kitty: remember the light/dark mode across restarts

kitty gives *-theme.auto.conf priority over everything -- includes and
even --override -- and has no option to stop following the OS. So the
only way to start in a chosen mode is to control what those files
contain. Make them generated:

  themes/{light,dark,no-preference}.conf  canonical, the real themes
  theme-mode                              auto | light | dark
  apply-theme-mode.sh                      writes the three .auto.conf

Under `auto` each appearance keeps its own theme, so kitty follows the
OS as before. Pinned, all three get the pinned theme, so kitty starts in
it whatever the OS says and a config reload no longer resets it.

`theme` now records the mode and reloads instead of calling set-colors,
which is why the setting survives restarts. A bare `theme` records
`auto` rather than pinning when the toggle lands on the macOS
appearance, so nothing is pinned unless it actually differs.

The kitten shim hashes the automatic theme files before running `kitten
themes` and copies whichever changed into themes/, so picking a new
light theme while pinned to dark is kept and applied on the next switch.
Covered by tests/test_theme_mode.sh.

conf.d/kitty_theme.fish is gone: theme-mode is now the source of truth,
so the universal-variable tracker it maintained is redundant.

private_dot_config/kitty/private_executable_apply-theme-mode.sh

@@ -0,0 +1,68 @@
+#!/bin/sh
+
+# Regenerate the *-theme.auto.conf files kitty reads at startup from the
+# canonical themes in ./themes, honouring the mode recorded in ./theme-mode:
+#
+#   auto   every appearance keeps its own theme, so kitty follows the OS
+#   light  every appearance gets the light theme, so kitty stays light
+#   dark   every appearance gets the dark theme, so kitty stays dark
+#
+# kitty gives the automatic theme files priority over everything else -- includes
+# and even --override -- so pinning a mode means writing the wanted theme into
+# whichever file the OS makes kitty pick. That is why the real themes live in
+# ./themes and these three files are generated.
+
+set -eu
+
+script_dir="$(CDPATH= cd -- "$(dirname -- "$0")" && pwd)"
+config_dir=${1:-"$script_dir"}
+canonical_dir="$config_dir/themes"
+mode_file="$config_dir/theme-mode"
+
+mode=auto
+if [ -f "$mode_file" ]; then
+    mode=$(tr -d ' \t\r\n' < "$mode_file")
+fi
+case "$mode" in
+    auto | light | dark) ;;
+    *) mode=auto ;;
+esac
+
+mkdir -p "$canonical_dir"
+
+# Adopt the current automatic themes as canonical when they have not been
+# captured yet. Only safe while following the OS: under a pinned mode the
+# generated files all hold the pinned theme and would overwrite the others.
+if [ "$mode" = auto ]; then
+    for appearance in dark light no-preference; do
+        canonical="$canonical_dir/$appearance.conf"
+        generated="$config_dir/$appearance-theme.auto.conf"
+        if [ ! -f "$canonical" ] && [ -f "$generated" ]; then
+            cp "$generated" "$canonical"
+        fi
+    done
+fi
+
+for appearance in dark light no-preference; do
+    if [ "$mode" = auto ]; then
+        source_name=$appearance
+    else
+        source_name=$mode
+    fi
+
+    canonical="$canonical_dir/$source_name.conf"
+    [ -f "$canonical" ] || continue
+
+    generated="$config_dir/$appearance-theme.auto.conf"
+    mode_bits=600
+    [ -f "$generated" ] && mode_bits=$(stat -f '%Lp' "$generated")
+
+    tmp=$(mktemp "$generated.tmp.XXXXXX")
+    trap 'rm -f "$tmp"' EXIT HUP INT TERM
+    cat "$canonical" > "$tmp"
+    chmod "$mode_bits" "$tmp"
+    mv -f "$tmp" "$generated"
+    trap - EXIT HUP INT TERM
+done
+
+"$script_dir/repair-auto-themes.sh" "$config_dir"

