[CD Cursor] Add DisplayTopologyValidator

Add a DisplayTopologyValidator to verify assumptions made in the
PointerChoreographer and InputDispatcher, some sanity checks on the
topology graph to flag issues realted to topology for debugging.

The validator will be used in the InputManager to validated and discard
invalid topology updates.

Test: atest inputflinger_tests
Bug: 401219231
Flag: com.android.input.flags.enable_display_topology_validation

Change-Id: I624bc32b73144cc047f317ef889f7f07cc1c3dfc

6 files changed, 239 insertions, 0 deletions

diff --git a/include/input/DisplayTopologyGraph.h b/include/input/DisplayTopologyGraph.h
index 3ae865a33a..ce7259e09a 100644
--- a/include/input/DisplayTopologyGraph.h
+++ b/include/input/DisplayTopologyGraph.h
@@ -55,6 +55,8 @@ struct DisplayTopologyGraph {
     ui::LogicalDisplayId primaryDisplayId = ui::LogicalDisplayId::INVALID;
     std::unordered_map<ui::LogicalDisplayId, std::vector<DisplayTopologyAdjacentDisplay>> graph;
     std::unordered_map<ui::LogicalDisplayId, int> displaysDensity;
+
+    bool isValid() const;
 };
 
 } // namespace android
diff --git a/libs/input/Android.bp b/libs/input/Android.bp
index ff26184a33..0a180a4304 100644
--- a/libs/input/Android.bp
+++ b/libs/input/Android.bp
@@ -225,6 +225,7 @@ cc_library {
     srcs: [
         "AccelerationCurve.cpp",
         "CoordinateFilter.cpp",
+        "DisplayTopologyGraph.cpp",
         "Input.cpp",
         "InputConsumer.cpp",
         "InputConsumerNoResampling.cpp",
diff --git a/libs/input/DisplayTopologyGraph.cpp b/libs/input/DisplayTopologyGraph.cpp
new file mode 100644
index 0000000000..7ad9f163b8
--- /dev/null
+++ b/libs/input/DisplayTopologyGraph.cpp
@@ -0,0 +1,105 @@
+/*
+ * Copyright 2025 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.
+ */
+
+#define LOG_TAG "DisplayTopologyValidator"
+
+#include <android-base/logging.h>
+#include <ftl/enum.h>
+#include <input/DisplayTopologyGraph.h>
+#include <ui/LogicalDisplayId.h>
+
+#include <algorithm>
+
+namespace android {
+
+namespace {
+DisplayTopologyPosition getOppositePosition(DisplayTopologyPosition position) {
+    switch (position) {
+        case DisplayTopologyPosition::LEFT:
+            return DisplayTopologyPosition::RIGHT;
+        case DisplayTopologyPosition::TOP:
+            return DisplayTopologyPosition::BOTTOM;
+        case DisplayTopologyPosition::RIGHT:
+            return DisplayTopologyPosition::LEFT;
+        case DisplayTopologyPosition::BOTTOM:
+            return DisplayTopologyPosition::TOP;
+    }
+}
+
+bool validatePrimaryDisplay(const android::DisplayTopologyGraph& displayTopologyGraph) {
+    return displayTopologyGraph.primaryDisplayId != ui::LogicalDisplayId::INVALID &&
+            displayTopologyGraph.graph.contains(displayTopologyGraph.primaryDisplayId);
+}
+
+bool validateTopologyGraph(const android::DisplayTopologyGraph& displayTopologyGraph) {
+    for (const auto& [sourceDisplay, adjacentDisplays] : displayTopologyGraph.graph) {
+        for (const DisplayTopologyAdjacentDisplay& adjacentDisplay : adjacentDisplays) {
+            const auto adjacentGraphIt = displayTopologyGraph.graph.find(adjacentDisplay.displayId);
+            if (adjacentGraphIt == displayTopologyGraph.graph.end()) {
+                LOG(ERROR) << "Missing adjacent display in topology graph: "
+                           << adjacentDisplay.displayId << " for source " << sourceDisplay;
+                return false;
+            }
+            const auto reverseEdgeIt =
+                    std::find_if(adjacentGraphIt->second.begin(), adjacentGraphIt->second.end(),
+                                 [sourceDisplay](const DisplayTopologyAdjacentDisplay&
+                                                         reverseAdjacentDisplay) {
+                                     return sourceDisplay == reverseAdjacentDisplay.displayId;
+                                 });
+            if (reverseEdgeIt == adjacentGraphIt->second.end()) {
+                LOG(ERROR) << "Missing reverse edge in topology graph for: " << sourceDisplay
+                           << " -> " << adjacentDisplay.displayId;
+                return false;
+            }
+            DisplayTopologyPosition expectedPosition =
+                    getOppositePosition(adjacentDisplay.position);
+            if (reverseEdgeIt->position != expectedPosition) {
