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

[Jason Rumney <jasonr@gnu.org>]

David Kastrup wrote:
> storm@cua.dk (Kim F. Storm) writes:
>
>   
>> So I tried to do fix that (in a way similar to the one proposed for
>> display-mm-*) some time ago, but didn't complete it, as it wasn't
>> really clear what had to be done.
>>
>> First of all, it had to be done per-display (at least X supports
>> multiple display),
>>
>> Secondly, it was not clear to me whether this problem was specific
>> to X, but I guessed it was not, so changes had to be done for
>> all platforms (as it involved added stuff to "display-info".)
>>
>> Last, but not least, it was unclear what other parts of the code
>> would also need changes -- e.g. display-mm-* -- which would have
>> to be reworked to not just use some X-macro like WidthMMOfScreen.
>>     
>
> Whatever solution is chosen in the end: it is important that the same
> algorithm is used for converting point size of fonts into pixel size
> and vice versa.
>
> preview-latex needs to guess how many pixels a given font will occupy
> on the screen in order to create graphics matching in size.  And the
> font sizes are returned in points, namely physical dimensions
At least on Windows, point sizes for fonts are based on user 
configuration, not the actual physical size of the monitor.
So I don't think you should be using display-mm-* for calculating sizes 
you expect to be relative to fonts anyway.
Why not use the pixel size of the font? Surely that will be more 
accurate for the purpose you want.