Error in MovieClip.height Property

Question

I've found that Flash inserts an extra area around objects
drawn in a MovieClip. This causes problems when trying to scale an
object to match a desired pixel size. To see the error, try this:
Create a new MovieClip symbol and export for ActionScript.
Create a new rectangle object inside the new MC symbol.
While editing the MC, select the entire rectangle and, in the
Properties panel, set the height to 50.0
In AS create a new instance of it and set scaleY = 10.0 and
turn on its opaqueBackground as shown in code snippet below:
var test_mc:MovieClip = new Symbol6();
trace(test_mc.height);
addChild(test_mc);
test_mc.opaqueBackground = 0xdd0000; // shows that the movie
clip actually extends beyond the visible portion and when scaling
more than 2x that adds up to a lot of pixels
test_mc.scaleY = 10.0;
You will see that the trace statement reports the height as
52, not 50 and you will also see a thick red border surrounding the
drawn rect. This spurious addition of two pixels introduces errors
when trying to calculate scaleX/Y properties in code to match some
desired dimension.
David Salahi

Answer 1

yes this is a known issue with flash and it is completely to
do with the width of the stroke surrounding your rectangle. you
will notice if you remove the stroke from your rectangle, or select
no stroke(the square with a red diagonal line), test_mc.height will
be traced as 50.
when the flash ide reports a symbol height, it ignores the
width of the stroke around the edges, while actionscript adds the
width of the stroke/2.
so the formula for determining the height of a rectangle for
example, would be:
rectangle height in AS=height returned by
IDE+(strokeWidth/2)*2
we multiply by 2 for the top and the bottom. or a simpler way
of putting this would be:
rectangle height in AS=height returned by IDE+strokeWidth
or in your case:
rectangle height in AS(52)=height returned by
IDE(50)+strokeWidth(i'm betting your rectangle has a strokeWidth of
2)
i went into this in more detail last year
in
my blog
i'm not sure exactly why you're seeing a thick red border.
the only thing i can think of is that you're rectangle's stroke is
transparent.
craig