refactor: improve browser UI and initialization

- Update Light theme color palette for better contrast
- Implement manual WebView directory initialization
- Add unit test for navigation logic
- Enable configurable toolbar positioning
- Add home button to address bar component
- Fix emulator-specific high refresh rate issue

Author: aanneion

app/src/main/java/com/example/MainActivity.kt

@@ -34,6 +34,7 @@ class MainActivity : ComponentActivity() {
 
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
+        initializeWebViewDirectories()
         enableEdgeToEdge()
         enableHighRefreshRate()
 
@@ -66,12 +67,24 @@ class MainActivity : ComponentActivity() {
         }
     }
 
+    private fun initializeWebViewDirectories() {
+        try {
+            val cacheDir = applicationContext.cacheDir
+            val webViewCache = java.io.File(cacheDir, "WebView/Default/HTTP Cache")
+            val codeCacheJs = java.io.File(webViewCache, "Code Cache/js")
+            val codeCacheWasm = java.io.File(webViewCache, "Code Cache/wasm")
+            val indexDir = java.io.File(webViewCache, "index-dir")
+            codeCacheJs.mkdirs()
+            codeCacheWasm.mkdirs()
+            indexDir.mkdirs()
+        } catch (e: Throwable) {
+            // Safe fallback
+        }
+    }
+
     private fun enableHighRefreshRate() {
+        if (com.example.browser.DeviceUtils.isEmulator) return
         try {
-            window.setFlags(
-                WindowManager.LayoutParams.FLAG_HARDWARE_ACCELERATED,
-                WindowManager.LayoutParams.FLAG_HARDWARE_ACCELERATED
-            )
             if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.R) {
                 val currentDisplay = display
                 val modes = currentDisplay?.supportedModes

app/src/main/java/com/example/browser/BrowserModels.kt

@@ -22,6 +22,27 @@ enum class NewTabStyle(val displayName: String) {
     MINIMALIST("Zen Minimal")
 }
 
+enum class ToolbarPosition(val displayName: String, val description: String) {
+    BOTTOM("Bottom (Ergonomic)", "Easy one-handed thumb reachability"),
+    TOP("Top (Classic)", "Traditional address bar layout at the top")
+}
+
+data class ReaderArticle(
+    val title: String = "",
+    val byline: String = "",
+    val domain: String = "",
+    val contentText: String = "",
+    val wordCount: Int = 0,
+    val readingTimeMinutes: Int = 1
+)
+
+enum class ReaderTheme(val displayName: String, val bgHex: String, val textHex: String) {
+    LIGHT("Crisp Light", "#FFFFFF", "#0F172A"),
+    SEPIA("Warm Paper", "#FBF0D9", "#2C221E"),
+    NORDIC("Nordic Slate", "#1E293B", "#F8FAFC"),
+    AMOLED("OLED Black", "#000000", "#E4E4E7")
+}
+
 enum class DownloadProvider(val displayName: String, val description: String) {
     BUILT_IN("Built-in Manager", "Standard system download manager"),
     EXTERNAL_APP("External / Ask Every Time", "Open 1DM, ADM, IDM, or system app chooser")
@@ -51,7 +72,8 @@ enum class ActiveSheet {
     SETTINGS,
     CLEAR_DATA,
     NEW_PROFILE_DIALOG,
-    EDIT_BOOKMARK_DIALOG
+    EDIT_BOOKMARK_DIALOG,
+    READER_MODE
 }
 
 enum class ContextMenuType {
@@ -128,3 +150,24 @@ object UrlUtils {
         return url.startsWith("https://", ignoreCase = true)
     }
 }
+
+object DeviceUtils {
+    val isEmulator: Boolean by lazy {
+        val fingerprint = android.os.Build.FINGERPRINT.lowercase()
+        val model = android.os.Build.MODEL.lowercase()
+        val hardware = android.os.Build.HARDWARE.lowercase()
+        val brand = android.os.Build.BRAND.lowercase()
+        val device = android.os.Build.DEVICE.lowercase()
+        val product = android.os.Build.PRODUCT.lowercase()
+
+        fingerprint.startsWith("generic")
+            || fingerprint.startsWith("unknown")
+            || model.contains("google_sdk")
+            || model.contains("emulator")
+            || model.contains("android sdk built for")
+            || hardware.contains("goldfish")
+            || hardware.contains("ranchu")
+            || (brand.startsWith("generic") && device.startsWith("generic"))
+            || product.contains("sdk")
+    }
+}

app/src/main/java/com/example/browser/BrowserViewModel.kt

@@ -101,7 +101,7 @@ class BrowserViewModel(application: Application) : AndroidViewModel(application)
         val now = System.currentTimeMillis()
 
