Hi Mitchell,
> I like to use a thin margin for markers in conjunction with SC_MARK_LEFTRECT. If I enable change history, the change history markers are drawn a single pixel in width. I’d like to propose a minimum width: 4 pixels (2 for the left and right foreground border, and 2 for the background fill).
2 and 3 pixel wide bars seem reasonable to me and are used by other applications. 2 pixel wide bars don't have space for any background fill but just showing the frame colour is a fine decay path.
Even 1 pixel isn't dreadful if you place another light-coloured margin to the left (like line numbers). On low-resolution (800x600) screens it's fairly clear.
Some tweaks to the size could be made like using ceil instead of floor on the width but requiring it to always be at least 4 pixels wide seems limiting to me.
Neil