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#18636
24.4.50; doc of `display-monitor-attributes-list' - DISPLAY? FRAME?
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Reported by: Drew Adams <drew.adams <at> oracle.com>
Date: Sun, 5 Oct 2014 19:06:02 UTC
Severity: minor
Found in version 24.4.50
Done: Eli Zaretskii <eliz <at> gnu.org>
Bug is archived. No further changes may be made.
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Your bug report
#18636: 24.4.50; doc of `display-monitor-attributes-list' - DISPLAY? FRAME?
which was filed against the emacs package, has been closed.
The explanation is attached below, along with your original report.
If you require more details, please reply to 18636 <at> debbugs.gnu.org.
--
18636: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=18636
GNU Bug Tracking System
Contact help-debbugs <at> gnu.org with problems
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> Date: Sun, 5 Oct 2014 19:41:21 -0700 (PDT)
> From: Drew Adams <drew.adams <at> oracle.com>
> Cc: 18636 <at> debbugs.gnu.org
>
> > > 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.
Done on the emacs-24 branch (revision 117559).
> 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.
That's not what happens, though. Each function extracts the info it
needs from whatever kind of argument it is passed, and then uses that
info.
> > > 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.
Done.
> > 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.
Done.
> > > In (elisp) `Basic Parameters' I see this description of frame
> > > parameter `display':
> > >
> > > The display on which to open this frame. It should be a string
> > > of the form `"HOST:DPY.SCREEN"', just like the `DISPLAY'
> > > environment variable.
> > >
> > > But if I evaluate `(frame-parameters)' on MS Windows I see this
> > > value for parameter `display': "w32".
> > >
> > > "w32" does not seem to fit the form `"HOST:DPY.SCREEN"'. What
> > > gives?
> >
> > Emacs on MS-Windows doesn't support the notion of 'display', so all
> > frames return the same value of that parameter.
>
> OK, then the doc should mention this, or at least say that the
> string might not take the form "HOST:DPY.SCREEN" on some platforms,
> and preferably say something about what to expect on the
> exceptional platforms (and perhaps give some idea of what use the
> exceptional value is - what it can be used for, or what info it
> conveys).
Done.
> > > And why is that string surrounded by `...'?
> >
> > An artifact of Texinfo markup.
>
> I see. Is that then correct, or should the `...' be absent?
> There are strings in the manual that are not surrounded by `...'.
I fixed the markup.
> > > And why aren't the components of that "form" described: What are
> > > acceptable values for HOST, DPY, and SCREEN?
> >
> > Users on X already know what they are; users on other systems don't
> > need to know, because this is not supported. Either way, this
> > notion is not an Emacs invention, it is a feature of the X
> > window system.
>
> Then please say that. E.g., say that the value is useful only for
> X Window, or only relevant for it. If the function itself has no
> use beyond X Window, then please make that clear.
Done, and also improved the description of the X form.
> From: Andy Moreton <andrewjmoreton <at> gmail.com>
> Date: Tue, 07 Oct 2014 19:35:28 +0100
>
> > Oh, and I think this is no longer about the docs, so probably a new
> > bug report is in order, specifically about restoring frames on
> > multi-monitor displays.
> True, as long as the meaning of geometry/workarea and the coordinate
> system are given a little more detail in the docs.
Done.
I'm closing this bug.
[Message part 3 (message/rfc822, inline)]
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?
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.
And there is a frame parameter `display', whose value is "The display on
which to open this frame. It should be a string of the form
`"HOST:DPY.SCREEN"', just like the `DISPLAY' environment variable.
This suggests that a display is not a frame. So how is it that
`frame-monitor-attributes' passes a FRAME to
`display-monitor-attributes-list', which supposedly expects a display
instead?
Please try to clear up some of this confusion in the doc and doc
strings.
In GNU Emacs 24.4.50.1 (i686-pc-mingw32)
of 2014-09-15 on LEG570
Bzr revision: 117884 dancol <at> dancol.org-20140915050944-sqsajysnwef51f9m
Windowing system distributor `Microsoft Corp.', version 6.1.7601
Configured using:
`configure --enable-checking 'CFLAGS=-O0 -g3' CPPFLAGS=-DGLYPH_DEBUG=1'
This bug report was last modified 10 years and 286 days ago.
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