[Pager] Add VerticalPager

pager/api/pager.api

@@ -3,6 +3,7 @@ public abstract interface annotation class com/google/accompanist/pager/Experime
 
 public final class com/google/accompanist/pager/Pager {
 	public static final fun HorizontalPager (Lcom/google/accompanist/pager/PagerState;Landroidx/compose/ui/Modifier;ZILandroidx/compose/animation/core/DecayAnimationSpec;Landroidx/compose/animation/core/AnimationSpec;Lkotlin/jvm/functions/Function4;Landroidx/compose/runtime/Composer;II)V
+	public static final fun VerticalPager (Lcom/google/accompanist/pager/PagerState;Landroidx/compose/ui/Modifier;ZILandroidx/compose/animation/core/DecayAnimationSpec;Landroidx/compose/animation/core/AnimationSpec;Lkotlin/jvm/functions/Function4;Landroidx/compose/runtime/Composer;II)V
 }
 
 public abstract interface class com/google/accompanist/pager/PagerScope : androidx/compose/foundation/layout/BoxScope {

pager/src/androidTest/java/com/google/accompanist/pager/HorizontalPagerTest.kt

@@ -0,0 +1,140 @@
+/*
+ * Copyright 2021 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
+ *
+ *      https://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.google.accompanist.pager
+
+import androidx.compose.foundation.background
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.aspectRatio
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.text.BasicText
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.platform.testTag
+import androidx.compose.ui.test.SemanticsNodeInteraction
+import androidx.compose.ui.test.assertHeightIsAtLeast
+import androidx.compose.ui.test.assertLeftPositionInRootIsEqualTo
+import androidx.compose.ui.test.assertTopPositionInRootIsEqualTo
+import androidx.compose.ui.test.assertWidthIsEqualTo
+import androidx.compose.ui.test.getUnclippedBoundsInRoot
+import androidx.compose.ui.test.onRoot
+import androidx.compose.ui.unit.LayoutDirection
+import androidx.compose.ui.unit.height
+import androidx.compose.ui.unit.width
+import androidx.test.filters.LargeTest
+import org.junit.runner.RunWith
+import org.junit.runners.Parameterized
+
+@OptIn(ExperimentalPagerApi::class) // Pager is currently experimental
+@LargeTest
+@RunWith(Parameterized::class)
+class HorizontalPagerTest(
+    private val itemWidthFraction: Float,
+    offscreenLimit: Int,
+    layoutDirection: LayoutDirection,
+) : PagerTest(
+    offscreenLimit = offscreenLimit,
+    layoutDirection = layoutDirection,
+) {
+    companion object {
+        @JvmStatic
+        @Parameterized.Parameters
+        fun data(): Collection<Array<Any>> = listOf(
+            // itemWidthFraction, offscreenLimit, layoutDirection
+
+            // Test typical full-width items
+            arrayOf(1f, 2, LayoutDirection.Ltr),
+            arrayOf(1f, 2, LayoutDirection.Rtl),
+
+            // Test an increased offscreenLimit
+            arrayOf(1f, 4, LayoutDirection.Ltr),
+            arrayOf(1f, 4, LayoutDirection.Rtl),
+
+            // Test items with 80% widths
+            arrayOf(0.8f, 2, LayoutDirection.Ltr),
+            arrayOf(0.8f, 2, LayoutDirection.Rtl),
+        )
+    }
+
+    override fun SemanticsNodeInteraction.swipeAcrossCenter(
+        velocity: Float,
+        distancePercentage: Float
+    ): SemanticsNodeInteraction = swipeAcrossCenterWithVelocity(
+        distancePercentageX = when (layoutDirection) {
+            LayoutDirection.Rtl -> -distancePercentage
+            else -> distancePercentage
+        },
+        velocity = velocity,
+    )
+
+    override fun SemanticsNodeInteraction.assertLaidOutItemPosition(
+        page: Int,
+        currentPage: Int,
+    ): SemanticsNodeInteraction {
+        val rootBounds = composeTestRule.onRoot().getUnclippedBoundsInRoot()
+        val expectedItemSize = rootBounds.width * itemWidthFraction
+
+        // The expected coordinates. This uses the implicit fact that Pager
+        // centers items horizontally, and that we're using items with an aspect ratio of 1:1
+        val expectedTop = (rootBounds.height - expectedItemSize) / 2
+        val expectedFirstItemLeft = (rootBounds.width - expectedItemSize) / 2
+
+        return assertWidthIsEqualTo(expectedItemSize)
+            .assertHeightIsAtLeast(expectedItemSize)
+            .assertTopPositionInRootIsEqualTo(expectedTop)
+            .run {
+                if (layoutDirection == LayoutDirection.Ltr) {
+                    assertLeftPositionInRootIsEqualTo(
+                        expectedFirstItemLeft + (expectedItemSize * (page - currentPage))
+                    )
+                } else { // layoutDirection = RTL
+                    assertLeftPositionInRootIsEqualTo(
+                        expectedFirstItemLeft - (expectedItemSize * (page - currentPage))
+                    )
+                }
+            }
+    }
+
+    override fun setPagerContent(
+        layoutDirection: LayoutDirection,
+        pageCount: Int,
+        offscreenLimit: Int,
+    ): PagerState {
+        val pagerState = PagerState(pageCount = pageCount)
+        composeTestRule.setContent(layoutDirection) {
+            HorizontalPager(
+                state = pagerState,
+                offscreenLimit = offscreenLimit,
+                modifier = Modifier.fillMaxSize()
+            ) { page ->
+                Box(
+                    modifier = Modifier
+                        .fillMaxWidth(itemWidthFraction)
+                        .aspectRatio(1f)
+                        .background(randomColor())
+                        .testTag(page.toString())
+                ) {
+                    BasicText(
+                        text = page.toString(),
+                        modifier = Modifier.align(Alignment.Center)
+                    )
+                }
+            }
+        }
+        return pagerState
+    }
+}

pager/src/androidTest/java/com/google/accompanist/pager/PagerUnitTest.kt → pager/src/androidTest/java/com/google/accompanist/pager/PagerStateUnitTest.kt

@@ -24,7 +24,7 @@ import org.junit.runners.JUnit4
 
 @OptIn(ExperimentalPagerApi::class) // Pager is currently experimental
 @RunWith(JUnit4::class)
-class PagerUnitTest {
+class PagerStateUnitTest {
     @get:Rule
     val composeTestRule = createComposeRule()