AboutScreen: basic version

Update navigation to work with AboutScreen

app/src/main/java/org/mydomain/myscan/MainActivity.kt

@@ -38,6 +38,7 @@ import kotlinx.coroutines.launch
 import kotlinx.coroutines.suspendCancellableCoroutine
 import kotlinx.coroutines.withContext
 import org.mydomain.myscan.ui.theme.MyScanTheme
+import org.mydomain.myscan.view.AboutScreen
 import org.mydomain.myscan.view.CameraScreen
 import org.mydomain.myscan.view.DocumentScreen
 import org.opencv.android.OpenCVLoader
@@ -57,21 +58,27 @@ class MainActivity : ComponentActivity() {
             val liveAnalysisState by viewModel.liveAnalysisState.collectAsStateWithLifecycle()
             val pageIds by viewModel.pageIds.collectAsStateWithLifecycle()
             MyScanTheme {
+                val navigation = Navigation(
+                    toCameraScreen = { viewModel.navigateTo(Screen.Camera) },
+                    toDocumentScreen = { viewModel.navigateTo(Screen.Document()) },
+                    toAboutScreen = { viewModel.navigateTo(Screen.About) },
+                    back = { viewModel.navigateBack() }
+                )
                 when (val screen = currentScreen) {
                     is Screen.Camera -> {
                         CameraScreen(
                             viewModel,
                             liveAnalysisState,
                             onImageAnalyzed = { image -> viewModel.liveAnalysis(image) },
-                            onFinalizePressed = { viewModel.navigateTo(Screen.FinalizeDocument()) },
+                            onFinalizePressed = { viewModel.navigateTo(Screen.Document()) },
                         )
                     }
-                    is Screen.FinalizeDocument -> {
+                    is Screen.Document -> {
                         DocumentScreen (
                             pageIds,
                             initialPage = screen.initialPage,
                             imageLoader = { id -> viewModel.getBitmap(id) },
-                            toCameraScreen = { viewModel.navigateTo(Screen.Camera) },
+                            navigation = navigation,
                             pdfActions = PdfGenerationActions(
                                 startGeneration = viewModel::startPdfGeneration,
                                 cancelGeneration = viewModel::cancelPdfGeneration,
@@ -87,6 +94,9 @@ class MainActivity : ComponentActivity() {
                             onDeleteImage =  { id -> viewModel.deletePage(id) }
                         )
                     }
+                    is Screen.About -> {
+                        AboutScreen(onBack = navigation.back)
+                    }
                 }
             }
         }

app/src/main/java/org/mydomain/myscan/MainViewModel.kt

@@ -29,10 +29,12 @@ import androidx.lifecycle.viewmodel.CreationExtras
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.Job
 import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.SharingStarted
 import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.flow.asStateFlow
 import kotlinx.coroutines.flow.filterNotNull
 import kotlinx.coroutines.flow.map
+import kotlinx.coroutines.flow.stateIn
 import kotlinx.coroutines.flow.update
 import kotlinx.coroutines.launch
 import kotlinx.coroutines.withContext
@@ -63,8 +65,9 @@ class MainViewModel(
     private var _liveAnalysisState = MutableStateFlow(LiveAnalysisState())
     val liveAnalysisState: StateFlow<LiveAnalysisState> = _liveAnalysisState.asStateFlow()
 
-    private val _currentScreen = MutableStateFlow<Screen>(Screen.Camera)
+    private val _screenStack = MutableStateFlow<List<Screen>>(listOf(Screen.Camera))
-    val currentScreen: StateFlow<Screen> = _currentScreen.asStateFlow()
+    val currentScreen: StateFlow<Screen> = _screenStack.map { it.last() }
+        .stateIn(viewModelScope, SharingStarted.Eagerly, Screen.Camera)
 
     private val _pageIds = MutableStateFlow<List<String>>(imageRepository.imageIds())
     val pageIds: StateFlow<List<String>> = _pageIds
@@ -135,7 +138,11 @@ class MainViewModel(
     }
 
     fun navigateTo(screen: Screen) {
-        _currentScreen.value = screen
+        _screenStack.update { it + screen }
+    }
+
+    fun navigateBack() {
+        _screenStack.update { stack -> if (stack.size > 1) stack.dropLast(1) else stack }
     }
 
     fun onImageCaptured(imageProxy: ImageProxy?) {

app/src/main/java/org/mydomain/myscan/Navigation.kt

@@ -16,5 +16,13 @@ package org.mydomain.myscan
 
 sealed class Screen {
     object Camera : Screen()
-    data class FinalizeDocument(val initialPage: Int = 0) : Screen()
+    data class Document(val initialPage: Int = 0) : Screen()
+    object About : Screen()
 }
+
+data class Navigation(
+    val toCameraScreen: () -> Unit,
+    val toDocumentScreen: () -> Unit,
+    val toAboutScreen: () -> Unit,
+    val back: () -> Unit,
+)

