Remove the brightness dip in screen transition crossfades

- Fading the outgoing and incoming screens simultaneously makes content
  present on both (the camera FAB) dip to ~75% opacity mid-transition
- Fade only one layer: hold the outgoing destination opaque under the
  fading-in incoming one, and reveal the destination instantly under the
  fading-out one on back

app/src/main/java/com/example/onecamera/data/preferences/UserPreferencesRepository.kt

@@ -9,8 +9,13 @@ import androidx.datastore.preferences.core.floatPreferencesKey
 import androidx.datastore.preferences.core.stringPreferencesKey
 import androidx.datastore.preferences.preferencesDataStore
 import dagger.hilt.android.qualifiers.ApplicationContext
-import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.SupervisorJob
+import kotlinx.coroutines.flow.SharingStarted
+import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.flow.map
+import kotlinx.coroutines.flow.stateIn
 import javax.inject.Inject
 import javax.inject.Singleton
 
@@ -41,17 +46,26 @@ class UserPreferencesRepository @Inject constructor(
         val SCREEN_TRANSITIONS_ENABLED = booleanPreferencesKey("screen_transitions_enabled")
     }
 
-    val userPreferencesFlow: Flow<UserPreferences> = context.dataStore.data.map { prefs ->
-        UserPreferences(
-            rootFolderUri = prefs[Keys.ROOT_FOLDER_URI],
-            cameraFabXFraction = prefs[Keys.CAMERA_FAB_X_FRACTION]?.coerceIn(0f, 1f) ?: 1f,
-            cameraFabYFraction = prefs[Keys.CAMERA_FAB_Y_FRACTION]?.coerceIn(0f, 1f) ?: 1f,
-            gallerySortAscending = prefs[Keys.GALLERY_SORT_ASCENDING] ?: true,
-            galleryGridMode = prefs[Keys.GALLERY_GRID_MODE] ?: true,
-            zipJpegCompression = prefs[Keys.ZIP_JPEG_COMPRESSION] ?: true,
-            screenTransitionsEnabled = prefs[Keys.SCREEN_TRANSITIONS_ENABLED] ?: true,
+    // Hot, process-wide cache: the DataStore file is read once, and every screen
+    // created later receives the current value synchronously on subscription,
+    // instead of re-reading disk per screen and flashing default positions.
+    val userPreferencesFlow: StateFlow<UserPreferences> = context.dataStore.data
+        .map { prefs ->
+            UserPreferences(
+                rootFolderUri = prefs[Keys.ROOT_FOLDER_URI],
+                cameraFabXFraction = prefs[Keys.CAMERA_FAB_X_FRACTION]?.coerceIn(0f, 1f) ?: 1f,
+                cameraFabYFraction = prefs[Keys.CAMERA_FAB_Y_FRACTION]?.coerceIn(0f, 1f) ?: 1f,
+                gallerySortAscending = prefs[Keys.GALLERY_SORT_ASCENDING] ?: true,
+                galleryGridMode = prefs[Keys.GALLERY_GRID_MODE] ?: true,
+                zipJpegCompression = prefs[Keys.ZIP_JPEG_COMPRESSION] ?: true,
+                screenTransitionsEnabled = prefs[Keys.SCREEN_TRANSITIONS_ENABLED] ?: true,
+            )
+        }
+        .stateIn(
+            scope = CoroutineScope(SupervisorJob() + Dispatchers.IO),
+            started = SharingStarted.Eagerly,
+            initialValue = UserPreferences(),
         )
-    }
 
     suspend fun setRootFolderUri(uri: String) {
         context.dataStore.edit { prefs ->

app/src/main/java/com/example/onecamera/navigation/OneCameraNavGraph.kt

@@ -32,7 +32,10 @@ import kotlinx.serialization.Serializable
 object FoldersRoute
 
 @Serializable
-data class GalleryRoute(val folderUri: String)
+data class GalleryRoute(
+    val folderUri: String,
+    val folderName: String = "",
+)
 
