I think the bug is related to the line below
I make a breakpoint on this line, and find fontDef.pixelSize is always 12 when point size of the font is 10 whatever DPI is changed to 120,144 or even 192.
I try to find where fontDef.pixelSize is changed but failed.
Can somebody tell me why the variable is always 12? I'm sure that it leads to fonts in some point sizes look still less anti aliased for after I make the text larger, the text is anti aliased.
An screenshot is in attachment.