private_dot_config/kitty/private_tests/private_executable_test_theme_mode.sh

@@ -0,0 +1,152 @@
+#!/bin/sh
+
+# Behavioural regression for the remembered light/dark mode:
+#   - apply-theme-mode.sh generates the automatic theme files from ./themes
+#   - a pinned mode puts one theme in all three, so kitty starts in it
+#   - `theme auto` restores per-appearance themes without losing any
+#   - `kitten themes` changes are captured even while a mode is pinned
+#   - a bare `theme` records `auto` when the result already matches macOS
+
+set -eu
+
+root=$(CDPATH= cd -- "$(dirname -- "$0")/.." && pwd)
+fish_bin=${FISH:-$(command -v fish)}
+tmpdir=$(mktemp -d)
+trap 'rm -rf "$tmpdir"' EXIT HUP INT TERM
+
+config_dir="$tmpdir/config"
+fake_bin="$tmpdir/bin"
+mkdir -p "$config_dir/themes" "$fake_bin"
+
+DARK='#111111'
+LIGHT='#eeeeee'
+NOPREF='#222222'
+NEW_LIGHT='#abcdef'
+
+printf 'background %s\nmacos_titlebar_color background\n' "$DARK" \
+    >"$config_dir/themes/dark.conf"
+printf 'background %s\nmacos_titlebar_color background\n' "$LIGHT" \
+    >"$config_dir/themes/light.conf"
+printf 'background %s\nmacos_titlebar_color background\n' "$NOPREF" \
+    >"$config_dir/themes/no-preference.conf"
+
+bg() {
+    awk '/^background/ { print $2; exit }' "$1"
+}
+
+expect() {
+    # expect <label> <file> <wanted>
+    got=$(bg "$2")
+    if [ "$got" != "$3" ]; then
+        echo "not ok - $1: expected $3, got $got" >&2
+        exit 1
+    fi
+}
+
+run_fish() {
+    # run_fish <macos-appearance> <fish code>
+    appearance=$1
+    shift
+    if [ "$appearance" = dark ]; then
+        printf '#!/bin/sh\necho Dark\n' >"$fake_bin/defaults"
+    else
+        printf '#!/bin/sh\nexit 1\n' >"$fake_bin/defaults"
+    fi
+    chmod +x "$fake_bin/defaults"
+
+    env -u KITTY_WINDOW_ID PATH="$fake_bin:/usr/bin:/bin:/usr/sbin" \
+        KITTY_CONFIG_DIRECTORY="$config_dir" \
+        "$fish_bin" --no-config -c "
+for f in __kitty_config_dir __kitty_macos_appearance \
+         __kitty_theme_mode_setting __kitty_theme_current theme kitten
+    source \$HOME/.config/fish/functions/\$f.fish
+end
+$*"
+}
+
+# --- auto keeps every appearance on its own theme -------------------------
+echo auto >"$config_dir/theme-mode"
+"$root/apply-theme-mode.sh" "$config_dir"
+expect "auto/dark" "$config_dir/dark-theme.auto.conf" "$DARK"
+expect "auto/light" "$config_dir/light-theme.auto.conf" "$LIGHT"
+expect "auto/no-preference" "$config_dir/no-preference-theme.auto.conf" "$NOPREF"
+
+# --- a pinned mode wins for every appearance ------------------------------
+for pinned in dark light; do
+    echo "$pinned" >"$config_dir/theme-mode"
+    "$root/apply-theme-mode.sh" "$config_dir"
+    case $pinned in
+        dark) want=$DARK ;;
+        light) want=$LIGHT ;;
