bug#53478: 26.3; Document text-terminal (non)support of pixel-relevant features

[Eli Zaretskii]

> From: Drew Adams <drew.adams@oracle.com>
> Date: Sun, 23 Jan 2022 16:25:12 +0000
> 
> I tried to help with this user question:
> 
> https://emacs.stackexchange.com/q/70231/105
> 
> I'm no expert on this.  I guessed that Emacs in terminal mode can't
> support most pixel-level operations.

That question has nothing to do with pixel-level operations.  It asks
about functions like x-display-pixel-width that are not available in a
build --without-x.

> I wanted to point the user to the Emacs manual about this.  I tried to
> find info about it with `i' using keyword `terminal' (even with
> substring matching for completions).  I found nothing.  Likewise, with
> keyword `pixel'.

I see no reason to say in the manual anything about this that we don't
already do.  Every place that talks about pixels either says it's
relevant to graphical displays, or discusses stiff that is only
relevant to GUI.  The doc string of x-display-pixel-width, for
example, says:

  Return the width in pixels of the X display TERMINAL.
                                    ^^^^^^^^^
So I don't think we should do anything here, and I'm closing this bug
report.