Set GC threshold high at start

I did have this in here before and the code to set it back was still
at the end of the file, so not sure what happened there.  I guess I
accidentally removed it at some point.

config.org

@@ -233,6 +233,35 @@
      (yas-reload-all)
    #+end_src
 
+* Calendar / Diary
+  Weeks start on Sunday by default, this can be changed to start on
+  Monday by setting [[help:calendar-week-start-day][calendar-week-start-day]] to 1:
+
+  #+begin_src emacs-lisp
+    (setq calendar-week-start-day 1)
+  #+end_src
+
+  Set latitute, longitude and location name to Bristol to get sunrise
+  and sunset times:
+
+  #+begin_src emacs-lisp
+    (setq calendar-latitude 51.45)
+    (setq calendar-longitude -2.58)
+    (setq calendar-location-name "Bristol, UK")
+  #+end_src
+
+  Emacs needs to be told where the diary file is, of course:
+
+  #+begin_src emacs-lisp
+    (setq diary-file "~/Documents/diary")
+  #+end_src
+
+  I want to use ISO-style dates in there:
+
+  #+begin_src emacs-lisp
+    (calendar-set-date-style 'iso)
+  #+end_src
+
 * Org
 ** Code and Quote block shortcuts
    I am a big fan of using =<s= for source blocks and =<q= for quotes;
@@ -264,6 +293,91 @@
                              'org-insert-heading-after-current)))
    #+end_src
 
+** Journal Files
+   Sometimes I like to make a todo list for a day if I've a lot to do,
+   or write a little bit about a day if it's been particularly
+   eventful. In both of these cases, it would be nice to just be able
+   to hit a particular keybinding and have the right buffer pop up. I
+   was using =org-roam='s daily notes feature for this, but I ended up
+   getting annoyed with =org-roam= (too many features for my taste
+   lol).
+
+   The convention I'm going for is for is having a particular
+   directory for these journal entries and then give each file a name
+   like "2022-10-30.org". With that in mind, there are two obvious
+   variables to define:
+
+   #+begin_src emacs-lisp
+     (defvar journal-directory
+       "~/Documents/org/journal"
+       "Directory to store journal entries in.")
+
+     (defvar journal-filename-format
+       "%F"
+       "Date format to use for journal entries' filenames (not including
+     the \".org\" extension)")
+   #+end_src
+
+   I can't be bothered to handle [[help:journal-directory][journal-directory]] not existing in the
+   main code, so I'm just going to make sure it exists here. The
+   second argument to [[help:make-directory][make-directory]] specifies to create parent
+   directories too if necessary.
+
+   #+begin_src emacs-lisp
+     (unless (file-directory-p journal-directory)
+       (make-directory journal-directory t))
+   #+end_src
+
+   The next step is to define a function to determine the filename for
+   today's journal entry. This is fairly straightforward, using
+   [[help:format-time-string][format-time-string]] to get the current date in the right format,
+   then sticking that together with the directory, extension, etc.
+
+   #+begin_src emacs-lisp
+     (defun journal-entry-filename ()
+       "Returns the filename for today's journal entry."
+       (let ((date-string (format-time-string journal-filename-format)))
+         (concat journal-directory "/" date-string ".org")))
+   #+end_src
+
+   If the journal entry doesn't exist yet, I want it to be populated
+   with the long-form date as the title:
+
+   #+begin_src emacs-lisp
+     (defvar journal-title-date-format
+       "%A, %-e %B %+4Y"
+       "The date format to use for journal entries' titles.")
+
+     (defun insert-default-journal-entry-contents ()
+       "Insert the default journal entry contents (currently this is
+     just today's long-form date as a title) into the current buffer."
+       (insert "#+TITLE: "
+               (format-time-string journal-title-date-format)
+               "\n\n"))
+   #+end_src
+
+   We can now make a function to open today's journal entry fairly
+   trivially using [[help:find-file][find-file]], and the above utilities. It should be
+   interactive, as this is what we'll be calling in the key binding.
+
+   #+begin_src emacs-lisp
+     (defun open-journal-entry ()
+       "Opens today's journal entry, populating it with the default
+     contents if it does not already exist."
+       (interactive)
+       (let* ((filename (journal-entry-filename))
+              (new-entry (not (file-exists-p filename))))
+         (find-file filename)
+         (when new-entry
+           (insert-default-journal-entry-contents))))
+   #+end_src
+
+   Finally, [[help:open-journal-entry][open-journal-entry]] can be bound to a key:
+
+   #+begin_src emacs-lisp
+     (global-set-key (kbd "C-c t") 'open-journal-entry)
+   #+end_src
+
 ** Source Blocks
    Pressing tab inside a source block should indent appropriately for its
    language.
@@ -391,7 +505,116 @@
              (auto-mode . emacs)))
    #+end_src
 
