diff --git a/services/surfaceflinger/Layer.cpp b/services/surfaceflinger/Layer.cpp
index a34af17..2ed363a 100644
--- a/services/surfaceflinger/Layer.cpp
+++ b/services/surfaceflinger/Layer.cpp
@@ -1820,7 +1820,7 @@
         onRemovedFromCurrentState();
     }
 
-    if (callSetTransactionFlags || attachChildren()) {
+    if (attachChildren() || callSetTransactionFlags) {
         setTransactionFlags(eTransactionNeeded);
     }
     return true;
@@ -1848,9 +1848,9 @@
         if (client != nullptr && parentClient != client) {
             if (child->mLayerDetached) {
                 child->mLayerDetached = false;
+                child->attachChildren();
                 changed = true;
             }
-            changed |= child->attachChildren();
         }
     }
 
diff --git a/services/surfaceflinger/tests/Android.bp b/services/surfaceflinger/tests/Android.bp
index fe2af80..c96dfc7 100644
--- a/services/surfaceflinger/tests/Android.bp
+++ b/services/surfaceflinger/tests/Android.bp
@@ -21,6 +21,7 @@
         "CommonTypes_test.cpp",
         "Credentials_test.cpp",
         "DereferenceSurfaceControl_test.cpp",
+        "DetachChildren_test.cpp",
         "DisplayConfigs_test.cpp",
         "EffectLayer_test.cpp",
         "InvalidHandles_test.cpp",
diff --git a/services/surfaceflinger/tests/DetachChildren_test.cpp b/services/surfaceflinger/tests/DetachChildren_test.cpp
new file mode 100644
index 0000000..b6c2fe2
--- /dev/null
+++ b/services/surfaceflinger/tests/DetachChildren_test.cpp
@@ -0,0 +1,322 @@
+/*
+ * Copyright (C) 2020 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.
+ */
+
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wconversion"
+
+#include "LayerTransactionTest.h"
+
+namespace android {
+
+class DetachChildren : public LayerTransactionTest {
+protected:
+    virtual void SetUp() {
+        LayerTransactionTest::SetUp();
+
+        mMainSurface = createLayer(String8("Main Test Surface"), mMainSurfaceBounds.width(),
+                                   mMainSurfaceBounds.height(), 0, mBlackBgSurface.get());
+
+        ASSERT_TRUE(mMainSurface != nullptr);
+        ASSERT_TRUE(mMainSurface->isValid());
+
+        TransactionUtils::fillSurfaceRGBA8(mMainSurface, mMainSurfaceColor);
+
+        asTransaction([&](Transaction& t) {
+            t.setLayer(mMainSurface, INT32_MAX - 1)
+                    .setPosition(mMainSurface, mMainSurfaceBounds.left, mMainSurfaceBounds.top)
+                    .show(mMainSurface);
+        });
+    }
+
+    virtual void TearDown() {
+        LayerTransactionTest::TearDown();
+        mMainSurface = 0;
+    }
+
+    sp<SurfaceControl> mMainSurface;
+    Color mMainSurfaceColor = {195, 63, 63, 255};
+    Rect mMainSurfaceBounds = Rect(64, 64, 128, 128);
+    std::unique_ptr<ScreenCapture> mCapture;
+};
+
+TEST_F(DetachChildren, RelativesAreNotDetached) {
+    Color relativeColor = {10, 10, 10, 255};
+    Rect relBounds = Rect(64, 64, 74, 74);
+
+    sp<SurfaceControl> relative =
+            createLayer(String8("relativeTestSurface"), relBounds.width(), relBounds.height(), 0);
+    TransactionUtils::fillSurfaceRGBA8(relative, relativeColor);
+
+    Transaction{}
+            .setRelativeLayer(relative, mMainSurface->getHandle(), 1)
+            .setPosition(relative, relBounds.left, relBounds.top)
+            .apply();
+
+    {
+        // The relative should be on top of the FG control.