+                LOG(ERROR) << "Unexpected reverse edge for: " << sourceDisplay << " -> "
+                           << adjacentDisplay.displayId
+                           << " expected position: " << ftl::enum_string(expectedPosition)
+                           << " actual " << ftl::enum_string(reverseEdgeIt->position);
+                return false;
+            }
+            if (reverseEdgeIt->offsetDp != -adjacentDisplay.offsetDp) {
+                LOG(ERROR) << "Unexpected reverse edge offset: " << sourceDisplay << " -> "
+                           << adjacentDisplay.displayId
+                           << " expected offset: " << -adjacentDisplay.offsetDp << " actual "
+                           << reverseEdgeIt->offsetDp;
+                return false;
+            }
+        }
+    }
+    return true;
+}
+
+bool validateDensities(const android::DisplayTopologyGraph& displayTopologyGraph) {
+    for (const auto& [sourceDisplay, adjacentDisplays] : displayTopologyGraph.graph) {
+        if (!displayTopologyGraph.displaysDensity.contains(sourceDisplay)) {
+            LOG(ERROR) << "Missing density value in topology graph for display: " << sourceDisplay;
+            return false;
+        }
+    }
+    return true;
+}
+
+} // namespace
+
+bool DisplayTopologyGraph::isValid() const {
+    return validatePrimaryDisplay(*this) && validateTopologyGraph(*this) &&
+            validateDensities(*this);
+}
+
+} // namespace android
diff --git a/libs/input/input_flags.aconfig b/libs/input/input_flags.aconfig
index 1c0c9e7252..983bbdee6e 100644
--- a/libs/input/input_flags.aconfig
+++ b/libs/input/input_flags.aconfig
@@ -239,3 +239,13 @@ flag {
     purpose: PURPOSE_BUGFIX
   }
 }
+
+flag {
+  name: "enable_display_topology_validation"
+  namespace: "input"
+  description: "Set to true to enable display topology validation"
+  bug: "401219231"
+  metadata {
+    purpose: PURPOSE_BUGFIX
+  }
+}
diff --git a/services/inputflinger/tests/Android.bp b/services/inputflinger/tests/Android.bp
index 18d47f648b..677cf1e6c4 100644
--- a/services/inputflinger/tests/Android.bp
+++ b/services/inputflinger/tests/Android.bp
@@ -52,6 +52,7 @@ cc_test {
         "AnrTracker_test.cpp",
         "CapturedTouchpadEventConverter_test.cpp",
         "CursorInputMapper_test.cpp",
+        "DisplayTopologyGraph_test.cpp",
         "EventHub_test.cpp",
         "FakeEventHub.cpp",
         "FakeInputReaderPolicy.cpp",
diff --git a/services/inputflinger/tests/DisplayTopologyGraph_test.cpp b/services/inputflinger/tests/DisplayTopologyGraph_test.cpp
new file mode 100644
index 0000000000..fd2f21c4cb
--- /dev/null
+++ b/services/inputflinger/tests/DisplayTopologyGraph_test.cpp
@@ -0,0 +1,120 @@
+/*
+ * Copyright 2025 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.
+ */
+
+#include <gtest/gtest.h>
+#include <input/DisplayTopologyGraph.h>
+
+#include <string>
+#include <string_view>
+#include <tuple>
+
+namespace android {
+
+namespace {
+
+constexpr ui::LogicalDisplayId DISPLAY_ID_1{1};
+constexpr ui::LogicalDisplayId DISPLAY_ID_2{2};
+constexpr int DENSITY_MEDIUM = 160;
+
+} // namespace
+
+using DisplayTopologyGraphTestFixtureParam =
+        std::tuple<std::string_view /*name*/, DisplayTopologyGraph, bool /*isValid*/>;
+
+class DisplayTopologyGraphTestFixture
+      : public testing::Test,
+        public testing::WithParamInterface<DisplayTopologyGraphTestFixtureParam> {};
+
+TEST_P(DisplayTopologyGraphTestFixture, DisplayTopologyGraphTest) {
+    const auto& [_, displayTopology, isValid] = GetParam();
+    EXPECT_EQ(isValid, displayTopology.isValid());
+}
+
+INSTANTIATE_TEST_SUITE_P(
+        DisplayTopologyGraphTest, DisplayTopologyGraphTestFixture,
+        testing::Values(
+                std::make_tuple(
+                        "InvalidPrimaryDisplay",
+                        DisplayTopologyGraph{.primaryDisplayId = ui::LogicalDisplayId::INVALID,
+                                             .graph = {},
+                                             .displaysDensity = {}},
+                        false),
+                std::make_tuple("PrimaryDisplayNotInGraph",
+                                DisplayTopologyGraph{.primaryDisplayId = DISPLAY_ID_1,
+                                                     .graph = {},
