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Fix trickplay image grid Y-coordinate calculation (#943) (#1259)

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## 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.
This commit is contained in:
dudecuda 2026-04-18 17:07:18 -04:00 • committed by GitHub
parent 6e58a089f4
commit 5050b087e1
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GPG key ID: B5690EEEBB952194
2 changed files with 2 additions and 2 deletions
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2
app/src/main/java/com/github/damontecres/wholphin/ui/CoilTrickplayTransformation.kt
View file

@ -18,7 +18,7 @@ class CoilTrickplayTransformation(
val index: Int, val index: Int,
) : Transformation() { ) : Transformation() {
private val x: Int = imageIndex % numColumns private val x: Int = imageIndex % numColumns
private val y: Int = imageIndex / numRows private val y: Int = imageIndex / numColumns
override val cacheKey: String override val cacheKey: String
get() = "CoilTrickplayTransformation_$index,$x,$y" get() = "CoilTrickplayTransformation_$index,$x,$y"

2
app/src/main/java/com/github/damontecres/wholphin/ui/playback/SeekPreviewImage.kt
View file

@ -107,7 +107,7 @@ fun SeekPreviewImage(
val tileIndex = val tileIndex =
index % numberOfTilesPerImage // Index of tile within the current image index % numberOfTilesPerImage // Index of tile within the current image
val x = (tileIndex % trickPlayInfo.tileWidth) // x position within tile grid 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( Box(
modifier = modifier =
modifier modifier