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From "After24 (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (FLEX-34821) Improvement of the scroller perfomances on mobile devices
Date Sun, 19 Apr 2015 09:34:59 GMT

     [ https://issues.apache.org/jira/browse/FLEX-34821?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

After24 updated FLEX-34821:
    Attachment: ViewportCacheDemo.apk

> Improvement of the scroller perfomances on mobile devices
> ---------------------------------------------------------
>                 Key: FLEX-34821
>                 URL: https://issues.apache.org/jira/browse/FLEX-34821
>             Project: Apache Flex
>          Issue Type: Improvement
>            Reporter: After24
>         Attachments: ViewportCache.zip, ViewportCacheDemo.apk
> This is an experimentation on the flex Scroller component to improve the framerate of
the scrolling operations.
> This optimization based on the blitting technique.
> A new boolean property named cacheViewport is added to the Scroller component. When cacheViewPort
is set to true, all scrolling operations are performed according to the following cycle :
> 1 - A bitmap copy of the viewport is made just before the next scrolling operation (large
viewports are cached in multiple tiles if necessary)
> 2 - When the user starts a scrolling operation, the actual viewport is replaced by its
bitmap version and the scrolling is executed by drawing the viewport according to its verticalScrollPosition
and horizontalScrollPosition properties.
> 3 - At the end of the scroll operation, the bitmap viewport is replaced by its actual
> 4 - Between each scrolling operations, when the user interacts with the viewport content,
a process mark as 'dirty' every regions of the viewport that are likely to have changed during
those interactions. Every dirty region is redrawn before the next scrolling operation.
> Pros :
> - 60 FPS scrolling, even on old devices.
> - Performance is no longer dependant on the viewport complexity.
> - Can be used with the list component if it contains a moderate number of rows (useVirtualLayout
must be set to false though)
> Cons :
> - There is a slight lag (dependant on the device processor) during the viewport rasterization
and the process of redrawing every dirty regions.
> - Doesn't support virtualized layouts.
> - Animated elements of the viewport freezes during scrolling operations.
> - Render mode must be set to <renderMode>gpu</renderMode> on the current
> - Depending on its dimensions, the viewport rasterization process can consume large amounts
of memory.
> A demo application can be downloaded on the android play market here : https://play.google.com/store/apps/details?id=air.fr.after24.ViewportCacheDemo
> Source code is attached.

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