From 60bb24a9305bae2be11d8f1d01dc3dd5749cb121 Mon Sep 17 00:00:00 2001
From: huangdarwin <huangdarwin@google.com>
Date: Wed, 3 Apr 2024 09:16:50 -0700
Subject: [PATCH] Overlay: Add javadoc for why we fly overlays vertically.

Otherwise, apps overriding BitmapOverlay.getVertexTransformation may not
realize this is being done, and may ask why bitmaps are flipped vertically from
what they expect

Reference: https://github.com/androidx/media/issues/1128
PiperOrigin-RevId: 621544348
---
 .../src/main/java/androidx/media3/effect/BitmapOverlay.java | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/libraries/effect/src/main/java/androidx/media3/effect/BitmapOverlay.java b/libraries/effect/src/main/java/androidx/media3/effect/BitmapOverlay.java
index f39d1f5a10..6afcb9b97b 100644
--- a/libraries/effect/src/main/java/androidx/media3/effect/BitmapOverlay.java
+++ b/libraries/effect/src/main/java/androidx/media3/effect/BitmapOverlay.java
@@ -170,6 +170,12 @@ public abstract class BitmapOverlay extends TextureOverlay {
     return lastTextureId;
   }
 
+  /**
+   * {@inheritDoc}
+   *
+   * <p>Flips the overlay vertically to convert between Android and OpenGL texture coordinate
+   * systems.
+   */
   @Override
   public float[] getVertexTransformation(long presentationTimeUs) {
     // Whereas the Android system uses the top-left corner as (0,0) of the