Make erc-fill-wrap work with left-sided stamps

* etc/ERC-NEWS: Remove all mention of option `erc-timestamp-align-to'
supporting a value of `margin', which has been abandoned.  Do mention
leading white space before stamps now having stamp-related properties.
* lisp/erc/erc-backend.el (erc--reveal-prompt, erc--conceal-prompt):
New generic functions with default implementations factored out from
`erc--unhide-prompt' and `erc--hide-prompt'.
(erc--prompt-hidden-p): New internal predicate function.
(erc--unhide-prompt): Defer to `erc--reveal-prompt', and set
`erc-prompt' text property to t.
(erc--hide-prompt): Defer to `erc--conceal-prompt', and set
`erc-prompt' text property to `hidden'.
* lisp/erc/erc-compat.el (erc-compat--29-browse-url-irc): Don't
use `function-equal'.
* lisp/erc/erc-fill.el (erc-fill-wrap-margin-width,
erc-fill-wrap-margin-side): New options to control side and initial
width of `fill-wrap' margin.
(erc-fill--wrap-beginning-of-line): Fix bug involving non-string
valued `display' props.
(erc-fill-wrap-toggle-truncate-lines): New command to re-enable
`visual-line-mode' when toggling off `truncate-lines'.
(erc-fill-wrap-mode-map): Remap `toggle-truncate-lines' to
`erc-fill-wrap-toggle-truncate-lines'.
(erc-fill-wrap-mode, erc-fill-wrap-enable, erc-fill-wrap-disable):
Update doc string, persist a few local vars, and conditionally set
`erc-stamp--margin-left-p'.  When deactivating, disable
`visual-line-mode' first.
(erc-fill--wrap-continued-message-p): Use `erc-speaker' instead of
heuristics when comparing nicks between consecutive messages.
(erc-fill-wrap-nudge): Update doc string and account for left-sided
stamps.
(erc-timestamp-offset): Add comment regarding conditional guard based
on function-valued option.
* lisp/erc/erc-stamp.el (erc-timestamp-use-align-to): Remove value
variant `margin', which was originally intended to be new in ERC 5.6.
This functionality was all but useless without the internal minor mode
`erc-stamp--display-margin-mode' active.
(erc-stamp-right-margin-width): Remove unused option new in 5.6.
(erc-stamp--display-margin-force): Remove unused function.
(erc-stamp--margin-width, erc-stamp--margin-left-p): New internal
variables.
(erc-stamp--init-margins-on-connect): New function for initializing
mode-managed margin after connecting.
(erc-stamp--adjust-right-margin, erc-stamp--adjust-margin): Rename
function to latter and accommodate left-hand stamps.
(erc-stamp--inherited-props): Move definition higher up in same file.
(erc-stamp--display-margin-mode): Update function name, and adjust
setup and teardown to accommodate left-handed stamps.  Don't add
advice around `erc-insert-timestamp-function'.
(erc-stamp--last-prompt, erc-stamp--display-prompt-in-left-margin):
New function and helper var to convert a normal inserted prompt so
that it appears in the left margin.
(erc-stamp--refresh-left-margin-prompt): Helper for other modules to
quickly refresh prompt outside of insert hooks.
(erc--reveal-prompt, erc--conceal-prompt): New implementations for
when `erc-stamp--display-margin-mode' is active.
(erc-insert-timestamp-left): Convert to generic function and provide
implementation for `erc-stamp--display-margin-mode'.
(erc-stamp--omit-properties-on-folded-lines): New variable, an escape
hatch for propertizing white space before right-side stamps folded
over onto another line.
(erc-insert-timestamp-right): Don't expect `erc-timestamp-align-to' to
ever be the symbol `margin'.  Move handling for that case to one
contingent on the internal minor mode `erc-stamp--display-margin-mode'
being active.  Add text properties preceding stamps that occupy a line
by their lonesome.  See related news entry for rationale.  This is
arguably a breaking change.
* lisp/erc/erc.el (erc--refresh-prompt-hook): New hook variable for
modules to adjust prompt properties whenever it's refreshed.
(erc--refresh-prompt): Fix bug in which user-defined prompt functions
failed to hide when quitting in server buffers.  Run new hook
`erc--refresh-prompt-hook'.
(erc-display-prompt): Add comment noting that the text property
`erc-prompt' now actually matters: it's t while a session is running
and `hidden' when disconnected.
* test/lisp/erc/erc-fill-tests.el (erc-fill--left-hand-stamps): New
test.
* test/lisp/erc/erc-stamp-tests.el
(erc-stamp-tests--use-align-to--nil,
erc-stamp-tests--use-align-to--t): New functions forged from old test
bodies to allow optionally asserting pre-5.6 behavior regarding
leading white space on right-hand stamps that exist on their own line.
(erc-timestamp-use-align-to--nil, erc-timestamp-use-align-to--t):
Parameterize with compatibility flag.
(erc-timestamp-use-align-to--margin,
erc-stamp--display-margin-mode--right): Rename test to latter.
* test/lisp/erc/erc-tests.el (erc-hide-prompt): Add some assertions
for new possible value of `erc-prompt' text property.
* test/lisp/erc/resources/fill/snapshots/stamps-left-01.eld: New test
data file.  (Bug#60936)