+    esac
+    for appearance in dark light no-preference; do
+        expect "pinned $pinned/$appearance" \
+            "$config_dir/$appearance-theme.auto.conf" "$want"
+    done
+done
+
+# --- and auto restores them, so pinning never destroys a theme ------------
+echo auto >"$config_dir/theme-mode"
+"$root/apply-theme-mode.sh" "$config_dir"
+expect "restored dark" "$config_dir/dark-theme.auto.conf" "$DARK"
+expect "restored light" "$config_dir/light-theme.auto.conf" "$LIGHT"
+expect "restored no-preference" "$config_dir/no-preference-theme.auto.conf" "$NOPREF"
+
+# --- `kitten themes` is captured even while a mode is pinned --------------
+cat >"$fake_bin/kitten" <<EOF
+#!/bin/sh
+printf 'background %s\n' "$NEW_LIGHT" \
+    > "\$KITTY_CONFIG_DIRECTORY/light-theme.auto.conf"
+exit 0
+EOF
+printf '#!/bin/sh\nexit 0\n' >"$fake_bin/kitty"
+chmod +x "$fake_bin/kitten" "$fake_bin/kitty"
+
+run_fish light 'theme dark >/dev/null; kitten themes' >/dev/null
+expect "captured new light theme" "$config_dir/themes/light.conf" "$NEW_LIGHT"
+expect "pin still held after kitten themes" \
+    "$config_dir/light-theme.auto.conf" "$DARK"
+[ "$(tr -d ' \n' <"$config_dir/theme-mode")" = dark ] || {
+    echo "not ok - kitten themes cleared the pinned mode" >&2
+    exit 1
+}
+
+run_fish light 'theme light >/dev/null'
+expect "new light theme is used once selected" \
+    "$config_dir/light-theme.auto.conf" "$NEW_LIGHT"
+expect "dark theme survived the whole exchange" \
+    "$config_dir/themes/dark.conf" "$DARK"
+
+# --- a bare `theme` records auto when it lands on the macOS appearance ----
+echo auto >"$config_dir/theme-mode"
+"$root/apply-theme-mode.sh" "$config_dir"
+
+# macOS light, effective light -> toggles to dark, which differs -> pinned
+run_fish light 'theme >/dev/null'
+[ "$(tr -d ' \n' <"$config_dir/theme-mode")" = dark ] || {
+    echo "not ok - toggle away from the macOS appearance should pin" >&2
+    exit 1
+}
+
+# toggling back lands on light, which is what macOS says -> auto, not pinned
+run_fish light 'theme >/dev/null'
+[ "$(tr -d ' \n' <"$config_dir/theme-mode")" = auto ] || {
+    echo "not ok - toggle onto the macOS appearance should record auto" >&2
+    exit 1
+}
+
+# same shape with macOS in dark mode
+run_fish dark 'theme >/dev/null'
+[ "$(tr -d ' \n' <"$config_dir/theme-mode")" = light ] || {
+    echo "not ok - toggle away from a dark macOS should pin light" >&2
+    exit 1
+}
+run_fish dark 'theme >/dev/null'
+[ "$(tr -d ' \n' <"$config_dir/theme-mode")" = auto ] || {
+    echo "not ok - toggle onto a dark macOS should record auto" >&2
+    exit 1
+}
+
+"$root/tests/verify_auto_themes.sh" "$config_dir"
+
+echo "PASS: theme mode is remembered, survives kitten themes, and collapses to auto"

