Fix page transitions when reading with volume keys

app/src/main/kotlin/com/hippo/ehviewer/ui/reader/GalleryPager.kt

@@ -1,7 +1,5 @@
 package com.hippo.ehviewer.ui.reader
 
-import androidx.compose.foundation.gestures.animateScrollBy
-import androidx.compose.foundation.gestures.scrollBy
 import androidx.compose.foundation.layout.Arrangement
 import androidx.compose.foundation.layout.Box
 import androidx.compose.foundation.layout.PaddingValues
@@ -177,11 +175,10 @@ fun GalleryPager(
                             val size = lazyListState.layoutInfo.viewportSize
                             val x = it.x / size.width
                             val y = it.y / size.height
-                            val distance = size.height * 0.75f
                             when (navigatorState.value.getAction(x, y)) {
                                 NavigationRegion.MENU -> onMenuRegionClick()
-                                NavigationRegion.NEXT, NavigationRegion.RIGHT -> performScrollBy(distance)
-                                NavigationRegion.PREV, NavigationRegion.LEFT -> performScrollBy(-distance)
+                                NavigationRegion.NEXT, NavigationRegion.RIGHT -> scrollDown()
+                                NavigationRegion.PREV, NavigationRegion.LEFT -> scrollUp()
                             }
                         }
                     }
@@ -353,36 +350,6 @@ suspend fun ZoomableState.panRight(distance: Float): Boolean {
     return canPan
 }
 
-suspend fun PagerState.performScrollToPage(page: Int) {
-    if (Settings.pageTransitions.value) {
-        animateScrollToPage(page)
-    } else {
-        scrollToPage(page)
-    }
-}
-
-suspend fun PagerState.moveToPrevious() {
-    val target = currentPage - 1
-    if (target >= 0) {
-        performScrollToPage(target)
-    }
-}
-
-suspend fun PagerState.moveToNext() {
-    val target = currentPage + 1
-    if (target < pageCount) {
-        performScrollToPage(target)
-    }
-}
-
-suspend fun LazyListState.performScrollBy(value: Float) {
-    if (Settings.pageTransitions.value) {
-        animateScrollBy(value)
-    } else {
-        scrollBy(value)
-    }
-}
-
 object DoubleTapZoom : DoubleClickToZoomListener {
     override suspend fun onDoubleClick(state: ZoomableState, centroid: Offset) {
         if (Settings.doubleTapToZoom.value) {

app/src/main/kotlin/com/hippo/ehviewer/ui/reader/ReaderScreen.kt

@@ -36,6 +36,7 @@ import androidx.compose.runtime.State
 import androidx.compose.runtime.getValue
 import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.remember
+import androidx.compose.runtime.rememberUpdatedState
 import androidx.compose.runtime.setValue
 import androidx.compose.runtime.snapshotFlow
 import androidx.compose.ui.Alignment
@@ -160,7 +161,8 @@ fun AnimatedVisibilityScope.ReaderScreen(pageLoader: PageLoader2, info: BaseGall
     Box {
         var appbarVisible by remember { mutableStateOf(false) }
         val bgColor by collectBackgroundColorAsState()
-        syncState.Sync(ReadingModeType.isWebtoon(readingMode)) { appbarVisible = false }
+        val isWebtoon by rememberUpdatedState(ReadingModeType.isWebtoon(readingMode))
+        syncState.Sync(isWebtoon, appbarVisible) { appbarVisible = false }
         if (fullscreen) {
             LaunchedEffect(Unit) {
                 snapshotFlow { appbarVisible }.collect {
@@ -170,8 +172,12 @@ fun AnimatedVisibilityScope.ReaderScreen(pageLoader: PageLoader2, info: BaseGall
         }
         VolumeKeysHandler(
             enabled = { volumeKeysEnabled && !appbarVisible },
-            movePrevious = { syncState.sliderScrollTo(syncState.sliderValue - 1) },
-            moveNext = { syncState.sliderScrollTo(syncState.sliderValue + 1) },
+            movePrevious = {
+                if (isWebtoon) lazyListState.scrollUp() else pagerState.moveToPrevious()
+            },
+            moveNext = {
+                if (isWebtoon) lazyListState.scrollDown() else pagerState.moveToNext()
+            },
         )
         GalleryPager(
             type = readingMode,