 @Serializable
 data class CameraRoute(
@@ -64,14 +67,20 @@ fun OneCameraNavGraph(navController: NavHostController) {
         navController = navController,
         startDestination = FoldersRoute,
         enterTransition = { if (transitionsEnabled) fadeIn(tween(250)) else EnterTransition.None },
-        exitTransition = { if (transitionsEnabled) fadeOut(tween(250)) else ExitTransition.None },
-        popEnterTransition = { if (transitionsEnabled) fadeIn(tween(250)) else EnterTransition.None },
+        exitTransition = {
+            if (transitionsEnabled) {
+                ExitTransition.KeepUntilTransitionsFinished
+            } else {
+                ExitTransition.None
+            }
+        },
+        popEnterTransition = { EnterTransition.None },
         popExitTransition = { if (transitionsEnabled) fadeOut(tween(250)) else ExitTransition.None },
     ) {
         composable<FoldersRoute> {
             FoldersScreen(
-                onNavigateToGallery = { folderUri ->
-                    navController.navigate(GalleryRoute(folderUri))
+                onNavigateToGallery = { folderUri, folderName ->
+                    navController.navigate(GalleryRoute(folderUri, folderName))
                 },
                 onNavigateToCamera = { folderUri ->
                     navController.navigate(
@@ -93,8 +102,8 @@ fun OneCameraNavGraph(navController: NavHostController) {
                 onNavigateToCamera = { folderUri ->
                     navController.navigate(CameraRoute(folderUri))
                 },
-                onNavigateToSubfolder = { folderUri ->
-                    navController.navigate(GalleryRoute(folderUri))
+                onNavigateToSubfolder = { folderUri, folderName ->
+                    navController.navigate(GalleryRoute(folderUri, folderName))
                 },
                 onNavigateBack = { navController.popBackStack() },
             )

app/src/main/java/com/example/onecamera/ui/folders/FoldersScreen.kt

@@ -57,7 +57,7 @@ import com.example.onecamera.ui.components.oneCameraTopAppBarColors
 @OptIn(ExperimentalMaterial3Api::class, ExperimentalComposeUiApi::class)
 @Composable
 fun FoldersScreen(
-    onNavigateToGallery: (String) -> Unit,
+    onNavigateToGallery: (folderUri: String, folderName: String) -> Unit,
     onNavigateToCamera: (String) -> Unit,
     onNavigateToSettings: () -> Unit,
     viewModel: FoldersViewModel = hiltViewModel(),
@@ -230,7 +230,7 @@ fun FoldersScreen(
 
                                         onClick = {
                                             viewModel.prefetchFolderForNavigation(folder.uri.toString())
-                                            onNavigateToGallery(folder.uri.toString())
+                                            onNavigateToGallery(folder.uri.toString(), folder.name)
                                         },
                                         onCompress = { viewModel.zipFolderAndShare(folder) },
                                         onCompressJpeg85 = {

app/src/main/java/com/example/onecamera/ui/gallery/GalleryScreen.kt

@@ -49,8 +49,8 @@ import androidx.compose.runtime.snapshotFlow
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.ExperimentalComposeUiApi
 import androidx.compose.ui.Modifier
+import androidx.compose.ui.draw.alpha
 import androidx.compose.ui.graphics.Color
-import androidx.compose.ui.graphics.graphicsLayer
 import androidx.compose.ui.layout.ContentScale
 import androidx.compose.ui.platform.LocalContext
 import androidx.compose.ui.res.painterResource
@@ -93,7 +93,7 @@ import kotlinx.coroutines.flow.distinctUntilChanged
 fun GalleryScreen(
     folderUri: String,
     onNavigateToCamera: (String) -> Unit,
-    onNavigateToSubfolder: (String) -> Unit,
+    onNavigateToSubfolder: (folderUri: String, folderName: String) -> Unit,
     onNavigateBack: () -> Unit,
     viewModel: GalleryViewModel = hiltViewModel(),
 ) {
@@ -281,9 +281,7 @@ fun GalleryScreen(
                 title = {
                     Column {
                         Text(
-                            uiState.folderName.ifEmpty {
-                                stringResource(R.string.gallery_title)
-                            },
+                            uiState.folderName,
                             maxLines = 1,
                             overflow = TextOverflow.Ellipsis,
                         )
@@ -408,14 +406,6 @@ fun GalleryScreen(
                 Box(modifier = Modifier.fillMaxSize()) {
                     when {
 
