Add Shift+Tab to toggle select all/deselect all in MultiChoice prompts

[kevin-lee]

Close #55: Add Shift+Tab to toggle select all/deselect all in MultiChoice prompts

Add SHIFT_TAB key event that maps to the CSI sequence ESC[Z (backtab), supported universally across iTerm2, Apple Terminal, and Linux terminals.

In MultiChoice prompts, Shift+Tab now toggles all items at once:

• If all currently filtered items are selected, it deselects them all
• Otherwise, it selects them all
• Respects active text filter (only affects filtered items)
• Preserves selection state of non-filtered items

This also fixes a possible latent bug where pressing Shift+Tab would cause a MatchError in CharCollector since CSI_Started had no case for 'Z'.

The instruction text is updated to show the new keybinding: "Tab to toggle, Shift+Tab to toggle all, Enter to submit."

---

Update for Windows:

Add Windows support for SHIFT_TAB in CharCollector and Scala Native

The previous commit added Shift+Tab support via the ANSI ESC[Z sequence, which works on macOS and Linux.

On Windows, terminal input uses scan codes via _getch(), and Shift+Tab produces a 0x00 prefix followed by scan code 15 (0x0F), which was not handled.

• Add case 15 => SHIFT_TAB to ScanCode_Started in CharCollector so the Windows scan code path correctly decodes Shift+Tab.
• Normalize 0x00 to 0xE0 in Scala Native ChangeModeWindows.getchar() to match the existing JVM ChangeModeWindows behavior. Without this, the 0x00 prefix byte is silently skipped by KeyboardReadingThread's if lastRead != 0 guard, causing the subsequent scan code to be misinterpreted as a regular character.
• Add CharCollectorTests to verify SHIFT_TAB decoding through both the ANSI CSI path (ESC[Z) and the Windows scan code path (ScanCode_Started + 15).

---

Shift+Tab:

[keynmol]

Hi!

Directionally I'm okay with this, it's useful.

My only question is whether this will work on windows (which we currently support somewhat) - otherwise I'll take a closer look the PR once I'm back at my laptop in a couple of days.

[kevin-lee]

Hi!

Directionally I'm okay with this, it's useful.

My only question is whether this will work on windows (which we currently support somewhat) - otherwise I'll take a closer look the PR once I'm back at my laptop in a couple of days.

@keynmol Thank you! Oh, that’s a very good point. Sorry, I hadn’t done anything for Windows because my app was targeting macOS and Linux for now. My bad.

I’ve just made some updates for Windows and committed them.

My Windows machine is only for gaming, so it doesn't have a build env for this yet, but I'll still try building it there and see how it goes.

---

FYI, here is what I found.

Platform analysis:

Platform	Input mechanism	Shift+Tab encoding	Status
macOS / Linux (JVM, Native)	POSIX read() / getchar() → ANSI sequences	ESC[Z	Already works via CSI_Started → case 'Z'
Scala.js (Node.js, all OS)	Node.js readline keypress events	ESC[Z in key.sequence	Already works — Node.js abstracts platform differences
JVM Windows	_getch() via JNA → scan codes	0x00 + 0x0F (15)	Partially broken — 0x00 → 0xE0 mapping exists in ChangeModeWindows.java:54, but ScanCode_Started has no case 15
Scala Native Windows	_getch() via @extern → scan codes	0x00 + 0x0F (15)	Broken — 0x00 not normalized, gets skipped by KeyboardReadingThread; no case 15 in ScanCode_Started

1. CharCollector.ScanCode_Started has no mapping for scan code 15 (Shift+Tab)
2. ChangeModeWindows.scala (Scala Native) returns raw _getch() without normalising 0x00 -> 0xE0, unlike the JVM ChangeModeWindows.java which already does this

Why 0x00 → 0xE0 is safe on Windows:

• _getch() has no error return (Microsoft docs)

  Return value
  Returns the character read. There's no error return.