+        mCapture = screenshot();
+        mCapture->expectColor(relBounds, relativeColor);
+    }
+    Transaction{}.detachChildren(mMainSurface).apply();
+
+    {
+        // Nothing should change at this point.
+        mCapture = screenshot();
+        mCapture->expectColor(relBounds, relativeColor);
+    }
+
+    Transaction{}.hide(relative).apply();
+
+    {
+        // Ensure that the relative was actually hidden, rather than
+        // being left in the detached but visible state.
+        mCapture = screenshot();
+        mCapture->expectColor(mMainSurfaceBounds, mMainSurfaceColor);
+    }
+}
+
+TEST_F(DetachChildren, DetachChildrenSameClient) {
+    Color childColor = {200, 200, 200, 255};
+    Rect childBounds = Rect(74, 74, 84, 84);
+    sp<SurfaceControl> child = createLayer(String8("Child surface"), childBounds.width(),
+                                           childBounds.height(), 0, mMainSurface.get());
+    ASSERT_TRUE(child->isValid());
+
+    TransactionUtils::fillSurfaceRGBA8(child, childColor);
+
+    asTransaction([&](Transaction& t) {
+        t.show(child);
+        t.setPosition(child, childBounds.left - mMainSurfaceBounds.left,
+                      childBounds.top - mMainSurfaceBounds.top);
+    });
+
+    {
+        mCapture = screenshot();
+        // Expect main color around the child surface
+        mCapture->expectBorder(childBounds, mMainSurfaceColor);
+        mCapture->expectColor(childBounds, childColor);
+    }
+
+    asTransaction([&](Transaction& t) { t.detachChildren(mMainSurface); });
+
+    asTransaction([&](Transaction& t) { t.hide(child); });
+
+    // Since the child has the same client as the parent, it will not get
+    // detached and will be hidden.
+    {
+        mCapture = screenshot();
+        mCapture->expectColor(mMainSurfaceBounds, mMainSurfaceColor);
+    }
+}
+
+TEST_F(DetachChildren, DetachChildrenDifferentClient) {
+    Color childColor = {200, 200, 200, 255};
+    Rect childBounds = Rect(74, 74, 84, 84);
+
+    sp<SurfaceComposerClient> newComposerClient = new SurfaceComposerClient;
+    sp<SurfaceControl> childNewClient =
+            createSurface(newComposerClient, "New Child Test Surface", childBounds.width(),
+                          childBounds.height(), PIXEL_FORMAT_RGBA_8888, 0, mMainSurface.get());
+    ASSERT_TRUE(childNewClient->isValid());
+
+    TransactionUtils::fillSurfaceRGBA8(childNewClient, childColor);
+
+    asTransaction([&](Transaction& t) {
+        t.show(childNewClient);
+        t.setPosition(childNewClient, childBounds.left - mMainSurfaceBounds.left,
+                      childBounds.top - mMainSurfaceBounds.top);
+    });
+
+    {
+        mCapture = screenshot();
+        // Expect main color around the child surface
+        mCapture->expectBorder(childBounds, mMainSurfaceColor);
+        mCapture->expectColor(childBounds, childColor);
+    }
+
+    asTransaction([&](Transaction& t) { t.detachChildren(mMainSurface); });
+
+    asTransaction([&](Transaction& t) { t.hide(childNewClient); });
+
+    // Nothing should have changed.
