Use row length, not just stride, while iterating.
Use row length, not just stride, while iterating.

The stride is not necessarily the same as the row length, because the
row length contains possible scanline padding. I am not sure if this can
happen, but better be safe than sorry.

Signed-off-by: Tobias Stoeckmann <059b8b880f8441509ec8a65b50b4c6ae74ebea76@stoeckmann.org>

stoeckmann/xwallpaper,stoeckmann/xwallpaper