4 files changed, 66 insertions, 7 deletions

diff --git a/test/lisp/erc/erc-fill-tests.el b/test/lisp/erc/erc-fill-tests.el
index 99ec4a9635e..67622da9f3d 100644
--- a/test/lisp/erc/erc-fill-tests.el
+++ b/test/lisp/erc/erc-fill-tests.el
@@ -340,4 +340,41 @@
        (should (search-backward "ERC> " nil t))
        (execute-kbd-macro "\C-a")))))
 
+(ert-deftest erc-fill--left-hand-stamps ()
+  :tags '(:unstable)
+  (unless (>= emacs-major-version 29)
+    (ert-skip "Emacs version too low, missing `buffer-text-pixel-size'"))
+
+  (let ((erc-timestamp-only-if-changed-flag nil)
+        (erc-insert-timestamp-function #'erc-insert-timestamp-left))
+    (erc-fill-tests--wrap-populate
+     (lambda ()
+       (should (= 8 left-margin-width))
+       (pcase-let ((`((margin left-margin) ,displayed)
+                    (get-text-property erc-insert-marker 'display)))
+         (should (equal-including-properties
+                  displayed #("    ERC>" 4 8
+                              ( read-only t
+                                front-sticky t
+                                field erc-prompt
+                                erc-prompt t
+                                rear-nonsticky t
+                                font-lock-face erc-prompt-face)))))
+       (erc-fill-tests--compare "stamps-left-01")
+
+       (ert-info ("Shrink left margin by 1 col")
+         (erc-stamp--adjust-margin -1)
+         (with-silent-modifications (erc--refresh-prompt))
+         (should (= 7 left-margin-width))
+         (pcase-let ((`((margin left-margin) ,displayed)
+                      (get-text-property erc-insert-marker 'display)))
+           (should (equal-including-properties
+                    displayed #("   ERC>" 3 7
+                                ( read-only t
+                                  front-sticky t
+                                  field erc-prompt
+                                  erc-prompt t
+                                  rear-nonsticky t
+                                  font-lock-face erc-prompt-face))))))))))
+
 ;;; erc-fill-tests.el ends here
diff --git a/test/lisp/erc/erc-stamp-tests.el b/test/lisp/erc/erc-stamp-tests.el
index 6da7ed4503d..c448416cd69 100644
--- a/test/lisp/erc/erc-stamp-tests.el
+++ b/test/lisp/erc/erc-stamp-tests.el
@@ -56,7 +56,7 @@
     (advice-remove 'erc-format-timestamp
                    'ert-deftest--erc-timestamp-use-align-to)))
 