+    {
+        mCapture = screenshot();
+        mCapture->expectBorder(childBounds, mMainSurfaceColor);
+        mCapture->expectColor(childBounds, childColor);
+    }
+}
+
+TEST_F(DetachChildren, DetachChildrenThenAttach) {
+    Color childColor = {200, 200, 200, 255};
+    Rect childBounds = Rect(74, 74, 84, 84);
+
+    sp<SurfaceComposerClient> newComposerClient = new SurfaceComposerClient;
+    sp<SurfaceControl> childNewClient =
+            createSurface(newComposerClient, "New Child Test Surface", childBounds.width(),
+                          childBounds.height(), PIXEL_FORMAT_RGBA_8888, 0, mMainSurface.get());
+    ASSERT_TRUE(childNewClient->isValid());
+
+    TransactionUtils::fillSurfaceRGBA8(childNewClient, childColor);
+
+    Transaction()
+            .show(childNewClient)
+            .setPosition(childNewClient, childBounds.left - mMainSurfaceBounds.left,
+                         childBounds.top - mMainSurfaceBounds.top)
+            .apply();
+
+    {
+        mCapture = screenshot();
+        // Expect main color around the child surface
+        mCapture->expectBorder(childBounds, mMainSurfaceColor);
+        mCapture->expectColor(childBounds, childColor);
+    }
+
+    Transaction().detachChildren(mMainSurface).apply();
+    Transaction().hide(childNewClient).apply();
+
+    // Nothing should have changed.
+    {
+        mCapture = screenshot();
+        mCapture->expectBorder(childBounds, mMainSurfaceColor);
+        mCapture->expectColor(childBounds, childColor);
+    }
+
+    Color newParentColor = Color::RED;
+    Rect newParentBounds = Rect(20, 20, 52, 52);
+    sp<SurfaceControl> newParentSurface =
+            createLayer(String8("New Parent Surface"), newParentBounds.width(),
+                        newParentBounds.height(), 0);
+    TransactionUtils::fillSurfaceRGBA8(newParentSurface, newParentColor);
+    Transaction()
+            .setLayer(newParentSurface, INT32_MAX - 1)
+            .show(newParentSurface)
+            .setPosition(newParentSurface, newParentBounds.left, newParentBounds.top)
+            .reparent(childNewClient, newParentSurface->getHandle())
+            .apply();
+    {
+        mCapture = screenshot();
+        // Child is now hidden.
+        mCapture->expectColor(newParentBounds, newParentColor);
+    }
+}
+
+TEST_F(DetachChildren, DetachChildrenWithDeferredTransaction) {
+    Color childColor = {200, 200, 200, 255};
+    Rect childBounds = Rect(74, 74, 84, 84);
+
+    sp<SurfaceComposerClient> newComposerClient = new SurfaceComposerClient;
+    sp<SurfaceControl> childNewClient =
+            createSurface(newComposerClient, "New Child Test Surface", childBounds.width(),
+                          childBounds.height(), PIXEL_FORMAT_RGBA_8888, 0, mMainSurface.get());
+    ASSERT_TRUE(childNewClient->isValid());
+
+    TransactionUtils::fillSurfaceRGBA8(childNewClient, childColor);
+
+    Transaction()
+            .show(childNewClient)
+            .setPosition(childNewClient, childBounds.left - mMainSurfaceBounds.left,
+                         childBounds.top - mMainSurfaceBounds.top)
+            .apply();
+
+    {
+        mCapture = screenshot();
+        mCapture->expectBorder(childBounds, mMainSurfaceColor);
+        mCapture->expectColor(childBounds, childColor);
+    }
+
+    Transaction()
+            .deferTransactionUntil_legacy(childNewClient, mMainSurface->getHandle(),
+                                          mMainSurface->getSurface()->getNextFrameNumber())
+            .apply();
+    Transaction().detachChildren(mMainSurface).apply();
+    ASSERT_NO_FATAL_FAILURE(fillBufferQueueLayerColor(mMainSurface, Color::RED,
+                                                      mMainSurfaceBounds.width(),
+                                                      mMainSurfaceBounds.height()));
+
+    // BufferLayer can still dequeue buffers even though there's a detached layer with a
+    // deferred transaction.
