bug#60936: 30.0.50; ERC >5.5: Add erc-fill style based on visual-line-mode

["J.P." <jp@neverwas.me>]

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I'm thinking it might make sense to have `fill-wrap' formally depend on
`scrolltobottom', even though there's no technical reason to do so. The
rare user who prefers otherwise can still get their way via
`erc-scrolltobottom-mode-hook'. Alternatively, we could just enable
`scrolltobottom' by default in a future release.


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From 66a7f1a34924a7244ac27b25e8d6b36d9c3ceaf2 Mon Sep 17 00:00:00 2001
From: "F. Jason Park" <jp@neverwas.me>
Date: Mon, 13 Nov 2023 12:07:36 -0800
Subject: [PATCH] [5.6] Make erc-fill-wrap depend on scrolltobottom

* lisp/erc/erc-fill.el (erc-fill-mode, erc-fill-function): Add
reference to `erc-fill-wrap-mode' in doc string.
(erc--fill-scrolltobottom-exempt-p): New variable.
(erc-fill--wrap-ensure-dependencies): Warn and enable
`erc-scrolltobottom-mode' if necessary.
(erc-fill-wrap-mode): Mention workaround for users who don't want this
module to automatically enable `scrolltobottom'.
* test/lisp/erc/erc-fill-tests.el (erc-fill-tests--wrap-populate):
Exempt tests from `scrolltobottom' dependency.  (Bug#60936)
---
 lisp/erc/erc-fill.el            | 44 +++++++++++++++++++--------------
 test/lisp/erc/erc-fill-tests.el |  1 +
 2 files changed, 26 insertions(+), 19 deletions(-)

diff --git a/lisp/erc/erc-fill.el b/lisp/erc/erc-fill.el
index e48d5540c86..457e51e6053 100644
--- a/lisp/erc/erc-fill.el
+++ b/lisp/erc/erc-fill.el
@@ -44,11 +44,7 @@ erc-fill
 (define-erc-module fill nil
   "Manage filling in ERC buffers.
 ERC fill mode is a global minor mode.  When enabled, messages in
-the channel buffers are filled."
-  ;; FIXME ensure a consistent ordering relative to hook members from
-  ;; other modules.  Ideally, this module's processing should happen
-  ;; after "morphological" modifications to a message's text but
-  ;; before superficial decorations.
+the channel buffers are filled.  See also `erc-fill-wrap-mode'."
   ((add-hook 'erc-insert-modify-hook #'erc-fill 60)
    (add-hook 'erc-send-modify-hook #'erc-fill 60))
   ((remove-hook 'erc-insert-modify-hook #'erc-fill)
@@ -86,11 +82,12 @@ erc-fill-function
 
 A third style resembles static filling but \"wraps\" instead of
 fills, thanks to `visual-line-mode' mode, which ERC automatically
-enables when this option is `erc-fill-wrap' or when the module
-`fill-wrap' is active.  Use `erc-fill-static-center' to specify
-an initial \"prefix\" width and `erc-fill-wrap-margin-width'
-instead of `erc-fill-column' for influencing initial message
-width.  For adjusting these during a session, see the commands
+enables when this option is set to `erc-fill-wrap' or when the
+module `fill-wrap' is active \(see `erc-fill-wrap-mode' for
+details).  Use `erc-fill-static-center' to specify an initial
+\"prefix\" width and `erc-fill-wrap-margin-width' instead of
+`erc-fill-column' for influencing initial message width.  For
+adjusting these during a session, see the commands
 `erc-fill-wrap-nudge' and `erc-fill-wrap-refill-buffer'."
   :type '(choice (const :tag "Variable Filling" erc-fill-variable)
                  (const :tag "Static Filling" erc-fill-static)
@@ -367,8 +364,11 @@ erc-fill-wrap-mode-map
   "<remap> <erc-bol>" #'erc-fill--wrap-beginning-of-line)
 
 (defvar erc-button-mode)
+(defvar erc-scrolltobottom-mode)
 (defvar erc-legacy-invisible-bounds-p)
 
+(defvar erc--fill-scrolltobottom-exempt-p nil)
+
 (defun erc-fill--wrap-ensure-dependencies ()
   (with-suppressed-warnings ((obsolete erc-legacy-invisible-bounds-p))
     (when erc-legacy-invisible-bounds-p
@@ -381,6 +381,10 @@ erc-fill--wrap-ensure-dependencies
     (unless erc-fill-mode
       (push 'fill missing-deps)
       (erc-fill-mode +1))
+    (unless (or erc-scrolltobottom-mode (memq 'scrolltobottom erc-modules)
+                erc--fill-scrolltobottom-exempt-p)
+      (push 'scrolltobottom missing-deps)
+      (erc-scrolltobottom-mode +1))
     (when erc-fill-wrap-merge
       (require 'erc-button)
       (unless erc-button-mode
@@ -401,20 +405,22 @@ erc-fill--wrap-ensure-dependencies
 ;;;###autoload(put 'fill-wrap 'erc--feature 'erc-fill)
 (define-erc-module fill-wrap nil
   "Fill style leveraging `visual-line-mode'.
+
 This module displays nicks overhanging leftward to a common
 offset, as determined by the option `erc-fill-static-center'.
 And it \"wraps\" messages at a common margin width, as determined
 by the option `erc-fill-wrap-margin-width'.  To use it, either
 include `fill-wrap' in `erc-modules' or set `erc-fill-function'
-to `erc-fill-wrap'.  Most users will want to enable the
-`scrolltobottom' module as well.  Once active, use
-\\[erc-fill-wrap-nudge] to adjust the width of the indent and the
-stamp margin, and use \\[erc-fill-wrap-toggle-truncate-lines] for
-cycling between logical- and screen-line oriented command
-movement.  Similarly, use \\[erc-fill-wrap-refill-buffer] to fix
-alignment problems after running certain commands, like
-`text-scale-adjust'.  Also see related stylistic options
-`erc-fill-line-spacing' and `erc-fill-wrap-merge'.
+to `erc-fill-wrap'.  Once active, use \\[erc-fill-wrap-nudge] to
+adjust the width of the indent and the stamp margin, and use
+\\[erc-fill-wrap-toggle-truncate-lines] for cycling between
+logical- and screen-line oriented command movement.  Similarly,
+use \\[erc-fill-wrap-refill-buffer] to fix alignment problems
+after running certain commands, like `text-scale-adjust'.  Also
+see related stylistic options `erc-fill-line-spacing' and
+`erc-fill-wrap-merge'.  Note that this module currently ensures
+`erc-scrolltobottom-mode' is active.  Users wishing otherwise can
+suppress that behavior by leveraging `erc-fill-wrap-mode-hook'.
 
 This module imposes various restrictions on the appearance of
 timestamps.  Most notably, it insists on displaying them in the
diff --git a/test/lisp/erc/erc-fill-tests.el b/test/lisp/erc/erc-fill-tests.el
index c21f3935503..d54204eb0ce 100644
--- a/test/lisp/erc/erc-fill-tests.el
+++ b/test/lisp/erc/erc-fill-tests.el
@@ -47,6 +47,7 @@ erc-fill-tests--insert-privmsg
 
 (defun erc-fill-tests--wrap-populate (test)
   (let ((original-window-buffer (window-buffer (selected-window)))
+        (erc--fill-scrolltobottom-exempt-p t)
         (erc-stamp--tz t)
         (erc-fill-function 'erc-fill-wrap)
         (pre-command-hook pre-command-hook)
-- 
2.41.0