-(ert-deftest erc-timestamp-use-align-to--nil ()
+(defun erc-stamp-tests--use-align-to--nil (compat)
   (erc-stamp-tests--insert-right
    (lambda ()
 
@@ -83,12 +83,20 @@
          (erc-display-message nil 'notice (current-buffer)
                               "twenty characters"))
        (should (search-forward-regexp (rx bol (+ "\t") (* " ") "[") nil t))
-       ;; Field excludes leading whitespace (arguably undesirable).
-       (should (eql ?\[ (char-after (field-beginning (point)))))
+       ;; Field includes leading whitespace.
+       (should (eql (if compat ?\[ ?\n)
+                    (char-after (field-beginning (point)))))
        ;; Timestamp extends to the end of the line.
        (should (eql ?\n (char-after (field-end (point)))))))))
 
-(ert-deftest erc-timestamp-use-align-to--t ()
+(ert-deftest erc-timestamp-use-align-to--nil ()
+  (ert-info ("Field starts on stamp text (compat)")
+    (let ((erc-stamp--omit-properties-on-folded-lines t))
+      (erc-stamp-tests--use-align-to--nil 'compat)))
+  (ert-info ("Field includes leaidng white space")
+    (erc-stamp-tests--use-align-to--nil nil)))
+
+(defun erc-stamp-tests--use-align-to--t (compat)
   (erc-stamp-tests--insert-right
    (lambda ()
 
@@ -110,10 +118,17 @@
            (erc-display-message nil nil (current-buffer) msg)))
        ;; Indented to pos (this is arguably a bug).
        (should (search-forward-regexp (rx bol (+ "\t") (* " ") "[") nil t))
-       ;; Field starts *after* leading space (arguably bad).
-       (should (eql ?\[ (char-after (field-beginning (point)))))
+       ;; Field includes leading space.
+       (should (eql (if compat ?\[ ?\n) (char-after (field-beginning (point)))))
        (should (eql ?\n (char-after (field-end (point)))))))))
 
+(ert-deftest erc-timestamp-use-align-to--t ()
+  (ert-info ("Field starts on stamp text (compat)")
+    (let ((erc-stamp--omit-properties-on-folded-lines t))
+      (erc-stamp-tests--use-align-to--t 'compat)))
+  (ert-info ("Field includes leaidng white space")
+    (erc-stamp-tests--use-align-to--t nil)))
+
 (ert-deftest erc-timestamp-use-align-to--integer ()
   (erc-stamp-tests--insert-right
    (lambda ()
@@ -140,7 +155,7 @@
        (should (eql ?\s (char-after (field-beginning (point)))))
        (should (eql ?\n (char-after (field-end (point)))))))))
 
-(ert-deftest erc-timestamp-use-align-to--margin ()
+(ert-deftest erc-stamp--display-margin-mode--right ()
   (erc-stamp-tests--insert-right
    (lambda ()
      (erc-stamp--display-margin-mode +1)
diff --git a/test/lisp/erc/erc-tests.el b/test/lisp/erc/erc-tests.el
index b5db5fe8764..fff3c4cb704 100644
--- a/test/lisp/erc/erc-tests.el
+++ b/test/lisp/erc/erc-tests.el
@@ -219,6 +219,7 @@
       (setq erc-hide-prompt '(server))
       (with-current-buffer "ServNet"
         (erc--hide-prompt erc-server-process)
+        (should (eq (get-text-property erc-insert-marker 'erc-prompt) 'hidden))
         (should (string= ">" (get-text-property erc-insert-marker 'display))))
 
       (with-current-buffer "#chan"
@@ -229,6 +230,7 @@
 
       (with-current-buffer "ServNet"
         (erc--unhide-prompt)
+        (should (eq (get-text-property erc-insert-marker 'erc-prompt) t))
         (should-not (get-text-property erc-insert-marker 'display))))
 
