Organize itches into a folder hierarchy

Maybe having subfolders dedicated to developing test cases and patches
will help.

2 files changed, 473 insertions, 0 deletions

diff --git a/personal/itches/emacs/bulk.md b/personal/itches/emacs/bulk.md
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+# Emacs
+
+- center/top point when
+    - moving to text/tag search hit
+    - going to man page section
+    - opening eww on an anchor
+    - visiting a function from its Help buffer
+- make font-lock stop background at fill-column or max(len(line) for
+  line in paragraph) rather than window-width when text spans >1 lines
+- shell-mode
+    - add faces instead of reusing font-lock-{comment,string}
+    - understand `autocd` and `cd !$`
+    - use Bash completions (e.g. `ls TAB` in a folder with one file)
+- [.dir-locals changed priorities][bug#30008] between subfolder and
+  major mode from 25 to 26
+- eshell: `ls --group-directories-first` does not color folders
+- emoji support
+- eww, gnus-article: adapt filling to window width changes
+- scroll-lock-mode
+    - cursor stuck on lines wrapped by visual-line-mode
+    - cursor stuck on lines with 😛
+    - scroll when going down newline with forward-…
+- matching-paren analysis fails: `;; (here is\n;; a comment)`
+- some modes redefine C-M-h, which makes this binding hard to
+  override; could mark-defun consult functions/values exposed by major
+  modes instead?
+- make ellipses for "invisible" text easily customizable (src/xdisp.c)
+- Man-mode: make isearch skip end-of-line hyphens
+- when opening `.gpg` files in a TTY, some characters (e.g. TAB) are
+  swallowed by Emacs instead of being forwarded to the gpg prompt;
+  these characters are then inserted in the decrypted file's buffer
+  (see `epa-file-insert-file-contents`)
+- let TRAMP fetch Google Drive credentials from .authinfo.gpg
+- icomplete's C-j does not choose the first completion as advertised
+  on empty input; it chooses ".", which AFAICT comes from the fact
+  that icomplete-exhibit calls completion-pcm--filename-try-filter
+  while icomplete-force-complete-and-exit simply calls
+  minibuffer-force-complete-and-exit
+    - likewise, if a folder contains foo.c and foo.o, "C-x C-f foo"
+      hides foo.o, yet C-j completes to foo.o
+- calendar uses default X resources when run in its own frame; see
+  `calendar-frame-parameters`, `x-handle-named-frame-geometry`,
+  `(make-frame '((name . "")))` vs `(make-frame '((title . "")))`
+- use compilation-mode-line-… faces for compilation-num-… indicators
+- "é" is not erased with a single DEL stroke, despite [Unicode
+  conventions]
+- sort tar archive members by name; serving suggestion:
+
+    ``` elisp
+    (defun my/tar-sort (info)
+      (sort info (lambda (a b) (string< (tar-header-name a) (tar-header-name b)))))
+    ;; Apply to tar-parse-info in tar-summarize-buffer.
+    ```
+
+- add a command or minor mode to highlight marks; serving suggestion:
+
+    ``` elisp
+    (save-excursion
+      (dolist (m mark-ring)
+        (goto-char (marker-position m))
+        (pulse-momentary-highlight-region (point) (point-at-eol))
+        (sit-for 0.1)))
+    ```
+
+- StackOverflow-like suggestions when reporting bugs
+- match data vs. `:eval` during redisplay: cf. [bug#31586]
+- make vc honour `.gitignore` so that `project-find-file` completion
+  is not cluttered with ignored files
+- in a folder with a .git folder and a .gitignore file,
+    - `C-x C-f .gi TAB` completes to .gitignore
+    - `C-x C-f .git TAB` says "not unique"
+- add some Custom machinery to save additions/removals to list
+  variables; as things stand, once I add/remove items and save the
+  variable, I miss out on changes to the variable's default value:
+  e.g. `git-commit-setup-hook` recently added `bug-reference-mode`,
+  but I never realized it because I customized the hook to add some
+  personal functions
+- e-pair-mode inserts a closing `$` after point in tex-mode, but
+  inserts a new pair instead of overwriting when pressing `$` again
+
+[bug#30008]: https://debbugs.gnu.org/cgi/bugreport.cgi?bug=30008
+[bug#31586]: https://debbugs.gnu.org/cgi/bugreport.cgi?bug=31586
+[Unicode conventions]: https://lists.gnu.org/archive/html/emacs-devel/2018-07/msg00961.html
+
+## Better out-of-the-box display for FORM FEED
+
+By default, FORM FEED is displayed as a dumb `^L` glyph.  This is
+surprising considering it shows up in so many places: Emacs source
+files, help buffers (e.g. `describe-mode`)…  You can even see it in
+source files of other GNU projects, like GCC.
