X, dpi and fonts

[T <mlist4suntong@yahoo.com>]

Hi

Several questions about X and dpi:

- How can I determine the dpi of current X session?

- Is there any relation between X dpi and font selection? 

- How does X map font request such as
'-*-lucidatypewriter-medium-r-*-*-*-100-*-*-*-*-*-*' to actual font name?

I think for the '-*-lucidatypewriter-medium-r-*-*-*-100-*-*-*-*-*-*'
font request, my xorg 6.9 chooses
'-b&h-lucidatypewriter-medium-r-normal-sans-10-100-75-75-m-60-iso10646-1'.

In my xorg 7.0, I think it chooses
-b&h-lucidatypewriter-medium-r-normal-sans-14-100-100-100-m-80-iso10646-1

Is there any way that I can tell it for sure? 

These are my '-*-lucidatypewriter-medium-r-*-*-*-100-*-*-*-*-*-*' fonts in
my xorg 7.0:

$ xlsfonts | grep -- -lucidatypewriter-medium-r-.*100
-b&h-lucidatypewriter-medium-r-normal-sans-0-0-100-100-m-0-iso10646-1
-b&h-lucidatypewriter-medium-r-normal-sans-0-0-100-100-m-0-iso8859-1
-b&h-lucidatypewriter-medium-r-normal-sans-10-100-75-75-m-60-iso10646-1
-b&h-lucidatypewriter-medium-r-normal-sans-10-100-75-75-m-60-iso8859-1
-b&h-lucidatypewriter-medium-r-normal-sans-11-80-100-100-m-70-iso10646-1
-b&h-lucidatypewriter-medium-r-normal-sans-11-80-100-100-m-70-iso8859-1
-b&h-lucidatypewriter-medium-r-normal-sans-14-100-100-100-m-80-iso10646-1
-b&h-lucidatypewriter-medium-r-normal-sans-14-100-100-100-m-80-iso8859-1
-b&h-lucidatypewriter-medium-r-normal-sans-17-120-100-100-m-100-iso10646-1
-b&h-lucidatypewriter-medium-r-normal-sans-17-120-100-100-m-100-iso8859-1
-b&h-lucidatypewriter-medium-r-normal-sans-20-140-100-100-m-120-iso10646-1
[...]

Why X (xorg7.0) choose 14-100-100, instead of 11-80-100-100, or
10-100-75-75 fonts?

thanks

tong