+                                                     .displaysDensity = {}},
+                                false),
+                std::make_tuple("DisplayDensityMissing",
+                                DisplayTopologyGraph{.primaryDisplayId = DISPLAY_ID_1,
+                                                     .graph = {{DISPLAY_ID_1, {}}},
+                                                     .displaysDensity = {}},
+                                false),
+                std::make_tuple("ValidSingleDisplayTopology",
+                                DisplayTopologyGraph{.primaryDisplayId = DISPLAY_ID_1,
+                                                     .graph = {{DISPLAY_ID_1, {}}},
+                                                     .displaysDensity = {{DISPLAY_ID_1,
+                                                                          DENSITY_MEDIUM}}},
+                                true),
+                std::make_tuple(
+                        "MissingReverseEdge",
+                        DisplayTopologyGraph{.primaryDisplayId = DISPLAY_ID_1,
+                                             .graph = {{DISPLAY_ID_1,
+                                                        {{DISPLAY_ID_2,
+                                                          DisplayTopologyPosition::TOP, 0}}}},
+                                             .displaysDensity = {{DISPLAY_ID_1, DENSITY_MEDIUM},
+                                                                 {DISPLAY_ID_2, DENSITY_MEDIUM}}},
+                        false),
+                std::make_tuple(
+                        "IncorrectReverseEdgeDirection",
+                        DisplayTopologyGraph{.primaryDisplayId = DISPLAY_ID_1,
+                                             .graph = {{DISPLAY_ID_1,
+                                                        {{DISPLAY_ID_2,
+                                                          DisplayTopologyPosition::TOP, 0}}},
+                                                       {DISPLAY_ID_2,
+                                                        {{DISPLAY_ID_1,
+                                                          DisplayTopologyPosition::TOP, 0}}}},
+                                             .displaysDensity = {{DISPLAY_ID_1, DENSITY_MEDIUM},
+                                                                 {DISPLAY_ID_2, DENSITY_MEDIUM}}},
+                        false),
+                std::make_tuple(
+                        "IncorrectReverseEdgeOffset",
+                        DisplayTopologyGraph{.primaryDisplayId = DISPLAY_ID_1,
+                                             .graph = {{DISPLAY_ID_1,
+                                                        {{DISPLAY_ID_2,
+                                                          DisplayTopologyPosition::TOP, 10}}},
+                                                       {DISPLAY_ID_2,
+                                                        {{DISPLAY_ID_1,
+                                                          DisplayTopologyPosition::BOTTOM, 20}}}},
+                                             .displaysDensity = {{DISPLAY_ID_1, DENSITY_MEDIUM},
+                                                                 {DISPLAY_ID_2, DENSITY_MEDIUM}}},
+                        false),
+                std::make_tuple(
+                        "ValidMultiDisplayTopology",
+                        DisplayTopologyGraph{.primaryDisplayId = DISPLAY_ID_1,
+                                             .graph = {{DISPLAY_ID_1,
+                                                        {{DISPLAY_ID_2,
+                                                          DisplayTopologyPosition::TOP, 10}}},
+                                                       {DISPLAY_ID_2,
+                                                        {{DISPLAY_ID_1,
+                                                          DisplayTopologyPosition::BOTTOM, -10}}}},
+                                             .displaysDensity = {{DISPLAY_ID_1, DENSITY_MEDIUM},
+                                                                 {DISPLAY_ID_2, DENSITY_MEDIUM}}},
+                        true)),
+        [](const testing::TestParamInfo<DisplayTopologyGraphTestFixtureParam>& p) {
+            return std::string{std::get<0>(p.param)};
+        });
+
+} // namespace android