I've noticed an inconsistency of behavior in xclock between the -render and the
-norender options. If I choose -norender and I resize the clock window, the
clock is appropriately scaled in whichever direction necessary, preserving the
aspect ratio of the clock. If I use -render instead and resize the window, the
aspect ratio of the clock is set to the aspect ratio of the window, which causes
distortion of the clock window. I don't see how that stretched image would be
useful to anyone. 

Instead, when the Render extension is used, the clock image should be scaled,
but while keeping the aspect ratio.