-** Indentation
+** Workflow States
+   I like to have =IN-PROGRESS= and =CANCELLED= workflow states as
+   well as the standard =TODO= and =DONE=. Cancelled items also want a
+   note attached explaining why. All this can be added by setting
+   [[help:org-todo-keywords][org-todo-keywords]]:
+
+   #+begin_src emacs-lisp
+     (setq org-todo-keywords
+           '((sequence "TODO" "IN-PROGRESS" "|" "DONE" "CANCELLED(@)")))
+   #+end_src
+
+   The ="|"= separates /needs further action/ states (before it) from
+   /no further action needed/ states (after it).
+
+   I also want to log the date and time when a note is marked as done:
+
+   #+begin_src emacs-lisp
+     (setq org-log-done 'time)
+   #+end_src
+
+** Agenda
+   Time to try org-mode's agenda feature again I think. Last time I
+   didn't end up using it much, but I am /much/ more of an Emacs
+   addict now so I do forsee it actually surviving (this will be funny
+   to read in the future if not).
+
+   I want to show all TODOs in =.org= files under my top-level
+   =~/Documents/org= directory and any in this config itself. This is
+   done by enumerating all files under =~/Documents/org= with
+   [[help:directory-files-recursively][directory-files-recursively]], then setting [[help:org-agenda-files][org-agenda-files]] to this,
+   along with this config's path.
+
+   #+begin_src emacs-lisp
+     (let ((org-docs
+            (directory-files-recursively "~/Documents/org" ".+\.org$")))
+       (setq org-agenda-files `("~/.emacs.d/config.org" ,@org-docs)))
+   #+end_src
+
+   Also I find it really very annoying that the the current window
+   layout is destroyed when you run =org-agenda=. That behaviour is
+   changed by setting [[help:org-agenda-window-setup][org-agenda-window-setup]]:
+
+   #+begin_src emacs-lisp
+     (setq org-agenda-window-setup 'current-window)
+   #+end_src
+
+   Include events from my diary:
+
+   #+begin_src emacs-lisp
+     (setq org-agenda-include-diary t)
+   #+end_src
+
+   Though I don't like the time grid being on by default.
+
+   #+begin_src emacs-lisp
+     (setq org-agenda-use-time-grid nil)
+   #+end_src
+
+   I primarily use the TODO list to keep track of un-scheduled tasks,
+   so I don't want those displayed in there:
+
+   #+begin_src emacs-lisp
+     (setq org-agenda-todo-ignore-scheduled t)
+   #+end_src
+
+   Finally, I want a keybinding for the weekly agenda and global TODO
+   list agenda view:
+
+   #+begin_src emacs-lisp
+     (defun org-weekly-agenda-and-todo-list ()
+       (interactive)
+       (org-agenda nil "n"))
+
+     (global-set-key (kbd "C-c a") 'org-weekly-agenda-and-todo-list)
+   #+end_src
+
+** Habits
+   Habit tracking requires the habits org module to be loaded. This is
+   done by adding the symbol ~'habits~ to [[help:org-modules][org-modules]], if it's not in
+   there already. I originally didn't have the surrounding ~unless~,
+   but it causes problems when re-loading the config using
+   [[help:org-babel-load-file][org-babel-load-file]].
+
+   #+begin_src emacs-lisp
+     (unless (member 'habits org-modules)
+       (add-to-list 'org-modules 'org-habit)
+       (org-load-modules-maybe t))
+   #+end_src
+
+   The [[help:org-load-modules-maybe][org-load-modules-maybe]] call forces org to load the modules in
+   [[help:org-modules][org-modules]]. Not sure it's needed, but I ran into some weird issues
+   and I think it fixed them.
+
+   The consistency graph is very nice but overlaps a lot of the habit
+   names, so I want to move it to the right a little:
+
+   #+begin_src emacs-lisp
+     (setq org-habit-graph-column 42)
+   #+end_src
+
+   Also it displays days that you did a habit in red if the habit was
+   overdue on that day, which makes a sort of sense, but always
+   showing days you did things in green makes more sense to me. The
+   variable [[help:org-habit-show-done-always-green][org-habit-show-done-always-green]] controls this.
+
+   #+begin_src emacs-lisp
+     (setq org-habit-show-done-always-green t)
+   #+end_src
+
+** Identation
    Setting [[help:org-adapt-indentation][org-adapt-indentation]] to ~t~ ensures that Org will indent text
    under a headline:
 