         // When near page top, always smoothly restore bars
-        if (scrollY <= 40) {
+        if (scrollY <= 35) {
             accumulatedScrollY = 0
             if (!_isBarsVisible.value) {
                 _isBarsVisible.value = true
@@ -110,29 +110,25 @@ class BrowserViewModel(application: Application) : AndroidViewModel(application)
             return
         }
 
-        // Reduced cooldown (150ms) to ensure swift responsiveness without toggle jitter
-        if (now - lastVisibilityToggleTime < 150) {
-            accumulatedScrollY = 0
-            return
-        }
-
-        // Filter out microscopic finger tremors or resting hand jitter (< 3px)
+        // Filter out microscopic finger tremors (< 3px)
         if (kotlin.math.abs(deltaY) < 3) return
 
-        // Direction reversal reset
+        // Direction reversal: clean reset so sudden scroll direction changes respond immediately
         if ((deltaY > 0 && accumulatedScrollY < 0) || (deltaY < 0 && accumulatedScrollY > 0)) {
             accumulatedScrollY = 0
         }
         accumulatedScrollY += deltaY
 
         // Deliberate user scroll threshold to trigger hide or show
-        if (accumulatedScrollY > 55) {
-            if (_isBarsVisible.value) {
+        if (accumulatedScrollY > 60) {
+            // Scrolling down: hide bars with light debounce to prevent flapping
+            if (_isBarsVisible.value && now - lastVisibilityToggleTime > 120) {
                 _isBarsVisible.value = false
                 lastVisibilityToggleTime = now
             }
             accumulatedScrollY = 0
-        } else if (accumulatedScrollY < -30) {
+        } else if (accumulatedScrollY < -25) {
+            // Scrolling up: show bars promptly without artificial lag or dropped touch frames
             if (!_isBarsVisible.value) {
                 _isBarsVisible.value = true
                 lastVisibilityToggleTime = now
@@ -202,6 +198,59 @@ class BrowserViewModel(application: Application) : AndroidViewModel(application)
     val downloadProvider = MutableStateFlow(preferences.getDownloadProvider())
     val isWeatherOnNewTab = MutableStateFlow(preferences.isWeatherOnNewTab())
     val isWeatherFahrenheit = MutableStateFlow(preferences.isWeatherFahrenheit())
+    val toolbarPosition = MutableStateFlow(preferences.getToolbarPosition())
+
+    // Reader Mode State
+    private val _readerArticle = MutableStateFlow<ReaderArticle?>(null)
+    val readerArticle: StateFlow<ReaderArticle?> = _readerArticle.asStateFlow()
+
+    private val _readerTheme = MutableStateFlow(ReaderTheme.SEPIA)
+    val readerTheme: StateFlow<ReaderTheme> = _readerTheme.asStateFlow()
+
+    private val _readerFontSize = MutableStateFlow(18)
+    val readerFontSize: StateFlow<Int> = _readerFontSize.asStateFlow()
+
+    private val _readerIsSerif = MutableStateFlow(true)
+    val readerIsSerif: StateFlow<Boolean> = _readerIsSerif.asStateFlow()
+
+    fun setToolbarPosition(position: ToolbarPosition) {
+        toolbarPosition.value = position
+        preferences.setToolbarPosition(position)
+    }
+
+    fun setReaderTheme(theme: ReaderTheme) { _readerTheme.value = theme }
+    fun setReaderFontSize(size: Int) { _readerFontSize.value = size.coerceIn(12, 28) }
+    fun setReaderIsSerif(isSerif: Boolean) { _readerIsSerif.value = isSerif }
+    fun setReaderArticle(article: ReaderArticle?) { _readerArticle.value = article }
+
+    fun openReaderMode() {
+        val tabId = _activeTabId.value
+        val currentTab = _activeTabState.value
+        if (tabId.isBlank() || currentTab == null || currentTab.url.isBlank() || currentTab.url == "about:blank") return
+
+        viewModelScope.launch {
+            _webViewActionEvent.emit(WebViewAction.ExtractReaderContent(
+                callback = { extracted ->
+                    if (extracted != null && extracted.contentText.isNotBlank()) {
+                        _readerArticle.value = extracted
+                        openSheet(ActiveSheet.READER_MODE)
+                    } else {
+                        // Fallback article if extraction returns sparse text
+                        val fallback = ReaderArticle(
+                            title = currentTab.title,
+                            domain = UrlUtils.extractDomain(currentTab.url),
+                            contentText = "Unable to extract formatted article content for this page. The page may not contain long-form text or may be an interactive web application.",
+                            wordCount = 25,
+                            readingTimeMinutes = 1
+                        )
+                        _readerArticle.value = fallback
+                        openSheet(ActiveSheet.READER_MODE)
+                    }
+                },
+                targetTabId = tabId
+            ))
+        }
+    }
 
