Unable to get document.execCommand('undo')

Question

I have some code implementing a context menu on a textbox, the context menu is to have an Undo and Redo item that calls the browsers native methods by using document.execCommand('undo').

This code functions as I require on Chromium based browsers but on FireFox and Opera the results are not as expected.

My expectation is that undo and redo will function like the native browser context menu for an input element. The result is that the input elements do not undo and redo, however div elements with the contenteditable attribute set, do function as expected.

So I'm wondering if this is a bug in one of the browsers, either Chromium or FireFox/Opera, or if I am not implementing the code correctly?

The following code gives an example of the issue that I'm facing. All help is appreciated.

<input contenteditable id="input" type="text"></input>
<div contenteditable id="div" class="inputLike" type="text"></div>
<button id="button1" type="button">Undo</button>
<button id="button2" type="button">Redo</button>

var input = document.getElementById("input"),
    button1 = document.getElementById("button1"),
    button2 = document.getElementById("button2"),
    div = document.getElementById("div");

console.log("Undo", document.queryCommandSupported("undo"));
console.log("Redo", document.queryCommandSupported("redo"));

function doUndo() {
    document.execCommand('undo', false, null);
}

function doRedo() {
    document.execCommand('redo', false, null);
}

button1.addEventListener("click", doUndo, false);
button2.addEventListener("click", doRedo, false);

On jsfiddle

If you want to look at the actual context menu code, then it is also available on jsfiddle.

Answer 1

As I discovered from the question I asked, the undoManager API in Firefox DOES work. I looked at the jsFiddle link (http://jsfiddle.net/DULV4/1/) posted by Tim Down, and there appear to be a couple issues:

• An undoScope attribute must be set to true (either in-line or programmatically). This enables the undoManager for that element.
• Anything you undo has to first be created by the undoManager.transact() function (though I'm wondering if there is any way to incorporate the native undo stack into the current undoManager's transaction history).

I'm only a novice with this, so take what I say with a grain of salt and see https://dvcs.w3.org/hg/undomanager/raw-file/tip/undomanager.html for all the information on using it.

Answer 2

I don't think it's possible with document.execCommand(), in Firefox at least. You could make your own undo stack, or in future use the new UndoManager API (implemented in Firefox 20 but disabled by default).

Here's an example of using your own undo stack by taking snapshots of the value and selection using the input event. You could improve this by merging consecutive typing events into a single undo item, for example. There is also some inconsistency between browsers with the caret position, but it's just a proof of concept.

http://jsfiddle.net/FMSsL/

Using the new DOM UndoManager API seems to be simple: if I understand it right and if the browser supports it, the <input> element will have an undoManager property, which is an object with undo() and redo() methods, so the task is as simple as

document.getElementById("input").undoManager.undo();

Unfortunately only Firefox 20 and above supports the UndoManager API and it's disabled by default. Even once it's enabled, the following demo does not work even though I think it should, so this option is some way off being viable.

http://jsfiddle.net/DULV4/2/