implement correct border-radius scaling on overlapping radii (#47886)

Summary:
Pull Request resolved: #47886

We were not scaling border radii properly when they overlap.

We were relying on Android's handling of the issue which is not compliant with the web algorithm leading to **visible gaps between layers when the radii overlapped**

We are now following web spec https://www.w3.org/TR/css-backgrounds-3/#corner-overlap

Changelog: [Android] [Added] Add overlapping radii resolution logic preventing incorrect rendering

Reviewed By: NickGerleman

Differential Revision: D66269809

fbshipit-source-id: 4ab7025dc1e41be6205ff6b828617e1e222536a9

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/uimanager/drawable/BackgroundDrawable.kt

@@ -21,7 +21,7 @@ import android.graphics.RectF
 import android.graphics.Shader
 import android.graphics.drawable.Drawable
 import com.facebook.react.uimanager.PixelUtil.dpToPx
-import com.facebook.react.uimanager.PixelUtil.toDIPFromPixel
+import com.facebook.react.uimanager.PixelUtil.pxToDp
 import com.facebook.react.uimanager.style.BackgroundImageLayer
 import com.facebook.react.uimanager.style.BorderInsets
 import com.facebook.react.uimanager.style.BorderRadiusStyle
@@ -184,10 +184,7 @@ internal class BackgroundDrawable(
     computedBorderInsets = computeBorderInsets()
     computedBorderRadius =
         borderRadius?.resolve(
-            layoutDirection,
-            context,
-            toDIPFromPixel(bounds.width().toFloat()),
-            toDIPFromPixel(bounds.height().toFloat()))
+            layoutDirection, context, bounds.width().pxToDp(), bounds.height().pxToDp())
 
     if (computedBorderRadius?.hasRoundedBorders() == true &&
         computedBorderRadius?.isUniform() == false) {

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/uimanager/drawable/BorderDrawable.kt

@@ -24,8 +24,8 @@ import android.graphics.drawable.Drawable
 import android.os.Build
 import com.facebook.react.uimanager.FloatUtil.floatsEqual
 import com.facebook.react.uimanager.LengthPercentage
-import com.facebook.react.uimanager.PixelUtil
 import com.facebook.react.uimanager.PixelUtil.dpToPx
+import com.facebook.react.uimanager.PixelUtil.pxToDp
 import com.facebook.react.uimanager.Spacing
 import com.facebook.react.uimanager.style.BorderColors
 import com.facebook.react.uimanager.style.BorderInsets
@@ -703,8 +703,8 @@ internal class BorderDrawable(
         this.borderRadius?.resolve(
             layoutDirection,
             this.context,
-            PixelUtil.toDIPFromPixel(outerClipTempRectForBorderRadius?.width() ?: 0f),
-            PixelUtil.toDIPFromPixel(outerClipTempRectForBorderRadius?.height() ?: 0f),
+            outerClipTempRectForBorderRadius?.width()?.pxToDp() ?: 0f,
+            outerClipTempRectForBorderRadius?.height()?.pxToDp() ?: 0f,
         )
 
     val topLeftRadius = computedBorderRadius?.topLeft?.toPixelFromDIP() ?: CornerRadii(0f, 0f)

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/uimanager/drawable/OutlineDrawable.kt

@@ -18,7 +18,7 @@ import android.graphics.PathEffect
 import android.graphics.PixelFormat
 import android.graphics.RectF
 import android.graphics.drawable.Drawable
-import com.facebook.react.uimanager.PixelUtil.dpToPx
+import com.facebook.react.uimanager.PixelUtil.pxToDp
 import com.facebook.react.uimanager.style.BorderRadiusStyle
 import com.facebook.react.uimanager.style.ComputedBorderRadius
 import com.facebook.react.uimanager.style.CornerRadii
@@ -123,7 +123,7 @@ internal class OutlineDrawable(
 
     computedBorderRadius =
         borderRadius?.resolve(
-            layoutDirection, context, bounds.width().dpToPx(), bounds.height().dpToPx())
+            layoutDirection, context, bounds.width().pxToDp(), bounds.height().pxToDp())
 
     updateOutlineRect()
     if (computedBorderRadius != null && computedBorderRadius?.hasRoundedBorders() == true) {

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/uimanager/style/BorderRadiusStyle.kt