private_dot_config/kitty/theme-mode

@@ -0,0 +1 @@
+auto

private_dot_config/kitty/themes/private_dark.conf

@@ -0,0 +1,31 @@
+background            #1c2836
+foreground            #ffffff
+cursor                #bbbbbb
+selection_background  #b4d5ff
+color0                #000000
+color8                #545454
+color1                #f9555f
+color9                #fa8b8e
+color2                #20af89
+color10               #34bb99
+color3                #fdf029
+color11               #ffff55
+color4                #589cf5
+color12               #589cf5
+color5                #934d95
+color13               #e75598
+color6                #1e9ee6
+color14               #3978bb
+color7                #bbbbbb
+color15               #ffffff
+selection_foreground #1c2836
+
+# START_AUTOGENERATED_TAB_STYLE
+# Feel free to update these colors manually and remove these comments.
+active_tab_foreground   #1c2836
+active_tab_background   #2e84e6
+inactive_tab_foreground #2e84e6
+inactive_tab_background #1c2836
+# END_AUTOGENERATED_TAB_STYLE
+
+macos_titlebar_color background

private_dot_config/kitty/themes/private_light.conf

@@ -0,0 +1,31 @@
+background #f8f8f8
+foreground #2a2b33
+cursor #bbbbbb
+selection_background #e5e5e6
+color0 #000000
+color8 #000000
+color1 #de3d35
+color9 #de3d35
+color2 #3e953a
+color10 #3e953a
+color3 #d2b67b
+color11 #d2b67b
+color4 #2f5af3
+color12 #2f5af3
+color5 #950095
+color13 #a00095
+color6 #3e953a
+color14 #3e953a
+color7 #bbbbbb
+color15 #ffffff
+selection_foreground #2a2b33
+
+# START_AUTOGENERATED_TAB_STYLE
+# Feel free to update these colors manually and remove these comments.
+active_tab_foreground   #f8f8f8
+active_tab_background   #2f5af3
+inactive_tab_foreground #2f5af3
+inactive_tab_background #f8f8f8
+# END_AUTOGENERATED_TAB_STYLE
+
+macos_titlebar_color background

private_dot_config/kitty/themes/private_no-preference.conf

@@ -0,0 +1,28 @@
+background            #1c2836
+foreground            #ffffff
+cursor                #bbbbbb
+selection_background  #b4d5ff
+color0                #000000
+color8                #545454
+color1                #f9555f
+color9                #fa8b8e
+color2                #20af89
+color10               #34bb99
+color3                #fdf029
+color11               #ffff55
+color4                #589cf5
+color12               #589cf5
+color5                #934d95
+color13               #e75598
+color6                #1e9ee6
+color14               #3978bb
+color7                #bbbbbb
+color15               #ffffff
+selection_foreground #1c2836
+
+active_tab_foreground   #1c2836
+active_tab_background   #2e84e6
+inactive_tab_foreground #2e84e6
+inactive_tab_background #1c2836
+
+macos_titlebar_color background

private_dot_config/private_fish/conf.d/kitty_theme.fish

@@ -1,16 +0,0 @@
-status is-interactive
-or exit
-
-# Keep $kitty_theme_mode tracking what the terminal actually reports, so that
-# `theme` toggles from the real state even after kitty follows an OS appearance
-# change on its own. fish populates $fish_terminal_color_theme at the first
-# prompt and again whenever the terminal signals a palette change.
-function __kitty_theme_track --on-variable fish_terminal_color_theme
-    contains -- "$fish_terminal_color_theme" light dark
-    or return
-
-    test "$kitty_theme_mode" = "$fish_terminal_color_theme"
-    and return
-
-    set --universal kitty_theme_mode $fish_terminal_color_theme
-end

private_dot_config/private_fish/functions/__kitty_config_dir.fish

@@ -0,0 +1,7 @@
+function __kitty_config_dir --description 'Path to the kitty config directory'
+    if set -q KITTY_CONFIG_DIRECTORY
+        echo $KITTY_CONFIG_DIRECTORY
+    else
+        echo $HOME/.config/kitty
+    end
+end

private_dot_config/private_fish/functions/__kitty_macos_appearance.fish

@@ -0,0 +1,7 @@
+function __kitty_macos_appearance --description 'Report the macOS appearance as light or dark'
+    if test "$(defaults read -g AppleInterfaceStyle 2>/dev/null)" = Dark
+        echo dark
+    else
+        echo light
+    end
+end

