Non-rectangular display object mask gives rectangular display

This is for a project with assets stored in a Flash swf file and project build to HTML5.

I made a symbol which is a rectangle with rounded corners and an animation as a MovieClip, both stored in a swf file. In my code I add the MovieClip to the background and apply the mask to it.

After the build to html 5, the mask does work in that only a portion of the MovieClip is visible. But the visible area is a rectangle with square corners, not rounded corners like the mask.

Is this a known problem? Does it just apply to HTML5 builds?

I don’t know if this will help, but for HTML5 I found that in your project.xml file, using

<window hardware="true">

will break your masking.

You must set:

<window hardware="false">

I don’t set the window hardware value and don’t know what the default is. My solution in this particular case was to change the art so there would be an image with a transparent section overlaying the image being masked.

If I encounter this situation again that can’t be solved with that method, I’ll try the suggestion about the window hardware setting.