@@ -1185,7 +1408,7 @@
      (setq Man-notify-method 'pushy)
    #+end_src
 
-** Script-Fu
+** Script-Fu Mode
    GIMP has a scheme-based language -- Script-Fu -- built into it that
    you can use to script things (based).  Sadly, the built-in console
    is rather lackluster as a coding environment.  Happily, there /is/
@@ -1195,12 +1418,12 @@
 
    It's things like this that make me really glad I switched to Emacs
    because this is ridiculously cool.  By my definition of "cool"
-   anyway (what can I say, I'm a massive nerd).
+   anyway -- what can I say, I'm a massive nerd.
 
    I should probably extract this and make a standalone package out of
    it and stick it on Melpa at some point.
 
-*** REPL
+*** REPL Mode
     The Script-Fu server request format is very simple:
 
     | Bytes | Description                                   |
@@ -1255,7 +1478,7 @@
 
     The response format is similarly simple:
 
-    | Bytes | Description                             |
+    | Bytes | Content                                 |
     |-------+-----------------------------------------|
     |     0 | 'G' magic byte (47h)                    |
     |     1 | Status code -- 0 on success, 1 on error |
@@ -1312,8 +1535,8 @@
         (interactive)
         (let ((buffer (get-buffer-create "*Script-Fu REPL*")))
           (when (not (comint-check-proc buffer))
-            (make-comint-in-buffer "Script-Fu REPL"
+            (make-comint-in-buffer "Script-Fu REPL" buffer
-                                   buffer script-fu-repl-server)
+                                   script-fu-repl-server)
             (with-current-buffer buffer (script-fu-repl-mode)))
           (pop-to-buffer buffer '((display-buffer-in-direction)
                                   (direction . below)
@@ -1321,7 +1544,7 @@
           buffer))
     #+end_src
 
-*** Code Editing
+*** Code Editing Mode
     With the client stuff done, we can define the code editing mode:
 
     #+begin_src emacs-lisp
@@ -1329,9 +1552,7 @@
     #+end_src
 
     Now to define something to send an expression or region to the
-    REPL.  Since =script-fu-repl= returns the buffer we can use that
+    REPL:
-    to transparently start a REPL or get the existing one if one's
-    already running.
 
     #+begin_src emacs-lisp
       (defun script-fu-mode-send-region-or-sexp ()
@@ -1342,19 +1563,21 @@
                           (buffer-substring-no-properties start end))
                       (thing-at-point 'sexp t))))
           (if (not code) (message "No code to send.")
-            (let* ((repl-proc (get-buffer-process (script-fu-repl))))
+            (let* ((repl-buffer (script-fu-repl))
+                   (repl-proc (get-buffer-process repl-buffer)))
               (script-fu-repl-send repl-proc code)))))
 
       (define-key script-fu-mode-map (kbd "C-c C-c")
                   'script-fu-mode-send-region-or-sexp)
     #+end_src
 
-    And finally, a similar thing for the whole file:
+    And finally a similar thing for the whole file:
 
     #+begin_src emacs-lisp
       (defun script-fu-mode-send-file ()
         (interactive)
-        (let* ((repl-proc (get-buffer-process (script-fu-repl)))
+        (let* ((repl-buffer (script-fu-repl))
+               (repl-proc (get-buffer-process repl-buffer))
                (buffer-contents
                 (buffer-substring-no-properties (point-min)
                                                 (point-max))))