Subject: RE: bug#18636: 24.4.50; doc of `display-monitor-attributes-list' - DISPLAY? FRAME?

From: Drew Adams <[email-masked]>
Date: Sun, 5 Oct 2014 19:41:21 -0700 (PDT)

> > I find it unclear that the optional parameter of
> > `display-monitor-attributes-list' is named DISPLAY, and is
> > referred to as a display in the doc string, and yet in
> > `frame-monitor-attributes' it is arg FRAME that is passed
> > to `display-monitor-attributes-list'.
> >
> > Is the argument of `display-monitor-attributes-list' a
> > display or a frame?
> 
> It can be either.

OK.  Then the doc should say so.  And it should call out the
relation between the two.  For example, if a frame is passed
and its display is used (= its `display' frame parameter),
then say so.

> > What about other functions, such as `display-pixel-height', which
> > call `display-monitor-attributes-list'?  They seem to pass their
> > DISPLAY arg to it.  Is this arg too something that can be (or
> > is always?) a frame? The doc string of `display-pixel-height'
> > (for example) says:
> >
> >   "If DISPLAY is omitted or nil, it defaults to the selected
> >    frame's display."
> >
> > That would seem to suggest that a frame is not a display, but
> > rather it _has_ a display.
> 
> A frame is not a display, but these functions accept either one.

Their doc should say so.

> If you make a list of the functions where the doc string is not
> explicit about this fact, I will fix them.

Thank you.  I think this is the case for all of the 20 functions
described in (elisp) `Display Feature Testing', but there might
be others as well.