Fix background composable

Change-Id: I548612191b0b99620777c3e2ad0ace56b228d27d

app/src/main/java/com/google/samples/apps/nowinandroid/ui/NiaApp.kt

@@ -66,6 +66,7 @@ import com.google.samples.apps.nowinandroid.core.designsystem.component.NiaTopAp
 import com.google.samples.apps.nowinandroid.core.designsystem.icon.Icon.DrawableResourceIcon
 import com.google.samples.apps.nowinandroid.core.designsystem.icon.Icon.ImageVectorIcon
 import com.google.samples.apps.nowinandroid.core.designsystem.icon.NiaIcons
+import com.google.samples.apps.nowinandroid.core.designsystem.theme.LocalGradientColors
 import com.google.samples.apps.nowinandroid.feature.settings.R as settingsR
 import com.google.samples.apps.nowinandroid.feature.settings.SettingsDialog
 import com.google.samples.apps.nowinandroid.navigation.NiaNavHost
@@ -86,109 +87,119 @@ fun NiaApp(
         windowSizeClass = windowSizeClass
     ),
 ) {
-    val background: @Composable (@Composable () -> Unit) -> Unit =
+    val showGradientBackground = appState.currentTopLevelDestination == TopLevelDestination.FOR_YOU
-        when (appState.currentTopLevelDestination) {
-            TopLevelDestination.FOR_YOU -> {
-                content ->
-                NiaGradientBackground(content = content)
-            }
-            else -> { content -> NiaBackground(content = content) }
-        }
 
-    background {
+    NiaBackground {
+        NiaGradientBackground(
+            topColor = if (showGradientBackground) {
+                LocalGradientColors.current.top
+            } else {
+                Color.Unspecified
+            },
+            bottomColor = if (showGradientBackground) {
+                LocalGradientColors.current.bottom
+            } else {
+                Color.Unspecified
+            },
+            containerColor = if (showGradientBackground) {
+                LocalGradientColors.current.container
+            } else {
+                Color.Unspecified
+            },
+        ) {
+            val snackbarHostState = remember { SnackbarHostState() }
 
-        val snackbarHostState = remember { SnackbarHostState() }
+            Scaffold(
+                modifier = Modifier.semantics {
+                    testTagsAsResourceId = true
+                },
+                containerColor = Color.Transparent,
+                contentColor = MaterialTheme.colorScheme.onBackground,
+                contentWindowInsets = WindowInsets(0, 0, 0, 0),
+                snackbarHost = { SnackbarHost(snackbarHostState) },
+                topBar = {
+                    // Show the top app bar on top level destinations.
+                    val destination = appState.currentTopLevelDestination
+                    if (destination != null) {
+                        NiaTopAppBar(
+                            // When the nav rail is displayed, the top app bar will, by default
+                            // overlap it. This means that the top most item in the nav rail
+                            // won't be tappable. A workaround is to position the top app bar
+                            // behind the nav rail using zIndex.
+                            modifier = Modifier.zIndex(-1F),
+                            titleRes = destination.titleTextId,
+                            actionIcon = NiaIcons.Settings,
+                            actionIconContentDescription = stringResource(
+                                id = settingsR.string.top_app_bar_action_icon_description
+                            ),
+                            colors = TopAppBarDefaults.centerAlignedTopAppBarColors(
+                                containerColor = Color.Transparent
+                            ),
+                            onActionClick = { appState.setShowSettingsDialog(true) }
+                        )
+                    }
+                },
+                bottomBar = {
+                    if (appState.shouldShowBottomBar) {
+                        NiaBottomBar(
+                            destinations = appState.topLevelDestinations,
+                            onNavigateToDestination = appState::navigateToTopLevelDestination,
+                            currentDestination = appState.currentDestination,
+                            modifier = Modifier.testTag("NiaBottomBar")
+                        )
+                    }
+                }
+            ) { padding ->
 
