Use correct scroll bar sizes in ShadowViewConfiguration

The scroll bar size logic in ShadowViewConfiguration was likely copied from Ice
Cream Sandwich (SDK 14), or perhaps earlier.

In O_MR1 (SDK 27), the scroll bar size went from 10dp to 4dp.

Update the logic ShadowViewConfiguration to reflect this. Also add a ctesque
test to ensure consistency between Robolectric and real Android.

This is part of the effort to eventually eliminate ShadowViewConfiguration
entirely.

PiperOrigin-RevId: 626199502

3 files changed, 92 insertions, 20 deletions

diff --git a/integration_tests/ctesque/src/sharedTest/java/android/view/ViewConfigurationTest.java b/integration_tests/ctesque/src/sharedTest/java/android/view/ViewConfigurationTest.java
new file mode 100644
index 000000000..afc2edbbb
--- /dev/null
+++ b/integration_tests/ctesque/src/sharedTest/java/android/view/ViewConfigurationTest.java
@@ -0,0 +1,45 @@
+package android.view;
+
+import static android.os.Build.VERSION_CODES.O_MR1;
+import static com.google.common.truth.Truth.assertThat;
+
+import android.os.Build;
+import androidx.test.core.app.ApplicationProvider;
+import androidx.test.ext.junit.runners.AndroidJUnit4;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.robolectric.annotation.internal.DoNotInstrument;
+
+/** Tests that {@link android.view.ViewConfiguration} behavior is consistent with real Android. */
+@DoNotInstrument
+@RunWith(AndroidJUnit4.class)
+public final class ViewConfigurationTest {
+
+  private float density;
+
+  @Before
+  public void setUp() {
+    density =
+        ApplicationProvider.getApplicationContext().getResources().getDisplayMetrics().density;
+  }
+
+  @Test
+  public void scrollbar_configuration() {
+    ViewConfiguration viewConfiguration =
+        ViewConfiguration.get(ApplicationProvider.getApplicationContext());
+    int scrollBarSize = ViewConfiguration.getScrollBarSize();
+    int scaledScrollBarSizeDp = pxToDp(viewConfiguration.getScaledScrollBarSize());
+    if (Build.VERSION.SDK_INT >= O_MR1) {
+      assertThat(scrollBarSize).isEqualTo(4);
+      assertThat(scaledScrollBarSizeDp).isEqualTo(4);
+    } else {
+      assertThat(scrollBarSize).isEqualTo(10);
+      assertThat(scaledScrollBarSizeDp).isEqualTo(10);
+    }
+  }
+
+  public int pxToDp(int px) {
+    return Math.round(px / density);
+  }
+}
diff --git a/robolectric/src/test/java/org/robolectric/shadows/ShadowViewConfigurationTest.java b/robolectric/src/test/java/org/robolectric/shadows/ShadowViewConfigurationTest.java
index d0dfeadfb..fd98c1a5e 100644
--- a/robolectric/src/test/java/org/robolectric/shadows/ShadowViewConfigurationTest.java
+++ b/robolectric/src/test/java/org/robolectric/shadows/ShadowViewConfigurationTest.java
@@ -1,5 +1,6 @@
 package org.robolectric.shadows;
 
+import static android.os.Build.VERSION_CODES.O_MR1;
 import static com.google.common.truth.Truth.assertThat;
 import static org.junit.Assert.assertEquals;
 import static org.robolectric.Shadows.shadowOf;
@@ -11,6 +12,7 @@ import androidx.test.ext.junit.runners.AndroidJUnit4;
 import org.junit.Before;
 import org.junit.Test;
 import org.junit.runner.RunWith;
+import org.robolectric.RuntimeEnvironment;
 import org.robolectric.annotation.Config;
 