private_dot_config/private_fish/functions/__kitty_theme_current.fish

@@ -1,14 +1,9 @@
 function __kitty_theme_current --description 'Report the color mode kitty is currently using'
-    # $kitty_theme_mode is kept in sync with the terminal by conf.d/kitty_theme.fish
+    set -l mode (__kitty_theme_mode_setting)
-    # and by `theme` itself; the rest are fallbacks for shells that have not yet
+
-    # seen an interactive prompt.
+    if test "$mode" = auto
-    if contains -- "$kitty_theme_mode" light dark
+        __kitty_macos_appearance
-        echo $kitty_theme_mode
-    else if contains -- "$fish_terminal_color_theme" light dark
-        echo $fish_terminal_color_theme
-    else if test "$(defaults read -g AppleInterfaceStyle 2>/dev/null)" = Dark
-        echo dark
     else
-        echo light
+        echo $mode
     end
 end

private_dot_config/private_fish/functions/__kitty_theme_mode_setting.fish

@@ -0,0 +1,13 @@
+function __kitty_theme_mode_setting --description 'Report the recorded kitty theme mode: auto, light or dark'
+    set -l config_dir (__kitty_config_dir)
+    set -l mode auto
+
+    if test -r $config_dir/theme-mode
+        set mode (string trim -- (cat $config_dir/theme-mode 2>/dev/null))
+    end
+
+    contains -- "$mode" auto light dark
+    or set mode auto
+
+    echo $mode
+end

private_dot_config/private_fish/functions/private_kitten.fish

@@ -1,16 +1,53 @@
 function kitten --description 'Run kitten and restore Kitty theme overrides'
+    set -l config_dir "$HOME/.config/kitty"
+    if set -q KITTY_CONFIG_DIRECTORY
+        set config_dir "$KITTY_CONFIG_DIRECTORY"
+    end
+
+    set -l is_themes false
+    if test (count $argv) -gt 0; and test "$argv[1]" = themes
+        set is_themes true
+    end
+
+    # The automatic theme files are generated from $config_dir/themes, so record
+    # their state first: whichever one the kitten rewrites is the theme just
+    # chosen for that appearance, and has to be captured before the mode is
+    # re-applied over the top of it.
+    set -l appearances dark light no-preference
+    set -l before
+    if test $is_themes = true
+        for appearance in $appearances
+            set -l file "$config_dir/$appearance-theme.auto.conf"
+            if test -r "$file"
+                set -a before (command shasum <"$file" | string split -f1 ' ')
+            else
+                set -a before missing
+            end
+        end
+    end
+
     command kitten $argv
     set -l kitten_status $status
 
     if test $kitten_status -eq 0
-        and test (count $argv) -gt 0
+        and test $is_themes = true
-        and test "$argv[1]" = themes
+        for index in (seq (count $appearances))
-        set -l config_dir "$HOME/.config/kitty"
+            set -l appearance $appearances[$index]
-        if set -q KITTY_CONFIG_DIRECTORY
+            set -l file "$config_dir/$appearance-theme.auto.conf"
-            set config_dir "$KITTY_CONFIG_DIRECTORY"
+            test -r "$file"
+            or continue
+
+            set -l now (command shasum <"$file" | string split -f1 ' ')
+            test "$now" = "$before[$index]"
+            and continue
+
+            command mkdir -p "$config_dir/themes"
+            or return $status
+            command cp "$file" "$config_dir/themes/$appearance.conf"
+            or return $status
         end
 
-        "$HOME/.config/kitty/repair-auto-themes.sh" "$config_dir"
+        "$HOME/.config/kitty/apply-theme-mode.sh" "$config_dir"
         or return $status
 
         if set -q KITTY_WINDOW_ID

private_dot_config/private_fish/functions/theme.fish

@@ -1,7 +1,5 @@
 function theme --description 'Switch kitty between its light and dark color themes'
-    set -l config_dir $HOME/.config/kitty
+    set -l config_dir (__kitty_config_dir)
-    set -q KITTY_CONFIG_DIRECTORY
-    and set config_dir $KITTY_CONFIG_DIRECTORY
 