• 0x00 from _getch() is always a scan code prefix, never EOF
• The scan codes following 0x00 and 0xE0 prefixes don't conflict
• The JVM implementation already does this, and it's proven

[keynmol]

Looked at the PR:

1. It works fine on my Mac, JVM, JS and Native
2. I assume it works on Linux as well
3. It doesn't work on Windows – on JVM Shift+Tab just doesn't work, on Native it's completely broken (but it's not the fault of this PR, I messed something up)

I recorded a video in my windows VM:

CleanShot.2026-04-07.at.09.06.49.mp4

Given I don't have a windows machine to comfortably develop this, I will merge and release this PR with a windows caveat and address it later.

Thanks for your work!

[kevin-lee]

@keynmol Thank you!

I had a really long journey building it on Windows, and finally found that even the main branch (Native) isn't working on Windows.

main branch

After exampleNative/nativeLink:

TicTacToe:

cue4s>modules\example\target\native-3\example.exe
�[?25l�[0A�[0GException in thread "cue4s-keyboard-input-thread" scala.NotImplementedError: an implementation is missing
        at java.lang.Throwable.fillInStackTrace(Unknown Source)
        at scala.scalanative.runtime.Throwable.<init>(Unknown Source)
        at scala.Predef$.$qmark$qmark$qmark(Unknown Source)
        at cue4s.ChangeModeWindows$.read(Unknown Source)
        at cue4s.InputProviderImpl.$anonfun$6(Unknown Source)
        at cue4s.InputProviderImpl$$Lambda$8.apply(Unknown Source)
        at scala.Function0.apply$mcI$sp(Unknown Source)
        at cue4s.KeyboardReadingThread.run(Unknown Source)
        at scala.scalanative.runtime.NativeThread$.threadEntryPoint(Unknown Source)
        at scala.scalanative.runtime.NativeThread$.threadRoutine$$anonfun$1(Unknown Source)
        at <none>.SM49scala.scalanative.runtime.NativeThread$$$Lambda$1G17$extern$forwarder(Unknown Source)
        at <none>.ProxyThreadStartRoutine(ImmixGC.c:142)
        at <none>.BaseThreadInitThunk(Unknown Source)
        at <none>.RtlUserThreadStart(Unknown Source)
�[?25l�[0A�[0G�[?25l�[0A�[0G�[?25l�[0A�[0G�[?25l�[0A�[0G�[?25l�[0A�[0G�[?25l�[0A�[0G�[?25l�[0A�[0G

sync with only multiple selection code

I used ('A' to 'Z').zip('B' to 'Z') to have more than one char.

cue4s>modules\example\target\native-3\example.exe
�[?25l�[32m? �[39m�[36mWhat are your favourite letters?�[39m�[36m 쨩 �[39m
�[0G�[1mTab�[0m to toggle, �[1mEnter�[0m to submit.
�[0G�[32m _ (A,B)�[39m
�[0G _ (B,C)
�[0G _ (C,D)
�[0G _ (D,E)
�[0G _ (E,F)
�[0G _ (F,G)
�[0G v (G,H)
�[0G�[9A�[0GException in thread "cue4s-keyboard-input-thread" scala.NotImplementedError: an implementation is missing
        at java.lang.Throwable.fillInStackTrace(Unknown Source)
        at scala.scalanative.runtime.Throwable.<init>(Unknown Source)
        at scala.Predef$.$qmark$qmark$qmark(Unknown Source)
        at cue4s.ChangeModeWindows$.read(Unknown Source)
        at cue4s.InputProviderImpl.$anonfun$6(Unknown Source)
        at cue4s.InputProviderImpl$$Lambda$8.apply(Unknown Source)
        at scala.Function0.apply$mcI$sp(Unknown Source)
        at cue4s.KeyboardReadingThread.run(Unknown Source)
        at scala.scalanative.runtime.NativeThread$.threadEntryPoint(Unknown Source)
        at scala.scalanative.runtime.NativeThread$.threadRoutine$$anonfun$1(Unknown Source)
        at <none>.SM49scala.scalanative.runtime.NativeThread$$$Lambda$1G17$extern$forwarder(Unknown Source)
        at <none>.ProxyThreadStartRoutine(ImmixGC.c:142)
        at <none>.BaseThreadInitThunk(Unknown Source)
        at <none>.RtlUserThreadStart(Unknown Source)

