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Commit 62c483b1 authored by omarmt's avatar omarmt
Browse files

Do not draw elements that are not part of the transition 

When transitioning between Transition, avoid drawing elements that are
not part of the new transition.

Test: atest ElementTest
Bug: 332586311
Flag: NA
Change-Id: I1afefb05d0324dbc9b39418b8d5e2507f310f6fa
parent 059ac2d1

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

+13 −10
Original line number Diff line number Diff line
@@ -261,16 +261,19 @@ private fun shouldDrawElement( 
    scene: Scene,

    element: Element,

): Boolean {

    val transition = layoutImpl.state.currentTransition



    // Always draw the element if there is no ongoing transition or if the element is not shared or

    // if the current scene is the one that is currently over scrolling with [OverscrollSpec].

    if (

        transition == null ||

            transition.fromScene !in element.sceneStates ||

            transition.toScene !in element.sceneStates ||

            transition.currentOverscrollSpec?.scene == scene.key

    ) {

    val transition = layoutImpl.state.currentTransition ?: return true



    val inFromScene = transition.fromScene in element.sceneStates

    val inToScene = transition.toScene in element.sceneStates



    // If an element is not present in any scene, it should not be drawn.

    if (!inFromScene && !inToScene) {

        return false

    }



    // Always draw if the element is not shared or if the current scene is the one that is currently

    // over scrolling with [OverscrollSpec].

    if (!inFromScene || !inToScene || transition.currentOverscrollSpec?.scene == scene.key) {

        return true

    }

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

+55 −0
Original line number Diff line number Diff line
@@ -45,6 +45,7 @@ import androidx.compose.ui.Modifier 
import androidx.compose.ui.geometry.Offset

import androidx.compose.ui.layout.intermediateLayout

import androidx.compose.ui.platform.LocalViewConfiguration

import androidx.compose.ui.test.assertIsNotDisplayed

import androidx.compose.ui.test.assertTopPositionInRootIsEqualTo

import androidx.compose.ui.test.junit4.createComposeRule

import androidx.compose.ui.test.onNodeWithTag
@@ -174,6 +175,60 @@ class ElementTest { 
        }

    }



    @Test

    fun elementsNotInTransition_shouldNotBeDrawn() {

        val nFrames = 20

        val frameDuration = 16L

        val tween = tween<Float>(nFrames * frameDuration.toInt())

        val layoutSize = 100.dp

        val elementSize = 50.dp

        val elementOffset = 20.dp



        lateinit var changeScene: (SceneKey) -> Unit



        rule.testTransition(

            from = TestScenes.SceneA,

            to = TestScenes.SceneB,

            transitionLayout = { currentScene, onChangeScene ->

                changeScene = onChangeScene



                SceneTransitionLayout(

                    currentScene,

                    onChangeScene,

                    transitions {

                        from(TestScenes.SceneA, to = TestScenes.SceneB) { spec = tween }

                        from(TestScenes.SceneB, to = TestScenes.SceneC) { spec = tween }

                    },

                ) {

                    scene(TestScenes.SceneA) {

                        Box(Modifier.size(layoutSize)) {

                            // Transformed element

                            Element(

                                TestElements.Bar,

                                elementSize,

                                elementOffset,

                            )

                        }

                    }

                    scene(TestScenes.SceneB) { Box(Modifier.size(layoutSize)) }

                    scene(TestScenes.SceneC) { Box(Modifier.size(layoutSize)) }

                }

            },

        ) {

            // Start transition from SceneA to SceneB

            at(1 * frameDuration) {

                onElement(TestElements.Bar).assertExists()



                // Start transition from SceneB to SceneC

                changeScene(TestScenes.SceneC)

            }



            at(2 * frameDuration) { onElement(TestElements.Bar).assertIsNotDisplayed() }



            at(3 * frameDuration) { onElement(TestElements.Bar).assertDoesNotExist() }

        }

    }



    @Test

    fun onlyMovingElements_noLayout_onlyPlacement() {

        val nFrames = 20