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<virtual-content> #152
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<virtual-content> #152
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…le DOM. (...) This new implementation is based around the assumption that all of the features enabled by searchable invisible DOM require those elements to actually be in the main document.
…dren] now handles inserting children.
…r. (...) ChildManager doesn't serve any purpose: MutationObserver is needed to discover parser-inserted children and MutationObserver callbacks are called before the next paint, giving overridden Node methods no performance advantage.
…move `top` cache.
…height estimate error.
…eight estimates from being set to 0.
…sing scroll event targets. (...) The target of scroll events isn't always the element that needs to have its `scrollTop` corrected when height estimates are found to be incorrect during an update. This can happen if the virtual content is nested in multiple scrollable elements and the user scrolls more of the virtual content into view using one of the outer scrollable elements.
…th scrolling interruption. (...) https://bugzilla.mozilla.org/show_bug.cgi?id=1502059
…with the viewport.
…rt intersection with unrendered space. (...) Before this change, the virtual-content did not update if its nearest scroll container (possibly the window) resized in a way that made more of the virtual-content visible. To fix this, sentinel elements sized to fill the space between visible elements are inserted and monitored with an IntersectionObserver, using the viewport as the root. This has the convenient side effect of covering all of the cases that were previously handled by listening to scroll events. Additionally, this prevents any virtual-content elements that do not intersect the viewport from updating for scroll events.
…tent's viewport intersection state is unnecessary. (...) Tracking the state of the virtual-content element's intersection with the viewport isn't necessary because the callback won't be called if the virtual-content element's intersection with the viewport didn't change or the virtual-content element doesn't intersect the viewport (meaning none of its descendants intersect the viewport).
…es the scroll event listener with an IntersectionObserver.
…erver will handle this case.
…ing construction. (...) Reading `childNodes` at this time violates the "Requirements for custom element constructors and reactions". https://html.spec.whatwg.org/multipage/custom-elements.html#custom-element-conformance
Commit ed9b9a3 makes this check unnecessary by making sure that all nodes are processed by the MutationObserver callback before any update.
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Would be nice with some update to the readme or so, as this is removing all the existing implementation. Also, I assume that means that most of the demos will be broken. |
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So, the intent here is to actually have two side-by-side branches, master and Eventually, the virtual-content-2 branch may have the same capabilities and demos as the master branch, at which point it can replace it. But that's some ways off. |
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Sorry, @kenchris, I should have included a description with this PR! |
domenic
suggested changes
Jan 29, 2019
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Review complete! Going to move this to a new clean |
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The virtual-content element is a different approach to implementing virtual list. This branch assumes that searchable-invisible DOM / display locking is available and necessary for allowing the content of the virtual list to be searchable, work with same-page anchor navigation, etc. This assumption means that all content that the user of the virtual-content is aware of should be inserted into the virtual-content element, which will manage the visibility of that content automatically. Additionally, because all content that the user of the virtual-content is aware of must be in the tree, this means that most of the original API isn't needed by virtual-content. (Concepts like element recycling and lazy item fetch / instantiation should be implemented on top of virtual-content.) See #147 for more info.
For this PR:
For later PRs?
This PR is only meant for code review of the current content of the branch, without merging it into master (a separate PR).