711312 - Key event listeners iterated over for every keystroke - consider hashtable lookup

Status: RESOLVED WONTFIX

(Core :: XBL, defect)

Description

[Alex Vincent [:WeirdAl]]

In reading over XBL key event handling, it appears we iterate over every handler for every keystroke:
http://hg.mozilla.org/mozilla-central/diff/ad45243a5cd9/content/xbl/src/nsXBLEventHandler.cpp

I think it might be faster if the key event handlers were stored in a hashtable where the hashkeys were char codes.  Specifically:

* Define an event listener array type (typedef nsCOMArray<nsIDOMEventListener> ListenerArray)
* Define a nsDataHashtable<PRUint32, ListenerArray> mKeyListeners;
* In nsXBLKeyEventHandler::ExecuteMatchedHandlers, look up the ListenerArray by the charCode we're so helpfully given, and if there isn't a match, bail out.
* If there is a match, iterate over the found ListenerArray.
* Remove the charCode test from nsXBLKeyEventHandler::Matches in nsXBLKeyEventHandler.h.

I don't know if this will really yield much of a perf improvement, but consider that there are many char codes (VK_DOWN, VK_UP, VK_PAGE_DOWN, VK_ENTER, VK_A, etc.) that will probably not match a given event listener.

Comment 1

[Boris Zbarsky [:bzbarsky]]

XBL is now disabled in Firefox (Bug 1583314) and is in the process of being removed from Gecko (Bug 1566221), so closing bugs requesting changes to its implementation as wontfix.