fix(Android): separate transitions of sheet and dimming view (#2542)

## Description

This PR allows the form sheet on Android to be dismissed using
`slide-down` animation. Currently the sheet fades-out together with the
dimming view due to using regular [Tween
animations](https://developer.android.com/guide/topics/resources/animation-resource#Tween),
which apply animation whole view hierarchy from the fragment's root view
down - this does not allow for separate animations for the sheet and
dimming view.

`Transition API` was considered as an implementation measure, however
due to numerous encountered problems, most prominent example being
"disappearing shadows during pop transitions", I rejected it.

The implementation settled on using custom value / object evaluators.
This approach comes with its own series of issues, with the most
prominent one:

* on old architecture the fragment transaction execution (transition)
starts before initial frame for content wrapper is received - I decided
to defer the transaction to the moment of receiving the layout.


> [!caution]
This PR changes current default animation for formsheets on Android.
This is potentially a breaking change. I haven't decided yet whether to
treat is as a fix or hide this new animation behind some prop.

WIP recordings of the changes.


## Changes


* Form Sheet screens use now custom animators instead of tween animation
(`setCustomTransition`) defined in `ScreenStack.onUpdate`.
* Removed `DimmingFragment` as there is no longer "nested fragment
strcuture". Dimming view is now attached directly into hierarchy (under
coordinator layout) w/o hosting it in separate fragment.
* Refactored native dismiss code

> [!note]
During testing I've noticed that for some reason the form sheet screens
do not receive `onWill(dis)appear` events on navigator. This is
something to investigate, however it seems that this is not a
regression.


## Test code and steps to reproduce

`TestFormSheet` / `TestAndroidTransitions` examples

## Checklist

- [x] Included code example that can be used to test this change
- [x] Ensured that CI passes

android/src/main/java/com/swmansion/rnscreens/Screen.kt

@@ -5,6 +5,7 @@ import android.content.pm.ActivityInfo
 import android.graphics.Paint
 import android.os.Parcelable
 import android.util.SparseArray
+import android.view.MotionEvent
 import android.view.View
 import android.view.ViewGroup
 import android.view.WindowManager
@@ -17,20 +18,24 @@ import androidx.swiperefreshlayout.widget.SwipeRefreshLayout
 import com.facebook.react.bridge.GuardedRunnable
 import com.facebook.react.bridge.ReactContext
 import com.facebook.react.uimanager.PixelUtil
+import com.facebook.react.uimanager.ThemedReactContext
 import com.facebook.react.uimanager.UIManagerHelper
 import com.facebook.react.uimanager.UIManagerModule
 import com.facebook.react.uimanager.events.EventDispatcher
 import com.google.android.material.bottomsheet.BottomSheetBehavior
 import com.google.android.material.shape.CornerFamily
 import com.google.android.material.shape.MaterialShapeDrawable
 import com.google.android.material.shape.ShapeAppearanceModel
+import com.swmansion.rnscreens.bottomsheet.isSheetFitToContents
+import com.swmansion.rnscreens.bottomsheet.usesFormSheetPresentation
 import com.swmansion.rnscreens.events.HeaderHeightChangeEvent
 import com.swmansion.rnscreens.events.SheetDetentChangedEvent
+import com.swmansion.rnscreens.ext.parentAsViewGroup
 import java.lang.ref.WeakReference
 
 @SuppressLint("ViewConstructor") // Only we construct this view, it is never inflated.
 class Screen(
-    val reactContext: ReactContext,
+    val reactContext: ThemedReactContext,
 ) : FabricEnabledViewGroup(reactContext),
     ScreenContentWrapper.OnLayoutCallback {
     val fragment: Fragment?
@@ -81,6 +86,13 @@ class Screen(
     var sheetClosesOnTouchOutside = true
     var sheetElevation: Float = 24F
 
+    /**
+     * When using form sheet presentation we want to delay enter transition **on Paper** in order
+     * to wait for initial layout from React, otherwise the animator-based animation will look
+     * glitchy. *This is not needed on Fabric*.
+     */
+    var shouldTriggerPostponedTransitionAfterLayout = false
+
     var footer: ScreenFooter? = null
         set(value) {
             if (value == null && field != null) {
@@ -110,7 +122,7 @@ class Screen(
      * `fitToContents` for formSheets, as this is first entry point where we can acquire
      * height of our content.
      */
-    override fun onLayoutCallback(
+    override fun onContentWrapperLayout(
         changed: Boolean,
         left: Int,
         top: Int,
@@ -119,12 +131,23 @@ class Screen(
     ) {
         val height = bottom - top
 
-        if (sheetDetents.count() == 1 && sheetDetents.first() == SHEET_FIT_TO_CONTENTS) {
+        if (isSheetFitToContents()) {
             sheetBehavior?.let {
                 if (it.maxHeight != height) {
                     it.maxHeight = height
                 }
             }
+
+            if (!BuildConfig.IS_NEW_ARCHITECTURE_ENABLED) {
+                // On old architecture we delay enter transition in order to wait for initial frame.
+                shouldTriggerPostponedTransitionAfterLayout = true
+                val parent = parentAsViewGroup()
+                if (parent != null && !parent.isInLayout) {
+                    // There are reported cases (irreproducible) when Screen is not laid out after
+                    // maxHeight is set on behaviour.
+                    parent.requestLayout()
+                }
+            }
         }
     }
 
@@ -162,6 +185,17 @@ class Screen(
 
             footer?.onParentLayout(changed, l, t, r, b, container!!.height)
             notifyHeaderHeightChange(t)
+
+            if (!BuildConfig.IS_NEW_ARCHITECTURE_ENABLED) {
+                maybeTriggerPostponedTransition()
+            }
+        }
+    }
+
+    private fun maybeTriggerPostponedTransition() {
+        if (shouldTriggerPostponedTransitionAfterLayout) {
+            shouldTriggerPostponedTransitionAfterLayout = false
+            fragment?.startPostponedEnterTransition()
         }
     }
 