 @RunWith(AndroidJUnit4.class)
@@ -26,8 +28,10 @@ public class ShadowViewConfigurationTest {
   @Test
   public void methodsShouldReturnAndroidConstants() {
     ViewConfiguration viewConfiguration = ViewConfiguration.get(context);
-
-    assertEquals(10, ViewConfiguration.getScrollBarSize());
+    // Most of the constants here are private statics from ViewConfiguration circa Jelly Bean:
+    // https://cs.android.com/android/platform/superproject/+/android-4.1.1_r1:frameworks/base/core/java/android/view/ViewConfiguration.java
+    final int expectedScrollBarSize = RuntimeEnvironment.getApiLevel() >= O_MR1 ? 4 : 10;
+    assertEquals(expectedScrollBarSize, ViewConfiguration.getScrollBarSize());
     assertEquals(250, ViewConfiguration.getScrollBarFadeDuration());
     assertEquals(300, ViewConfiguration.getScrollDefaultDelay());
     assertEquals(12, ViewConfiguration.getFadingEdgeLength());
@@ -48,7 +52,7 @@ public class ShadowViewConfigurationTest {
 
     assertThat(context.getResources().getDisplayMetrics().density).isEqualTo(1f);
 
-    assertEquals(10, viewConfiguration.getScaledScrollBarSize());
+    assertEquals(expectedScrollBarSize, viewConfiguration.getScaledScrollBarSize());
     assertEquals(12, viewConfiguration.getScaledFadingEdgeLength());
     assertEquals(12, viewConfiguration.getScaledEdgeSlop());
     assertEquals(16, viewConfiguration.getScaledTouchSlop());
@@ -62,11 +66,14 @@ public class ShadowViewConfigurationTest {
   }
 
   @Test
+  @Config(qualifiers = "hdpi")
   public void methodsShouldReturnScaledAndroidConstantsDependingOnPixelDensity() {
-    context.getResources().getDisplayMetrics().density = 1.5f;
+    // Most of the constants here are private statics from ViewConfiguration circa Jelly Bean:
+    // https://cs.android.com/android/platform/superproject/+/android-4.1.1_r1:frameworks/base/core/java/android/view/ViewConfiguration.java
+    // They are multiplied by the scaling factor 1.5 for HDPI.
     ViewConfiguration viewConfiguration = ViewConfiguration.get(context);
-
-    assertEquals(15, viewConfiguration.getScaledScrollBarSize());
+    final int expectedScaledScrollBarSize = RuntimeEnvironment.getApiLevel() >= O_MR1 ? 6 : 15;
+    assertEquals(expectedScaledScrollBarSize, viewConfiguration.getScaledScrollBarSize());
     assertEquals(18, viewConfiguration.getScaledFadingEdgeLength());
     assertEquals(18, viewConfiguration.getScaledEdgeSlop());
     assertEquals(24, viewConfiguration.getScaledTouchSlop());
diff --git a/shadows/framework/src/main/java/org/robolectric/shadows/ShadowViewConfiguration.java b/shadows/framework/src/main/java/org/robolectric/shadows/ShadowViewConfiguration.java
index 682f53b6a..8cd68ee34 100644
--- a/shadows/framework/src/main/java/org/robolectric/shadows/ShadowViewConfiguration.java
+++ b/shadows/framework/src/main/java/org/robolectric/shadows/ShadowViewConfiguration.java
@@ -20,23 +20,28 @@
 
 package org.robolectric.shadows;
 
+import static android.os.Build.VERSION_CODES.P;
+import static android.os.Build.VERSION_CODES.Q;
 import static org.robolectric.util.reflector.Reflector.reflector;
 
 import android.content.Context;
+import android.content.res.Resources;
 import android.util.DisplayMetrics;
 import android.view.ViewConfiguration;
 import org.robolectric.RuntimeEnvironment;
 import org.robolectric.annotation.Implementation;
 import org.robolectric.annotation.Implements;
+import org.robolectric.annotation.RealObject;
 import org.robolectric.shadow.api.Shadow;
 import org.robolectric.util.reflector.Accessor;
 import org.robolectric.util.reflector.ForType;
+import org.robolectric.util.reflector.Static;
 
