backend/player/player.go

@@ -71,6 +71,19 @@ type Player struct {
 	// not something the user chose.
 	duckAmount float64
 
+	// systemVolume is what SystemOwnsVolume answers: the platform's own
+	// control is the only one, so ours neither acts nor persists.  It is
+	// a field rather than the build constant read directly so that a
+	// test can exercise both sides on any machine.  See systemvolume.go.
+	systemVolume bool
+
+	// storedVolume and storedMuted hold the persisted level as it was
+	// found at restore, for a platform whose volume we do not own: the
+	// maximum we then run at is not a level the user chose, so saveState
+	// writes back what it read rather than overwriting it.
+	storedVolume UserVolume
+	storedMuted  bool
+
 	// trackLengthMs holds the authoritative track duration in
 	// milliseconds, sourced from the database (which uses the
 	// custom header parser).  The go-mp3 decoder's Len() can be
@@ -156,6 +169,8 @@ func NewPlayer(logger *slog.Logger, db *database.DB) *Player {
 		logger:       logger,
 		db:           db,
 		state:        Stopped,
+		systemVolume: platformOwnsVolume,
+		storedVolume: DefaultUserVol,
 		baseStreamer: generators.Silence(-1),
 		format: beep.Format{
 			SampleRate: speakerSampleRate,
@@ -875,6 +890,10 @@ func (p *Player) SetVolume(desiredVolume UserVolume) {
 	p.mu.Lock()
 	defer p.mu.Unlock()
 
+	if p.systemVolume {
+		return
+	}
+
 	p.setVolumeLocked(desiredVolume)
 	p.emitVolumeChanged()
 	p.saveState()
@@ -923,6 +942,10 @@ func (p *Player) ChangeVolume(deltaVolume int) error {
 	p.mu.Lock()
 	defer p.mu.Unlock()
 
+	if p.systemVolume {
+		return nil
+	}
+
 	p.setVolumeLocked(p.getUserVolume() + UserVolume(deltaVolume))
 	p.emitVolumeChanged()
 	p.saveState()
@@ -953,6 +976,14 @@ func (p *Player) MuteToggle() error {
 		return errNoAudioFileLoaded
 	}
 
+	// Mute is a level of zero by another name, so it goes with the rest
+	// of the volume where the system owns it -- and it would be the one
+	// state on such a platform the user could not get out of, since with
+	// no control rendered there is nothing left to un-mute with.
+	if p.systemVolume {
+		return nil
+	}
+
 	speaker.Lock()
 	p.volume.Silent = !p.volume.Silent
 	speaker.Unlock()
@@ -1403,7 +1434,15 @@ func (p *Player) saveState() {
 	volume := int64(DefaultUserVol)
 	muted := false
 
-	if p.volume != nil {
+	switch {
+	case p.systemVolume:
+		// The maximum this platform runs at is not a level anybody
+		// chose, so it is not one to remember.  Writing back what
+		// restore found keeps the row a description of the user's
+		// setting without needing a second query that omits the column.
+		volume = int64(p.storedVolume)
+		muted = p.storedMuted
+	case p.volume != nil:
 		volume = int64(p.getUserVolume())
 		muted = p.volume.Silent
 	}
@@ -1487,11 +1526,20 @@ func (p *Player) restoreStateLocked() {
 		}
 	}
 
-	vol := clampVolume(UserVolume(state.Volume))
-	p.setVolumeLocked(vol)
+	if p.systemVolume {
+		// Remembered, not applied: the device's keys are the volume
+		// control here, so the player runs wide open and hands the
+		// stored level back untouched at the next save.
+		p.storedVolume = clampVolume(UserVolume(state.Volume))
+		p.storedMuted = state.Muted
+		p.setVolumeLocked(MaxUserVol)
+	} else {
+		vol := clampVolume(UserVolume(state.Volume))
+		p.setVolumeLocked(vol)
 
-	if state.Muted {
-		p.volume.Silent = true
+		if state.Muted {
+			p.volume.Silent = true
+		}
 	}
 
 	// Restore last track if the file still exists.
@@ -1531,8 +1579,9 @@ func (p *Player) restoreStateLocked() {
 	}
 
 	p.logger.Info("Player state restored",
-		"volume", vol,
-		"muted", state.Muted,
+		"volume", p.getUserVolume(),
+		"muted", p.volume.Silent,
+		"systemVolume", p.systemVolume,
 		"trackPath", state.LastTrackPath,
 		"positionSeconds", state.LastPositionSeconds,
 	)