     // Weather Repository & UI State Flow
     val weatherRepository = WeatherRepository(application)
@@ -452,6 +501,22 @@ class BrowserViewModel(application: Application) : AndroidViewModel(application)
         dismissSheet()
     }
 
+    fun switchToNextProfile() {
+        val list = profiles.value
+        if (list.size <= 1) return
+        val currentIndex = list.indexOfFirst { it.id == _currentProfileId.value }
+        val nextIndex = if (currentIndex >= 0) (currentIndex + 1) % list.size else 0
+        switchProfile(list[nextIndex].id)
+    }
+
+    fun switchToPrevProfile() {
+        val list = profiles.value
+        if (list.size <= 1) return
+        val currentIndex = list.indexOfFirst { it.id == _currentProfileId.value }
+        val prevIndex = if (currentIndex > 0) currentIndex - 1 else list.size - 1
+        switchProfile(list[prevIndex].id)
+    }
+
     fun togglePrivateMode() {
         val newPrivate = !_isPrivateMode.value
         _isPrivateMode.value = newPrivate
@@ -690,19 +755,41 @@ class BrowserViewModel(application: Application) : AndroidViewModel(application)
         setBarsVisible(true)
         _isFindInPageActive.value = true
         _findQuery.value = ""
+        _activeTabState.update {
+            it?.copy(
+                searchMatchCurrent = 0,
+                searchMatchCount = 0
+            )
+        }
     }
 
     fun closeFindInPage() {
         val tabId = _activeTabId.value
         _isFindInPageActive.value = false
         _findQuery.value = ""
+        _activeTabState.update {
+            it?.copy(
+                searchMatchCurrent = 0,
+                searchMatchCount = 0
+            )
+        }
         viewModelScope.launch { _webViewActionEvent.emit(WebViewAction.ClearFindMatches(targetTabId = tabId)) }
     }
 
     fun setFindQuery(query: String) {
         val tabId = _activeTabId.value
         _findQuery.value = query
-        viewModelScope.launch { _webViewActionEvent.emit(WebViewAction.FindAllAsync(query, targetTabId = tabId)) }
+        if (query.isBlank()) {
+            _activeTabState.update {
+                it?.copy(
+                    searchMatchCurrent = 0,
+                    searchMatchCount = 0
+                )
+            }
+            viewModelScope.launch { _webViewActionEvent.emit(WebViewAction.ClearFindMatches(targetTabId = tabId)) }
+        } else {
+            viewModelScope.launch { _webViewActionEvent.emit(WebViewAction.FindAllAsync(query, targetTabId = tabId)) }
+        }
     }
 
     fun findNext(forward: Boolean) {
@@ -1034,4 +1121,8 @@ sealed class WebViewAction {
     data class FindAllAsync(val query: String, override val targetTabId: String? = null) : WebViewAction()
     data class FindNext(val forward: Boolean, override val targetTabId: String? = null) : WebViewAction()
     data class ClearFindMatches(override val targetTabId: String? = null) : WebViewAction()
+    data class ExtractReaderContent(
+        val callback: (ReaderArticle?) -> Unit,
+        override val targetTabId: String? = null
+    ) : WebViewAction()
 }

app/src/main/java/com/example/data/BrowserPreferences.kt

@@ -25,6 +25,20 @@ class BrowserPreferences(context: Context) {
         private const val KEY_DOWNLOAD_PROVIDER = "pref_download_provider"
         private const val KEY_WEATHER_ON_NEW_TAB = "pref_weather_on_new_tab"
         private const val KEY_WEATHER_FAHRENHEIT = "pref_weather_fahrenheit"
+        private const val KEY_TOOLBAR_POSITION = "pref_toolbar_position"
+    }
+
+    fun getToolbarPosition(): com.example.browser.ToolbarPosition {
+        val name = prefs.getString(KEY_TOOLBAR_POSITION, com.example.browser.ToolbarPosition.BOTTOM.name)
+        return try {
+            com.example.browser.ToolbarPosition.valueOf(name ?: com.example.browser.ToolbarPosition.BOTTOM.name)
+        } catch (e: Exception) {
+            com.example.browser.ToolbarPosition.BOTTOM
+        }
+    }
+
+    fun setToolbarPosition(pos: com.example.browser.ToolbarPosition) {
+        prefs.edit().putString(KEY_TOOLBAR_POSITION, pos.name).apply()
     }
 
     fun isWeatherOnNewTab(): Boolean {