Chinese punctuations show in half width in Qt 4 about source-han-sans HOT 5 CLOSED

The punctuation marks that are shown are full-width by default in the Simplified Chinese subset OTFs and Simplified Chinese OTC font instances. What is being invoked is the 'palt' GPOS feature, which is turned on if the 'kern' GPOS feature is present and turned on. My guess is that Qt 4 automatically invokes the 'kern' GPOS feature, which is present in all Source Han Sans font resources, which has the effect of also turning on the 'pwid' GPOS feature, which is present. While actual kerning is not being used, because these glyphs don't have any kerning values (because none were deemed necessary), they are getting proportional (actually, half-width, if you look at the actual values) metrics via the 'palt' GPOS feature.

Adobe Song Std L doesn't exhibit this because it lacks both the 'palt' and 'kern' GPOS features. The same is true of Droid Sans Fallback. It is interesting that your screenshot suggests that Qt 5 fixes this.

from source-han-sans.

Thanks, Dr. Ken Lunde.

from source-han-sans.

Thank you for closing this. I am not familiar with Qt 4. If there is a toggle for turning off kerning, you should try doing that to confirm that the 'palt' GPOS feature is no longer turned on.

from source-han-sans.

You are right. The width of punctuations looks nice when kerning is set off. I'll report the bug to Qt project properly when I have enough time. Thanks again.

from source-han-sans.

Many thanks for checking this.

from source-han-sans.