Keep Android chat still when selecting text (#7131)

Android's scroll guard now reads the view's transform matrix, so React Native's inverted chat list (scale: -1, decomposed into a 180-degree rotation with positive scaleY) no longer scrolls on text focus or selection.

Closes #7125

Co-authored-by: luke <luopeihuan@gmail.com>
Co-authored-by: RoundRedDot <roundreddot@gmail.com>

docs/android.md

@@ -124,7 +124,9 @@ This is the Android counterpart of the iOS local-simulator flow in [development.
 
 Android focus and selection visibility requests must not reposition inverted timelines. The
 `modules/paseo-scroll` package keeps React Native's scroll manager interface and returns zero for
-child-reveal scroll calculations when the vertical scale is inverted. Dragging and explicit scroll
+child-reveal scroll calculations when the view's transform matrix inverts the vertical axis. React
+Native's Android list uses `scale: -1`, which decomposes into a 180-degree rotation with positive
+`scaleY`; checking the scale property alone misses it. Dragging and explicit scroll
 commands still work; non-inverted scroll views keep Android's default behavior.
 
 Register this package before React Native's core package through its Expo config plugin. Normal

packages/app/modules/paseo-scroll/android/src/androidTest/java/sh/paseo/scroll/ScrollSelectionTest.kt

@@ -9,7 +9,11 @@ import android.widget.TextView
 import androidx.test.ext.junit.runners.AndroidJUnit4
 import androidx.test.platform.app.InstrumentationRegistry
 import com.facebook.react.bridge.BridgeReactContext
+import com.facebook.react.bridge.JavaOnlyArray
+import com.facebook.react.bridge.JavaOnlyMap
 import com.facebook.react.soloader.OpenSourceMergedSoMapping
+import com.facebook.react.uimanager.DisplayMetricsHolder
+import com.facebook.react.uimanager.ReactStylesDiffMap
 import com.facebook.react.uimanager.ThemedReactContext
 import com.facebook.react.views.scroll.ReactScrollView
 import com.facebook.react.views.scroll.ReactScrollViewManager
@@ -47,16 +51,29 @@ class ScrollSelectionTest {
     assertNotEquals(before, scroll.scrollY)
   }
 
-  private fun withScroll(inverted: Boolean, check: (ReactScrollView, TextView) -> Unit) {
+  @Test fun verticalScaleStillKeepsFocusAndSelectionInPlace() = withScroll(inverted = true, transform = "scaleY") { scroll, text ->
+    val before = scroll.scrollY
+    assertTrue(text.requestFocus())
+    text.requestRectangleOnScreen(Rect(0, 0, 80, 40), true)
+    assertEquals(before, scroll.scrollY)
+  }
+
+  @Test fun horizontalScaleStillRevealsSelectedText() = withScroll(inverted = true, transform = "scaleX") { scroll, text ->
+    val before = scroll.scrollY
+    text.requestRectangleOnScreen(Rect(0, 0, 80, 40), true)
+    assertNotEquals(before, scroll.scrollY)
+  }
+
+  private fun withScroll(inverted: Boolean, transform: String = "scale", check: (ReactScrollView, TextView) -> Unit) {
     val instrumentation = InstrumentationRegistry.getInstrumentation()
     instrumentation.runOnMainSync {
       val appContext = instrumentation.targetContext
+      DisplayMetricsHolder.initDisplayMetricsIfNotInitialized(appContext)
       SoLoader.init(appContext, OpenSourceMergedSoMapping)
       val reactContext = BridgeReactContext(appContext)
       val context = ThemedReactContext(reactContext, appContext)
       val manager = PaseoScrollPackage().createViewManager(reactContext, ReactScrollViewManager.REACT_CLASS) as ReactScrollViewManager
       val scroll = manager.createViewInstance(context)
-      scroll.scaleY = if (inverted) -1f else 1f
       val content = FrameLayout(context)
       val text = TextView(context).apply {
         setText("Selectable timeline text", TextView.BufferType.SPANNABLE)
@@ -68,6 +85,13 @@ class ScrollSelectionTest {
       content.layout(0, 0, 300, 2000)
       scroll.measure(exact(300), exact(300))
       scroll.layout(0, 0, 300, 300)
+      // Apply RN's actual Android inversion through the manager's transform decomposition.
+      val transforms = JavaOnlyArray.of(JavaOnlyMap.of(transform, if (inverted) -1.0 else 1.0))
+      manager.updateProperties(scroll, ReactStylesDiffMap(JavaOnlyMap.of("transform", transforms)))
+      if (inverted && transform == "scale") {
+        assertEquals(1f, scroll.scaleY, 0f)
+        assertEquals(180f, kotlin.math.abs(scroll.rotation), 0f)
+      }
       scroll.scrollTo(0, 400)
       check(scroll, text)
     }

packages/app/modules/paseo-scroll/android/src/main/java/sh/paseo/scroll/PaseoScrollPackage.kt

@@ -1,5 +1,6 @@
 package sh.paseo.scroll
 
+import android.graphics.Matrix
 import android.graphics.Rect
 import com.facebook.react.ReactPackage
 import com.facebook.react.ViewManagerOnDemandReactPackage
@@ -27,9 +28,15 @@ private class PaseoScrollViewManager : ReactScrollViewManager() {
 }
 
 private class PaseoScrollView(context: ThemedReactContext) : ReactScrollView(context) {
+  private val transformValues = FloatArray(9)
+
   // Both RN focus handling and Android selection visibility requests use this calculation.
   // Its coordinates ignore inversion. Keep focus/selection bookkeeping, but leave timeline
   // movement to user gestures and explicit scroll commands.
-  override fun computeScrollDeltaToGetChildRectOnScreen(rect: Rect): Int =
-    if (scaleY < 0) 0 else super.computeScrollDeltaToGetChildRectOnScreen(rect)
+  override fun computeScrollDeltaToGetChildRectOnScreen(rect: Rect): Int {
+    // RN's Android scale: -1 becomes a 180-degree rotation with positive scaleY.
+    matrix.getValues(transformValues)
+    if (transformValues[Matrix.MSCALE_Y] < 0) return 0
+    return super.computeScrollDeltaToGetChildRectOnScreen(rect)
+  }
 }