[lucida] Lucida OT equality symbol looks faint in Adobe Acrobat

[Kai von Fintel]

On 11 Aug 2022, at 10:06, Bruno Voisin wrote:

>> On 11 Aug 2022, at 15:19, Kai von Fintel <tex at fintel.mailworks.org> 
>> wrote:
>>
>> Thanks for the confirmation, Bruno. It is indeed a rendering issue 
>> that arises with Acrobat and Lucida OT. Other OT fonts (like the TeX 
>> Gyre fonts) do not show this. So, I was wondering whether any Lucida 
>> OT experts had any thoughts on what might be happening.
>
> What's puzzling is that in your example the issue only arises with = 
> from the text font (LucidaBrightOT.otf), not = from the math font 
> (LucidaBrightMathOT.otf).
>
> Opening the two fonts in FontForge and looking at the EQUAL glyphs, 
> these look exactly the same, except for the presence of additional 
> horizontal fat lines made of a bluish cross patterns at vertical 
> positions 349 and 615 in the text font. I've no idea what that means, 
> whether it's connected to hinting.
>
> I tried to look at the FontForge doc at 
> <https://fontforge.org/docs/ui/mainviews/charview.html> , there are 
> three such lines visible in an illustration in the Pointer section, 
> but I couldn't find any explanation of what these lines are meant to 
> be, or even how they are called.

Right, the problem is with the text font =. We’ve worked around it by 
either using the math = (coding it as $=$) or using the boldface text = 
(\textbf{=}). Neither seems optimal but what workaround ever does?

I have no competence in the internal workings of fonts, so your 
discovery doesn’t translate into an obvious fix that I can come up 
with.

— Kai.
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