[ros-dev] Explanation needed on TryToTranslateChar...

[art yerkes]

On Thu, 10 Mar 2005 18:29:29 GMT 
"Johannes Olofsson" <johannes_olofsson at spray.se> wrote:

> Hi!
> Could somebody help me out and explain how the TryToTranslateChar function in \reactos\subsys\win32k\ntuser\keyboard.c is supposed to work...
> 
> First there is the following definition:
> shift = keyLayout->pCharModifiers->ModNumber[ModBits];

ModNumber[ModBits] looks up to a column number in the vkToWchar tables, as I
remember.

> 
> which is later used in:
> CapsMod = shift | ((CapsState & CAPITAL_BIT) ? vkPtr->Attributes : 0);

Here, we're putting vkPtr->Attributes (either CAPS or NOCAPS) into the
shift number if it isn't there already.  Now that you point it out, this
is wrong because shift does not negate capslock.  I think it is close in
other respects though.

> 
> which is used for the translation:
> *pwcTranslatedChar = vkPtr->wch[CapsMod];
> 
> Doesn't shift contain the index for the VK_TO_CHARSx table in the keyboard layout data structure?

It contains the index of a column to look inside.  That's why we scan the
tables to determine which table the vk lies in.  If vk is in a narrower table,
we must do something.  I truncate CapsMod but this may not be totally correct.
I believe we need to tolerate extra modifiers so that Alt modifer can be used
to generate syskey messages.  This may be handled as a special case in real
windows however.

> 
> Why is it then |:ed with vkPtr->Attributes , which I suppose corresponds to the CAPS/NOCAPS constants in the keyboard layout files ?
> 
> Shouldn't it be something like:
> shift = keyLayout->pCharModifiers->ModNumber[ModBits ^ ((CapsState & CAPITAL_BIT) ? vkPtr->Attributes : 0];
> 

You are likely right that Attributes should affect the set modifier bits
rather than column number.  They happen to correspond in most instances
(shift-a adds both 1 to modifier bits and 1 to column number), which is
probably why this hasn't come up before.
-- 
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