Possible to add new precomposed characters for local language in Togo?

Philippe Verdy verdy_p at wanadoo.fr
Sat Nov 5 23:32:23 CDT 2016

2016-11-06 4:11 GMT+01:00 Marcel Schneider <charupdate at orange.fr>:

> On Fri, 04 Nov 2016 15:30:48 -0700, Doug Ewell wrote:
> — And with LATIN CAPITAL LETTER OPEN E? Why not this way (as has been
> suggested):
> /*TILDE&AIGU */ DEADTRANS( 0x0190 ,0x1e4d ,{0x0190,0x0303,0x0301} ,DKF_0

This snippet cannot work as is, because the DEADTRANS() macro maps
gernerates a 8-BYTE structure only has a single WCHAR for storing the
result of the map of a (VKEY+modifier number):

  typedef struct _DEADKEY {
    DWORD dwBoth;
    WCHAR wchComposed;
    USHORT uFlags;

So it will need to map a WCH_LGTR instead, and then use a "ligature" table
to store the string containing the 3 code units you want.

Then there's an unused BYTE in the DEADTRANS structure for the flags, that
can be used (specifically for entries mapped to WCH_LGTR) to pass flags to
the LIGATURE(n) table (where there's also a free BYTE in the indexing key,
allowing to pass an identifier needed for the lookup in the LIGATURE(n)
table; alternatively, instead of mapping WCH_LGTR (a PUA), you could as
well map another PUA there in 0xE001.0xE0FF for passing a byte for the
deadkey state into the lookup of ligatures:

typedef struct _LIGATURE ## i { \
 BYTE VirtualKey; \
 WORD ModificationNumber; \
 WCHAR wch[i]; \

which can safely be changed to:

typedef struct _LIGATURE ## i { \
 BYTE VirtualKey, DeadKeyState; \
 WORD ModificationNumber; \
 WCHAR wch[i]; \

(in the current definition of <kbd.h> the extra byte is implicit for the
alignment, but not declared explicitly, it is implicitly filled with zeroes
by C compilers when declaring the structure, but in my opinion this extra
byte should have been declared explicitly.)

But now it's up to the OS to support it, may be it works already if the
lookup in the LIGATURE(n) table already scans for values of a DWORD,
including this free padding byte, however there's a need to change some
code in the kernel-level to check the PUA values mapped in DEADKEY
structures and extract a DeadKeyState from it.

The alternative is to map the combination of two deadkeys to a bit in the
modifier number (this can be instructed by the uFlags, which will set the
modifier bit number specified in the mapped PUA). In all cases there's
still space for extension there.

The last alternative is to extend the KBDTABLES structure to append new
members for a table of extended DEADKEYS, and a separate table of LIGATURE
for DEADKEYs (the KBDTABLE does not specify its own size, but it has a
fLocaleFlags field just before the table of ligatures, which can indicate
the presence of these extensions.
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