@@ -377,6 +411,28 @@ class Screen(
         }
     }
 
+    fun endRemovalTransition() {
+        if (!isBeingRemoved) {
+            return
+        }
+        isBeingRemoved = false
+        endTransitionRecursive(this)
+    }
+
+    private fun endTransitionRecursive(parent: ViewGroup) {
+        parent.children.forEach { childView ->
+            parent.endViewTransition(childView)
+
+            if (childView is ScreenStackHeaderConfig) {
+                endTransitionRecursive(childView.toolbar)
+            }
+
+            if (childView is ViewGroup) {
+                endTransitionRecursive(childView)
+            }
+        }
+    }
+
     private fun startTransitionRecursive(parent: ViewGroup?) {
         parent?.let {
             for (i in 0 until it.childCount) {
@@ -407,6 +463,17 @@ class Screen(
         }
     }
 
+    // We do not want to perform any action, therefore do not need to override the associated method.
+    @SuppressLint("ClickableViewAccessibility")
+    override fun onTouchEvent(event: MotionEvent?): Boolean =
+        if (usesFormSheetPresentation()) {
+            // If we're a form sheet we want to consume the gestures to prevent
+            // DimmingView's callback from triggering when clicking on the sheet itself.
+            true
+        } else {
+            super.onTouchEvent(event)
+        }
+
     private fun notifyHeaderHeightChange(headerHeight: Int) {
         val screenContext = context as ReactContext
         val surfaceId = UIManagerHelper.getSurfaceId(screenContext)

android/src/main/java/com/swmansion/rnscreens/ScreenContentWrapper.kt

@@ -17,7 +17,7 @@ class ScreenContentWrapper(
     internal var delegate: OnLayoutCallback? = null
 
     interface OnLayoutCallback {
-        fun onLayoutCallback(
+        fun onContentWrapperLayout(
             changed: Boolean,
             left: Int,
             top: Int,
@@ -33,6 +33,6 @@ class ScreenContentWrapper(
         right: Int,
         bottom: Int,
     ) {
-        delegate?.onLayoutCallback(changed, left, top, right, bottom)
+        delegate?.onContentWrapperLayout(changed, left, top, right, bottom)
     }
 }

android/src/main/java/com/swmansion/rnscreens/ScreenFragment.kt

@@ -15,7 +15,6 @@ import com.facebook.react.bridge.UiThreadUtil
 import com.facebook.react.uimanager.UIManagerHelper
 import com.facebook.react.uimanager.events.Event
 import com.facebook.react.uimanager.events.EventDispatcher
-import com.swmansion.rnscreens.bottomsheet.DimmingFragment
 import com.swmansion.rnscreens.events.HeaderBackButtonClickedEvent
 import com.swmansion.rnscreens.events.ScreenAppearEvent
 import com.swmansion.rnscreens.events.ScreenDisappearEvent
@@ -290,12 +289,7 @@ open class ScreenFragment :
         // since we subscribe to parent's animation start/end and dispatch events in child from there
         // check for `isTransitioning` should be enough since the child's animation should take only
         // 20ms due to always being `StackAnimation.NONE` when nested stack being pushed
-        val parent =
-            if (parentFragment is DimmingFragment) {
-                parentFragment?.parentFragment
-            } else {
-                parentFragment
-            }
+        val parent = parentFragment
         if (parent == null || (parent is ScreenFragment && !parent.isTransitioning)) {
             // onViewAnimationStart/End is triggered from View#onAnimationStart/End method of the fragment's root
             // view. We override an appropriate method of the StackFragment's

android/src/main/java/com/swmansion/rnscreens/ScreenStack.kt

@@ -7,11 +7,10 @@ import android.view.View
 import com.facebook.react.bridge.ReactContext
 import com.facebook.react.uimanager.UIManagerHelper
 import com.swmansion.rnscreens.Screen.StackAnimation
-import com.swmansion.rnscreens.bottomsheet.DimmingFragment
+import com.swmansion.rnscreens.bottomsheet.isSheetFitToContents
 import com.swmansion.rnscreens.events.StackFinishTransitioningEvent
 import java.util.Collections
 import kotlin.collections.ArrayList
-import kotlin.collections.HashSet
 
 class ScreenStack(
     context: Context?,
@@ -50,7 +49,7 @@ class ScreenStack(
 
     override fun adapt(screen: Screen): ScreenStackFragmentWrapper =
         when (screen.stackPresentation) {
-            Screen.StackPresentation.FORM_SHEET -> DimmingFragment(ScreenStackFragment(screen))
+            Screen.StackPresentation.FORM_SHEET -> ScreenStackFragment(screen)
             else -> ScreenStackFragment(screen)
         }
 
@@ -242,7 +241,6 @@ class ScreenStack(
                     }
                 }
             }
-
             // animation logic end
             goingForward = shouldUseOpenAnimation
 
@@ -302,6 +300,12 @@ class ScreenStack(
                     }
                 }
             } else if (newTop != null && !newTop.fragment.isAdded) {
+                if (!BuildConfig.IS_NEW_ARCHITECTURE_ENABLED && newTop.screen.isSheetFitToContents()) {
+                    // On old architecture the content wrapper might not have received its frame yet,
+                    // which is required to determine height of the sheet after animation. Therefore
+                    // we delay the transition and trigger it after views receive the layout.
+                    newTop.fragment.postponeEnterTransition()
+                }
                 it.add(id, newTop.fragment)
             }
             topScreenWrapper = newTop as? ScreenStackFragmentWrapper