![]() ![]() Optimizing Web Content in UIWebViews and Websites on iOS.Minimizing browser reflow | PageSpeed Insights | Google Developers.We spent a week making Trello boards load extremely fast.Rendering: repaint, reflow/relayout, restyle / Stoyan.Preventing 'layout thrashing' | Wilson Page.Timeline demo: Diagnosing forced synchronous layouts - Google Chrome.Fixing Layout thrashing in the real world | Matt Andrews.Avoiding layout thrashing - Web Fundamentals The best resource on identifying and fixing this topic.No concrete data on IE or EdgeHTML, but they likely were roughly the same, as the return values for these properties are spec'd.Results: FrameNeedsReflow - mozilla-central searchfox Gecko's reflow appears to be requested via FrameNeedsReflow.Modern WebKit's instances of forced layout are mostly consistent: updateLayoutIgnorePendingStylesheets - GitHub search - WebKit/WebKit.Tony Gentilcore's Layout Triggering List was for 2011 WebKit and generally aligns with the above.You can browse them yourself in the Chromium source tree. The above data was built by reading the Blink source, so it's true for Chrome, Opera, Brave, Edge and most android browsers.Outbrain is forcing layout repeatedly, probably in a loop. Read your metrics at the begininng of the frame (very very start of rAF, scroll handler, etc), when the numbers are still identical to the last time layout was done. Batch your writes & reads to the DOM (via FastDOM or a virtual DOM implementation).You may be surprised to see how often your app code and library code hits this. Use DevTools Performance Panel to see where this happens.for loops that force layout & change the DOM are the worst, avoid them.What should you do about all this? Well, the More on forced layout section below covers everything in more detail, but the short version is:.Their costs are very dependent on the content/situation, but typically both operations are similar in cost. So forced layout triggers both operations. If layout is forced, style must be recalculated first.Typically, this is because the DOM was changed (classes modified, nodes added/removed, even adding a psuedo-class like :focus). Reflow only has a cost if the document has changed and invalidated the style or layout.Lots & lots of stuff, …including copying an image to clipboard ( source).Use the "chromium source tree link" below to explore on your own! contenteditable SVGTextContent: getCharNumAtPosition(), getComputedTextLength(), getEndPositionOfChar(), getExtentOfChar(), getNumberOfChars(), getRotationOfChar(), getStartPositionOfChar(), getSubStringLength(), selectSubString().Quite a lot of properties/methods force, but I haven't made an exhaustive list. ![]()
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