x-display-pixel-width/height inconsistency

[YAMAMOTO Mitsuharu]

There is an inconsistency about the behavior of
x-display-pixel-width/height among multiple platforms under
multi-monitor environments.

The elisp info nodes "Multiple Terminals" and "Display Feature
Testing" say:

  ...

     On some "multi-monitor" setups, a single X display outputs to more
  than one physical monitor.  Currently, there is no way for Emacs to
  distinguish between the different physical monitors.

  ...

   -- Function: display-pixel-height &optional display
       This function returns the height of the screen in pixels.  On a
       character terminal, it gives the height in characters.

       For graphical terminals, note that on "multi-monitor" setups this
       refers to the pixel width for all physical monitors associated with
       DISPLAY.  *Note Multiple Terminals::.

   -- Function: display-pixel-width &optional display
       This function returns the width of the screen in pixels.  On a
       character terminal, it gives the width in characters.

       For graphical terminals, note that on "multi-monitor" setups this
       refers to the pixel width for all physical monitors associated with
       DISPLAY.  *Note Multiple Terminals::.

But the actual return value is different among the platforms:

  * X11 and Mac port: Dimension for all physical monitors, as
    documented above.

  * NS port: Dimension of some particular physical monitor determined
    by the argument.

  * W32 port: Dimension of the primary monitor. (Not actually tested,
    but guessed from the code and API documentations.)

I think these functions should behave consistently among multiple
platforms (probably in line with X11).

                                     YAMAMOTO Mitsuharu
                                address@hidden