From 5050b087e13d8b49b32869dcaf2d8e56e204cdba Mon Sep 17 00:00:00 2001
From: dudecuda <94335388+dudecuda@users.noreply.github.com>
Date: Sat, 18 Apr 2026 17:07:18 -0400
Subject: [PATCH] Fix trickplay image grid Y-coordinate calculation (#943)
 (#1259)

## Description
Issue 943 where trickplay images were misaligned with seek preview
mages. I made a post in issues but figured i'd go ahead and make the
pull request.

per gemini:
In SeekPreviewImage.kt, the code calculates which tile in the grid to
display based on the current timestamp:

val x = (tileIndex % trickPlayInfo.tileWidth) // x position within tile
grid
val y = (tileIndex / trickPlayInfo.tileHeight) // y position <-- BUG IS
HERE
To find the correct row (y) in a grid, you are supposed to divide the
current index by the width of the row (the number of columns), not the
height.

Why this breaks: Let's assume a standard trickplay grid that is 10
images wide (tileWidth = 10) and 5 images tall (tileHeight = 5).

If you are looking at the 12th image (tileIndex = 11), it should be on
Row 1 (the second row).

The code calculates y = 11 / 5 = 2. It skips to Row 2!

Because it divides by the smaller height value, the y coordinate
increases much faster than it should. This causes the preview to
visually "jump" down to future rows prematurely, and then snap back as
the x coordinate resets, causing the exact "flashing back and forth" you
saw with the credits and intros.

### Related issue
Fixes #943

### Testing
Tested in Android TV (Android 9) and it does indeed display proper seek
previews using trickplay images.


## AI or LLM usage
Gemini Pro was used to find and fix this bug.
---
 .../damontecres/wholphin/ui/CoilTrickplayTransformation.kt      | 2 +-
 .../github/damontecres/wholphin/ui/playback/SeekPreviewImage.kt | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/app/src/main/java/com/github/damontecres/wholphin/ui/CoilTrickplayTransformation.kt b/app/src/main/java/com/github/damontecres/wholphin/ui/CoilTrickplayTransformation.kt
index ace495bf..dc91eb3b 100644
--- a/app/src/main/java/com/github/damontecres/wholphin/ui/CoilTrickplayTransformation.kt
+++ b/app/src/main/java/com/github/damontecres/wholphin/ui/CoilTrickplayTransformation.kt
@@ -18,7 +18,7 @@ class CoilTrickplayTransformation(
     val index: Int,
 ) : Transformation() {
     private val x: Int = imageIndex % numColumns
-    private val y: Int = imageIndex / numRows
+    private val y: Int = imageIndex / numColumns
 
     override val cacheKey: String
         get() = "CoilTrickplayTransformation_$index,$x,$y"
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 8be0b509..4d8ee0e5 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
@@ -107,7 +107,7 @@ fun SeekPreviewImage(
         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
+        val y = (tileIndex / trickPlayInfo.tileWidth) // y position
         Box(
             modifier =
                 modifier