-        Scaffold(
+                val isOffline by appState.isOffline.collectAsStateWithLifecycle()
-            modifier = Modifier.semantics {
+
-                testTagsAsResourceId = true
+                // If user is not connected to the internet show a snack bar to inform them.
-            },
+                val notConnected = stringResource(R.string.not_connected)
-            containerColor = Color.Transparent,
+                LaunchedEffect(isOffline) {
-            contentColor = MaterialTheme.colorScheme.onBackground,
+                    if (isOffline) snackbarHostState.showSnackbar(
-            contentWindowInsets = WindowInsets(0, 0, 0, 0),
+                        message = notConnected,
-            snackbarHost = { SnackbarHost(snackbarHostState) },
+                        duration = Indefinite
-            topBar = {
-                // Show the top app bar on top level destinations.
-                val destination = appState.currentTopLevelDestination
-                if (destination != null) {
-                    NiaTopAppBar(
-                        // When the nav rail is displayed, the top app bar will, by default
-                        // overlap it. This means that the top most item in the nav rail
-                        // won't be tappable. A workaround is to position the top app bar
-                        // behind the nav rail using zIndex.
-                        modifier = Modifier.zIndex(-1F),
-                        titleRes = destination.titleTextId,
-                        actionIcon = NiaIcons.Settings,
-                        actionIconContentDescription = stringResource(
-                            id = settingsR.string.top_app_bar_action_icon_description
-                        ),
-                        colors = TopAppBarDefaults.centerAlignedTopAppBarColors(
-                            containerColor = Color.Transparent
-                        ),
-                        onActionClick = { appState.setShowSettingsDialog(true) }
                     )
                 }
-            },
+
-            bottomBar = {
+                if (appState.shouldShowSettingsDialog) {
-                if (appState.shouldShowBottomBar) {
+                    SettingsDialog(
-                    NiaBottomBar(
+                        onDismiss = { appState.setShowSettingsDialog(false) }
-                        destinations = appState.topLevelDestinations,
-                        onNavigateToDestination = appState::navigateToTopLevelDestination,
-                        currentDestination = appState.currentDestination,
-                        modifier = Modifier.testTag("NiaBottomBar")
                     )
                 }
-            }
-        ) { padding ->
 
-            val isOffline by appState.isOffline.collectAsStateWithLifecycle()
+                Row(
-
+                    Modifier
-            // If user is not connected to the internet show a snack bar to inform them.
+                        .fillMaxSize()
-            val notConnected = stringResource(R.string.not_connected)
+                        .windowInsetsPadding(
-            LaunchedEffect(isOffline) {
+                            WindowInsets.safeDrawing.only(
-                if (isOffline) snackbarHostState.showSnackbar(
+                                WindowInsetsSides.Horizontal
-                    message = notConnected,
+                            )
-                    duration = Indefinite
+                        )
-                )
+                ) {
-            }
+                    if (appState.shouldShowNavRail) {
+                        NiaNavRail(
+                            destinations = appState.topLevelDestinations,
+                            onNavigateToDestination = appState::navigateToTopLevelDestination,
+                            currentDestination = appState.currentDestination,
+                            modifier = Modifier
+                                .testTag("NiaNavRail")
+                                .safeDrawingPadding()
+                        )
+                    }
 
-            if (appState.shouldShowSettingsDialog) {
+                    NiaNavHost(
-                SettingsDialog(
+                        navController = appState.navController,
-                    onDismiss = { appState.setShowSettingsDialog(false) }
+                        onBackClick = appState::onBackClick,
-                )
-            }
 
-            Row(
-                Modifier
-                    .fillMaxSize()
-                    .windowInsetsPadding(
-                        WindowInsets.safeDrawing.only(
-                            WindowInsetsSides.Horizontal
-                        )
-                    )
-            ) {
-                if (appState.shouldShowNavRail) {
-                    NiaNavRail(
-                        destinations = appState.topLevelDestinations,
-                        onNavigateToDestination = appState::navigateToTopLevelDestination,
-                        currentDestination = appState.currentDestination,
                         modifier = Modifier
-                            .testTag("NiaNavRail")
+                            .padding(padding)
-                            .safeDrawingPadding()
+                            .consumedWindowInsets(padding)
                     )
-                }
 
-                NiaNavHost(
+                    // TODO: We may want to add padding or spacer when the snackbar is shown so that
-                    navController = appState.navController,
+                    //  content doesn't display behind it.
-                    onBackClick = appState::onBackClick,
+                }
-
-                    modifier = Modifier
-                        .padding(padding)
-                        .consumedWindowInsets(padding)
-                )
-
-                // TODO: We may want to add padding or spacer when the snackbar is shown so that
-                //  content doesn't display behind it.
             }
         }
     }