Details
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Improvement
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Resolution: Unresolved
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Major
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None
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14.1-rc-1
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Unknown
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Description
Reproduction steps
- Visit a page that contains no image, for instance http://localhost:8080/xwiki/bin/view/Sandbox/
- Open the browser debugger and make sure "disable cache" is checked
- Reload the page and look at the network tab
Expected
The image lightbox code is not loaded, since there is no image on the page to open in a lightbox. In particular moment-timezone-with-data.min.js is not downloaded.
Actual
About 821 KB of JavaScript and CSS are downloaded on every page view:
- moment-timezone-with-data.min.js — 727 KB
- moment.min.js — 59 KB, plus moment-jdateformatparser
- blueimp-gallery-bundle.min.js — 36 KB
- blueimp-gallery.min.css — 8 KB, plus lightbox.css
A 3.7 KB inline JSON template is also serialized into the HTML of every page and appended to <body>.
Guests get all of it too, on every page.
Analysis
The UI extension in XWiki/Lightbox/WebHome.xml is registered on org.xwiki.platform.template.header.after with scope=wiki, and that extension point is rendered unconditionally by flamingo/global.vm. The only guard is the isLightboxEnabled configuration flag: there is no check on the action and no check on whether the page actually contains an image.
The JSX it pulls consists of a single statement:
require(['xwiki-lightbox'], function(lightbox) {});
xwiki-lightbox then statically depends on xwiki-lightbox-description, which statically depends on moment, moment-jdateformatparser and moment-timezone — and moment-timezone resolves to the with-data build in flamingo/javascript.vm, hence the 727 KB.
moment-timezone is used in exactly one place, updateDescriptionMetadata in lightbox.js, to format the attachment date shown in the lightbox description panel. That code only runs once a slide has actually been opened. The source already carries a comment pointing at XWIKI-19808 as the proper long-term fix for the date formatting itself.
Suggested fix
Two independent steps, either of which is worthwhile on its own:
- Make xwiki-lightbox-description a lazy dependency of xwiki-lightbox (through the deferred! RequireJS plugin, or a nested require([...]) inside addSlideDescription), so the moment stack is only fetched when a slide is opened. This alone accounts for about 790 KB.
- Do not load xwiki-lightbox at all until the page actually contains an image. initLightboxFunctionality in lightbox.js already computes the set of eligible images — it simply does not act on the set being empty.
This is the same class of problem as XWIKI-22936.
Attachments
Issue Links
- is related to
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- Open
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- relates to
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XWIKI-22936 XWiki.SearchSuggestCode is loaded too early
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- Closed
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- Open
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