From 7ab39eba579ba1c89e3c4e4b026b440781286fbc Mon Sep 17 00:00:00 2001
From: damontecres <154766448+damontecres@users.noreply.github.com>
Date: Sun, 14 Dec 2025 19:04:01 -0500
Subject: [PATCH] Improve trickplay image preview speed (#467)

Moves the clipping of trickplay images from the image loading layer to
the composition/graphics layer.

Effectively, this PR loads and renders the entire trickplay image which
is then moved around to the right position and finally is clipped so
only a single tile is shown. Since moving the image around on screen
plsu clipping is 1) very fast and 2) done during recompositions, this
means it is _much_ faster at rendering each trickplay tile image and
Coil only has to load the image once.

Fixes #432
---
 .../wholphin/ui/data/ItemDetailsDialogInfo.kt |   2 +
 .../wholphin/ui/playback/PlaybackOverlay.kt   |   8 +-
 .../wholphin/ui/playback/PlaybackViewModel.kt |  12 +-
 .../wholphin/ui/playback/SeekPreviewImage.kt  | 105 +++++++++++-------
 4 files changed, 77 insertions(+), 50 deletions(-)

diff --git a/app/src/main/java/com/github/damontecres/wholphin/ui/data/ItemDetailsDialogInfo.kt b/app/src/main/java/com/github/damontecres/wholphin/ui/data/ItemDetailsDialogInfo.kt
index 32dc213d..4947fda6 100644
--- a/app/src/main/java/com/github/damontecres/wholphin/ui/data/ItemDetailsDialogInfo.kt
+++ b/app/src/main/java/com/github/damontecres/wholphin/ui/data/ItemDetailsDialogInfo.kt
@@ -53,6 +53,7 @@ fun ItemDetailsDialog(
     val audioLabel = stringResource(R.string.audio)
     val subtitleLabel = stringResource(R.string.subtitle)
     val bitrateLabel = stringResource(R.string.bitrate)
+    val unknown = stringResource(R.string.unknown)
 
     ScrollableDialog(
         onDismissRequest = onDismissRequest,
@@ -100,6 +101,7 @@ fun ItemDetailsDialog(
                                 source.container?.let { add(containerLabel to it) }
                                 if (showFilePath) {
                                     source.path?.let { add(pathLabel to it) }
+                                    add("ID" to (source.id ?: unknown))
                                 }
                                 source.size?.let {
                                     add(fileSizeLabel to formatBytes(it))
diff --git a/app/src/main/java/com/github/damontecres/wholphin/ui/playback/PlaybackOverlay.kt b/app/src/main/java/com/github/damontecres/wholphin/ui/playback/PlaybackOverlay.kt
index eefc176b..2200b954 100644
--- a/app/src/main/java/com/github/damontecres/wholphin/ui/playback/PlaybackOverlay.kt
+++ b/app/src/main/java/com/github/damontecres/wholphin/ui/playback/PlaybackOverlay.kt
@@ -398,17 +398,13 @@ fun PlaybackOverlay(
                         val tilesPerImage = trickplayInfo.tileWidth * trickplayInfo.tileHeight
                         val index =
                             (seekProgressMs / trickplayInfo.interval).toInt() / tilesPerImage
-                        val imageUrl = trickplayUrlFor(index)
+                        val imageUrl = remember(index) { trickplayUrlFor(index) }
 
