Add eww lyrics scroll widget, pinned over other windows

.config/eww/eww.scss

@@ -0,0 +1,55 @@
+* {
+    all: unset;
+}
+
+.lyrics-box {
+    background-color: rgba(0, 0, 0, 0.55);
+    border-radius: 12px;
+    padding: 14px 20px;
+    font-family: "DejaVu Sans Mono", monospace;
+    /* Fixed regardless of how long/short the current line's text is --
+       otherwise the box (not the window, which is already a fixed
+       620px) visibly shrinks and grows to fit whichever line is
+       currently longest. 580px = 620px window width minus this box's
+       own 20px left/right padding. */
+    min-width: 580px;
+}
+
+.lyrics-context, .lyrics-current {
+    font-size: 15px;
+    margin: 2px 0;
+}
+
+.lyrics-context {
+    color: #888888;
+}
+
+.lyrics-current {
+    /* Same weight as the context lines on purpose -- font-size is set
+       per-instance via the bound :style attribute (shrinks for long
+       lines, see lyrics-listen.sh's font_size_for), not here. */
+    color: #ffe66d;
+    opacity: 1;
+    transition: opacity 300ms ease;
+}
+
+.lyrics-current.dim {
+    /* The brief in-between state on a line change -- see
+       lyrics-listen.sh's two-phase "reveal" emission. Opacity only, so
+       this row's own height never changes and nothing above/below it
+       moves. */
+    opacity: 0.15;
+}
+
+.lyrics-close {
+    color: #888888;
+    font-size: 12px;
+    margin: 4px 6px 0 0;
+    padding: 2px 5px;
+    border-radius: 6px;
+}
+
+.lyrics-close:hover {
+    color: #ffffff;
+    background-color: rgba(255, 255, 255, 0.15);
+}

.config/eww/eww.yuck

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+;; Lyrics scroll widget -- pinned always-on-top overlay showing the
+;; current synced (.lrc) lyrics line with 1 line of context above and 2
+;; below, sourced from "mpdtui -lyrics-line" via scripts/lyrics-listen.sh
+;; (see that script for why this is deflisten/push rather than
+;; defpoll/pull -- it needs to emit an intermediate "dimmed" frame for
+;; the current line's opacity transition below to animate from).
+;;
+;; The current line's own opacity (not a `revealer`, which was tried
+;; first -- it collapses its child to zero height while hidden, shrinking
+;; then re-growing the whole box on every line change) fades between
+;; `reveal`'s two states; its font-size is bound to `current_size`
+;; (scripts/lyrics-listen.sh's font_size_for) so a long line shrinks
+;; instead of overflowing the box's fixed width.
+;;
+;; The outer revealer (visible) auto-hides the whole widget when MPD
+;; isn't actively playing -- collapsing it rather than "eww close"-ing
+;; the window itself, which would kill the very deflisten script that's
+;; supposed to bring it back (see lyrics-listen.sh's own doc comment).
+
+(deflisten lyrics :initial "{\"visible\": false, \"reveal\": true, \"current_size\": 15, \"above\": \"\", \"current\": \"\", \"below1\": \"\", \"below2\": \"\"}"
+  "~/.config/eww/scripts/lyrics-listen.sh")
+
+;; :close-window closes lyrics-window, not the daemon -- but note (see
+;; lyrics-listen.sh and personal-systemd-services.md §7) this is a
+;; *manual* close, not the auto-hide-on-pause path: it does kill the
+;; deflisten script backing `lyrics` (eww only keeps one running while
+;; some open window uses its variable), and won't come back on its own.
+;; Run "eww open lyrics-window" to bring it back afterward.
+(defwidget lyrics-widget []
+  (revealer :transition "slidedown" :duration "400ms" :reveal {lyrics.visible}
+    (overlay
+      (box :orientation "v" :space-evenly false :halign "center" :class "lyrics-box"
+        (label :class "lyrics-context" :text {lyrics.above} :limit-width 70)
+        (label :class {lyrics.reveal ? "lyrics-current" : "lyrics-current dim"}
+               :style "font-size: ${lyrics.current_size}px;"
+               :text {lyrics.current} :limit-width 70)
+        (label :class "lyrics-context" :text {lyrics.below1} :limit-width 70)
+        (label :class "lyrics-context" :text {lyrics.below2} :limit-width 70))
+      (button :class "lyrics-close" :halign "end" :valign "start"
+              :onclick "eww close lyrics-window" "✕"))))
+
+(defwindow lyrics-window
+  :monitor 0
+  :geometry (geometry :x "0%" :y "4%" :width "620px" :height "1px" :anchor "top center")
+  :stacking "fg"
+  :windowtype "normal"
+  (lyrics-widget))

