The first unofficial Apache Flex release, (known as Apache Flex 4.8.0 Incubating) had the goal of being equivalent to Adobe Flex 4.6. There were some subtle differences, such as, some of the embedded assets used as cursors, DataGrid column separators, etc. had to be converted from SWF assets to FXG assets which make them slightly heavier and might have resulted in subtle pixel differences.

In each subsequent release, new features have been added and bugs have been fixed. This can cause noticeable differences in behavior and break existing code. The Apache Flex committers are motivated to keep each release as backwards compatible as possible with the one before it, but backwards compatibility cannot be guaranteed, partly because ActionScript does not support method overloading, and partly because efficient implementation of new features and bug fixes often outweighs the decision to remain backwards compatible.

Users are invited to share their backwards compatibility issues and how the dealt with them in comments on this page.

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2 Comments

  1. Anonymous

    GridItemRender mxml has changed form release 4.6.0 to 4.10

    So make sure that you migrate all your GridItemRenderer.

    Old:

       <s:Scroller minViewportInset="1" hasFocusableChildren="false" height="100%">                   

             <s:Grid id="grid" itemRenderer="spark.skins.spark.DefaultGridItemRenderer">

      <s:GridLayer name="backgroundLayer"/>

                     <s:GridLayer name="selectionLayer"/>

                     <s:GridLayer name="editorIndicatorLayer"/>                           

                     <s:GridLayer name="rendererLayer"/>

                     <s:GridLayer name="overlayLayer"/>

             </s:Grid>                   

       </s:Scroller>

    New:

    <s:Scroller id="scroller" minViewportInset="1" hasFocusableChildren="false" height="100%">                                                                           

                    <s:Grid itemRenderer="spark.skins.spark.DefaultGridItemRenderer">

                                   <s:gridView>

                                                   <fx:Component>

                                                                   <s:GridView>

                                                                                  <s:GridLayer name="backgroundLayer"/>

                                                                                  <s:GridLayer name="selectionLayer"/>

                                                                                  <s:GridLayer name="editorIndicatorLayer"/>                           

                                                                                  <s:GridLayer name="rendererLayer"/>

                                                                                  <s:GridLayer name="overlayLayer"/>

                                                                   </s:GridView>

                                                   </fx:Component>

                                   </s:gridView>

                    </s:Grid>                   

    </s:Scroller>

  2. Tom Chiverton

    See the 'blurry fonts' thread on the mailing list for a solution to fonts looking worse when the Adobe Flex code used particular hinting options : http://mail-archives.apache.org/mod_mbox/flex-users/201310.mbox/%3CDUB124-W478EA6B9D294250D6EA041CB1C0@phx.gbl%3E