Fixes long term issue with the video in the Shorts feed not aligning with the padding of the screen

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/feeds/RememberForeverStates.kt

@@ -20,7 +20,6 @@
  */
 package com.vitorpamplona.amethyst.ui.feeds
 
-import androidx.compose.foundation.ExperimentalFoundationApi
 import androidx.compose.foundation.lazy.LazyListState
 import androidx.compose.foundation.lazy.grid.LazyGridState
 import androidx.compose.foundation.pager.PagerState
@@ -115,20 +114,35 @@ fun rememberForeverLazyListState(
     return scrollState
 }
 
-@OptIn(ExperimentalFoundationApi::class)
 @Composable
 fun rememberForeverPagerState(
     key: String,
     initialFirstVisibleItemIndex: Int = 0,
     initialFirstVisibleItemScrollOffset: Float = 0.0f,
     pageCount: () -> Int,
+): PagerState =
+    rememberForeverPagerState(key, initialFirstVisibleItemIndex, initialFirstVisibleItemScrollOffset, pageCount) { initialPage, initialPageOffsetFraction, pageCount ->
+        rememberPagerState(initialPage, initialPageOffsetFraction, pageCount)
+    }
+
+@Composable
+fun rememberForeverPagerState(
+    key: String,
+    initialFirstVisibleItemIndex: Int = 0,
+    initialFirstVisibleItemScrollOffset: Float = 0.0f,
+    pageCount: () -> Int,
+    rememberPagerStateFunction: @Composable (
+        initialPage: Int,
+        initialPageOffsetFraction: Float,
+        pageCount: () -> Int,
+    ) -> PagerState,
 ): PagerState {
     val savedValue = savedScrollStates[key]
     val savedIndex = savedValue?.index ?: initialFirstVisibleItemIndex
     val savedOffset = savedValue?.scrollOffsetFraction ?: initialFirstVisibleItemScrollOffset
 
     val scrollState =
-        rememberPagerState(
+        rememberPagerStateFunction(
             savedIndex,
             savedOffset,
             pageCount,

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/video/PagerStateHack.kt

@@ -0,0 +1,111 @@
+/**
+ * Copyright (c) 2024 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.ui.screen.loggedIn.video
+
+import androidx.annotation.FloatRange
+import androidx.compose.foundation.MutatePriority
+import androidx.compose.foundation.gestures.ScrollScope
+import androidx.compose.foundation.pager.PagerState
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.saveable.Saver
+import androidx.compose.runtime.saveable.listSaver
+import androidx.compose.runtime.saveable.rememberSaveable
+import com.vitorpamplona.amethyst.ui.feeds.rememberForeverPagerState
+import kotlin.math.abs
+
+/**
+ * This file only exists to fix an interference between the Disappearing Top
+ * and Bottom Scaffold bars and the offsetFraction of the pager. The current
+ * implementation ends the scroll at a state where some fraction is still present
+ * which places videos away from their natural position in the page.
+ *
+ * The fix simply animates it back to the fraction = 0.
+ */
+
+@Composable
+fun myRememberPagerState(
+    initialPage: Int = 0,
+    @FloatRange(from = -0.5, to = 0.5) initialPageOffsetFraction: Float = 0f,
+    pageCount: () -> Int,
+): PagerState =
+    rememberSaveable(saver = DefaultPagerState.Saver) {
+        DefaultPagerState(
+            initialPage,
+            initialPageOffsetFraction,
+            pageCount,
+        )
+    }.apply {
+        pageCountState.value = pageCount
+    }
+
+@Composable
+fun myRememberForeverPagerState(
+    key: String,
+    initialFirstVisibleItemIndex: Int = 0,
+    initialFirstVisibleItemScrollOffset: Float = 0.0f,
+    pageCount: () -> Int,
+): PagerState =
+    rememberForeverPagerState(key, initialFirstVisibleItemIndex, initialFirstVisibleItemScrollOffset, pageCount) { initialPage, initialPageOffsetFraction, pageCount ->
+        myRememberPagerState(initialPage, initialPageOffsetFraction, pageCount)
+    }
+
+private class DefaultPagerState(
+    currentPage: Int,
+    currentPageOffsetFraction: Float,
+    updatedPageCount: () -> Int,
+) : PagerState(currentPage, currentPageOffsetFraction) {
+    var pageCountState = mutableStateOf(updatedPageCount)
+    override val pageCount: Int get() = pageCountState.value.invoke()
+
+    override suspend fun scroll(
+        scrollPriority: MutatePriority,
+        block: suspend ScrollScope.() -> Unit,
+    ) {
+        super.scroll(scrollPriority, block)
+        if (abs(currentPageOffsetFraction) > 0) {
+            animateScrollToPage(currentPage, 0f)
+        }
+    }
+
+    companion object {
+        /**
+         * To keep current page and current page offset saved
+         */
+        val Saver: Saver<DefaultPagerState, *> =
+            listSaver(
+                save = {
+                    listOf(
+                        it.currentPage,
+                        (it.currentPageOffsetFraction).coerceIn(-0.5f, 0.5f),
+                        it.pageCount,
+                    )
+                },
+                restore = {
+                    DefaultPagerState(
+                        currentPage = it[0] as Int,
+                        currentPageOffsetFraction = it[1] as Float,
+                        updatedPageCount = { it[2] as Int },
+                    )
+                },
+            )
+    }
+}

