QuickTime media content is often sensitive to the size and proportions of screen space that it uses -- for instance, a movie that is made to display at 320 x 240 pixels can look bad or have serious performance repercussions if drawn at 600 x 60 pixels on the screen.
The QTCanvas provides flags for controlling how the Java layout managers allocate space to it (resizeFlags) and where, within that space, the QTCanvas client actually draws (alignmentFlags). You can also set the minimum, preferred, and maximum sizes of the QTCanvas, as with any other java.awt.Component. The preferred size is automatically set for you as the initial size of the QTCanvas client if your application does not specifically set the preferred size itself.