+
+"Pages" are important enough to have their own navigation and
+narrowing commands, yet their default delimiter is displayed as an
+unassuming control character.
+
+I like the way form feeds are displayed with [`page-break-lines`];
+magit's `show-lines` blaming style achieves a similar look.
+
+Having this kind of display by default would make it more obvious that
+this character serves an actual purpose; as it stands, it looks no
+different from some stray CARRIAGE RETURN.
+
+This could be re-used by e.g.:
+
+- `describe-symbol`, which uses the following method to visually break
+  up multiple symbol definitions:
+
+  ``` lisp
+  (insert "\n\n"
+          (eval-when-compile
+            (propertize "\n" 'face '(:height 0.1 :inverse-video t)))
+          "\n")
+  ```
+
+- Custom buffers, where sections are delimited visually with a
+  999-character wide underlined space.
+
+Full disclosure
+:   This reflection started because moving over this underlined space
+    with `truncate-lines` on causes the screen to jump horizontally.
+    This specific problem should be fixable without dragging FORM FEED
+    display into the discussion, but I feel like the latter is the
+    more interesting issue ([who on Earth] enables `truncate-lines` by
+    default anyway).
+
+[`page-break-lines`]: https://github.com/purcell/page-break-lines
+[who on Earth]: https://gitlab.com/peniblec/dotfiles/blob/master/.emacs-custom.el
+
+## Dired
+
+- allow "columns" to be toggled; more specifically, make it possible
+  to hide ownership, permissions, number of hard links…
+
+- make the filename stand out
+
+- `% r` does not support some `\` constructs (`\#`, `\,`)
+
+- add a face for broken symbolic links
+
+## ERC
+
+- move timestamp to a better position (see `stamp` module)
+- play well with whitespace-mode
+
+## Org
+
+- dissociate sub- and super-script fontification from everything else
+  in org-toggle-pretty-entities
+
+- org-clocktable trips on DST:
+
+    ``` org
+    #+BEGIN: clocktable :scope file :maxlevel 2 :step day :stepskip0 t :tstart "[2018-10-15]" :tend "[2018-11-15]"
+    #+END:
+
+    * foo
+    :LOGBOOK:
+    CLOCK: [2018-10-26 Fri 08:00]--[2018-10-26 Fri 17:00] =>  9:00
+    :END:
+
+    * bar
+    :LOGBOOK:
+    CLOCK: [2018-10-29 Mon 08:00]--[2018-10-29 Mon 17:00] =>  9:00
+    :END:
+    ```
+
+- make org-ctrl-c-ctrl-c call `(org-clock-update-mode-line t)` when
+  point is on the clocked-in heading
+
+- new command `org-clock-in-late` to clock out x minutes ago from
+  previous task, and clock in x ago on task at point
+
+## Language support
+
+- fix builtin/keyword distinction for Bash & Python3
+- highlight variables inside strings, eg
+    - `"a ${variable} inside a double-quoted string"` (Bash)
+    - `'a format string's {variable}` (Python)
+- do not highlight a single-quoted command substitution
+
+## read-passwd
+
+- prevent kills from ending up in the clipboard
+- add command to temporarily reveal password
+
+## whitespace-mode
+
+- skip line/wrap-prefix variables and properties
+
+- highlights the adaptive-wrap prefix, although weirdly enough the
+  whitespace *faces* are not applied
+
+- in org-indent-mode, adds a spurious (unfaced) space marker before
+  paragraphs; somehow transient-mark-mode knows not to highlight this
+  space, maybe the answer lies there
+
+## External libraries
+
+### adaptive-wrap
+
+- a commented-out line with no space between the comment delimiter and
+  its text will get padded with the comment delimiter:
+
+        ;(some very long line)
+        ;; ⇒ wrapped with adaptive-wrap-extra-indent set to 4:
+        ;(some very
+        ;;;;;long line)
+
+### magit
+
+- customize current-tag function so that one can add `--first-parent`
+- prevent section highlight overlay from hiding tag face background
+- when quitting ediff conflict resolution, the "save buffer" prompt is
