[isabelle-dev] Isabelle DejaVu against old Isabelle Text font

Makarius makarius at sketis.net
Tue Feb 5 20:19:13 CET 2019

On 05.02.19 11:43, Peter Lammich wrote:
> I just updated my Isabelle devel version (now on d21789843f01), and
> immediately noticed that the displayed fonts are significantly blurry.
> Find attached a side-by-side comparison of Isabelle-d21789843f01 (left)
> and Isabelle-2018 (right). At least on my monitor, the font display on
> the left side is significantly worse (blurred). Both use font size 18
> with standard anti-aliasing method.
> Is this worsening due to another Java version, due to the new Isabelle
> font, or has it some other reasons? How to find out?

 From a distance, I would say that this is a matter of the Java 11 
font-renderer, which is provided by https://adoptopenjdk.net. The one by 
Oracle is much worse -- OpenJdk not the non-free Java. (Note that the 
license change of non-free Oracle Java no longer allows to bundle it.)

You can find out yourself by trying the IsabelleText font that is 
distributed with Isabelle2018: the ttf files need to go into ~/.fonts on 
Ubuntu; or elsewhere on other systems. It is important to remove the 
fonts after the experiment!

Generally, the new fonts should be slightly better than before: the 
quality should be that of the original Deja Vu fonts without any 
censorship. I merely trim it to a well-defined collection of glyphs and 
add our Isabelle math symbols from the TeX family -- see "isabelle 
build_fonts" (e.g. in Isabelle/2c3e5e58d93f).

 > How to fix it?

You know already that "fix" and "bug" is not in my vocabulary -- I don't 
use such street language.

On up-to-date UHD displays the quality should of the new Java 11 + new 
fonts should be higher than ever before, so you can improve your overall 
situation by getting a new display. My huge UHD display at home was 
actually quite cheap: approx. 350 EUR.

I do see the slight blurring on my ancient HD Sony Vaio from 2013, but I 
am not using that very often. Buying a new laptop is certainly more 
expensive than just a display -- nonetheless I am surprised how many 100 
EUR displays are still standing on desks and stared at every day.


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