>>> Note, however, that I have also noticed the behaviour when
>>> *SHIFTING RIGHT* as well as left!
>> It's probably some common piece of code.
> Of course...

>> I've had a brief look at the rasterconsole code.  [speculation]

I now think it's not rasops_copycols; there is code that looks as
though it uses a 1bpp-specific version when appropriate.  The 1bpp
version of copycols (dev/rasops/rasops_bitops.h, as included by
rasops1.c) in question is complicated and not easy to follow; I may
pull it out into a userland program where I can use more debugging
techniques on it, or I may try replacing it with something slower but
easier to understand and see if it helps (which might not really fix
it, unless you run the slow code, but could at least be pretty definite
the bug is in that code)....

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