My branch

After exampleNative/nativeLink:

TicTacToe:

cue4s>modules\example\target\native-3\example.exe
�[?25l�[0A�[0GException in thread "cue4s-keyboard-input-thread" scala.NotImplementedError: an implementation is missing
        at java.lang.Throwable.fillInStackTrace(Unknown Source)
        at scala.scalanative.runtime.Throwable.<init>(Unknown Source)
        at scala.Predef$.$qmark$qmark$qmark(Unknown Source)
        at cue4s.ChangeModeWindows$.read(Unknown Source)
        at cue4s.InputProviderImpl.$anonfun$6(Unknown Source)
        at cue4s.InputProviderImpl$$Lambda$8.apply(Unknown Source)
        at scala.Function0.apply$mcI$sp(Unknown Source)
        at cue4s.KeyboardReadingThread.run(Unknown Source)
        at scala.scalanative.runtime.NativeThread$.threadEntryPoint(Unknown Source)
        at scala.scalanative.runtime.NativeThread$.threadRoutine$$anonfun$1(Unknown Source)
        at <none>.SM49scala.scalanative.runtime.NativeThread$$$Lambda$1G17$extern$forwarder(Unknown Source)
        at <none>.ProxyThreadStartRoutine(ImmixGC.c:142)
        at <none>.BaseThreadInitThunk(Unknown Source)
        at <none>.RtlUserThreadStart(Unknown Source)
�[?25l�[0A�[0G�[?25l�[0A�[0G�[?25l�[0A�[0G�[?25l�[0A�[0G�[?25l�[0A�[0G�[?25l�[0A�[0G

sync with only multiple selection code

cue4s>modules\example\target\native-3\example.exe
�[?25l�[32m? �[39m�[36mWhat are your favourite letters?�[39m�[36m 쨩 �[39m
�[0G�[1mTab�[0m to toggle, �[1mShift+Tab�[0m to toggle all, �[1mEnter�[0m to submit.
�[0G�[32m _ (A,B)�[39m
�[0G _ (B,C)
�[0G _ (C,D)
�[0G _ (D,E)
�[0G _ (E,F)
�[0G _ (F,G)
�[0G v (G,H)
�[0G�[9A�[0GException in thread "cue4s-keyboard-input-thread" scala.NotImplementedError: an implementation is missing
        at java.lang.Throwable.fillInStackTrace(Unknown Source)
        at scala.scalanative.runtime.Throwable.<init>(Unknown Source)
        at scala.Predef$.$qmark$qmark$qmark(Unknown Source)
        at cue4s.ChangeModeWindows$.read(Unknown Source)
        at cue4s.InputProviderImpl.$anonfun$6(Unknown Source)
        at cue4s.InputProviderImpl$$Lambda$8.apply(Unknown Source)
        at scala.Function0.apply$mcI$sp(Unknown Source)
        at cue4s.KeyboardReadingThread.run(Unknown Source)
        at scala.scalanative.runtime.NativeThread$.threadEntryPoint(Unknown Source)
        at scala.scalanative.runtime.NativeThread$.threadRoutine$$anonfun$1(Unknown Source)
        at <none>.SM49scala.scalanative.runtime.NativeThread$$$Lambda$1G17$extern$forwarder(Unknown Source)
        at <none>.ProxyThreadStartRoutine(ImmixGC.c:142)
        at <none>.BaseThreadInitThunk(Unknown Source)
        at <none>.RtlUserThreadStart(Unknown Source)

Sorry, I haven't tried the JVM one.

[kevin-lee]

@keynmol Oh, it’s already out?! 😃 That’s awesome! Thanks so much!