+    {
+        SCOPED_TRACE("new buffer");
+        mCapture = screenshot();
+        mCapture->expectBorder(childBounds, Color::RED);
+        mCapture->expectColor(childBounds, childColor);
+    }
+}
+
+TEST_F(DetachChildren, ReparentParentLayerOfDetachedChildren) {
+    Color childColor = {200, 200, 200, 255};
+    Rect childBounds = Rect(74, 74, 94, 94);
+    Color grandchildColor = Color::RED;
+    Rect grandchildBounds = Rect(80, 80, 90, 90);
+
+    sp<SurfaceComposerClient> newClient1 = new SurfaceComposerClient;
+    sp<SurfaceComposerClient> newClient2 = new SurfaceComposerClient;
+
+    sp<SurfaceControl> childSurface =
+            createSurface(newClient1, "Child surface", childBounds.width(), childBounds.height(),
+                          PIXEL_FORMAT_RGBA_8888, 0, mMainSurface.get());
+    sp<SurfaceControl> grandchildSurface =
+            createSurface(newClient2, "Grandchild Surface", grandchildBounds.width(),
+                          grandchildBounds.height(), PIXEL_FORMAT_RGBA_8888, 0, childSurface.get());
+
+    TransactionUtils::fillSurfaceRGBA8(childSurface, childColor);
+    TransactionUtils::fillSurfaceRGBA8(grandchildSurface, grandchildColor);
+
+    Transaction()
+            .show(childSurface)
+            .show(grandchildSurface)
+            .setPosition(childSurface, childBounds.left - mMainSurfaceBounds.left,
+                         childBounds.top - mMainSurfaceBounds.top)
+            .setPosition(grandchildSurface, grandchildBounds.left - childBounds.left,
+                         grandchildBounds.top - childBounds.top)
+            .apply();
+
+    {
+        mCapture = screenshot();
+        mCapture->expectBorder(childBounds, mMainSurfaceColor);
+        mCapture->expectBorder(grandchildBounds, childColor);
+        mCapture->expectColor(grandchildBounds, grandchildColor);
+    }
+
+    Transaction().detachChildren(childSurface).apply();
+
+    // Remove main surface offscreen
+    Transaction().reparent(mMainSurface, nullptr).apply();
+    {
+        mCapture = screenshot();
+        mCapture->expectColor(mMainSurfaceBounds, Color::BLACK);
+    }
+
+    Transaction().reparent(mMainSurface, mBlackBgSurface->getHandle()).apply();
+    {
+        mCapture = screenshot();
+        mCapture->expectBorder(childBounds, mMainSurfaceColor);
+        mCapture->expectBorder(grandchildBounds, childColor);
+        mCapture->expectColor(grandchildBounds, grandchildColor);
+    }
+
+    Transaction().hide(grandchildSurface).apply();
+
+    // grandchild is still detached so it will not hide
+    {
+        mCapture = screenshot();
+        mCapture->expectBorder(childBounds, mMainSurfaceColor);
+        mCapture->expectBorder(grandchildBounds, childColor);
+        mCapture->expectColor(grandchildBounds, grandchildColor);
+    }
+}
+
+} // namespace android
\ No newline at end of file
diff --git a/services/surfaceflinger/tests/LayerUpdate_test.cpp b/services/surfaceflinger/tests/LayerUpdate_test.cpp
index cdd9d92..84823f5 100644
--- a/services/surfaceflinger/tests/LayerUpdate_test.cpp
+++ b/services/surfaceflinger/tests/LayerUpdate_test.cpp
@@ -103,41 +103,6 @@
     sp<SurfaceControl> mSyncSurfaceControl;
 };
 
-TEST_F(LayerUpdateTest, RelativesAreNotDetached) {
-    std::unique_ptr<ScreenCapture> sc;
-
-    sp<SurfaceControl> relative = createLayer(String8("relativeTestSurface"), 10, 10, 0);
-    TransactionUtils::fillSurfaceRGBA8(relative, 10, 10, 10);
-    waitForPostedBuffers();
-
-    Transaction{}
-            .setRelativeLayer(relative, mFGSurfaceControl->getHandle(), 1)
-            .setPosition(relative, 64, 64)
-            .apply();
-
-    {
-        // The relative should be on top of the FG control.
-        ScreenCapture::captureScreen(&sc);
-        sc->checkPixel(64, 64, 10, 10, 10);
-    }
-    Transaction{}.detachChildren(mFGSurfaceControl).apply();
-
-    {
-        // Nothing should change at this point.
