Re: display-mm-width return value off on Windows

[David Kastrup]

Eli Zaretskii <address@hidden> writes:

>> From: Ralf Angeli <address@hidden>
>> Date: Thu, 06 Jul 2006 19:50:26 +0200
>> 
>> On Windows the return values of `display-mm-width' and
>> `display-mm-height' don't really reflect the screen width and height
>> in millimeters.  I attached a patch which yields more realistic
>> results.
>
> Thanks.
>
>> In my case:
>> 
>>                    display-mm-*   display-mm-*
>>         Real size  without patch  with patch
>> Width   285mm      370            279
>> Height  215mm      277            203
>> 
>> For a preview-latex user who originally reported the problem:
>> 
>>                    display-mm-*   display-mm-*
>>         Real size  without patch  with patch
>> Width   330mm      320            305
>> Height  207mm      240            203
>
> That is still not a very good approximation, is it?
>
>> -  cap = GetDeviceCaps (hdc, VERTSIZE);
>> +  height = round (GetDeviceCaps (hdc, VERTRES)
>> +              / GetDeviceCaps (hdc, LOGPIXELSY) * 25.4);
>
> What is this magic constant 25.4?  I think we at least should use a
> single macro instead of having the literal constant scattered across
> the sources.

Millimeters per inch.

-- 
David Kastrup, Kriemhildstr. 15, 44793 Bochum