-                        uiState.selectedPhoto != null -> {
-                            Box(
-                                modifier = Modifier
-                                    .fillMaxSize()
-                                    .background(Color.Black),
-                            )
-                        }
-
                         !uiState.viewPreferencesLoaded -> {
                             Box(modifier = Modifier.fillMaxSize())
                         }
@@ -442,7 +432,7 @@ fun GalleryScreen(
 
                                 onFolderClick = {
                                     viewModel.prefetchFolderForNavigation(it.uri.toString())
-                                    onNavigateToSubfolder(it.uri.toString())
+                                    onNavigateToSubfolder(it.uri.toString(), it.name)
                                 },
                                 onFolderCompress = { viewModel.zipFolderAndShare(it) },
                                 onFolderCompressJpeg85 = { viewModel.zipFolderCompressedJpegsAndShare(it) },
@@ -484,12 +474,14 @@ fun GalleryScreen(
         enter = fadeIn(tween(250)),
         exit = fadeOut(tween(150)),
     ) {
-        DraggableCameraFab(
-            xFraction = uiState.cameraFabXFraction,
-            yFraction = uiState.cameraFabYFraction,
-            onPositionChange = viewModel::saveCameraFabPosition,
-            onClick = { onNavigateToCamera(uiState.currentFolderUri ?: folderUri) },
-        )
+        if (uiState.viewPreferencesLoaded) {
+            DraggableCameraFab(
+                xFraction = uiState.cameraFabXFraction,
+                yFraction = uiState.cameraFabYFraction,
+                onPositionChange = viewModel::saveCameraFabPosition,
+                onClick = { onNavigateToCamera(uiState.currentFolderUri ?: folderUri) },
+            )
+        }
     }
 
     SelectionActionsBar(
@@ -670,16 +662,16 @@ private fun ZoomablePhoto(
 
     Box(modifier = modifier.fillMaxSize()) {
 
-        AsyncImage(
-            model = remember(photo.uri, context, fadeMs) {
-                thumbnailDraftRequest(context, photo.uri, crossfadeMillis = fadeMs)
-            },
-            contentDescription = null,
-            contentScale = ContentScale.Fit,
-            modifier = Modifier
-                .fillMaxSize()
-                .graphicsLayer { alpha = 1f - fullAlpha },
-        )
+        if (fullAlpha < 1f) {
+            AsyncImage(
+                model = remember(photo.uri, context, fadeMs) {
+                    thumbnailDraftRequest(context, photo.uri, crossfadeMillis = fadeMs)
+                },
+                contentDescription = null,
+                contentScale = ContentScale.Fit,
+                modifier = Modifier.fillMaxSize(),
+            )
+        }
         CoilZoomAsyncImage(
             model = fullImageRequest,
             contentDescription = photo.name,
@@ -688,7 +680,7 @@ private fun ZoomablePhoto(
             onError = { isFullReady = false },
             modifier = Modifier
                 .fillMaxSize()
-                .graphicsLayer { alpha = fullAlpha },
+                .alpha(fullAlpha),
             zoomState = zoomState,
         )
     }

app/src/main/java/com/example/onecamera/ui/gallery/GalleryViewModel.kt

@@ -4,6 +4,7 @@ import android.content.Context
 import android.net.Uri
 import androidx.compose.runtime.Immutable
 import androidx.core.net.toUri
+import androidx.lifecycle.SavedStateHandle
 import androidx.lifecycle.ViewModel
 import androidx.lifecycle.viewModelScope
 import coil3.SingletonImageLoader
@@ -113,6 +114,7 @@ data class GalleryUiState(
 