-        ScreenCapture::captureScreen(&sc);
-        sc->checkPixel(64, 64, 10, 10, 10);
-    }
-
-    Transaction{}.hide(relative).apply();
-
-    {
-        // Ensure that the relative was actually hidden, rather than
-        // being left in the detached but visible state.
-        ScreenCapture::captureScreen(&sc);
-        sc->expectFGColor(64, 64);
-    }
-}
-
 class GeometryLatchingTest : public LayerUpdateTest {
 protected:
     void EXPECT_INITIAL_STATE(const char* trace) {
@@ -588,174 +553,6 @@
     }
 }
 
-TEST_F(ChildLayerTest, DetachChildrenSameClient) {
-    asTransaction([&](Transaction& t) {
-        t.show(mChild);
-        t.setPosition(mChild, 10, 10);
-        t.setPosition(mFGSurfaceControl, 64, 64);
-    });
-
-    {
-        mCapture = screenshot();
-        // Top left of foreground must now be visible
-        mCapture->expectFGColor(64, 64);
-        // But 10 pixels in we should see the child surface
-        mCapture->expectChildColor(74, 74);
-        // And 10 more pixels we should be back to the foreground surface
-        mCapture->expectFGColor(84, 84);
-    }
-
-    asTransaction([&](Transaction& t) { t.detachChildren(mFGSurfaceControl); });
-
-    asTransaction([&](Transaction& t) { t.hide(mChild); });
-
-    // Since the child has the same client as the parent, it will not get
-    // detached and will be hidden.
-    {
-        mCapture = screenshot();
-        mCapture->expectFGColor(64, 64);
-        mCapture->expectFGColor(74, 74);
-        mCapture->expectFGColor(84, 84);
-    }
-}
-
-TEST_F(ChildLayerTest, DetachChildrenDifferentClient) {
-    sp<SurfaceComposerClient> mNewComposerClient = new SurfaceComposerClient;
-    sp<SurfaceControl> mChildNewClient =
-            createSurface(mNewComposerClient, "New Child Test Surface", 10, 10,
-                          PIXEL_FORMAT_RGBA_8888, 0, mFGSurfaceControl.get());
-
-    ASSERT_TRUE(mChildNewClient->isValid());
-
-    TransactionUtils::fillSurfaceRGBA8(mChildNewClient, 200, 200, 200);
-
-    asTransaction([&](Transaction& t) {
-        t.hide(mChild);
-        t.show(mChildNewClient);
-        t.setPosition(mChildNewClient, 10, 10);
-        t.setPosition(mFGSurfaceControl, 64, 64);
-    });
-
-    {
-        mCapture = screenshot();
-        // Top left of foreground must now be visible
-        mCapture->expectFGColor(64, 64);
-        // But 10 pixels in we should see the child surface
-        mCapture->expectChildColor(74, 74);
-        // And 10 more pixels we should be back to the foreground surface
-        mCapture->expectFGColor(84, 84);
-    }
-
-    asTransaction([&](Transaction& t) { t.detachChildren(mFGSurfaceControl); });
-
-    asTransaction([&](Transaction& t) { t.hide(mChildNewClient); });
-
-    // Nothing should have changed.
