[~100 mod] Uppercase characters in bold fonts appear one pixel shorter when using 7pt and slight hinting

[Daniel Luz]

1. Copy and paste this line into the address field of a Web browser:
data:text/html,<p style="font: 7pt Ubuntu">EXAMPLE <b>EXAMPLE</b> EXAMPLE</p>

When using slight hinting (which I believe is the default) and 7pt font size (or 9px), uppercase characters in bold variants are one pixel shorter than the regular-weight variants. This is particularly noticeable when there's a bold word in uppercase between normal-weight text, i.e.:

    <p style="font: 7pt Ubuntu">EXAMPLE <b>EXAMPLE</b> EXAMPLE</p>

Screenshot: https://launchpadlibrarian.net/56773241/Ubuntu.png

The screenshot was taken using the standard font picker dialog's preview area. "None" and "Full" hinting options are provided just for comparison; they are internally consistent. Subpixel smoothing was used, but the smoothing method has no influence on the problem.

UA String:

Mozilla/5.0 (X11; U; Linux x86_64; en-US) AppleWebKit/534.3 (KHTML, like Gecko) Chrome/6.0.472.63 Safari/534.3

[Paul Sladen (sladen)]

What version of the font do you have installed?

[Daniel Luz (mernen)]

ttf-ubuntu-font-family 0.68+ufl-0ubuntu1, the official public package.

[Daniel Luz (mernen)]

I don't see a link to the screenshot, did the attachment fail? I can resubmit it here.

[Paul Sladen (sladen)]

Yes, please can you provide a screenshot showing this.

[Daniel Luz (mernen)]

Here's the screenshot. Notice how, in the last column, the bold word is one pixel lower when using slight hinting.

[David Marshall (dave-daltonmaag)]

Am I correct in thinking that "Slight Hinting" is actually an autohinter
setting, not a rasterization setting? If so, nothing further can be done
to the font to change this - the work has been done in the hint code, as
seen in Full, which is being ignored if the autohinter is at work.

Dave

[Paul Sladen (sladen)]

Yes, slight is being done by the Autohinter. It /may/ be possible to do something to bring the auto-hinted outlines and manually hinted outlines closer together; but as you note the work has been put into the manually-hinted forms (Hinted=Full) already.

I'm thinking something along the lines of more effective blending between outline, autohinter implementation and manual hinted, rather than switching straight from one method to the other when the setting gets to "Full".

This will need investigation during the next six months or so, and is probably more likely to be on the Freetype or FontConfig side.