Stacked keyboards go chromatic when routed to a Sampler (v0.12.0)

A Sampler maps a pad to each MIDI note, so scale filtering left out-of-scale
pads greyed-out and unreachable. When the punch-in / audition keyboard's channel
routes to a bus with a Sampler instrument, bypass the scale filter and enable all
twelve keys; otherwise scale filtering is unchanged. Non-destructive - the
project's scale/root setting is untouched, and switching the channel back to a
synth/SF2 restores filtering.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

app/build.gradle.kts

@@ -22,8 +22,8 @@ android {
         // (android.media.midi) and AAudio low-latency audio we rely on.
         minSdk = 26
         targetSdk = 34
-        versionCode = 30
+        versionCode = 31
-        versionName = "0.11.2"
+        versionName = "0.12.0"
 
         // We provide our own instrumentation runner if/when tests are added.
         testInstrumentationRunner = "androidx.test.runner.AndroidJUnitRunner"

app/src/main/java/space/rcmd/android/sizzle/ui/AppViewModel.kt

@@ -221,6 +221,18 @@ class AppViewModel(
     fun kbdNoteOn(midi: Int) { markNoteOn(midi); engine.busNoteOn(kbdChannel, midi, kbdVelocity) }
     fun kbdNoteOff(midi: Int) { markNoteOff(midi); engine.busNoteOff(kbdChannel, midi) }
 
+    /** True if the on-screen keyboard's MIDI channel routes to any bus whose instrument
+     *  is a Sampler. A Sampler maps a pad to each MIDI note, so scale filtering would
+     *  hide pads — the stacked keyboards go fully chromatic in that case. */
+    fun kbdRoutesToSampler(): Boolean {
+        for (ch in project.mixer.channels) {
+            if (ch.midiChannel != kbdChannel) continue
+            val slot = project.toolbox.getOrNull(ch.instrumentSlot) ?: continue
+            if (slot.type == space.rcmd.android.sizzle.model.ToolboxType.SAMPLER) return true
+        }
+        return false
+    }
+
     /** Live VU level (peak, ~0..1+) for mixer bus [ch] — polled at frame rate by the
      *  mixer's fader VU meters. */
     fun channelMeter(ch: Int): Float = engine.channelMeter(ch)

app/src/main/java/space/rcmd/android/sizzle/ui/StackedKeyboard.kt

@@ -28,6 +28,9 @@ import space.rcmd.android.sizzle.ui.theme.LocalRetro
 
 private const val VEL_STEP = 8
 
+/** All twelve pitch classes — used when scale filtering is bypassed (Sampler routing). */
+private val CHROMATIC: Set<Int> = (0..11).toSet()
+
 /**
  * A stacked two-octave keyboard shared by the Toolbox (audition) and Tracker
  * (punch-in) tabs. Its channel, octave range and velocity live on the
@@ -41,9 +44,14 @@ fun StackedKeyboard(vm: AppViewModel, punchIn: Boolean, modifier: Modifier) {
     val c = LocalRetro.current
     @Suppress("UNUSED_VARIABLE") val rev = vm.revision // refresh key filtering on scale/root change
     // Only in-scale keys are playable on BOTH the tracker punch-in and the toolbox
-    // audition keyboard (Chromatic yields all twelve = every key stays enabled).
+    // audition keyboard (Chromatic yields all twelve = every key stays enabled). But a
+    // Sampler maps a pad to each MIDI note, so scale filtering would hide pads — when
+    // the keyboard's channel routes to a Sampler, go fully chromatic so every pad is
+    // reachable.
     val root = vm.project.rootNote
-    val inKey: Set<Int> = vm.project.scale.intervals.map { (it + root) % 12 }.toSet()
+    val inKey: Set<Int> =
+        if (vm.kbdRoutesToSampler()) CHROMATIC
+        else vm.project.scale.intervals.map { (it + root) % 12 }.toSet()
     Column(
         modifier.fillMaxWidth().background(c.background).padding(6.dp),
         verticalArrangement = Arrangement.spacedBy(4.dp),