app/src/main/java/org/mydomain/myscan/view/AboutScreen.kt

@@ -0,0 +1,112 @@
+/*
+ * Copyright 2025 Pierre-Yves Nicolas
+ *
+ * This program is free software: you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation, either version 3 of the License, or (at your option)
+ * any later version.
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ * You should have received a copy of the GNU General Public License along with
+ * this program. If not, see <https://www.gnu.org/licenses/>.
+ */
+package org.mydomain.myscan.view
+
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.Spacer
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.foundation.layout.height
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.rememberScrollState
+import androidx.compose.foundation.verticalScroll
+import androidx.compose.material.icons.Icons
+import androidx.compose.material.icons.automirrored.filled.ArrowBack
+import androidx.compose.material3.ExperimentalMaterial3Api
+import androidx.compose.material3.HorizontalDivider
+import androidx.compose.material3.Icon
+import androidx.compose.material3.IconButton
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Scaffold
+import androidx.compose.material3.Text
+import androidx.compose.material3.TopAppBar
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.tooling.preview.Preview
+import androidx.compose.ui.unit.dp
+
+@OptIn(ExperimentalMaterial3Api::class)
+@Composable
+fun AboutScreen(onBack: () -> Unit) {
+    Scaffold(
+        topBar = {
+            TopAppBar(
+                title = { Text("About") },
+                navigationIcon = {
+                    IconButton(onClick = onBack) {
+                        Icon(Icons.AutoMirrored.Filled.ArrowBack, contentDescription = "Back")
+                    }
+                },
+            )
+        }
+    ) { paddingValues ->
+        AboutContent(Modifier.padding(paddingValues))
+    }
+}
+
+@Composable
+fun AboutContent(modifier: Modifier = Modifier) {
+    Column(
+        modifier = modifier
+            .fillMaxSize()
+            .padding(16.dp)
+            .verticalScroll(rememberScrollState())
+    ) {
+        Text(
+            "MyScan",
+            style = MaterialTheme.typography.headlineSmall
+        )
+        Spacer(Modifier.height(8.dp))
+
+        Text(
+            "A simple and respectful application to scan your documents.",
+            style = MaterialTheme.typography.bodyMedium
+        )
+
+        Spacer(Modifier.height(16.dp))
+        HorizontalDivider()
+        Spacer(Modifier.height(16.dp))
+
+        Text(
+            "Version",
+            style = MaterialTheme.typography.titleSmall
+        )
+        Text("1.0.0")
+
+        Spacer(Modifier.height(16.dp))
+
+        Text(
+            "License",
+            style = MaterialTheme.typography.titleSmall
+        )
+        Text("This application is published under the GPLv3 license.")
+
+        Spacer(Modifier.height(16.dp))
+
+        Text(
+            "This application is based on the following open-source libraries",
+            style = MaterialTheme.typography.titleSmall
+        )
+        Text("• CameraX\n• Jetpack Compose\n• LiteRT\n• OpenCV\n• PDFBox")
+
+        Spacer(Modifier.height(32.dp))
+    }
+}
+
+
+@Preview
+@Composable
+fun AboutScreenPreview() {
+    AboutScreen(onBack = {})
+}

app/src/main/java/org/mydomain/myscan/view/CameraScreen.kt

@@ -45,7 +45,10 @@ import androidx.compose.foundation.shape.CircleShape
 import androidx.compose.foundation.shape.RoundedCornerShape
 import androidx.compose.material.icons.Icons
 import androidx.compose.material.icons.filled.Done
+import androidx.compose.material.icons.outlined.Info
 import androidx.compose.material3.BottomAppBar
+import androidx.compose.material3.Icon
+import androidx.compose.material3.IconButton
 import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.Scaffold
 import androidx.compose.material3.Surface
@@ -146,7 +149,7 @@ fun CameraScreen(
             CommonPageList(
                 pageIds = pageIds,
                 imageLoader = { id -> viewModel.getBitmap(id) },
-                onPageClick = { index -> viewModel.navigateTo(Screen.FinalizeDocument(index)) },
+                onPageClick = { index -> viewModel.navigateTo(Screen.Document(index)) },
                 listState = listState,
                 onLastItemPosition =
                     { offset -> thumbnailCoords.value = offset }
@@ -170,6 +173,7 @@ fun CameraScreen(
         onFinalizePressed = onFinalizePressed,
         onDebugModeSwitched = { isDebugMode = !isDebugMode },
         thumbnailCoords = thumbnailCoords,
+        toAboutScreen = { viewModel.navigateTo(Screen.About) }
     )
 }
 
