feat(tools): pace recordings by the shell prompt

tools/record-lib.sh

@@ -5,6 +5,7 @@ set -euo pipefail
 ROOT=$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)
 FONT=${FONT:-JetBrainsMono Nerd Font Mono}
 FPS=${FPS:-12}
+DELAY=${DELAY:-42}
 
 start_xvfb() {
     local geometry=$1
@@ -41,12 +42,34 @@ stop_capture() {
 
 send_line() {
     local text=$1 pause=${2:-0.9}
-    xdotool type --delay 42 -- "$text"
+    xdotool type --delay "$DELAY" -- "$text"
     sleep 0.35
     xdotool key Return
     sleep "$pause"
 }
 
+# Fixed sleeps race a build that takes longer than expected, and the keystrokes
+# land in the middle of its output. PROMPT_COMMAND appends a byte every time the
+# shell draws a prompt, so the recorder can wait for the command to actually end.
+wait_prompt() {
+    local before=$1 limit=${2:-600}
+    for _ in $(seq "$limit"); do
+        [ "$(wc -c <"$PROMPT_FILE" 2>/dev/null || echo 0)" != "$before" ] && return 0
+        sleep 0.1
+    done
+}
+
+run_line() {
+    local text=$1 settle=${2:-0.8}
+    local before
+    before=$(wc -c <"$PROMPT_FILE" 2>/dev/null || echo 0)
+    xdotool type --delay "$DELAY" -- "$text"
+    sleep 0.35
+    xdotool key Return
+    wait_prompt "$before"
+    sleep "$settle"
+}
+
 to_gif() {
     local src=$1 out=$2 fps=${3:-11}
     local palette=${src%.mkv}.png

tools/record-showcase.sh

@@ -5,6 +5,7 @@ GEOMETRY=${GEOMETRY:-1280x720}
 LUA=${LUA:-$HOME/projects/lua}
 OUT="$ROOT/assets/showcase.mp4"
 WORK=$(mktemp -d)
+PROMPT_FILE="$WORK/prompt"
 
 cp -a "$LUA" "$WORK/lua"
 rm -rf "$WORK/lua/build"
@@ -28,22 +29,22 @@ for _ in $(seq 30); do
     sleep 1
 done
 xdotool search --onlyvisible --class kitty windowactivate >/dev/null 2>&1 || true
-xdotool type --delay 10 -- 'export PS1="lua-5.4.7 $ " WINEDEBUG=-all LIBGL_ALWAYS_SOFTWARE=1 MESA_DEBUG=silent PATH='"$WORK"'/bin:$PATH; clear'
+xdotool type --delay 10 -- 'export PS1="lua-5.4.7 $ " PROMPT_COMMAND="printf . >> '"$PROMPT_FILE"'" PATH='"$WORK"'/bin:$PATH; clear'
 xdotool key Return
 sleep 1
 
 start_capture "$GEOMETRY" "$WORK/showcase.mkv"
 
-send_line 'meowc build' 8.5
+run_line 'meowc build' 1.6
-send_line './build/bin/lua -v' 1.8
+run_line 'touch src/*.c src/*.h' 0.6
-send_line 'meowc --target x86_64-w64-mingw32 build' 13
+run_line 'meowc build' 1.8
-send_line 'file build/x86_64-w64-mingw32/bin/lua.exe' 2.2
+run_line 'echo "int lua_added_decl (lua_State *L);" >> src/lua.h' 0.6
-send_line 'wine build/x86_64-w64-mingw32/bin/lua.exe -v' 3.2
+run_line 'meowc build' 2.5
 
 stop_capture
 
 # Fit the cut to the target length rather than truncating the ending off it
-LIMIT=${LIMIT:-29.5}
+LIMIT=${LIMIT:-45}
 raw=$(ffprobe -v error -show_entries format=duration -of csv=p=0 "$WORK/showcase.mkv")
 speed=$(python3 -c "print(max(1.0, $raw / $LIMIT))")
 ffmpeg -v error -y -i "$WORK/showcase.mkv" -an -vf "setpts=PTS/$speed" \