Block Glyphs (U+2580-U+25A0) are not enough tall.
Vertical size of the blocks must be equal to E+2502 for example.
For SansMono, it's not nice to use blocks in a terminal application (with ncursesw), because there is a vertical gap between blocks !
For shades (U+2591-U+2593), it would be much nicer to use "square virtual pixel"
instead of just of 8x8 grid (where the pixels are not square at all).
Using current proportion with full height block, it would lead to a 6x10 grid,
allowing a best rendering at all size.