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Message-ID: <4e2fbdb7-d558-4272-8d71-97e9370f422a@acm.org>
Date: Fri, 26 Sep 2025 10:21:30 -0700
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Subject: Re: mintty character cell "detritus"
Content-Language: en-US
To: cygwin AT cygwin DOT com
References: <9ec858de-c2a5-463c-af1a-b28fde7f5174 AT acm DOT org>
 <19690aac-9b01-4d35-98cc-a9bf7611c7e6 AT towo DOT net>
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In-Reply-To: <19690aac-9b01-4d35-98cc-a9bf7611c7e6@towo.net>
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From: Jim Garrison via Cygwin <cygwin AT cygwin DOT com>
Reply-To: Jim Garrison <jhg AT acm DOT org>
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On 9/25/2025 23:03, Thomas Wolff via Cygwin wrote:
> 
> Am 26.09.2025 um 07:33 schrieb Jim Garrison via Cygwin:
>> This is a very minor and totally cosmetic issue, but it's been around 
>> "forever" so I'm curious if I'm the only one seeing it.
>>
>> When displaying colored text in mintty configured with a block cursor 
>> and dark background, as the cursor moves across text (in vi, say) it 
>> will change the color of the rightmost pixel column of certain 
>> characters (not all).  This happens when moving the cursor left-to- 
>> right, and the discolored bits disappear (or go back to their original 
>> color) when moving right-to-left.
>>
>> I'm pretty sure this has to do with anti-aliasing, and may not even be 
>> mintty's problem, but I've never seen it anywhere else.
>>
>> I put a couple of small demonstration screenshots on Google Drive:
>>
>> Actual size: https://drive.google.com/file/ 
>> d/1gF86FJMJqQJDaFHTVZXEZrMNIyRtTCSL/view?usp=sharing
>>
>> Enlarged view: https://drive.google.com/file/ 
>> d/15zWPNZQvryILvqRhaiFE3O35L057R8jQ/view?usp=sharing
>>
> Is this effect affected by the Font smooting setting?
> 

Good catch!  Changing Font-Smoothing to Partial or None greatly reduces 
the problem but it doesn't go away completely. After further 
experimentation I find that it also depends on the font.

I tried a few:

Affected: 	Lucida Console, Courier, Cascadia Code
Not affected: 	Lucida Sans Typewriter, Consolas, Brougham

The "Not affected" fonts don't display the problem with any 
font-smoothing setting, while for the affected fonts the problem is 
still present but affects fewer characters with font-smoothing None or 
Partial.

[Also, I got the directions backwards in my original message.  The issue 
occurs when moving the cursor R-to-L, and "corrects" when moving L-to-R.]

-- 
Jim Garrison
jhg AT acm DOT org

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