See the PNG in the URL. That's xmms' "Simple Spectrum Analyzer" plugin under
xcompmgr. Note the offset on both axes. This happens under all four xcompmgr
modes so it's most likely a server bug.
The offset is 100 pixels in the Y direction and 5 in the X direction. Note the
wrapping occurs for both axes, though the screenshot only shows it for the X axis.
I can confirm this on PowerPC/Radeon. Here the offsets exactly match the
height and width of the enlightenment16 window decorations. I traced and
played around with some index in the code path but did not found yes a
location where indeces get used/computerd(?) incoccetly ... :-(
Reported fixed with fix to bug #1101. Thanks!