<div dir="ltr"><span class="inbox-inbox-author-a-u0hiz80z6z122znz74zz70zz78zkqez72zd">For some time now we've been talking about moving away from XUL and XBL. The </span><span class="inbox-inbox-author-a-z81zz66zz65z21z65ztz88zz86zz84zguuz75zxz79z">b</span><span class="inbox-inbox-author-a-u0hiz80z6z122znz74zz70zz78zkqez72zd">rowser </span><span class="inbox-inbox-author-a-z81zz66zz65z21z65ztz88zz86zz84zguuz75zxz79z">a</span><span class="inbox-inbox-author-a-u0hiz80z6z122znz74zz70zz78zkqez72zd">rchitecture team has been hard at work figuring out how to go about doing that and we're ready to share the first of our proposals more widely. We have developed a plan to remove XBL from Firefox. It's been through a successful design review with some of the key engineers and now is the time for more comments if you have them. We're </span><span class="inbox-inbox-author-a-z81zz66zz65z21z65ztz88zz86zz84zguuz75zxz79z">planning to start</span><span class="inbox-inbox-author-a-u0hiz80z6z122znz74zz70zz78zkqez72zd"> s</span><span class="inbox-inbox-author-a-z81zz66zz65z21z65ztz88zz86zz84zguuz75zxz79z">ome of the</span><span class="inbox-inbox-author-a-u0hiz80z6z122znz74zz70zz78zkqez72zd"> work this quarter with it really ramping up next quarter.</span><div id="inbox-inbox-magicdomid556" class="inbox-inbox-ace-line"><br></div><div id="inbox-inbox-magicdomid1082" class="inbox-inbox-ace-line"><span class="inbox-inbox-author-a-u0hiz80z6z122znz74zz70zz78zkqez72zd">Take a look at <a href="https://mozilla.github.io/firefox-browser-architecture/text/0007-xbl-design-review-packet.html">the plan</a></span><span class="inbox-inbox-author-a-u0hiz80z6z122znz74zz70zz78zkqez72zd"> and let us know what you think. There are a couple of areas where we are still investigating concerns:</span></div><div id="inbox-inbox-magicdomid675" class="inbox-inbox-ace-line"><br></div><div id="inbox-inbox-magicdomid1087" class="inbox-inbox-ace-line"><span class="inbox-inbox-author-a-u0hiz80z6z122znz74zz70zz78zkqez72zd">Performance is of key interest</span><span class="inbox-inbox-author-a-z81zz66zz65z21z65ztz88zz86zz84zguuz75zxz79z">,</span><span class="inbox-inbox-author-a-u0hiz80z6z122znz74zz70zz78zkqez72zd"> so we're actively doing experiments to validate that </span><span class="inbox-inbox-author-a-z81zz66zz65z21z65ztz88zz86zz84zguuz75zxz79z">C</span><span class="inbox-inbox-author-a-u0hiz80z6z122znz74zz70zz78zkqez72zd">ustom </span><span class="inbox-inbox-author-a-z81zz66zz65z21z65ztz88zz86zz84zguuz75zxz79z">E</span><span class="inbox-inbox-author-a-u0hiz80z6z122znz74zz70zz78zkqez72zd">lements can be <a href="https://bugzilla.mozilla.org/show_bug.cgi?id=1387125">as performant as XBL</a>.</span></div><div id="inbox-inbox-magicdomid1137" class="inbox-inbox-ace-line"><span class="inbox-inbox-author-a-u0hiz80z6z122znz74zz70zz78zkqez72zd">The plan relies on being able to use </span><span class="inbox-inbox-author-a-z81zz66zz65z21z65ztz88zz86zz84zguuz75zxz79z">C</span><span class="inbox-inbox-author-a-u0hiz80z6z122znz74zz70zz78zkqez72zd">ustom </span><span class="inbox-inbox-author-a-z81zz66zz65z21z65ztz88zz86zz84zguuz75zxz79z">E</span><span class="inbox-inbox-author-a-u0hiz80z6z122znz74zz70zz78zkqez72zd">lements in XUL</span><span class="inbox-inbox-author-a-z81zz66zz65z21z65ztz88zz86zz84zguuz75zxz79z">,</span><span class="inbox-inbox-author-a-u0hiz80z6z122znz74zz70zz78zkqez72zd"> so we're working on getting <a href="https://bugzilla.mozilla.org/show_bug.cgi?id=1404420">a patch </a></span><a href="https://bugzilla.mozilla.org/show_bug.cgi?id=1404420"><span class="inbox-inbox-author-a-z81zz66zz65z21z65ztz88zz86zz84zguuz75zxz79z">for</span><span class="inbox-inbox-author-a-u0hiz80z6z122znz74zz70zz78zkqez72zd"> that landed</span></a><span class="inbox-inbox-author-a-z81zz66zz65z21z65ztz88zz86zz84zguuz75zxz79z">.</span></div><div id="inbox-inbox-magicdomid1000" class="inbox-inbox-ace-line"><span class="inbox-inbox-author-a-u0hiz80z6z122znz74zz70zz78zkqez72zd">We have a list of <tree> elements in the product and we're evaluating what the future is for them.</span></div><div id="inbox-inbox-magicdomid1002" class="inbox-inbox-ace-line"><br></div><div id="inbox-inbox-magicdomid1098" class="inbox-inbox-ace-line"><span class="inbox-inbox-author-a-u0hiz80z6z122znz74zz70zz78zkqez72zd">Are there any other concerns that we're missing?</span></div>

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