Pencil tool not working at extremes

[bdezonia]

Make a new 1-bit 5x5 image filled with 0.
Set Options > Channels fg to 1 and bg to 0.
Zoom up on the 5x5 image so that it fills a decent part of screen (32X is fine).
Select the pencil tool (and then right click on tool to verify width == 1)
Draw with tool.
Nothing is drawn.

(This might just be a drawing in binary error due to truncing. Or it could be an off by some pixels due to zoomed up and bad coord calx. Not sure.)

[bdezonia]

Later testing: cannot duplicate situation where nothing is drawn. But somehow the fg & bg both reported being set to 0 when in fact they had been set to 1 and 0. Lurking bug?

Once that was straightened out drawing happens but can't reach border pixels. And drawing happens one row lower than mouse location.