Flash automatically merges shapes at compile time

Here be dragons.

Flash automatically combines shapes at compile time.

So if you were expecting to place two or more shapes on the stage and be able to access them via the stage's getChildAt method, you're in for an interesting time.

It's not as simple as "Flash combines all shapes into a single shape". It seems to work based on z-index.

Suppose you add two shapes to the stage, then add a textbox, then add a third shape.

You'll discover at runtime that the first two shapes have been merged into one, but the third has not.

If you play with the z-index ("send to back", "send to front") in the Flash IDE, you'll discover that the ONLY thing that controls whether or not two particular shapes get merged at compile time is whether or not they are neighbours in the z-index.

(Technically, they need to be part of the same unbroken sequence of shapes in the z-index, so for example if you add three shapes to the stage in succession, they will be combined into a single shape at compilation time, because they will appear one after the other in the z-index.)

Unfortunately, I failed to find any documentation which mentions this, or any other Flash developers having their plans thwarted by this 'feature'. So I hereby post my "here be dragons" flag.

The solution? If you NEED the shapes to be drawn in Flash (as opposed to drawn in ActionScript at runtime) and you NEED them to be separate shapes at runtime, then cut them out of your document and paste them into a temporary document, then paste one shape back, then create an off-stage dynamic text field (to form a z-index divider), then paste in the next shape, and so on, and so forth.

Of course, it should be very rare that you need to do this kind of thing, but I came across such an instance today, and lost several hours due to this seemingly undocumented 'feature'.