app/src/main/kotlin/com/hippo/ehviewer/ui/reader/SliderPagerDoubleSync.kt

@@ -32,10 +32,10 @@ class SliderPagerDoubleSync(
     }
 
     @Composable
-    fun Sync(webtoon: Boolean, onPageSelected: () -> Unit) {
+    fun Sync(webtoon: Boolean, appbarVisible: Boolean, onPageSelected: () -> Unit) {
         val fling by lazyListState.interactionSource.collectIsDraggedAsState()
         val pagerFling by pagerState.interactionSource.collectIsDraggedAsState()
-        if (fling || pagerFling) sliderFollowPager = true
+        if (fling || pagerFling || !appbarVisible) sliderFollowPager = true
         val currentIndexFlow = remember(webtoon) {
             val initialIndex = sliderValue - 1
             if (webtoon) {

app/src/main/kotlin/com/hippo/ehviewer/ui/reader/Utils.kt

@@ -3,6 +3,10 @@ package com.hippo.ehviewer.ui.reader
 import android.app.Activity
 import android.view.Window
 import android.view.WindowManager
+import androidx.compose.foundation.gestures.animateScrollBy
+import androidx.compose.foundation.gestures.scrollBy
+import androidx.compose.foundation.lazy.LazyListState
+import androidx.compose.foundation.pager.PagerState
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.LaunchedEffect
 import androidx.compose.runtime.Stable
@@ -82,3 +86,44 @@ fun ContentScale.Companion.fromPreferences(value: Int, srcSize: Size, dstSize: S
     6 -> if (srcSize.width > srcSize.height) FillHeight else FillWidth
     else -> Fit
 }
+
+suspend fun PagerState.performScrollToPage(page: Int) {
+    if (Settings.pageTransitions.value) {
+        animateScrollToPage(page)
+    } else {
+        scrollToPage(page)
+    }
+}
+
+suspend fun PagerState.moveToPrevious() {
+    val target = currentPage - 1
+    if (target >= 0) {
+        performScrollToPage(target)
+    }
+}
+
+suspend fun PagerState.moveToNext() {
+    val target = currentPage + 1
+    if (target < pageCount) {
+        performScrollToPage(target)
+    }
+}
+
+suspend fun LazyListState.performScrollBy(value: Float) {
+    if (Settings.pageTransitions.value) {
+        animateScrollBy(value)
+    } else {
+        scrollBy(value)
+    }
+}
+
+suspend fun LazyListState.scrollUp() {
+    performScrollBy(-scrollDistance)
+}
+
+suspend fun LazyListState.scrollDown() {
+    performScrollBy(scrollDistance)
+}
+
+private val LazyListState.scrollDistance
+    get() = layoutInfo.viewportSize.height * 0.75f

app/src/main/kotlin/com/hippo/ehviewer/ui/reader/VolumeKeysHandler.kt

@@ -8,12 +8,15 @@ import androidx.compose.runtime.DisposableEffect
 import androidx.compose.ui.platform.LocalView
 import androidx.core.view.ViewCompat
 import com.hippo.ehviewer.Settings
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.launch
 
+context(CoroutineScope)
 @Composable
 fun VolumeKeysHandler(
     enabled: () -> Boolean,
-    movePrevious: () -> Unit,
-    moveNext: () -> Unit,
+    movePrevious: suspend () -> Unit,
+    moveNext: suspend () -> Unit,
 ) {
     val view = LocalView.current
     DisposableEffect(view) {
@@ -24,10 +27,12 @@ fun VolumeKeysHandler(
                     val interval = Settings.readWithVolumeKeysInterval.value + 1
                     val inverted = Settings.readWithVolumeKeysInverted.value
                     if (event.action == ACTION_DOWN && event.repeatCount % interval == 0) {
-                        if (inverted.xor(keyCode == KEYCODE_VOLUME_UP)) {
-                            movePrevious()
-                        } else {
-                            moveNext()
+                        launch {
+                            if (inverted.xor(keyCode == KEYCODE_VOLUME_UP)) {
+                                movePrevious()
+                            } else {
+                                moveNext()
+                            }
                         }
                     }
                     true