+  out of focus, one must ALT-TAB out of the ediff control panel first
+  (noticed in Emacs 27; 25.1 works fine); possible culprits:
+    - magit
+    - ediff
+    - smerge
+    - yes-or-no-p
+    - read-answer
+- if deleting a remote branch fails (e.g. due to wrong credentials),
+  `update-ref -d` is still run
+- make status buffer understand and display `typechange` e.g. when
+  replacing a replacing a regular file with a symlink
+- when ignoring a file in a subdirectory, magit attempts to
+  `git add .gitignore` (i.e. toplevel `.gitignore`), which fails
+
+### markdown-mode
+
+- support [shortcut reference links]
+- move point past header after C-c C-t !/@
+- update sub-superscript regex to allow L~i+1~
+- make justification work with indented blockquotes
+- add "ini ↦ conf-mode" to markdown-code-lang-modes
+
+[shortcut reference links]: http://spec.commonmark.org/0.27/#shortcut-reference-link
+
+### rg-mode
+
+- make -project DTRT in dired
+
+### page-break-lines
+
+- borked in magit-diff
+
+### diff-hl
+
+- colored fringe line is discontinued on lines featuring faces with
+  heights greater than 1
+
+  ``` shell
+  $ git init
+  $ echo "* foo" > README.org
+  $ git add README.org ; git commit -m README.org README.org
+  $ echo "* bar" >> README.org
+  $ echo "* baz" >> README.org
+  ```
+
+  ``` elisp
+  (load-file "…/diff-hl.el")
+  (global-diff-hl-mode)
+  (set-face-attribute 'org-level-1 nil :height 1.2)
+  (find-file "README.org")
+  ```
diff --git a/personal/itches/emacs/narrow-lighter.md b/personal/itches/emacs/narrow-lighter.md
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+# Make " Narrow" lighter customizable
+
+The " Narrow" string comes from `src/xdisp.c:decode_mode_spec`:
+
+``` c
+case 'n':
+  if (BUF_BEGV (b) > BUF_BEG (b) || BUF_ZV (b) < BUF_Z (b))
+    return " Narrow";
+```
+
+This is probably just a matter of returning the contents of a Lisp
+variable instead of this constant string.
+
+TODO:
+
+1. get the string value of a variable in C
+2. define a customizable string variable
+3. write a news entry
+4. write a patch
+5. extra credits: display string properties
+
+## Get the string value of a variable in C
+
+`decode_mode_spec` has some relevant snippets:
+
+- Given a `Lisp_Object obj`, `SSDATA(obj)` gives the string value as a
+  `char*`.
+
+- How to get a variable's `Lisp_Object`?
+    - `BVAR` works for buffer-local variables
+    - `V${lispname//-/_}`
+
+## Define a customizable string variable
+
+### Defining variables visible to C code
+
+The C macro `DEFVAR_LISP(string-name, field-name)` does the following:
+
+    define a static `Lisp_Objfwd` variable v
+    get the address of globals._f##field-name &f
+
+    defvar_lisp(v, string-name, &f)
+
+As explained in the comments above `DEFVAR_LISP`, `globals` is a
+global variable defined in `globals.h`, which is "auto-generated by
+make-docfile" and exposes fields, `#define`s and `Lisp_Object`s for
+every global variable.
+
+make-docfile (`lib-src/make-docfile.c`) takes C files as input and
+searches all occurences of `^ +DEFSYM[ \t(]`, `^ +DEFVAR_[ILB]` or
+`^DEFU`, analyses what comes after and generates appropriate
+definitions for `globals.h`.
+
+`defvar_lisp` allocates a symbol using `Fmake_symbol`.
+
+### Making it customizable
+
+`lisp/cus-start.el` defines customizable properties of symbols defined
+by C code.
+
+AFAICT, there is no need to assign the default value right after
+defining the variable with `DEFVAR_LISP`: e.g. `shell-file-name` is
+`DEFVAR_LISP`ed in `src/callproc.c` and its default value is set in…
+Mmm.  Not in `cus-start.el`.  There is this snippet in
+`callproc.c:init_callproc`:
+
+  ``` c
+sh = getenv ("SHELL");
+Vshell_file_name = build_string (sh ? sh : "/bin/sh");
+  ```
+
+But when starting with `SHELL=rofl emacs -Q`, Custom says that the
+value "has been changed outside Customize".  Changed from what to
+what?