@@ -182,6 +186,7 @@ private fun CameraScreenScaffold(
     onFinalizePressed: () -> Unit,
     onDebugModeSwitched: () -> Unit,
     thumbnailCoords: MutableState<Offset>,
+    toAboutScreen: () -> Unit,
 ) {
     Box {
         Scaffold(
@@ -199,6 +204,19 @@ private fun CameraScreenScaffold(
                     .padding(bottom = innerPadding.calculateBottomPadding())
                     .fillMaxSize()
             ) {
+                Box(
+                    modifier = Modifier.fillMaxSize().padding(innerPadding)
+                ) {
+                    IconButton(
+                        onClick = toAboutScreen,
+                        modifier = Modifier.align(Alignment.TopEnd)
+                    ) {
+                        Icon(
+                            imageVector = Icons.Outlined.Info,
+                            contentDescription = "About",
+                            tint = MaterialTheme.colorScheme.onSurface.copy(alpha = 0.6f))
+                    }
+                }
                 CameraPreviewWithOverlay(cameraPreview, cameraUiState, Modifier.align(Alignment.BottomCenter))
                 if (cameraUiState.isDebugMode) {
                     MessageBox(cameraUiState.liveAnalysisState.inferenceTime)
@@ -469,6 +487,7 @@ private fun ScreenPreview(captureState: CaptureState) {
             onFinalizePressed = {},
             onDebugModeSwitched = {},
             thumbnailCoords = thumbnailCoords,
+            toAboutScreen = {}
         )
     }
 }

app/src/main/java/org/mydomain/myscan/view/DocumentScreen.kt

@@ -19,6 +19,7 @@ import android.graphics.BitmapFactory
 import androidx.activity.compose.BackHandler
 import androidx.compose.foundation.Image
 import androidx.compose.foundation.background
+import androidx.compose.foundation.clickable
 import androidx.compose.foundation.layout.Arrangement
 import androidx.compose.foundation.layout.Box
 import androidx.compose.foundation.layout.Column
@@ -36,6 +37,7 @@ import androidx.compose.material.icons.filled.Add
 import androidx.compose.material.icons.filled.PictureAsPdf
 import androidx.compose.material.icons.filled.RestartAlt
 import androidx.compose.material.icons.outlined.Delete
+import androidx.compose.material.icons.outlined.Info
 import androidx.compose.material3.AlertDialog
 import androidx.compose.material3.BottomAppBar
 import androidx.compose.material3.ExperimentalMaterial3Api
@@ -65,6 +67,7 @@ import androidx.compose.ui.unit.dp
 import kotlinx.coroutines.flow.MutableStateFlow
 import net.engawapg.lib.zoomable.rememberZoomState
 import net.engawapg.lib.zoomable.zoomable
+import org.mydomain.myscan.Navigation
 import org.mydomain.myscan.PdfGenerationActions
 import org.mydomain.myscan.ui.PdfGenerationUiState
 import org.mydomain.myscan.ui.theme.MyScanTheme
@@ -75,7 +78,7 @@ fun DocumentScreen(
     pageIds: List<String>,
     initialPage: Int,
     imageLoader: (String) -> Bitmap?,
-    toCameraScreen: () -> Unit,
+    navigation: Navigation,
     pdfActions: PdfGenerationActions,
     onStartNew: () -> Unit,
     onDeleteImage: (String) -> Unit,
@@ -88,11 +91,11 @@ fun DocumentScreen(
         currentPageIndex.intValue = pageIds.size - 1
     }
     if (currentPageIndex.intValue < 0) {
-        toCameraScreen()
+        navigation.toCameraScreen()
         return
     }
     BackHandler {
-        toCameraScreen()
+        navigation.back()
     }
     Scaffold (
         topBar = {
@@ -103,15 +106,23 @@ fun DocumentScreen(
                 ),
                 title = { Text("Document") },
                 navigationIcon = {
-                    IconButton(onClick = toCameraScreen) {
+                    IconButton(onClick = navigation.toCameraScreen) {
                         Icon(Icons.AutoMirrored.Filled.ArrowBack, contentDescription = "Back")
                     }
                 },
+                actions = {
+                    IconButton(onClick = navigation.toAboutScreen) {
+                        Icon(
+                            imageVector = Icons.Outlined.Info,
+                            contentDescription = "About",
+                            tint = MaterialTheme.colorScheme.onSurface.copy(alpha = 0.6f))
+                    }
+                }
             )
         },
         bottomBar = {
             Column {
-                PageList(pageIds, imageLoader, currentPageIndex, toCameraScreen)
+                PageList(pageIds, imageLoader, currentPageIndex, navigation.toCameraScreen)
                 BottomBar(showPdfDialog, showNewDocDialog)
             }
         }
@@ -280,7 +291,7 @@ fun DocumentScreenPreview() {
                     BitmapFactory.decodeStream(input)
                 }
             },
-            toCameraScreen = {},
+            navigation = Navigation({}, {}, {}, {}),
             pdfActions = PdfGenerationActions(
                 {}, {}, {},
                 MutableStateFlow(PdfGenerationUiState()),