     if test (count $argv) -gt 1
         echo "theme: expected at most one argument" >&2
@@ -18,13 +16,21 @@ function theme --description 'Switch kitty between its light and dark color them
                 'Usage: theme [light|dark|auto|status]' \
                 '' \
                 '  theme         toggle between light and dark' \
-                '  theme light   switch to light' \
+                '  theme light   pin kitty to light' \
-                '  theme dark    switch to dark' \
+                '  theme dark    pin kitty to dark' \
                 '  theme auto    follow the macOS appearance again' \
-                '  theme status  print the current mode'
+                '  theme status  print the current mode' \
+                '' \
+                'The mode is remembered in '(__kitty_config_dir)'/theme-mode and' \
+                'applies to new kitty instances too.'
             return 0
         case status
-            __kitty_theme_current
+            set -l setting (__kitty_theme_mode_setting)
+            if test "$setting" = auto
+                printf '%s (auto, following macOS)\n' (__kitty_theme_current)
+            else
+                printf '%s (pinned)\n' $setting
+            end
             return 0
         case toggle
             if test (__kitty_theme_current) = dark
@@ -32,6 +38,10 @@ function theme --description 'Switch kitty between its light and dark color them
             else
                 set target dark
             end
+            # Nothing to pin when the result already matches macOS -- record
+            # `auto` so kitty keeps following the OS from here on.
+            test "$target" = (__kitty_macos_appearance)
+            and set target auto
         case auto light dark
             # handled below
         case '*'
@@ -39,45 +49,28 @@ function theme --description 'Switch kitty between its light and dark color them
             return 2
     end
 
-    if not set -q KITTY_WINDOW_ID
+    set -l apply "$HOME/.config/kitty/apply-theme-mode.sh"
-        echo "theme: not running inside kitty" >&2
+    if not test -x $apply
+        echo "theme: missing $apply" >&2
         return 1
     end
 
-    if test "$target" = auto
+    echo $target >$config_dir/theme-mode
-        # Re-reading the config restores kitty's own OS-appearance handling,
+    or return $status
-        # which a manual override suppresses until the OS appearance changes.
+
+    $apply "$config_dir"
+    or return $status
+
+    # Reloading is what makes kitty pick up the regenerated theme files.
+    if set -q KITTY_WINDOW_ID
         kitty @ load-config
         or return $status
-
-        if test "$(defaults read -g AppleInterfaceStyle 2>/dev/null)" = Dark
-            set target dark
-        else
-            set target light
-        end
-    else
-        set -l theme_file $config_dir/$target-theme.auto.conf
-        if not test -r $theme_file
-            echo "theme: cannot read $theme_file" >&2
-            return 1
-        end
-
-        # Only pass through settings whose value is a hex color; kitty's
-        # set-colors rejects everything else these files may contain.
-        set -l colors (awk 'NF == 2 && $1 !~ /^#/ && $2 ~ /^#[0-9a-fA-F]+$/ { print $1 "=" $2 }' $theme_file)
-        if test (count $colors) -eq 0
-            echo "theme: no colors found in $theme_file" >&2
-            return 1
-        end
-
-        kitty @ set-colors --all --configured $colors
-        or return $status
     end
 
-    set --universal kitty_theme_mode $target
+    set -l effective (__kitty_theme_current)
 
     if functions -q __tide_apply_terminal_appearance
-        __tide_apply_terminal_appearance $target
+        __tide_apply_terminal_appearance $effective
         set -l apply_status $status
         if test $apply_status -eq 0
             functions -q _tide_cache_variables
@@ -87,5 +80,9 @@ function theme --description 'Switch kitty between its light and dark color them
         end
     end
 
-    echo $target
+    if test "$target" = auto
+        printf '%s (auto, following macOS)\n' $effective
+    else
+        printf '%s (pinned)\n' $effective
+    end
 end