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/video/VideoScreen.kt

@@ -21,7 +21,6 @@
 package com.vitorpamplona.amethyst.ui.screen.loggedIn.video
 
 import androidx.compose.animation.core.tween
-import androidx.compose.foundation.ExperimentalFoundationApi
 import androidx.compose.foundation.layout.Arrangement
 import androidx.compose.foundation.layout.Box
 import androidx.compose.foundation.layout.Column
@@ -33,7 +32,6 @@ import androidx.compose.foundation.layout.fillMaxWidth
 import androidx.compose.foundation.layout.height
 import androidx.compose.foundation.layout.padding
 import androidx.compose.foundation.pager.VerticalPager
-import androidx.compose.foundation.pager.rememberPagerState
 import androidx.compose.material.icons.Icons
 import androidx.compose.material.icons.filled.MoreVert
 import androidx.compose.material3.Icon
@@ -47,11 +45,11 @@ import androidx.compose.runtime.remember
 import androidx.compose.runtime.setValue
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
-import androidx.compose.ui.platform.LocalLifecycleOwner
 import androidx.compose.ui.unit.dp
 import androidx.compose.ui.unit.sp
 import androidx.lifecycle.Lifecycle
 import androidx.lifecycle.LifecycleEventObserver
+import androidx.lifecycle.compose.LocalLifecycleOwner
 import androidx.lifecycle.compose.collectAsStateWithLifecycle
 import com.vitorpamplona.amethyst.R
 import com.vitorpamplona.amethyst.model.FeatureSetType
@@ -69,7 +67,6 @@ import com.vitorpamplona.amethyst.ui.feeds.LoadingFeed
 import com.vitorpamplona.amethyst.ui.feeds.RefresheableBox
 import com.vitorpamplona.amethyst.ui.feeds.ScrollStateKeys
 import com.vitorpamplona.amethyst.ui.feeds.WatchScrollToTop
-import com.vitorpamplona.amethyst.ui.feeds.rememberForeverPagerState
 import com.vitorpamplona.amethyst.ui.navigation.AppBottomBar
 import com.vitorpamplona.amethyst.ui.navigation.INav
 import com.vitorpamplona.amethyst.ui.navigation.Route
@@ -236,7 +233,6 @@ private fun LoadedState(
     }
 }
 
-@OptIn(ExperimentalFoundationApi::class)
 @Composable
 fun SlidingCarousel(
     loaded: FeedState.Loaded,
@@ -249,9 +245,9 @@ fun SlidingCarousel(
 
     val pagerState =
         if (pagerStateKey != null) {
-            rememberForeverPagerState(pagerStateKey, items.list.size) { items.list.size }
+            myRememberForeverPagerState(pagerStateKey, items.list.size) { items.list.size }
         } else {
-            rememberPagerState(items.list.size) { items.list.size }
+            myRememberPagerState(items.list.size) { items.list.size }
         }
 
     WatchScrollToTop(videoFeedContentState, pagerState)