.config/eww/scripts/lyrics-listen.sh

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+#!/bin/bash
+# Streams the current synced-lyrics window to eww's `lyrics` deflisten
+# variable as one JSON object per line, forever, one tick per second.
+#
+# Runs "mpdtui -lyrics-line" once per tick (its own 4-line window: 1 line
+# of context above the current line, the current line, 2 lines below --
+# see mpdtui's internal/lyricsline) and pushes the result straight
+# through -- except when the *current* line (line 2) has changed since
+# the previous tick: then it first pushes "reveal: false" (still showing
+# the *old* current text, dimmed) and sleeps briefly before pushing
+# "reveal: true" with the new text at full opacity, so eww.yuck's
+# opacity transition on the current-line label has two distinct states
+# to animate between. A poll-based (defpoll) variable can't do this: it
+# only ever holds one value at a time, so there's no way to briefly show
+# the "dimmed" state in between two polled snapshots -- deflisten's
+# whole point is pushing as many intermediate frames as needed, on our
+# own schedule, not eww's.
+#
+# "reveal" deliberately drives an *opacity* transition, not a `revealer`
+# widget wrapping the label -- a `revealer` was tried first and collapses
+# its child to zero height while hidden, which shrinks (then re-grows)
+# the whole box every single line change. Opacity leaves the label's own
+# row height untouched the entire time, so nothing above/below it moves.
+#
+# current_size scales the current line's own font down for long lines
+# (see font_size_for) so a long line doesn't overflow the box's fixed
+# width instead of needing the box to grow to fit it.
+#
+# Also emits "visible" (true only when MPD is actively [playing]), which
+# eww.yuck uses to wrap the *entire* widget in an outer revealer -- NOT
+# "eww close"/"eww open" on the window itself. Closing the window that
+# way was tried first and is a trap: eww only keeps a deflisten script
+# alive while some open window is actually using its variable, so a
+# script that closes its own window gets killed the moment it does --
+# nothing is left running to ever reopen it. Collapsing an outer
+# revealer keeps the window (and this script) alive the whole time,
+# avoiding that self-inflicted dead end entirely.
+
+# font_size_for: the current line's font shrinks in three steps as its
+# character count grows, so a long line stays inside the box's fixed
+# 580px content width rather than needing the box to widen or the text
+# to wrap. Thresholds picked for DejaVu Sans Mono at the base 15px size
+# (~9px/char): 45 chars is where it starts getting close to the box's
+# ~540px usable text width (580px minus the box's own 20px*2 padding).
+font_size_for() {
+    local len=$1
+    if [ "$len" -gt 60 ]; then
+        echo 11
+    elif [ "$len" -gt 45 ]; then
+        echo 13
+    else
+        echo 15
+    fi
+}
+
+prev_current=""
+while true; do
+    if mpc status 2>/dev/null | grep -q '\[playing\]'; then
+        playing="true"
+    else
+        playing="false"
+    fi
+
+    if [ "$playing" = "true" ]; then
+        mpdtui -lyrics-line >/tmp/mpdtui-lyrics-line.txt 2>/dev/null
+        above=$(sed -n '1p' /tmp/mpdtui-lyrics-line.txt)
+        current=$(sed -n '2p' /tmp/mpdtui-lyrics-line.txt)
+        below1=$(sed -n '3p' /tmp/mpdtui-lyrics-line.txt)
+        below2=$(sed -n '4p' /tmp/mpdtui-lyrics-line.txt)
+        current_size=$(font_size_for "${#current}")
+
+        if [ "$current" != "$prev_current" ] && [ -n "$prev_current" ]; then
+            jq -cn --argjson visible "$playing" --argjson size "$current_size" --arg above "$above" --arg current "$prev_current" --arg below1 "$below1" --arg below2 "$below2" \
+                '{visible: $visible, reveal: false, current_size: $size, above: $above, current: $current, below1: $below1, below2: $below2}'
+            sleep 0.2
+        fi
+
+        jq -cn --argjson visible "$playing" --argjson size "$current_size" --arg above "$above" --arg current "$current" --arg below1 "$below1" --arg below2 "$below2" \
+            '{visible: $visible, reveal: true, current_size: $size, above: $above, current: $current, below1: $below1, below2: $below2}'
+
+        prev_current="$current"
+    else
+        jq -cn --argjson visible "$playing" \
+            '{visible: $visible, reveal: true, current_size: 15, above: "", current: "", below1: "", below2: ""}'
+        prev_current=""
+    fi
+
+    sleep 1
+done

.config/systemd/user/eww.service

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+[Unit]
+Description=Eww Widget Daemon (lyrics scroll widget)
+After=graphical-session.target
+
+[Service]
+Type=simple
+# scripts/lyrics-listen.sh shells out to "mpdtui" (installed via Homebrew
+# at /home/linuxbrew/.linuxbrew/bin), which isn't on a systemd user
+# service's own minimal default PATH -- unlike an interactive shell, this
+# doesn't source .zshrc/.bashrc/.profile at all.
+Environment=PATH=/home/linuxbrew/.linuxbrew/bin:/usr/local/sbin:/usr/local/bin:/usr/bin:/bin
+ExecStart=/usr/bin/eww daemon --no-daemonize
+ExecStartPost=/usr/bin/sleep 2
+ExecStartPost=/usr/bin/eww open lyrics-window
+Restart=on-failure
+
+[Install]
+WantedBy=default.target personal-services.target