Windows keyboard restrictions (was: Re: Windows 10 release)

From: Doug Ewell <>
Date: Mon, 03 Aug 2015 11:02:38 -0700

Marcel Schneider <charupdate at orange dot fr> wrote:

> The bug on Windows I encountered at the end of July has been
> definitely identified and reconstructed. After ninety-five drivers
> compiled since the bug appeared, I can tell so much as that the
> problem is related to the length of the so-called ligatures. When the
> MSKLC was built, they were limited to four characters on Windows (see
> glossary in the MSKLC Help). On my machine the maximal length is 16
> characters. The problem is that this is not equal on all shift states
> and perhaps keys. Roughly, I can put five characters on modification
> number three, that is normally AltGr, but not on #4 (Shift+AltGr).

As far as I can tell, the limit for a ligature on a Windows keyboard
layout is four UTF-16 code points:

MSKLC help, under "Validation Reference":
"Ligatures cannot contain more than four UTF-16 code points"

Presentation from IUC 23 by Michael Kaplan (author of MSKLC) and Cathy



I understand that there are some tools (such as Keyboard Layout Manager)
that claim a higher limit, and it may even be possible in some cases to
assign more than four, but the DOCUMENTED limit appears to be four. (If
you claim that it is not, please provide a link to the relevant official
documentation, and note that C++ code showing 16 fields is not

It is not a bug for software to fail to perform BEYOND its documented

Since you are so very eager to declare this a bug, or a collection of
bugs, rather than a design limitation, I strongly recommend you get in
touch with Microsoft Technical Support and express your concerns to
them. Make sure to let them know just how certain you are that these are
bugs. See if they'll send you a T-shirt.

Doug Ewell | | Thornton, CO 🇺🇸
Received on Mon Aug 03 2015 - 13:03:47 CDT

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