                         if (imageUrl != null) {
                             SeekPreviewImage(
-                                modifier =
-                                Modifier,
+                                modifier = Modifier,
                                 previewImageUrl = imageUrl,
-                                duration = playerControls.duration,
                                 seekProgressMs = seekProgressMs,
-                                videoWidth = trickplayInfo.width,
-                                videoHeight = trickplayInfo.height,
                                 trickPlayInfo = trickplayInfo,
                             )
                         }
diff --git a/app/src/main/java/com/github/damontecres/wholphin/ui/playback/PlaybackViewModel.kt b/app/src/main/java/com/github/damontecres/wholphin/ui/playback/PlaybackViewModel.kt
index 524bcf03..88536176 100644
--- a/app/src/main/java/com/github/damontecres/wholphin/ui/playback/PlaybackViewModel.kt
+++ b/app/src/main/java/com/github/damontecres/wholphin/ui/playback/PlaybackViewModel.kt
@@ -411,7 +411,11 @@ class PlaybackViewModel
                 trickPlayInfo?.let { trickplayInfo ->
                     mediaSource.runTimeTicks?.ticks?.let { duration ->
                         viewModelScope.launchIO {
-                            prefetchTrickplay(duration, trickplayInfo)
+                            prefetchTrickplay(
+                                duration,
+                                trickplayInfo,
+                                mediaSource.id?.toUUIDOrNull(),
+                            )
                         }
                     }
                 }
@@ -737,16 +741,18 @@ class PlaybackViewModel
         private suspend fun prefetchTrickplay(
             duration: Duration,
             trickplayInfo: TrickplayInfo,
+            mediaSourceId: UUID?,
         ) {
             val tilesPerImage = trickplayInfo.tileWidth * trickplayInfo.tileHeight
             val totalCount =
                 (duration.inWholeMilliseconds / trickplayInfo.interval).toInt() / tilesPerImage + 1
             (0..<totalCount).forEach {
-                val url = getTrickplayUrl(it, trickplayInfo)
+                val url = getTrickplayUrl(it, trickplayInfo, mediaSourceId)
                 context.imageLoader.enqueue(
                     ImageRequest
                         .Builder(context)
                         .data(url)
+                        .size(coil3.size.Size.ORIGINAL)
                         .build(),
                 )
             }
@@ -755,10 +761,10 @@ class PlaybackViewModel
         fun getTrickplayUrl(
             index: Int,
             trickPlayInfo: TrickplayInfo? = currentMediaInfo.value?.trickPlayInfo,
+            mediaSourceId: UUID? = currentItemPlayback.value?.sourceId,
         ): String? =
             trickPlayInfo?.let {
                 val itemId = item.id
-                val mediaSourceId = currentItemPlayback.value?.sourceId
                 return api.trickplayApi.getTrickplayTileImageUrl(
                     itemId,
                     trickPlayInfo.width,
diff --git a/app/src/main/java/com/github/damontecres/wholphin/ui/playback/SeekPreviewImage.kt b/app/src/main/java/com/github/damontecres/wholphin/ui/playback/SeekPreviewImage.kt
index 1296bb78..99c3e9af 100644
--- a/app/src/main/java/com/github/damontecres/wholphin/ui/playback/SeekPreviewImage.kt
+++ b/app/src/main/java/com/github/damontecres/wholphin/ui/playback/SeekPreviewImage.kt
@@ -1,23 +1,29 @@
 package com.github.damontecres.wholphin.ui.playback
 
+import androidx.compose.foundation.Canvas
 import androidx.compose.foundation.background
 import androidx.compose.foundation.border
+import androidx.compose.foundation.layout.Box
 import androidx.compose.foundation.layout.height
 import androidx.compose.foundation.layout.width
 import androidx.compose.runtime.Composable
+import androidx.compose.runtime.remember
 import androidx.compose.ui.Modifier
+import androidx.compose.ui.draw.clip
+import androidx.compose.ui.geometry.Offset
+import androidx.compose.ui.geometry.Size
 import androidx.compose.ui.graphics.Color
-import androidx.compose.ui.graphics.painter.Painter
+import androidx.compose.ui.graphics.RectangleShape
+import androidx.compose.ui.graphics.drawscope.scale
+import androidx.compose.ui.graphics.drawscope.translate
 import androidx.compose.ui.layout.ContentScale
 import androidx.compose.ui.layout.layout
 import androidx.compose.ui.platform.LocalContext
 import androidx.compose.ui.platform.LocalDensity
 import androidx.compose.ui.unit.dp
 import androidx.tv.material3.MaterialTheme
-import coil3.compose.AsyncImage
+import coil3.compose.rememberAsyncImagePainter
 import coil3.request.ImageRequest
-import coil3.request.transformations
-import com.github.damontecres.wholphin.ui.CoilTrickplayTransformation
 import com.github.damontecres.wholphin.ui.isNotNullOrBlank
 import org.jellyfin.sdk.model.api.TrickplayInfo
 
