Add option to flash white screen on page change in reader for e-ink displays

Closes #2123

app/src/main/java/eu/kanade/tachiyomi/ui/reader/ReaderActivity.kt

@@ -43,6 +43,7 @@ import com.google.android.material.transition.platform.MaterialContainerTransfor
 import dev.chrisbanes.insetter.applyInsetter
 import eu.kanade.domain.base.BasePreferences
 import eu.kanade.presentation.reader.BrightnessOverlay
+import eu.kanade.presentation.reader.DisplayRefreshHost
 import eu.kanade.presentation.reader.OrientationModeSelectDialog
 import eu.kanade.presentation.reader.PageIndicatorText
 import eu.kanade.presentation.reader.ReaderPageActionsDialog
@@ -122,6 +123,7 @@ class ReaderActivity : BaseActivity() {
 
     private var menuToggleToast: Toast? = null
     private var readingModeToast: Toast? = null
+    private val displayRefreshHost = DisplayRefreshHost()
 
     private val windowInsetsController by lazy { WindowInsetsControllerCompat(window, binding.root) }
 
@@ -197,6 +199,9 @@ class ReaderActivity : BaseActivity() {
                     ReaderViewModel.Event.ReloadViewerChapters -> {
                         viewModel.state.value.viewerChapters?.let(::setChapters)
                     }
+                    ReaderViewModel.Event.PageChanged -> {
+                        displayRefreshHost.flash()
+                    }
                     is ReaderViewModel.Event.SetOrientation -> {
                         setOrientation(event.orientation)
                     }
@@ -323,6 +328,7 @@ class ReaderActivity : BaseActivity() {
 
             val isHttpSource = viewModel.getSource() is HttpSource
             val isFullscreen by readerPreferences.fullscreen().collectAsState()
+            val flashOnPageChange by readerPreferences.flashOnPageChange().collectAsState()
 
             val cropBorderPaged by readerPreferences.cropBorders().collectAsState()
             val cropBorderWebtoon by readerPreferences.cropBordersWebtoon().collectAsState()
@@ -375,6 +381,12 @@ class ReaderActivity : BaseActivity() {
                 value = state.brightnessOverlayValue,
             )
 
+            if (flashOnPageChange) {
+                DisplayRefreshHost(
+                    hostState = displayRefreshHost,
+                )
+            }
+
             val onDismissRequest = viewModel::closeDialog
             when (state.dialog) {
                 is ReaderViewModel.Dialog.Loading -> {

app/src/main/java/eu/kanade/tachiyomi/ui/reader/ReaderViewModel.kt

@@ -429,6 +429,8 @@ class ReaderViewModel @JvmOverloads constructor(
         if (inDownloadRange) {
             downloadNextChapters()
         }
+
+        eventChannel.trySend(Event.PageChanged)
     }
 
     private fun downloadNextChapters() {
@@ -917,6 +919,7 @@ class ReaderViewModel @JvmOverloads constructor(
 
     sealed interface Event {
         data object ReloadViewerChapters : Event
+        data object PageChanged : Event
         data class SetOrientation(val orientation: Int) : Event
         data class SetCoverResult(val result: SetAsCoverResult) : Event
 

app/src/main/java/eu/kanade/tachiyomi/ui/reader/setting/ReaderPreferences.kt

@@ -13,6 +13,8 @@ class ReaderPreferences(
 
     fun pageTransitions() = preferenceStore.getBoolean("pref_enable_transitions_key", true)
 
+    fun flashOnPageChange() = preferenceStore.getBoolean("pref_reader_flash", false)
+
     fun doubleTapAnimSpeed() = preferenceStore.getInt("pref_double_tap_anim_speed", 500)
 
     fun showPageNumber() = preferenceStore.getBoolean("pref_show_page_number_key", true)