1426856 - dispatchEvent is not working immediatly after synchronously setting disabled = false

Status: RESOLVED DUPLICATE of bug 963529

(Core :: DOM: Events, defect, P3)

Description

[alanwaiss]

What did you do?
================
1. Create a disabled text box (<input id="test" type="text" disabled="disabled" />)
2. Get a reference to the text box (var myTb = document.getElementById("test"))
3. Enabled the text box (myTB.disabled = false)
4. Initialize a new "blur" event
5. Execute dispatchEvent (myTB.dispatchEvent(event))

What happened?
==============
Nothing. The event was not executed.

What should have happened?
==========================
The event should be executed

Is there anything else we should know?
======================================
I don't know exactly what version this stopped working, but prior to Quantum, this worked as expected and does work in other browsers such as Chrome. If I set disabled = false then use setTimeout with a 1 millisecond delay to create and dispatch the event, it works as expected.

Comment 1

[alanwaiss]

Attachment: Sample file for testing

Note that the asyncTest doesn't always work if I reduce the timeout to 1 or 5 milliseconds instead of 25.

Comment 2

[John Whitlock [:jwhitlock]]

Thank you the bug report. What version of Firefox are you using?

Comment 3

[alanwaiss]

(In reply to John Whitlock [:jwhitlock] from comment #2)
> Thank you the bug report. What version of Firefox are you using?

57.0.2

Comment 4

[Hsin-Yi Tsai (she/her) [:hsinyi]]

I managed to reproduce this issue on old versions, firefox 44 and firefox 52. This seems not a recent regression.

Comment 5

[Hsin-Yi Tsai (she/her) [:hsinyi]]

Do you have ideas where our code behaves this way?

Comment 6

[Olli Pettay [:smaug][[e-mail]]]

Isn't this a dup... We don't flush the layout so 
https://searchfox.org/mozilla-central/rev/51cd1093c5c2113e7b041e8cc5c9bf2186abda13/layout/style/res/forms.css#432 still applies.
https://searchfox.org/mozilla-central/rev/51cd1093c5c2113e7b041e8cc5c9bf2186abda13/dom/html/nsGenericHTMLElement.cpp#2292

I don't have good ideas how to fix this though. We don't want to flush layout all the time.
Or, hmm, perhaps we could flush style when changing disabled state.

Comment 7

[:Gijs (he/him)]

Yes, this is a dupe.