-    {
-        mCapture = screenshot();
-        mCapture->expectFGColor(64, 64);
-        mCapture->expectChildColor(74, 74);
-        mCapture->expectFGColor(84, 84);
-    }
-}
-
-TEST_F(ChildLayerTest, DetachChildrenThenAttach) {
-    sp<SurfaceComposerClient> newComposerClient = new SurfaceComposerClient;
-    sp<SurfaceControl> childNewClient =
-            newComposerClient->createSurface(String8("New Child Test Surface"), 10, 10,
-                                             PIXEL_FORMAT_RGBA_8888, 0, mFGSurfaceControl.get());
-
-    ASSERT_TRUE(childNewClient != nullptr);
-    ASSERT_TRUE(childNewClient->isValid());
-
-    TransactionUtils::fillSurfaceRGBA8(childNewClient, 200, 200, 200);
-
-    Transaction()
-            .hide(mChild)
-            .show(childNewClient)
-            .setPosition(childNewClient, 10, 10)
-            .setPosition(mFGSurfaceControl, 64, 64)
-            .apply();
-
-    {
-        mCapture = screenshot();
-        // Top left of foreground must now be visible
-        mCapture->expectFGColor(64, 64);
-        // But 10 pixels in we should see the child surface
-        mCapture->expectChildColor(74, 74);
-        // And 10 more pixels we should be back to the foreground surface
-        mCapture->expectFGColor(84, 84);
-    }
-
-    Transaction().detachChildren(mFGSurfaceControl).apply();
-    Transaction().hide(childNewClient).apply();
-
-    // Nothing should have changed.
-    {
-        mCapture = screenshot();
-        mCapture->expectFGColor(64, 64);
-        mCapture->expectChildColor(74, 74);
-        mCapture->expectFGColor(84, 84);
-    }
-
-    sp<SurfaceControl> newParentSurface = createLayer(String8("New Parent Surface"), 32, 32, 0);
-    fillLayerColor(ISurfaceComposerClient::eFXSurfaceBufferQueue, newParentSurface, Color::RED, 32,
-                   32);
-    Transaction()
-            .setLayer(newParentSurface, INT32_MAX - 1)
-            .show(newParentSurface)
-            .setPosition(newParentSurface, 20, 20)
-            .reparent(childNewClient, newParentSurface->getHandle())
-            .apply();
-    {
-        mCapture = screenshot();
-        // Child is now hidden.
-        mCapture->expectColor(Rect(20, 20, 52, 52), Color::RED);
-    }
-}
-TEST_F(ChildLayerTest, DetachChildrenWithDeferredTransaction) {
-    sp<SurfaceComposerClient> newComposerClient = new SurfaceComposerClient;
-    sp<SurfaceControl> childNewClient =
-            newComposerClient->createSurface(String8("New Child Test Surface"), 10, 10,
-                                             PIXEL_FORMAT_RGBA_8888, 0, mFGSurfaceControl.get());
-
-    ASSERT_TRUE(childNewClient != nullptr);
-    ASSERT_TRUE(childNewClient->isValid());
-
-    TransactionUtils::fillSurfaceRGBA8(childNewClient, 200, 200, 200);
-
-    Transaction()
-            .hide(mChild)
-            .show(childNewClient)
-            .setPosition(childNewClient, 10, 10)
-            .setPosition(mFGSurfaceControl, 64, 64)
-            .apply();
-
-    {
-        mCapture = screenshot();
-        Rect rect = Rect(74, 74, 84, 84);
-        mCapture->expectBorder(rect, Color{195, 63, 63, 255});
-        mCapture->expectColor(rect, Color{200, 200, 200, 255});
-    }
-
-    Transaction()
-            .deferTransactionUntil_legacy(childNewClient, mFGSurfaceControl->getHandle(),
-                                          mFGSurfaceControl->getSurface()->getNextFrameNumber())
-            .apply();
-    Transaction().detachChildren(mFGSurfaceControl).apply();
-    ASSERT_NO_FATAL_FAILURE(fillBufferQueueLayerColor(mFGSurfaceControl, Color::RED, 32, 32));
-
-    // BufferLayer can still dequeue buffers even though there's a detached layer with a
-    // deferred transaction.
-    {
-        SCOPED_TRACE("new buffer");
-        mCapture = screenshot();
-        Rect rect = Rect(74, 74, 84, 84);
-        mCapture->expectBorder(rect, Color::RED);
-        mCapture->expectColor(rect, Color{200, 200, 200, 255});
-    }
-}
-
 TEST_F(ChildLayerTest, ChildrenInheritNonTransformScalingFromParent) {
     asTransaction([&](Transaction& t) {
         t.show(mChild);