[1 mod] Mono: comma and semi-colon render slightly differently

[Mladen Mijatov]

Comma and semi-colon characters render differently in smaller sizes, around 11pt.

See attached screenshot.

It may make sense to fix this bug at the same time as bug 869963.

[Paul Sladen (sladen)]

Right, what's happening here is that although the lower comma part of both the comma and semi-colon are identical, they are in a slightly different position horizontally within the design cell.

In this case, the ';' is placed slightly closed to the left edge, and the ',' slightly further away from the left-edge. This is very likely on purpose to give an overall more balanced feel in long runs of text.

In your example, the cells appear to be being rendered as 7x16 pixels[0]. Because of the offset in position, one is being drawn between the 4th and 5th pixel columns, and the other is being drawn mainly in the 5th pixel column.

The availability of grayscale and sub-pixel anti-aliasing is then causing the slight variation in the rendering. With the hinting work, we can likely make sure that the one are clamped to a pixel column in the same manner.

[0] (nominally 16 PPEM, although 11pt * 96 DPI / 72 pt/in would be 15 PPEM?). Slightly puzzled.

Is that a helpful answer, or have I just added more confusion? :-)

[Mladen Mijatov (meaneye-rcf)]

Yes, makes sense. Thank you.

[Matthew Paul Thomas (mpt)]

However, Ubuntu on PC -- like OS X -- does not pay attention to manual hinting by default. So if this bug is to be fixed for those platforms, it needs to be fixed in the design of the original characters. That might be enough to warrant lining up the comma and semi-colon exactly.

[Paul Sladen (sladen)]

(Note the fix here is in the manual hinting code; which isn't used most of the time).