AFDKO as well as FontForge include an autohint (the following image shows hints as blue and green rectangles):
FontForge's autohint is much more eager to fill the white spaces. Does anybody have experience with the different quality of the resulting bitmaps (AFDKO vs FontForge)? Which one should be preferred?
Comments
PostScript originally required that hints should not overlap. Now it requires that any active set of hints be non-overlapping, but it allows you to change sets as you move through the glyph.
So to implement hinting with hint substitution FontForge needs to know not only the position and width of the stem being hinted, but also where the stem should be active. And it needs to know what stems overlap which other stems.
Could you possibly post another example using a two-story lowercase g? (Since that's a place where hint replacement is more likely to be needed.)
PostScript hints are usually shown in font editors as bands that run completely horizontally or vertically to the edges of the character width and height, not segments like this.
The part you mentioned about overlapping hints refers to hints going the same direction, not intersections of horizontal and vertical hints. In the /g, the three vertical hints on the left overlap and the two on the right overlap. This is where replacement hints are used.