@@ -69,53 +75,70 @@ fun Modifier.offsetByPercent(xPercentage: Float) =
 @Composable
 fun SeekPreviewImage(
     previewImageUrl: String,
-    duration: Long,
     seekProgressMs: Long,
-    videoWidth: Int?,
-    videoHeight: Int?,
     trickPlayInfo: TrickplayInfo,
     modifier: Modifier = Modifier,
-    placeHolder: Painter? = null,
 ) {
     val context = LocalContext.current
 
-    if (previewImageUrl.isNotNullOrBlank() &&
-        videoWidth != null &&
-        videoHeight != null
-    ) {
+    if (previewImageUrl.isNotNullOrBlank()) {
         val height = 160.dp
-        val width = height * (videoWidth.toFloat() / videoHeight)
-        val heightPx = with(LocalDensity.current) { height.toPx().toInt() }
-        val widthPx = with(LocalDensity.current) { width.toPx().toInt() }
+        val width = height * (trickPlayInfo.width.toFloat() / trickPlayInfo.height)
+        val scale = LocalDensity.current.density
 
-        val index = (seekProgressMs.toDouble() / trickPlayInfo.interval).toInt() // Which tile
-        val numberOfTitlesPerImage = trickPlayInfo.tileHeight * trickPlayInfo.tileWidth
-        val imageIndex = index % numberOfTitlesPerImage
-
-        AsyncImage(
-            modifier =
-                modifier
-                    .width(width)
-                    .height(height)
-                    .background(Color.Black)
-                    .border(1.5.dp, color = MaterialTheme.colorScheme.border),
-            model =
+        val model =
+            remember(previewImageUrl) {
                 ImageRequest
                     .Builder(context)
                     .data(previewImageUrl)
-                    .transformations(
-                        CoilTrickplayTransformation(
-                            widthPx,
-                            heightPx,
-                            trickPlayInfo.tileHeight,
-                            trickPlayInfo.tileWidth,
-                            imageIndex,
-                            index,
-                        ),
-                    ).build(),
-            contentScale = ContentScale.None,
-            contentDescription = null,
-            placeholder = placeHolder,
-        )
+                    .size(coil3.size.Size.ORIGINAL)
+                    .build()
+            }
+        val painter =
+            rememberAsyncImagePainter(
+                model = model,
+                contentScale = ContentScale.None,
+            )
+        val index =
+            (seekProgressMs.toDouble() / trickPlayInfo.interval).toInt() // Index of tile across images
+        val numberOfTilesPerImage = trickPlayInfo.tileHeight * trickPlayInfo.tileWidth
+        val tileIndex =
+            index % numberOfTilesPerImage // Index of tile within the current image
+        val x = (tileIndex % trickPlayInfo.tileWidth) // x position within tile grid
+        val y = (tileIndex / trickPlayInfo.tileHeight) // y position
+        Box(
+            modifier =
+                modifier
+                    .border(1.5.dp, color = MaterialTheme.colorScheme.border)
+                    .background(Color.Black)
+                    .height(height)
+                    .width(width),
+        ) {
+            Canvas(
+                modifier =
+                    Modifier
+                        .height(height)
+                        .width(width)
+                        .clip(RectangleShape),
+            ) {
+                with(painter) {
+                    // Scale and translate to the right position in the tile grid
+                    scale(scale, scale, pivot = Offset.Zero) {
+                        translate(
+                            left = -x.toFloat() * trickPlayInfo.width,
+                            top = -y.toFloat() * trickPlayInfo.height,
+                        ) {
+                            draw(
+                                size =
+                                    Size(
+                                        trickPlayInfo.width * trickPlayInfo.tileWidth.toFloat(),
+                                        trickPlayInfo.height * trickPlayInfo.tileHeight.toFloat(),
+                                    ),
+                            )
+                        }
+                    }
+                }
+            }
+        }
     }
 }