emacs-28 06dcd2be5d: Improve rectangle-mark-mode documentation regarding mark activation

[Eli Zaretskii]

branch: emacs-28
commit 06dcd2be5d42362757e923bc5d1952a2bce509b9
Author: Sean Whitton <spwhitton@spwhitton.name>
Commit: Eli Zaretskii <eliz@gnu.org>

    Improve rectangle-mark-mode documentation regarding mark activation
    
    * doc/emacs/killing.texi: Describe how rectangle-mark-mode works when
    Transient Mark mode is off.  Qualify discussion of
    rectangle-exchange-point-and-mark to say that it cycles the four
    corners only when the region is active.
    * lisp/rect.el (rectangle-mark-mode): State that rectangle-mark-mode
    does not activate the mark when Transient Mark mode is off.  Reword
    sentence about how long the mode lasts to account for when Transient
    Mark mode is off.  (Bug#42663)
---
 doc/emacs/killing.texi | 16 +++++++++++-----
 lisp/rect.el           |  3 ++-
 2 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/doc/emacs/killing.texi b/doc/emacs/killing.texi
index 6e4fd77e8b..37243b6cd2 100644
--- a/doc/emacs/killing.texi
+++ b/doc/emacs/killing.texi
@@ -921,6 +921,11 @@ so in a rectangular fashion, and killing and yanking 
operate on the
 rectangle.  @xref{Killing}.  The mode persists only as long as the
 region is active.
 
+The region-rectangle works only when the mark is active.  In
+particular, when Transient Mark mode is off (@pxref{Disabled Transient
+Mark}), in addition to typing @kbd{C-x @key{SPC}} you will need to
+activate the mark.
+
 Unlike the standard region, the region-rectangle can have its corners
 extended past the end of buffer, or inside stretches of white space
 that point normally cannot enter, like in the middle of a TAB
@@ -929,11 +934,12 @@ character.
 @findex rectangle-exchange-point-and-mark
 @findex exchange-point-and-mark@r{, in rectangle-mark-mode}
 @kindex C-x C-x@r{, in rectangle-mark-mode}
-When the region is in rectangle-mark-mode, @kbd{C-x C-x} runs the
-command @code{rectangle-exchange-point-and-mark}, which cycles between
-the four corners of the region-rectangle.  This comes in handy if you
-want to modify the dimensions of the region-rectangle before invoking
-an operation on the marked text.
+When the region is active (@pxref{Mark}) and in rectangle-mark-mode,
+@kbd{C-x C-x} runs the command
+@code{rectangle-exchange-point-and-mark}, which cycles between the
+four corners of the region-rectangle.  This comes in handy if you want
+to modify the dimensions of the region-rectangle before invoking an
+operation on the marked text.
 
 @node CUA Bindings
 @section CUA Bindings
diff --git a/lisp/rect.el b/lisp/rect.el
index d288adfbaf..80f992e182 100644
--- a/lisp/rect.el
+++ b/lisp/rect.el
@@ -651,7 +651,8 @@ with a prefix argument, prompt for START-AT and FORMAT."
 (define-minor-mode rectangle-mark-mode
   "Toggle the region as rectangular.
 
-Activates the region if needed.  Only lasts until the region is deactivated."
+Activates the region if it's inactive and Transient Mark mode is
+on.  Only lasts until the region is next deactivated."
   :lighter nil
   (rectangle--reset-crutches)
   (when rectangle-mark-mode