     (ert-info ("Value: channel")
@@ -242,7 +244,9 @@
 
       (with-current-buffer "#chan"
         (should (string= ">" (get-text-property erc-insert-marker 'display)))
+        (should (eq (get-text-property erc-insert-marker 'erc-prompt) 'hidden))
         (erc--unhide-prompt)
+        (should (eq (get-text-property erc-insert-marker 'erc-prompt) t))
         (should-not (get-text-property erc-insert-marker 'display))))
 
     (ert-info ("Value: query")
@@ -253,7 +257,9 @@
 
       (with-current-buffer "bob"
         (should (string= ">" (get-text-property erc-insert-marker 'display)))
+        (should (eq (get-text-property erc-insert-marker 'erc-prompt) 'hidden))
         (erc--unhide-prompt)
+        (should (eq (get-text-property erc-insert-marker 'erc-prompt) t))
         (should-not (get-text-property erc-insert-marker 'display)))
 
       (with-current-buffer "#chan"
diff --git a/test/lisp/erc/resources/fill/snapshots/stamps-left-01.eld b/test/lisp/erc/resources/fill/snapshots/stamps-left-01.eld
new file mode 100644
index 00000000000..f62b65cd170
--- /dev/null
+++ b/test/lisp/erc/resources/fill/snapshots/stamps-left-01.eld
@@ -0,0 +1 @@
+#("\n\n[00:00]*** This server is in debug mode and is logging all user I/O. If you do not wish for everything you send to be readable by the server owner(s), please disconnect.\n[00:00]<alice> bob: come, you are a tedious fool: to the purpose. What was done to Elbow's wife, that he hath cause to complain of? Come me to what was done to her.\n[00:00]<bob> alice: Either your unparagoned mistress is dead, or she's outprized by a trifle.\n" 2 9 (erc-timestamp 0 display (#4=(margin left-margin) #("[00:00]" 0 7 (invisible timestamp font-lock-face erc-timestamp-face))) field erc-timestamp wrap-prefix #1=(space :width 27) line-prefix #2=(space :width (- 27 (4)))) 9 171 (erc-timestamp 0 wrap-prefix #1# line-prefix #2#) 172 179 (erc-timestamp 0 display (#4# #("[00:00]" 0 7 (invisible timestamp font-lock-face erc-timestamp-face))) field erc-timestamp wrap-prefix #1# line-prefix #3=(space :width (- 27 (8)))) 179 180 (erc-timestamp 0 wrap-prefix #1# line-prefix #3# erc-command PRIVMSG) 180 185 (erc-timestamp 0 wrap-prefix #1# line-prefix #3# erc-command PRIVMSG) 185 187 (erc-timestamp 0 wrap-prefix #1# line-prefix #3# erc-command PRIVMSG) 187 190 (erc-timestamp 0 wrap-prefix #1# line-prefix #3# erc-command PRIVMSG) 190 303 (erc-timestamp 0 wrap-prefix #1# line-prefix #3# erc-command PRIVMSG) 303 304 (erc-timestamp 0 erc-command PRIVMSG) 304 336 (erc-timestamp 0 wrap-prefix #1# line-prefix #3# erc-command PRIVMSG) 337 344 (erc-timestamp 0 display (#4# #("[00:00]" 0 7 (invisible timestamp font-lock-face erc-timestamp-face))) field erc-timestamp wrap-prefix #1# line-prefix #5=(space :width (- 27 (6)))) 344 345 (erc-timestamp 0 wrap-prefix #1# line-prefix #5# erc-command PRIVMSG) 345 348 (erc-timestamp 0 wrap-prefix #1# line-prefix #5# erc-command PRIVMSG) 348 350 (erc-timestamp 0 wrap-prefix #1# line-prefix #5# erc-command PRIVMSG) 350 355 (erc-timestamp 0 wrap-prefix #1# line-prefix #5# erc-command PRIVMSG) 355 430 (erc-timestamp 0 wrap-prefix #1# line-prefix #5# erc-command PRIVMSG))
\ No newline at end of file