re: the black gap tracks the OUTGOING screen -- direction and button ruled out

Applied my own log-line rule to my own instrument first, which is the "rule
written down is not a rule applied" failure I have on record three times. Every
branch of fade_decompose.sh now announces its EFFECTIVE configuration -- derived
from the variables in force, not from $WHERE, per sylpheed-port's sharpening --
and the run REFUSES if no branch announced itself. That is the guard that would
have caught last iteration's silent fall-through at a glance.

With it in place, took the measurement that failed last time: menu -> EXTRAS, the
reverse of the pair measured at a 2-frame gap. Navigation verified both ways
(extras margin 11.23, back on menu 11.60) and the config block confirmed the right
branch.

Result: outgoing quad rises across 5 frames matching build 5's declared 10-unit
close, then ONE logged empty frame. Quoted as 1 with an upward uncertainty, since
its two neighbours carry no frame header at all.

Five transitions now order by the screen being LEFT:

  menu -> title    (B)     0        outgoing menu
  menu -> EXTRAS   (A)     1        outgoing menu
  EXTRAS -> menu   (B)     2        outgoing EXTRAS
  title -> menu    (A) x3  3,3,3    outgoing title

Direction is ruled out: EXTRAS->menu (2) and menu->EXTRAS (1) are the same pair
both ways and differ. Button is ruled out: (B) gives 0 and 2, (A) gives 1 and 3.
Incoming screen is ruled out: an incoming menu takes 3 from the title and 2 from
EXTRAS.

NOT a rule, and recorded as such. Three outgoing screens with one value each means
"each outgoing screen has its own gap" restates the data rather than predicting,
and nothing declared predicts it -- outgoing closes are 5,5,5,4 frames against
gaps 0/1,2,3, inverted if anything, on three points.

What it changes for the port: a UNIFORM black_hold_units is now positively
excluded rather than merely unsupported.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Wuu56cE8vJGTBtn1ppsk8v

tools/re-capture/fade_decompose.sh

@@ -67,6 +67,7 @@ done
 
 WHERE="${WHERE:-menu}"
 if [ "$WHERE" = "menu" ]; then
+  BRANCH="menu: (A) on the boot title -> arm on the MENU -> press (B)"
   # 2. one (A) on the boot title -> main menu; we arm THERE and press (B).
   python3 "$SD/pad.py" tap A 0.5
   for _ in 1 2 3 4 5 6; do
@@ -76,6 +77,7 @@ if [ "$WHERE" = "menu" ]; then
   [ "$s" = "menu" ] || { echo "NO MENU (screen=$s)"; exit 2; }
   BTN=B
 elif [ "$WHERE" = "extras" ] || [ "$WHERE" = "menu2extras" ]; then
+  BRANCH="extras-family: navigate to EXTRAS"
   python3 "$SD/pad.py" tap A 0.5
   for _ in 1 2 3 4 5 6; do
     sleep 4; s="$(screen)"; echo "  after A: $s"
@@ -116,10 +118,13 @@ elif [ "$WHERE" = "extras" ] || [ "$WHERE" = "menu2extras" ]; then
     shot "$OUT/back-on-menu.png"
     echo "  back on menu: $(python3 "$SD/which_title_screen.py" "$OUT/back-on-menu.png")"
     BTN=A
+    BRANCH="menu2extras: back on the MENU with focus restored -> press (A)"
   else
     BTN=B
+    BRANCH="extras: arm on EXTRAS -> press (B)"
   fi
 else
+  BRANCH="title: arm on the BOOT TITLE -> press (A)"
   # arm on the title itself and press (A): the incoming screen is then build 5,
   # whose declared fade-in is 12 units where build 4's is 16.
   BTN=A
@@ -129,6 +134,19 @@ shot "$OUT/armed-on-$WHERE.png"
 # 3. arm the capture, dismiss the menu bar F10 opened, then press (B).
 #    Everything between F10 and (B) is spent inside the capture window, so keep
 #    it short: the window is FRAMES submitted frames, not seconds.
+# ── EFFECTIVE CONFIGURATION ──────────────────────────────────────────────────
+# Printed from the variables actually in force, NOT from $WHERE. A three-part
+# patch once left a branch condition unapplied, so WHERE=menu2extras silently ran
+# the `title` branch and produced a well-formed capture of a different transition.
+# The data looked fine; only the ABSENCE of this branch's log lines gave it away.
+# So: every run states what it is really about to do.
+echo "── EFFECTIVE CONFIG ──────────────────────────────"
+echo "   requested WHERE = ${WHERE}"
+echo "   branch taken    = ${BRANCH:-<none — no branch set itself, this is a BUG>}"
+echo "   button to press = ${BTN}"
+echo "   arming on       = $(screen)"
+echo "──────────────────────────────────────────────────"
+[ -n "${BRANCH:-}" ] || { echo "REFUSING: no branch announced itself"; exit 5; }
 xdotool windowactivate --sync "$win"; sleep 1
 xdotool key F10; sleep 0.6
 xdotool mousemove 900 400 click 1; sleep 0.6