@@ -107,11 +107,11 @@ public data class BorderRadiusStyle(
       width: Float,
       height: Float,
   ): ComputedBorderRadius {
-    val zeroRadii: CornerRadii = CornerRadii(0f, 0f)
+    val zeroRadii = CornerRadii(0f, 0f)
 
     return when (layoutDirection) {
       LayoutDirection.LTR ->
-          ComputedBorderRadius(
+          ensureNoOverlap(
               topLeft =
                   (startStart ?: topStart ?: topLeft ?: uniform)?.resolve(width, height)
                       ?: zeroRadii,
@@ -123,10 +123,12 @@ public data class BorderRadiusStyle(
               bottomRight =
                   (endEnd ?: bottomEnd ?: bottomRight ?: uniform)?.resolve(width, height)
                       ?: zeroRadii,
+              width = width,
+              height = height,
           )
       LayoutDirection.RTL ->
           if (I18nUtil.instance.doLeftAndRightSwapInRTL(context)) {
-            ComputedBorderRadius(
+            ensureNoOverlap(
                 topLeft =
                     (endStart ?: topEnd ?: topRight ?: uniform)?.resolve(width, height)
                         ?: zeroRadii,
@@ -139,9 +141,11 @@ public data class BorderRadiusStyle(
                 bottomRight =
                     (startEnd ?: bottomEnd ?: bottomLeft ?: uniform)?.resolve(width, height)
                         ?: zeroRadii,
+                width = width,
+                height = height,
             )
           } else {
-            ComputedBorderRadius(
+            ensureNoOverlap(
                 topLeft =
                     (endStart ?: topEnd ?: topLeft ?: uniform)?.resolve(width, height) ?: zeroRadii,
                 topRight =
@@ -153,9 +157,54 @@ public data class BorderRadiusStyle(
                 bottomRight =
                     (startEnd ?: bottomEnd ?: bottomRight ?: uniform)?.resolve(width, height)
                         ?: zeroRadii,
+                width = width,
+                height = height,
             )
           }
       else -> throw IllegalArgumentException("Expected?.resolved layout direction")
     }
   }
+
+  /**
+   * "Corner curves must not overlap: When the sum of any two adjacent border radii exceeds the size
+   * of the border box, UAs must proportionally reduce the used values of all border radii until
+   * none of them overlap." Source: https://www.w3.org/TR/css-backgrounds-3/#corner-overlap
+   */
+  private fun ensureNoOverlap(
+      topLeft: CornerRadii,
+      topRight: CornerRadii,
+      bottomLeft: CornerRadii,
+      bottomRight: CornerRadii,
+      width: Float,
+      height: Float
+  ): ComputedBorderRadius {
+    val leftInset = topLeft.horizontal + bottomLeft.horizontal
+    val topInset = topLeft.vertical + topRight.vertical
+    val rightInset = topRight.horizontal + bottomRight.horizontal
+    val bottomInset = bottomLeft.vertical + bottomRight.vertical
+
+    val leftInsetScale = if (leftInset > 0) minOf(1.0f, height / leftInset) else 0f
+    val topInsetScale = if (topInset > 0) minOf(1.0f, width / topInset) else 0f
+    val rightInsetScale = if (rightInset > 0) minOf(1.0f, height / rightInset) else 0f
+    val bottomInsetScale = if (bottomInset > 0) minOf(1.0f, width / bottomInset) else 0f
+
+    return ComputedBorderRadius(
+        topLeft =
+            CornerRadii(
+                topLeft.horizontal * minOf(topInsetScale, leftInsetScale),
+                topLeft.vertical * minOf(topInsetScale, leftInsetScale)),
+        topRight =
+            CornerRadii(
+                topRight.horizontal * minOf(topInsetScale, rightInsetScale),
+                topRight.vertical * minOf(topInsetScale, rightInsetScale)),
+        bottomLeft =
+            CornerRadii(
+                bottomLeft.horizontal * minOf(bottomInsetScale, leftInsetScale),
+                bottomLeft.vertical * minOf(bottomInsetScale, leftInsetScale)),
+        bottomRight =
+            CornerRadii(
+                bottomRight.horizontal * minOf(bottomInsetScale, rightInsetScale),
+                bottomRight.vertical * minOf(bottomInsetScale, rightInsetScale)),
+    )
+  }
 }