key is permissible or impermissible.
• The onChanging event is utilized to essentially detect whether a comma (,) has already been input or not. If a comma does not exists when each onChanging event fires we set the hasComma variable to false. By utilizing the onChanging event and the hasComma variable it provides us with a mechanism for restricting the input of only one comma (,) key.

Usage:

• Note in the "Usage" section of the example.jsx file we enable restricted key/character input by invoking the custom restrictInputKeys function and pass in a reference to the instance of the edittext element that we want to restrict. i.e.

  restrictInputKeys(edittext); //<-- Enable restricted input.
  

  If you wanted to enable restricted key input on the second edittext instance you just need to invoke the restrictInputKeys function again and pass in a reference to the second edittext instance. For example:

  restrictInputKeys(edittext2); //<-- Enable restricted input for the second instance.
  

_{Note I tested the example provided in PhotoShop CS5 and it worked successfully. It hasn’t been tested in PhotoShop CS6 – some changes may be necessary.}