wow. Animate change to left via CSS, ~500 paint/reflow events. Animate translateX - 16!
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@johnallsopp Changing left can require a reflow dbaron.org/css/test/2003/abs… But we should detect when not needed and optimize. Cc @davidbaron
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@SickingJ @johnallsopp @davidbaron technically both should cause minor reflows because both can impact the size and position of scrollbars
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@jaffathecake @SickingJ @johnallsopp When there's a change to scrollbars, we fall back to reflow.
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@davidbaron @SickingJ @johnallsopp interesting, how do you know there's a change to scrollbars without a reflow?
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@jaffathecake @SickingJ @johnallsopp frame classes have an UpdateOverflow method: hg.mozilla.org/mozilla-centr… hg.mozilla.org/mozilla-centr…
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@davidbaron @SickingJ @johnallsopp gotcha. Similar in Chrome I believe. A low cost reflow to determine if scrollbars need updating.
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Replying to @jaffathecake
@jaffathecake @SickingJ @johnallsopp No, this is Reflow only if scrollbars need updating, and normal cost (but we could improve if needed)

Sep 27, 2013 · 3:09 PM UTC

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Replying to @davidbaron
@davidbaron @SickingJ @johnallsopp I believe Chrome refers to calc'ing the element's position within scrollable elements as layout
Replying to @davidbaron
@davidbaron @SickingJ @johnallsopp so it needs to do a light layout to work out if scrollbars are valid & does a larger layout if not.