backend/player/systemvolume.go

@@ -0,0 +1,42 @@
+package player
+
+// Who owns the volume, and what follows when it is not us.
+//
+// On Android the hardware keys *are* the volume control and the
+// framework mixes our stream against the device level, so a second
+// control inside the app is a slider that moves something the user
+// already moved (#64).  Where that is true the player's own level sits
+// at maximum, nothing changes it, and nothing persists it.
+//
+// **The predicate is named after the capability, not the platform.**
+// The frontend asks "is there a volume for me to control", which is a
+// question about this build; asking "is this a phone" instead would
+// key the answer to a viewport, and an Android tablet at 600px or more
+// would then draw the bottom bar's slider over a level pinned at
+// maximum -- a control that cannot act, which is the thing
+// `library-status-indicator` already settled is worse than none.
+//
+// **Only `platformOwnsVolume` is behind a build tag**, in two files
+// that declare nothing else.  A tagged file is compiled by nothing
+// `make lint` or `make test` runs and is untestable off a phone, which
+// is the reasoning `mediacontrols/androidpayload.go` states for
+// keeping its contract out of one -- so everything decidable here is
+// decided against `Player.systemVolume`, a field a test sets either
+// way, and the tag decides only what that field starts as.
+//
+// The one thing this must not disturb is ducking.  `SetDuck` applies
+// its attenuation by re-applying the *user's* level through
+// `setVolumeLocked`, so pinning that level to maximum leaves the
+// offset arithmetic exactly as it was: an OS asking us to get out of
+// the way of a navigation prompt is not the user setting a volume, and
+// it is the only thing that may move the output on such a platform.
+
+// SystemOwnsVolume reports whether the platform's own control is the
+// only volume control there is, so this app neither offers one nor
+// remembers a level.
+//
+// It is bound: the frontend renders no `<volume-control>` when it is
+// true, at any width.
+func (p *Player) SystemOwnsVolume() bool {
+	return p.systemVolume
+}

backend/player/systemvolume_android.go

@@ -0,0 +1,11 @@
+//go:build android
+
+package player
+
+// platformOwnsVolume is true on Android: volume is the device's, set
+// with the hardware keys, and `mediacontrols`' Android handler
+// implements no volume callback for the same reason.
+//
+// See systemvolume.go for why this constant is the whole of what a
+// build tag decides here.
+const platformOwnsVolume = true

backend/player/systemvolume_other.go

@@ -0,0 +1,10 @@
+//go:build !android
+
+package player
+
+// platformOwnsVolume is false everywhere but Android: a desktop mixer
+// is per-application, so our level is the one the user reaches for.
+//
+// See systemvolume.go for why this constant is the whole of what a
+// build tag decides here.
+const platformOwnsVolume = false