+
+`cus-start.el` may contain a hint:
+
+``` elisp
+;; Elements of this list have the form:
+;; …
+;; REST is a set of :KEYWORD VALUE pairs.  Accepted :KEYWORDs are:
+;; :standard - standard value for SYMBOL (else use current value)
+;; …
+```
+
+Except that nope, this does not work.  Giving `:standard " Narrow"`
+and looking at the variable in Custom yields
+
+    narrow-lighter: nil
+        [State]: CHANGED outside Customize. (mismatch)
+
+A better example might be `overlay-arrow-string`, whose default value
+is set right after `DEFVAR_LISP` by calling `build_pure_c_string`.
+
+Why `build_pure_c_string` and not `build_string`?  From "(elisp) Pure
+Storage":
+
+> Emacs Lisp uses two kinds of storage for user-created Lisp objects:
+> “normal storage” and “pure storage”.  Normal storage is where all
+> the new data created during an Emacs session are kept (see Garbage
+> Collection).  Pure storage is used for certain data in the preloaded
+> standard Lisp files—data that should never change during actual use
+> of Emacs.
+>
+> Pure storage is allocated only while ‘temacs’ is loading the
+> standard preloaded Lisp libraries.  In the file ‘emacs’, it is
+> marked as read-only (on operating systems that permit this), so that
+> the memory space can be shared by all the Emacs jobs running on the
+> machine at once.
+
+"(elisp) Building Emacs" explains that "temacs" is the minimal Elisp
+interpreter built by compiling all C files in `src/`; temacs then
+loads Elisp sources and creates the "emacs" executable by dumping its
+current state into a file.
+
+## Debug stuff
+
+### Unicode characters represented as octal sequences
+
+Trying to customize the new variable to any string with non-ASCII
+characters fails: they show up as sequences of backslash-octal codes.
+For some reason they show up fine in the Help and Custom buffers.
+
+Things to investigate:
+
+1. Should the `Lisp_Object` be created with something other than
+   `build_pure_c_string`? 🙅
+2. What does the code calling `decode_mode_spec` do with the returned
+   string? **🎉**
+3. (Does `SSDATA` make some transformation before returning the
+   string? 🤷)
+4. (Should a specialized Custom setter be defined? 🤷)
+
+#### Should the `Lisp_Object` be created with something other than    `build_pure_c_string`?
+
+Maybe this would work?
+
+``` c
+Vnarrow_lighter = make_multibyte_string(" Narrow", strlen(" Narrow"),
+                                        strlen(" Narrow)");
+```
+
+That looks too ugly though, let's try something else.
+
+Maybe `STRING_SET_MULTIBYTE(Vnarrow_lighter)` would help?
+
+*compiles and tries*
+
+… Nope, it does not.
+
+#### What does the code calling `decode_mode_spec` do with the returned string?
+
+``` c
+spec = decode_mode_spec (it->w, c, field, &string);
+multibyte = STRINGP (string) && STRING_MULTIBYTE (string);
+```
+
+*slowly turns around*
+
+*finds `string` standing right there with a blank stare*
+
+Gah!  How long have you been there?
+
+``` c
+/* Return a string for the output of a mode line %-spec for window W,
+   generated by character C.  […]  Return a Lisp string in
+   *STRING if the resulting string is taken from that Lisp string.
+   […] */
+static const char *
+decode_mode_spec (struct window *w, register int c, int field_width,
+                  Lisp_Object *string)
+{
+  Lisp_Object obj;
+  /* … */
+  obj = Qnil;
+  *string = Qnil;
+
+  switch (c)
+    {
+    /* … */
+    }
+
+  if (STRINGP (obj))
+    {
+      *string = obj;
+      return SSDATA (obj);
+    }
+  else
+    return "";
+}
+```
+
+Alright then:
+
+``` c
+case 'n':
+  if (BUF_BEGV (b) > BUF_BEG (b) || BUF_ZV (b) < BUF_Z (b))
+      obj = Vnarrow_lighter;
+  break;
+```
+
+### Why do string properties not show up?
+
+🤷
+
+## Extra credit
+
+Maybe it would be simpler to have the narrowing lighter work like the
+" Compiling" lighter (cf. `compilation-in-progress` variable), i.e. adding an entry to `minor-mode-alist`.