 @HiltViewModel
 class GalleryViewModel @Inject constructor(
+    savedStateHandle: SavedStateHandle,
     private val preferencesRepository: UserPreferencesRepository,
     private val listGalleryUseCase: ListGalleryUseCase,
     private val listFolderTreeUseCase: ListFolderTreeUseCase,
@@ -128,7 +130,11 @@ class GalleryViewModel @Inject constructor(
 ) : ViewModel() {
 
     val uiState: StateFlow<GalleryUiState>
-        field: MutableStateFlow<GalleryUiState> = MutableStateFlow(GalleryUiState())
+        field: MutableStateFlow<GalleryUiState> = MutableStateFlow(
+            // Navigation puts type-safe route args into the SavedStateHandle, so the
+            // title is correct from the very first frame, before any listing completes.
+            GalleryUiState(folderName = savedStateHandle.get<String>("folderName").orEmpty()),
+        )
 
     private var forceReload = false
 
@@ -199,6 +205,9 @@ class GalleryViewModel @Inject constructor(
         loadJob = viewModelScope.launch {
             uiState.value = uiState.value.copy(
                 currentFolderUri = folderUriString,
+                folderName = state.folderName.ifEmpty {
+                    folderUriString.substringAfterLast(':').substringAfterLast('/')
+                },
                 isLoading = true,
                 error = null,
             )

app/src/main/res/drawable/ic_launcher_foreground.xml

@@ -4,20 +4,7 @@
     android:height="108dp"
     android:viewportWidth="108"
     android:viewportHeight="108">
-
     <path
-        android:strokeColor="#000000"
-        android:strokeWidth="3.375"
-        android:strokeLineJoin="round"
-        android:pathData="M 43.453125 32.90625 L 64.546875 32.90625 a 10.546875 10.546875 0 0 1 10.546875 10.546875 L 75.09375 64.546875 a 10.546875 10.546875 0 0 1 -10.546875 10.546875 L 43.453125 75.09375 a 10.546875 10.546875 0 0 1 -10.546875 -10.546875 L 32.90625 43.453125 a 10.546875 10.546875 0 0 1 10.546875 -10.546875 Z" />
-
-    <path
-        android:strokeColor="#000000"
-        android:strokeWidth="3.375"
-        android:pathData="M 41.34375 54 a 12.65625 12.65625 0 1 0 25.3125 0 a 12.65625 12.65625 0 1 0 -25.3125 0 Z" />
-
-    <path
-        android:fillColor="#d94e47"
-        android:pathData="M 68.71875 38.390625 a 2.53125 2.53125 0 1 0 5.0625 0 a 2.53125 2.53125 0 1 0 -5.0625 0 Z" />
-
+        android:fillColor="#C9584D"