backend/player/systemvolume_test.go

@@ -0,0 +1,215 @@
+package player
+
+import (
+	"log/slog"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"github.com/gopxl/beep/v2/effects"
+
+	"yellowjacket/backend/database"
+)
+
+// pinnedPlayer is a player on a platform whose volume belongs to the
+// device.  The field is set rather than the build constant read,
+// because the constant is true on exactly one platform and no tier
+// here runs on it -- see systemvolume.go.
+func pinnedPlayer(t *testing.T, db *database.DB) *Player {
+	t.Helper()
+
+	p := NewPlayer(slog.Default(), db)
+	p.systemVolume = true
+	p.volume = &effects.Volume{Base: 2}
+	p.setVolumeLocked(MaxUserVol)
+
+	return p
+}
+
+// TestSystemVolumeRefusesEveryWayToChangeTheLevel is the first half of
+// #64: where the device owns the volume, ours sits at maximum and none
+// of the three routes to a level moves it.  Mute is in that list
+// because it is a level of zero by another name, and because with no
+// control rendered it is the one state on such a platform there would
+// be nothing to get out of.
+func TestSystemVolumeRefusesEveryWayToChangeTheLevel(t *testing.T) {
+	t.Parallel()
+
+	p := pinnedPlayer(t, nil)
+
+	if !p.SystemOwnsVolume() {
+		t.Fatal("SystemOwnsVolume() = false on a pinned player")
+	}
+
+	if got := p.getUserVolume(); got != MaxUserVol {
+		t.Errorf("starting volume = %d, want %d", got, MaxUserVol)
+	}
+
+	p.SetVolume(20)
+
+	if got := p.getUserVolume(); got != MaxUserVol {
+		t.Errorf("volume after SetVolume(20) = %d, want %d", got, MaxUserVol)
+	}
+
+	if err := p.ChangeVolume(-30); err != nil {
+		t.Fatalf("ChangeVolume: %v", err)
+	}
+
+	if got := p.getUserVolume(); got != MaxUserVol {
+		t.Errorf("volume after ChangeVolume(-30) = %d, want %d", got, MaxUserVol)
+	}
+
+	if err := p.MuteToggle(); err != nil {
+		t.Fatalf("MuteToggle: %v", err)
+	}
+
+	if p.volume.Silent {
+		t.Error("MuteToggle silenced a player whose volume the system owns")
+	}
+}
+
+// TestAnUnpinnedPlayerStillChangesItsVolume is the other side of the
+// same switch.  Without it the test above passes on a player that
+// refuses everything, which is what a mis-wired field would produce.
+func TestAnUnpinnedPlayerStillChangesItsVolume(t *testing.T) {
+	t.Parallel()
+
+	p := NewPlayer(slog.Default(), nil)
+	p.volume = &effects.Volume{Base: 2}
+	p.setVolumeLocked(MaxUserVol)
+
+	if p.SystemOwnsVolume() {
+		t.Fatal("SystemOwnsVolume() = true off Android")
+	}
+
+	p.SetVolume(20)
+
+	if got := p.getUserVolume(); got != 20 {
+		t.Errorf("volume after SetVolume(20) = %d, want 20", got)
+	}
+
+	if err := p.MuteToggle(); err != nil {
+		t.Fatalf("MuteToggle: %v", err)
+	}
+
+	if !p.volume.Silent {
+		t.Error("MuteToggle did not silence an ordinary player")
+	}
+}
+
+// TestSystemVolumeStillDucks is the issue's second Finding, made a
+// test: pinning the user's level must leave the OS's attenuation
+// working, because a duck is not a volume the user chose and is the
+// only thing that may move the output on such a platform.
+func TestSystemVolumeStillDucks(t *testing.T) {
+	t.Parallel()
+
+	p := pinnedPlayer(t, nil)
+	open := p.volume.Volume
+
+	p.SetDuck(true)
+
+	if p.volume.Volume >= open {
+		t.Errorf(
+			"ducked output = %v, want less than %v", p.volume.Volume, open,
+		)
+	}
+
+	if got := p.getUserVolume(); got != MaxUserVol {
+		t.Errorf("user volume while ducked = %d, want %d", got, MaxUserVol)
+	}
+
+	// A refused SetVolume must not disturb the offset either: it
+	// returns before setVolumeLocked, which is what re-applies it.
+	ducked := p.volume.Volume
+
+	p.SetVolume(10)
+
+	if p.volume.Volume != ducked {
+		t.Errorf(
+			"output after a refused SetVolume = %v, want %v",
+			p.volume.Volume, ducked,
+		)
+	}
+
+	p.SetDuck(false)
+
+	if p.volume.Volume != open {
+		t.Errorf("output after unduck = %v, want %v", p.volume.Volume, open)
+	}
+}
+
+// TestSystemVolumeWritesBackTheLevelItFound is the rest of the
+// Direction: "make sure nothing writes a persisted volume from that
+// platform".  The maximum the player runs at is synthetic, so saving
+// must not record it over whatever the row already said.
+func TestSystemVolumeWritesBackTheLevelItFound(t *testing.T) {
+	t.Parallel()
+
+	db := database.NewTestDB(t)
+
+	// A level set by some earlier, unpinned session.
+	writer := NewPlayer(slog.Default(), db)
+	writer.volume = &effects.Volume{Base: 2}
+	writer.setVolumeLocked(30)
+	writer.SaveState()
+
+	p := pinnedPlayer(t, db)
+	p.RestoreState()
+
+	if got := p.getUserVolume(); got != MaxUserVol {
+		t.Errorf("restored volume = %d, want %d (the level is pinned)", got, MaxUserVol)
+	}
+
+	if p.volume.Silent {
+		t.Error("restore muted a player whose volume the system owns")
+	}
+
+	p.SaveState()
+
+	state, err := db.Queries.GetPlayerState(db.Ctx)
+	if err != nil {
+		t.Fatalf("GetPlayerState: %v", err)
+	}
+
+	if state.Volume != 30 {
+		t.Errorf("persisted volume = %d, want 30 (untouched)", state.Volume)
+	}
+}
+
+// TestPlatformVolumeOwnershipIsDeclaredOncePerPlatform sweeps the
+// source, because the pair of tagged files is the one thing here no
+// tier compiles both halves of: `make lint` and `make test` build the
+// `!android` side only, so a deleted or edited android file fails
+// nothing until somebody has a phone in their hand.
+func TestPlatformVolumeOwnershipIsDeclaredOncePerPlatform(t *testing.T) {
+	t.Parallel()
+
+	want := map[string]string{
+		"systemvolume_other.go":   "const platformOwnsVolume = false",
+		"systemvolume_android.go": "const platformOwnsVolume = true",
+	}
+
+	tags := map[string]string{
+		"systemvolume_other.go":   "//go:build !android",
+		"systemvolume_android.go": "//go:build android",
+	}
+
+	for name, decl := range want {
+		src, err := os.ReadFile(filepath.Join(".", name))
+		if err != nil {
+			t.Errorf("%s: %v", name, err)
+
+			continue
+		}
+
+		if !strings.Contains(string(src), decl) {
+			t.Errorf("%s does not declare %q", name, decl)
+		}
+
+		if !strings.Contains(string(src), tags[name]) {
+			t.Errorf("%s does not carry %q", name, tags[name])
+		}
+	}
+}

frontend/bindings/yellowjacket/backend/player/player.ts

@@ -142,6 +142,18 @@ export function SetVolume(desiredVolume: $models.UserVolume): $CancellablePromis
     return $Call.ByID(1375836663, desiredVolume);
 }
 
+/**
+ * SystemOwnsVolume reports whether the platform's own control is the
+ * only volume control there is, so this app neither offers one nor
+ * remembers a level.
+ * 
+ * It is bound: the frontend renders no `<volume-control>` when it is
+ * true, at any width.
+ */
+export function SystemOwnsVolume(): $CancellablePromise<boolean> {
+    return $Call.ByID(1027623185);
+}
+
 /**
  * TrackLengthInSeconds returns the duration of the current track.
  */