A few days ago I decided to upgrade my PosterMyWall* Flash/Flex development environment from Flex Builder 3 to the latest IDE, Flash Builder 4 (Adobe can’t seem to decide on a name …). Flash Builder 4 comes with the latest version of the Flex SDK, 4.1.*.
When I compiled and ran the poster maker with the new SDK, I was appalled to notice that all my BitmapImage’s were mirrored horizontally. After Googling around for a bit, and going through Flex bug-fix logs, I came across this bug which gave me a clue as to what might be wrong.
The culprit is the default value of the layoutDirection property of some elements. Sometimes, based on how an element is located in the DOM, the value of layoutDirection might not be set properly. You’ll need to manually set it to LTR (or RTL) so that your images show up correctly.
*If you haven’t checked it out already, PosterMyWall is a great online poster maker that allows you to create posters and collages from your photos, which you can share online or get printed as large high quality posters.