+        android:pathData="M66.90,53.85C66.90,54.93 66.82,56.08 66.67,57.08C66.53,58.07 66.30,58.95 66.00,59.80C65.71,60.66 65.34,61.46 64.91,62.20C64.48,62.94 63.97,63.63 63.41,64.25C62.86,64.87 62.23,65.42 61.56,65.90C60.89,66.38 60.16,66.79 59.39,67.11C58.61,67.44 57.82,67.69 56.92,67.85C56.02,68.02 54.97,68.10 54.00,68.10C53.03,68.10 51.98,68.02 51.08,67.85C50.18,67.69 49.39,67.44 48.61,67.11C47.84,66.79 47.11,66.38 46.44,65.90C45.77,65.42 45.14,64.87 44.59,64.25C44.03,63.63 43.52,62.94 43.09,62.20C42.66,61.46 42.29,60.66 42.00,59.80C41.70,58.95 41.47,58.07 41.33,57.08C41.18,56.08 41.10,54.93 41.10,53.85C41.10,52.77 41.18,51.62 41.33,50.62C41.47,49.63 41.70,48.75 42.00,47.90C42.29,47.04 42.66,46.24 43.09,45.50C43.52,44.76 44.03,44.07 44.59,43.45C45.14,42.83 45.77,42.28 46.44,41.80C47.11,41.32 47.84,40.91 48.61,40.59C49.39,40.26 50.18,40.01 51.08,39.85C51.98,39.68 53.03,39.60 54.00,39.60C54.97,39.60 56.02,39.68 56.92,39.85C57.82,40.01 58.61,40.26 59.39,40.59C60.16,40.91 60.89,41.32 61.56,41.80C62.23,42.28 62.86,42.83 63.41,43.45C63.97,44.07 64.48,44.76 64.91,45.50C65.34,46.24 65.71,47.04 66.00,47.90C66.30,48.75 66.53,49.63 66.67,50.62C66.82,51.62 66.90,52.77 66.90,53.85ZM61.50,54.00C61.50,53.30 61.46,52.54 61.37,51.90C61.29,51.25 61.16,50.67 60.99,50.12C60.82,49.56 60.61,49.03 60.36,48.55C60.12,48.07 59.83,47.62 59.51,47.21C59.20,46.81 58.84,46.45 58.46,46.14C58.08,45.83 57.66,45.56 57.22,45.35C56.78,45.13 56.33,44.97 55.81,44.86C55.30,44.75 54.70,44.70 54.15,44.70C53.60,44.70 53.00,44.75 52.49,44.86C51.97,44.97 51.52,45.13 51.08,45.35C50.64,45.56 50.22,45.83 49.84,46.14C49.46,46.45 49.10,46.81 48.79,47.21C48.47,47.62 48.18,48.07 47.94,48.55C47.69,49.03 47.48,49.56 47.31,50.12C47.14,50.67 47.01,51.25 46.93,51.90C46.84,52.54 46.80,53.30 46.80,54.00C46.80,54.70 46.84,55.46 46.93,56.10C47.01,56.75 47.14,57.33 47.31,57.88C47.48,58.44 47.69,58.97 47.94,59.45C48.18,59.93 48.47,60.38 48.79,60.79C49.10,61.19 49.46,61.55 49.84,61.86C50.22,62.17 50.64,62.44 51.08,62.65C51.52,62.87 51.97,63.03 52.49,63.14C53.00,63.25 53.60,63.30 54.15,63.30C54.70,63.30 55.30,63.25 55.81,63.14C56.33,63.03 56.78,62.87 57.22,62.65C57.66,62.44 58.08,62.17 58.46,61.86C58.84,61.55 59.20,61.19 59.51,60.79C59.83,60.38 60.12,59.93 60.36,59.45C60.61,58.97 60.82,58.44 60.99,57.88C61.16,57.33 61.29,56.75 61.37,56.10C61.46,55.46 61.50,54.70 61.50,54.00Z" />
 </vector>

