Keep mixed-direction text on screen with Android 15 start overhang (#59167)

Summary:
Pull Request resolved: #59167

On Android 15 and 16.0, `Layout.computeDrawingBoundingBox()` reuses a single `RectF` for every line and `TextLine.metrics()` does not reset it. A line whose paragraph direction is LTR, laid out after an RTL line, inherits the RTL line's bounds in RTL-relative (negative) coordinates. With `setShiftDrawingOffsetForStartOverhang(true)`, `Layout.draw()` then translates the whole text right by about one line width, so the text disappears or only a few glyphs stay visible at the right edge.

Common RTL content hits this: a blank line between Arabic or Hebrew paragraphs has no strong character and is laid out LTR. The platform fixed it in a later Android 16 release by resetting the rect per line.

When an exactly sized layout has mixed paragraph directions, rebuild it without the start-overhang drawing shift. Bounds-based line breaking is kept, so the measured line breaks are unchanged. Single-direction text keeps the existing start-overhang behavior.

Changelog:
[Android][Fixed] - Fix multi-paragraph RTL `Text` with blank or LTR lines being drawn off-screen on Android 15+

Reviewed By: Abbondanzo

Differential Revision: D125908523

fbshipit-source-id: 9955f447b3ab0eda603ce88971d1dab59eddb9d1

Author: fkgozali

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/views/text/TextLayoutManager.kt

@@ -913,6 +913,24 @@ internal object TextLayoutManager {
             enableStartOverhang,
         )
 
+    // Android 15/16 leak RTL line bounds into later LTR lines, shifting the whole drawing right.
+    if (enableStartOverhang && hasMixedParagraphDirections(layout)) {
+      return buildLayout(
+          text,
+          layoutWidth,
+          includeFontPadding,
+          textBreakStrategy,
+          hyphenationFrequency,
+          alignment,
+          justificationMode,
+          ellipsizeMode,
+          maxNumberOfLines,
+          paint,
+          enableStartOverhang,
+          shiftDrawingOffsetForStartOverhang = false,
+      )
+    }
+
     // Layout.draw shifts negative (left-side) overhang, but RTL line starts can overflow to the
     // right. Reserve that ink inside an EXACT layout without changing the width reported to Yoga.
     return if (enableStartOverhang) {
@@ -950,6 +968,15 @@ internal object TextLayoutManager {
     }
   }
 
+  @VisibleForTesting
+  internal fun hasMixedParagraphDirections(layout: Layout): Boolean {
+    if (Build.VERSION.SDK_INT < VERSION_CODE_VANILLA_ICE_CREAM || layout.lineCount == 0) {
+      return false
+    }
+    val firstDirection = layout.getParagraphDirection(0)
+    return (1 until layout.lineCount).any { layout.getParagraphDirection(it) != firstDirection }
+  }
+
   @VisibleForTesting
   internal fun getRtlRightOverhang(layout: Layout): Int {
     if (
@@ -979,6 +1006,7 @@ internal object TextLayoutManager {
       maxNumberOfLines: Int,
       paint: TextPaint,
       enableStartOverhang: Boolean,
+      shiftDrawingOffsetForStartOverhang: Boolean = enableStartOverhang,
   ): Layout {
     val builder =
         StaticLayout.Builder.obtain(text, 0, text.length, paint, layoutWidth)
@@ -1005,7 +1033,7 @@ internal object TextLayoutManager {
     // measurement returned to the caller.
     if (Build.VERSION.SDK_INT >= VERSION_CODE_VANILLA_ICE_CREAM) {
       setUseBoundsForWidth(builder, enableStartOverhang)
-      setShiftDrawingOffsetForStartOverhang(builder, enableStartOverhang)
+      setShiftDrawingOffsetForStartOverhang(builder, shiftDrawingOffsetForStartOverhang)
     }
 
     return builder.build()

packages/react-native/ReactAndroid/src/test/java/com/facebook/react/views/text/TextLayoutManagerStartOverhangTest.kt

@@ -115,6 +115,36 @@ class TextLayoutManagerStartOverhangTest {
     assertThat(layout).isSameAs(initialLayout)
   }
 
+  @Test
+  @Config(sdk = [35])
+  fun `mixed paragraph directions disable the start overhang drawing shift`() {
+    // The blank line between the RTL paragraphs has no strong character, so it is laid out LTR.
+    val layout =
+        createLayout(
+            YogaMeasureMode.EXACTLY,
+            text = SpannableString("שלום\n\nעולם"),
+            maxNumberOfLines = 0,
+        )
+
+    assertThat(TextLayoutManager.hasMixedParagraphDirections(layout)).isTrue()
+    assertThat(getBooleanLayoutProperty(layout, "getUseBoundsForWidth")).isTrue()
+    assertThat(getBooleanLayoutProperty(layout, "getShiftDrawingOffsetForStartOverhang")).isFalse()
+  }
+
+  @Test
+  @Config(sdk = [35])
+  fun `single paragraph direction keeps the start overhang drawing shift`() {
+    val layout =
+        createLayout(
+            YogaMeasureMode.EXACTLY,
+            text = SpannableString("שלום\nעולם"),
+            maxNumberOfLines = 0,
+        )
+
+    assertThat(TextLayoutManager.hasMixedParagraphDirections(layout)).isFalse()
+    assertThat(getBooleanLayoutProperty(layout, "getShiftDrawingOffsetForStartOverhang")).isTrue()
+  }
+
   @Test
   @Config(sdk = [34])
   fun `EXACTLY mode remains supported before Android 15`() {