 @SuppressWarnings({"UnusedDeclaration"})
 @Implements(ViewConfiguration.class)
 public class ShadowViewConfiguration {
+  @RealObject ViewConfiguration realViewConfiguration;
 
-  private static final int SCROLL_BAR_SIZE = 10;
   private static final int PRESSED_STATE_DURATION = 125;
   private static final int LONG_PRESS_TIMEOUT = 500;
   private static final int TAP_TIMEOUT = 115;
@@ -54,7 +59,6 @@ public class ShadowViewConfiguration {
   private int fadingEdgeLength;
   private int minimumFlingVelocity;
   private int maximumFlingVelocity;
-  private int scrollbarSize;
   private int touchSlop;
   private int pagingTouchSlop;
   private int doubleTapSlop;
@@ -70,7 +74,17 @@ public class ShadowViewConfiguration {
     fadingEdgeLength = (int) (density * ViewConfiguration.getFadingEdgeLength() + 0.5f);
     minimumFlingVelocity = (int) (density * ViewConfiguration.getMinimumFlingVelocity() + 0.5f);
     maximumFlingVelocity = (int) (density * ViewConfiguration.getMaximumFlingVelocity() + 0.5f);
-    scrollbarSize = (int) (density * SCROLL_BAR_SIZE + 0.5f);
+    int scrollbarSize;
+    if (RuntimeEnvironment.getApiLevel() >= P) {
+      scrollbarSize =
+          Resources.getSystem()
+              .getDimensionPixelSize(
+                  reflector(AndroidInternalDimenReflector.class).getConfigScrollbarSize());
+    } else {
+      scrollbarSize = (int) (density * ViewConfiguration.getScrollBarSize() + 0.5f);
+    }
+    reflector(ViewConfigurationReflector.class, realViewConfiguration)
+        .setScrollbarSize(scrollbarSize);
     touchSlop = (int) (density * TOUCH_SLOP + 0.5f);
     pagingTouchSlop = (int) (density * PAGING_TOUCH_SLOP + 0.5f);
     doubleTapSlop = (int) (density * DOUBLE_TAP_SLOP + 0.5f);
@@ -89,7 +103,7 @@ public class ShadowViewConfiguration {
     ShadowViewConfiguration shadowViewConfiguration = Shadow.extract(viewConfiguration);
     shadowViewConfiguration.setup(context);
 
-    if (RuntimeEnvironment.getApiLevel() >= android.os.Build.VERSION_CODES.Q) {
+    if (RuntimeEnvironment.getApiLevel() >= Q) {
       reflector(ViewConfigurationReflector.class, viewConfiguration)
           .setConstructedWithContext(true);
     }
@@ -98,16 +112,6 @@ public class ShadowViewConfiguration {
   }
 
   @Implementation
-  protected static int getScrollBarSize() {
-    return SCROLL_BAR_SIZE;
-  }
-
-  @Implementation
-  protected int getScaledScrollBarSize() {
-    return scrollbarSize;
-  }
-
-  @Implementation
   protected int getScaledFadingEdgeLength() {
     return fadingEdgeLength;
   }
@@ -200,5 +204,21 @@ public class ShadowViewConfiguration {
   interface ViewConfigurationReflector {
     @Accessor("mConstructedWithContext")
     void setConstructedWithContext(boolean value);
+
+    @Accessor("mScrollbarSize")
+    void setScrollbarSize(int value);
+  }
+
+  /**
+   * Reflection is needed to access internal Android dimen constants, which are static final ints,
+   * so referencing them directly causes inlining. Note {@link AndroidInternalDimenReflector} is
+   * designed to be temporary until the real {@link
+   * android.view.ViewConfiguration#get(android.content.Context)} is called.
+   */
+  @ForType(com.android.internal.R.dimen.class)
+  interface AndroidInternalDimenReflector {
+    @Static
+    @Accessor("config_scrollbarSize")
+    int getConfigScrollbarSize();
   }
 }