car preview: type with the phone's keyboard instead of drawing the car's

gearslip/src/main/java/app/seb3thehacker/gearslip/car/CarKeyboard.kt

@@ -44,6 +44,12 @@ object CarKeyboardVisibility {
     val state = mutableStateOf(false)
 }
 
+/**
+ * True for the car UI the phone's own car preview draws. The phone is in hand there, so a
+ * [CarKeyboard] draws nothing and the phone's keyboard does the typing instead (see [PhoneTyping]).
+ */
+val LocalCarPreview = compositionLocalOf { false }
+
 /**
  * A keyboard the host draws itself.
  *
@@ -73,10 +79,11 @@ fun CarKeyboard(
 ) {
     var symbols by remember { mutableStateOf(false) }
     var shifted by remember { mutableStateOf(false) }
+    val preview = LocalCarPreview.current
 
-    DisposableEffect(Unit) {
+    DisposableEffect(preview) {
-        CarKeyboardVisibility.state.value = true
+        if (!preview) CarKeyboardVisibility.state.value = true
-        onDispose { CarKeyboardVisibility.state.value = false }
+        onDispose { if (!preview) CarKeyboardVisibility.state.value = false }
     }
 
     // The same field on the phone, for typing on its own keyboard: see [PhoneTyping].
@@ -88,6 +95,7 @@ fun CarKeyboard(
     }
     DisposableEffect(phoneField) { onDispose { PhoneTyping.close(phoneField) } }
     LaunchedEffect(text) { PhoneTyping.carText(phoneField, text) }
+    if (preview) return
 
     val rows = if (symbols) SYMBOL_ROWS else LETTER_ROWS
     val keyHeight = keyHeight(LocalConfiguration.current.screenHeightDp)

gearslip/src/main/java/app/seb3thehacker/gearslip/ui/CarPreviewScreen.kt

@@ -76,7 +76,9 @@ fun CarPreviewScreen(onBack: () -> Unit) {
         // No surface yet: the SurfaceView below hands its own over once it exists, and the
         // display draws straight into it. Copying each frame into a Bitmap instead cost two
         // full-size allocations per frame on the main thread, and taps lagged with the size.
-        projector.start(null, width, height, density, name = "gearslip-preview") { CarUi() }
+        projector.start(null, width, height, density, name = "gearslip-preview") {
+            androidx.compose.runtime.CompositionLocalProvider(app.seb3thehacker.gearslip.car.LocalCarPreview provides true) { CarUi() }
+        }
         onDispose { projector.stop() }
     }
 

gearslip/src/main/java/app/seb3thehacker/gearslip/ui/GearslipApp.kt

@@ -148,8 +148,9 @@ fun GearslipApp(onDisconnect: () -> Unit, onRequestCallScreening: () -> Unit) {
                 )
             }
         }
-        // A car keyboard is open: offer the phone's own, for a passenger.
+        // A car keyboard is open: offer the phone's own, for a passenger. In the car preview it is
-        if (screen != Screen.CAR_PREVIEW) PhoneTypingBar()
+        // the only keyboard, since the preview draws none of its own.
+        PhoneTypingBar()
     }
 }