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Commit 593cfcf1 authored by Jordan Demeulenaere's avatar Jordan Demeulenaere
Browse files

Expose ElementKey.currentAlpha() in ContentScope 

This CL exposes a new ElementKey.currentAlpha() API in ContentScope that
can be used to get the computed alpha for a given element, reusing the
same logic used by Modifier.element() during transitions. This can be
used to share this logic with non compose elements like NSSL.

Bug: 437121774
Test: atest ContentTest
Flag: EXEMPT new API
Change-Id: Ic2bb2062f0f358309727a6c38545379b1d334f20
parent 75aa2493

packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/Element.kt

+2 −2
Original line number Diff line number Diff line
@@ -692,7 +692,7 @@ internal class ElementNode( 
}



/** The [TransitionState] that we should consider for [element]. */

private fun elementState(

internal fun elementState(

    layoutImpl: SceneTransitionLayoutImpl,

    element: Element,

    transitionStates: List<List<TransitionState>>,
@@ -1127,7 +1127,7 @@ private fun isElementOpaque( 
 * [isElementOpaque] is checked during placement and we don't want to read the transition progress

 * in that phase.

 */

private fun elementAlpha(

internal fun elementAlpha(

    layoutImpl: SceneTransitionLayoutImpl,

    element: Element,

    transition: TransitionState.Transition?,

packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/SceneTransitionLayout.kt

+9 −0
Original line number Diff line number Diff line
@@ -312,6 +312,15 @@ interface BaseContentScope : ElementStateScope { 
    fun Modifier.disableSwipesWhenScrolling(

        bounds: NestedScrollableBound = NestedScrollableBound.Any

    ): Modifier



    /**

     * Return the alpha of [this] element in this content, given the current transition state and

     * transition transformations (e.g. fade).

     *

     * Important: This should *not* be read during composition and should instead be read during

     * layout, drawing or in a LaunchedEffect.

     */

    fun ElementKey.currentAlpha(): Float?

}



@Stable

packages/SystemUI/compose/scene/src/com/android/compose/animation/scene/content/Content.kt

+14 −0
Original line number Diff line number Diff line
@@ -76,8 +76,12 @@ import com.android.compose.animation.scene.UserAction 
import com.android.compose.animation.scene.UserActionResult

import com.android.compose.animation.scene.ValueKey

import com.android.compose.animation.scene.animateSharedValueAsState

import com.android.compose.animation.scene.content.state.TransitionState

import com.android.compose.animation.scene.effect.GestureEffect

import com.android.compose.animation.scene.element

import com.android.compose.animation.scene.elementAlpha

import com.android.compose.animation.scene.elementState

import com.android.compose.animation.scene.getAllNestedTransitionStates

import com.android.compose.animation.scene.modifiers.noResizeDuringTransitions

import com.android.compose.gesture.NestedScrollControlState

import com.android.compose.gesture.NestedScrollableBound
@@ -422,6 +426,16 @@ internal class ContentScopeImpl( 
                it.fromContent == content || it.toContent == content

            }

    }



    override fun ElementKey.currentAlpha(): Float? {

        val element = layoutImpl.elements[this] ?: return null

        val stateInContent = element.stateByContent[contentKey] ?: return null

        val elementState =

            elementState(layoutImpl, element, getAllNestedTransitionStates(layoutImpl))

                ?: return null

        val transition = elementState as? TransitionState.Transition

        return elementAlpha(layoutImpl, element, transition, stateInContent)

    }

}



/** A [LifecycleOwner] that follows its [parentLifecycle] but is capped at [maxLifecycleState]. */

packages/SystemUI/compose/scene/tests/src/com/android/compose/animation/scene/ContentTest.kt

+53 −0
Original line number Diff line number Diff line
@@ -24,11 +24,13 @@ import androidx.compose.foundation.layout.fillMaxSize 
import androidx.compose.runtime.Composable

import androidx.compose.runtime.CompositionLocalProvider

import androidx.compose.runtime.DisposableEffect

import androidx.compose.runtime.LaunchedEffect

import androidx.compose.runtime.SideEffect

import androidx.compose.runtime.getValue

import androidx.compose.runtime.mutableStateOf

import androidx.compose.runtime.remember

import androidx.compose.runtime.setValue

import androidx.compose.runtime.snapshotFlow

import androidx.compose.ui.Modifier

import androidx.compose.ui.geometry.Offset

import androidx.compose.ui.platform.LocalViewConfiguration
@@ -380,4 +382,55 @@ class ContentTest { 
        assertThat(nestedMiddle.ancestors).containsExactly(outerState)

        assertThat(nestedInner.ancestors).containsExactly(outerState, middleState).inOrder()

    }



    @Test

    fun currentElementAlpha() {

        var lastAlpha: Float? = null



        val state =

            rule.runOnUiThread {

                MutableSceneTransitionLayoutStateForTests(

                    SceneA,

                    transitions =

                        transitions { from(SceneA, to = SceneB) { fade(TestElements.Foo) } },

                )

            }

        val scope =

            rule.setContentAndCreateMainScope {

                SceneTransitionLayout(state) {

                    scene(SceneA) {}

                    scene(SceneB) {

                        LaunchedEffect(Unit) {

                            snapshotFlow { TestElements.Foo.currentAlpha() }

                                .collect { lastAlpha = it }

                        }



                        Box(Modifier.element(TestElements.Foo).fillMaxSize())

                    }

                }

            }



        assertThat(lastAlpha).isNull()



        var progress by mutableStateOf(0f)

        scope.launch { state.startTransition(transition(SceneA, SceneB, progress = { progress })) }

        rule.waitForIdle()

        assertThat(lastAlpha).isWithin(0.01f).of(0f)



        progress = 0.25f

        rule.waitForIdle()

        assertThat(lastAlpha).isWithin(0.01f).of(0.25f)



        progress = 0.5f

        rule.waitForIdle()

        assertThat(lastAlpha).isWithin(0.01f).of(0.5f)



        progress = 0.75f

        rule.waitForIdle()

        assertThat(lastAlpha).isWithin(0.01f).of(0.75f)



        progress = 1f

        rule.waitForIdle()

        assertThat(lastAlpha).isWithin(0.01f).of(1f)

    }

}