Introduce ComposeScreenshotTestRule for Compose UIs

// Copyright (C) 2022 The Android Open Source Project

//

// Licensed under the Apache License, Version 2.0 (the "License");

// you may not use this file except in compliance with the License.

// You may obtain a copy of the License at

//

//      http://www.apache.org/licenses/LICENSE-2.0

//

// Unless required by applicable law or agreed to in writing, software

// distributed under the License is distributed on an "AS IS" BASIS,

// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

// See the License for the specific language governing permissions and

// limitations under the License.

package {

    // See: http://go/android-license-faq

    // A large-scale-change added 'default_applicable_licenses' to import

    // all of the 'license_kinds' from "frameworks_base_packages_SystemUI_license"

    // to get the below license kinds:

    //   SPDX-license-identifier-Apache-2.0

    default_applicable_licenses: ["frameworks_base_packages_SystemUI_license"],

}

android_library {

    name: "SystemUIComposeTesting",

    manifest: "AndroidManifest.xml",

    srcs: [

        "src/**/*.kt",

    ],

    static_libs: [

        "SystemUIComposeCore",

        "SystemUIScreenshotLib",

        "androidx.compose.runtime_runtime",

        "androidx.compose.material3_material3",

        "androidx.compose.ui_ui-test-junit4",

        "androidx.compose.ui_ui-test-manifest",

    ],

    kotlincflags: ["-Xjvm-default=all"],

}

<?xml version="1.0" encoding="utf-8"?>

<!--

     Copyright (C) 2022 The Android Open Source Project

     Licensed under the Apache License, Version 2.0 (the "License");

     you may not use this file except in compliance with the License.

     You may obtain a copy of the License at

          http://www.apache.org/licenses/LICENSE-2.0

     Unless required by applicable law or agreed to in writing, software

     distributed under the License is distributed on an "AS IS" BASIS,

     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

     See the License for the specific language governing permissions and

     limitations under the License.

-->

<manifest xmlns:android="http://schemas.android.com/apk/res/android"

    xmlns:tools="http://schemas.android.com/tools"

    package="com.android.systemui.testing.compose">

    <application

        android:appComponentFactory="androidx.core.app.AppComponentFactory"

        tools:replace="android:appComponentFactory">

    </application>

</manifest>

/*

 * Copyright (C) 2022 The Android Open Source Project

 *

 * Licensed under the Apache License, Version 2.0 (the "License");

 * you may not use this file except in compliance with the License.

 * You may obtain a copy of the License at

 *

 *      http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

package com.android.systemui.testing.compose

import androidx.compose.material3.MaterialTheme

import androidx.compose.material3.Surface

import androidx.compose.runtime.Composable

import androidx.compose.ui.platform.ViewRootForTest

import androidx.compose.ui.test.junit4.createAndroidComposeRule

import androidx.compose.ui.test.onRoot

import com.android.systemui.compose.theme.SystemUITheme

import com.android.systemui.testing.screenshot.ScreenshotActivity

import com.android.systemui.testing.screenshot.ScreenshotTestRule

import com.android.systemui.testing.screenshot.ScreenshotTestSpec

import org.junit.rules.RuleChain

import org.junit.rules.TestRule

import org.junit.runner.Description

import org.junit.runners.model.Statement

/** A rule for Compose screenshot diff tests. */

class ComposeScreenshotTestRule(testSpec: ScreenshotTestSpec) : TestRule {

    private val composeRule = createAndroidComposeRule<ScreenshotActivity>()

    private val screenshotRule = ScreenshotTestRule(testSpec)

    private val delegate = RuleChain.outerRule(screenshotRule).around(composeRule)

    override fun apply(base: Statement, description: Description): Statement {

        return delegate.apply(base, description)

    }

    /**

     * Compare [content] with the golden image identified by [goldenIdentifier] in the context of

     * [testSpec].

     */

    fun screenshotTest(

        goldenIdentifier: String,

        content: @Composable () -> Unit,

    ) {

        // Make sure that the activity draws full screen and fits the whole display instead of the

        // system bars.

        val activity = composeRule.activity

        activity.mainExecutor.execute { activity.window.setDecorFitsSystemWindows(false) }

        // Set the content using the AndroidComposeRule to make sure that the Activity is set up

        // correctly.

        composeRule.setContent {

            SystemUITheme {

                Surface(

                    color = MaterialTheme.colorScheme.background,

                ) {

                    content()

                }

            }

        }

        composeRule.waitForIdle()

        val view = (composeRule.onRoot().fetchSemanticsNode().root as ViewRootForTest).view

        screenshotRule.screenshotTest(goldenIdentifier, view)

    }

}