I am writing an Air app using Flex 3.5. I'm trying to create a graphical drag of user-drawn content from one panel to another using DragManager.doDrag. My dragImage is a Canvas containing a hierarchy of other Canvases with drawing in them. No matter what value I supply for imageAlpha, I am getting a completely opaque drag image. I also tried setting the alpha on the dragImage Canvas myself and it still displayed opaquely. If I set an alpha on the children of the Canvas, I do get transparency, but not the way I want it. I'd like the whole drawing to be transparent as if it were a single image, but that approach gets me a bunch of overlapping transparent parts and where they overlap I can see one through another.
Why is imageAlpha not working? I also looked for a way to draw all of the content to a bitmap and use that for the dragImage, but I'm not sure what class that implements IFlexDisplayObject allows me to supply its BitmapData.
I was able to work around this by drawing the Canvas to a BitmapData, wrapping it in a Bitmap, and adding the Bitmap to the rawChildren of another Canvas, which is then what I used for the dragImage. But to get transparency, I had to set the alpha on the Bitmap. The imageAlpha parameter of doDrag still didn't work. Is this a bug?