app/src/main/res/drawable/ic_launcher_monochrome.xml

@@ -4,20 +4,7 @@
     android:height="108dp"
     android:viewportWidth="108"
     android:viewportHeight="108">
-
-    <path
-        android:strokeColor="#FFFFFF"
-        android:strokeWidth="3.375"
-        android:strokeLineJoin="round"
-        android:pathData="M 43.453125 32.90625 L 64.546875 32.90625 a 10.546875 10.546875 0 0 1 10.546875 10.546875 L 75.09375 64.546875 a 10.546875 10.546875 0 0 1 -10.546875 10.546875 L 43.453125 75.09375 a 10.546875 10.546875 0 0 1 -10.546875 -10.546875 L 32.90625 43.453125 a 10.546875 10.546875 0 0 1 10.546875 -10.546875 Z" />
-
-    <path
-        android:strokeColor="#FFFFFF"
-        android:strokeWidth="3.375"
-        android:pathData="M 41.34375 54 a 12.65625 12.65625 0 1 0 25.3125 0 a 12.65625 12.65625 0 1 0 -25.3125 0 Z" />
-
     <path
         android:fillColor="#FFFFFF"
-        android:pathData="M 67.5 38.390625 a 2.109375 2.109375 0 1 0 4.21875 0 a 2.109375 2.109375 0 1 0 -4.21875 0 Z" />
-
+        android:pathData="M66.90,53.85C66.90,54.93 66.82,56.08 66.67,57.08C66.53,58.07 66.30,58.95 66.00,59.80C65.71,60.66 65.34,61.46 64.91,62.20C64.48,62.94 63.97,63.63 63.41,64.25C62.86,64.87 62.23,65.42 61.56,65.90C60.89,66.38 60.16,66.79 59.39,67.11C58.61,67.44 57.82,67.69 56.92,67.85C56.02,68.02 54.97,68.10 54.00,68.10C53.03,68.10 51.98,68.02 51.08,67.85C50.18,67.69 49.39,67.44 48.61,67.11C47.84,66.79 47.11,66.38 46.44,65.90C45.77,65.42 45.14,64.87 44.59,64.25C44.03,63.63 43.52,62.94 43.09,62.20C42.66,61.46 42.29,60.66 42.00,59.80C41.70,58.95 41.47,58.07 41.33,57.08C41.18,56.08 41.10,54.93 41.10,53.85C41.10,52.77 41.18,51.62 41.33,50.62C41.47,49.63 41.70,48.75 42.00,47.90C42.29,47.04 42.66,46.24 43.09,45.50C43.52,44.76 44.03,44.07 44.59,43.45C45.14,42.83 45.77,42.28 46.44,41.80C47.11,41.32 47.84,40.91 48.61,40.59C49.39,40.26 50.18,40.01 51.08,39.85C51.98,39.68 53.03,39.60 54.00,39.60C54.97,39.60 56.02,39.68 56.92,39.85C57.82,40.01 58.61,40.26 59.39,40.59C60.16,40.91 60.89,41.32 61.56,41.80C62.23,42.28 62.86,42.83 63.41,43.45C63.97,44.07 64.48,44.76 64.91,45.50C65.34,46.24 65.71,47.04 66.00,47.90C66.30,48.75 66.53,49.63 66.67,50.62C66.82,51.62 66.90,52.77 66.90,53.85ZM61.50,54.00C61.50,53.30 61.46,52.54 61.37,51.90C61.29,51.25 61.16,50.67 60.99,50.12C60.82,49.56 60.61,49.03 60.36,48.55C60.12,48.07 59.83,47.62 59.51,47.21C59.20,46.81 58.84,46.45 58.46,46.14C58.08,45.83 57.66,45.56 57.22,45.35C56.78,45.13 56.33,44.97 55.81,44.86C55.30,44.75 54.70,44.70 54.15,44.70C53.60,44.70 53.00,44.75 52.49,44.86C51.97,44.97 51.52,45.13 51.08,45.35C50.64,45.56 50.22,45.83 49.84,46.14C49.46,46.45 49.10,46.81 48.79,47.21C48.47,47.62 48.18,48.07 47.94,48.55C47.69,49.03 47.48,49.56 47.31,50.12C47.14,50.67 47.01,51.25 46.93,51.90C46.84,52.54 46.80,53.30 46.80,54.00C46.80,54.70 46.84,55.46 46.93,56.10C47.01,56.75 47.14,57.33 47.31,57.88C47.48,58.44 47.69,58.97 47.94,59.45C48.18,59.93 48.47,60.38 48.79,60.79C49.10,61.19 49.46,61.55 49.84,61.86C50.22,62.17 50.64,62.44 51.08,62.65C51.52,62.87 51.97,63.03 52.49,63.14C53.00,63.25 53.60,63.30 54.15,63.30C54.70,63.30 55.30,63.25 55.81,63.14C56.33,63.03 56.78,62.87 57.22,62.65C57.66,62.44 58.08,62.17 58.46,61.86C58.84,61.55 59.20,61.19 59.51,60.79C59.83,60.38 60.12,59.93 60.36,59.45C60.61,58.97 60.82,58.44 60.99,57.88C61.16,57.33 61.29,56.75 61.37,56.10C61.46,55.46 61.50,54.70 61.50,54.00Z" />
 </vector>

app/src/main/res/values/strings.xml

@@ -46,7 +46,6 @@
         <item quantity="other">%d photos</item>
     </plurals>
 
-    <string name="gallery_title">Gallery</string>
     <string name="gallery_create_subfolder">Create subfolder</string>
     <string name="gallery_sort_ascending">Sort ascending</string>
     <string name="gallery_sort_descending">Sort descending</string>