Re: xlib:create-glyph-cursor -- a spec issue

[Kerry Kimbrough <Kimbrough@dsg.csc.ti.com>]

   >     What is
   >     supposed to happen when mask-font is specified but mask-char is omitted?  The
   >     code just wires mask-char=0, which doesn't seem particularly useful. Several
   >     alternatives are possible.
   > 
   >     1. Signal error
   > 	
   >     2. Default to source-char
   > 
   >     3. Default to 0
   > 
   >     4. Default to (font-default-char mask-font)
   > 
   >     5. If (eq source-font mask-font), default to (1+ source-char), else signal
   >        error.
   > 
   >     I suggest #5.  Since the source/mask-char's have to be tightly coupled, it's not
   >     reasonable that any single value could serve as a default mask-char, so #2 is
   >     plausible but #1 is more correct.  But #5 also allows a short-hand for a common
   >     idiom based on a special font structure (like that of the "cursor" font).
   > 
   > 5 sounds reasonable, especially if mask-font defaults to source-font.


But it doesn't. Omitting mask-font means "no mask", i.e. "mask is all 1's".