CapturedTouchpadEventConverter: report relative axes

In the old touchpad stack, when a touchpad was captured we'd report
AXIS_RELATIVE_(X|Y) values for each finger, as offsets from the location
it had in the previous frame. When I implemented captured mode in the
new stack I didn't realize this, so the new stack introduced in Android
U doesn't report them. This causes problems for games that capture the
mouse pointer and use the relative axes for camera movement.

This is attempt 2; the original CL [0] had a unit test that was flaky
due to it accidentally making assertions about uninitialized memory. The
changes since that CL are to TwoFingers_motionReportedCorrectly in
CapturedTouchpadEventConverter_test.cpp (to change the last
WithPointerRelativeMotion call to WithRelativeMotion) and
TestEventMatchers.h (to use a class for WithPointerRelativeMotion and to
check for out-of-range pointer indexes).

[0]: Change ID I8a1caa4c9315dd41bc712fd9467146bb608cf6f3

Bug: 330522990
Bug: 365166534
Test: check the axis values using a test app
Test: $ atest inputflinger_tests:CapturedTouchpadEventConverterTest
Flag: com.android.input.flags.include_relative_axis_values_for_captured_touchpads
Change-Id: If6828f95e3aa359af479a708f95fbb5e31e5bc9a
diff --git a/services/inputflinger/reader/mapper/CapturedTouchpadEventConverter.cpp b/services/inputflinger/reader/mapper/CapturedTouchpadEventConverter.cpp
index c8e7790..dd46bbc 100644
--- a/services/inputflinger/reader/mapper/CapturedTouchpadEventConverter.cpp
+++ b/services/inputflinger/reader/mapper/CapturedTouchpadEventConverter.cpp
@@ -20,14 +20,19 @@
 #include <sstream>
 
 #include <android-base/stringprintf.h>
+#include <com_android_input_flags.h>
 #include <input/PrintTools.h>
 #include <linux/input-event-codes.h>
 #include <log/log_main.h>
 
+namespace input_flags = com::android::input::flags;
+
 namespace android {
 
 namespace {
 
+static constexpr uint32_t SOURCE = AINPUT_SOURCE_TOUCHPAD;
+
 int32_t actionWithIndex(int32_t action, int32_t index) {
     return action | (index << AMOTION_EVENT_ACTION_POINTER_INDEX_SHIFT);
 }
@@ -43,6 +48,12 @@
     return i;
 }
 
+void addRawMotionRange(InputDeviceInfo& deviceInfo, int32_t androidAxis,
+                       RawAbsoluteAxisInfo& evdevAxis) {
+    deviceInfo.addMotionRange(androidAxis, SOURCE, evdevAxis.minValue, evdevAxis.maxValue,
+                              evdevAxis.flat, evdevAxis.fuzz, evdevAxis.resolution);
+}
+
 } // namespace
 
 CapturedTouchpadEventConverter::CapturedTouchpadEventConverter(
@@ -108,8 +119,15 @@
 }
 
 void CapturedTouchpadEventConverter::populateMotionRanges(InputDeviceInfo& info) const {
-    tryAddRawMotionRange(/*byref*/ info, AMOTION_EVENT_AXIS_X, ABS_MT_POSITION_X);
-    tryAddRawMotionRange(/*byref*/ info, AMOTION_EVENT_AXIS_Y, ABS_MT_POSITION_Y);
+    if (input_flags::include_relative_axis_values_for_captured_touchpads()) {
+        tryAddRawMotionRangeWithRelative(/*byref*/ info, AMOTION_EVENT_AXIS_X,
+                                         AMOTION_EVENT_AXIS_RELATIVE_X, ABS_MT_POSITION_X);
+        tryAddRawMotionRangeWithRelative(/*byref*/ info, AMOTION_EVENT_AXIS_Y,
+                                         AMOTION_EVENT_AXIS_RELATIVE_Y, ABS_MT_POSITION_Y);
+    } else {
+        tryAddRawMotionRange(/*byref*/ info, AMOTION_EVENT_AXIS_X, ABS_MT_POSITION_X);
+        tryAddRawMotionRange(/*byref*/ info, AMOTION_EVENT_AXIS_Y, ABS_MT_POSITION_Y);
+    }
     tryAddRawMotionRange(/*byref*/ info, AMOTION_EVENT_AXIS_TOUCH_MAJOR, ABS_MT_TOUCH_MAJOR);
     tryAddRawMotionRange(/*byref*/ info, AMOTION_EVENT_AXIS_TOUCH_MINOR, ABS_MT_TOUCH_MINOR);
     tryAddRawMotionRange(/*byref*/ info, AMOTION_EVENT_AXIS_TOOL_MAJOR, ABS_MT_WIDTH_MAJOR);
@@ -135,8 +153,23 @@
                                                           int32_t evdevAxis) const {
     std::optional<RawAbsoluteAxisInfo> info = mDeviceContext.getAbsoluteAxisInfo(evdevAxis);
     if (info) {
-        deviceInfo.addMotionRange(androidAxis, SOURCE, info->minValue, info->maxValue, info->flat,
-                                  info->fuzz, info->resolution);
+        addRawMotionRange(/*byref*/ deviceInfo, androidAxis, *info);
+    }
+}
+
+void CapturedTouchpadEventConverter::tryAddRawMotionRangeWithRelative(InputDeviceInfo& deviceInfo,
+                                                                      int32_t androidAxis,
+                                                                      int32_t androidRelativeAxis,
+                                                                      int32_t evdevAxis) const {
+    std::optional<RawAbsoluteAxisInfo> axisInfo = mDeviceContext.getAbsoluteAxisInfo(evdevAxis);
+    if (axisInfo) {
+        addRawMotionRange(/*byref*/ deviceInfo, androidAxis, *axisInfo);
+
+        // The largest movement we could possibly report on a relative axis is from the minimum to
+        // the maximum (or vice versa) of the absolute axis.
+        float range = axisInfo->maxValue - axisInfo->minValue;
+        deviceInfo.addMotionRange(androidRelativeAxis, SOURCE, -range, range, axisInfo->flat,
+                                  axisInfo->fuzz, axisInfo->resolution);
     }
 }
 
@@ -163,7 +196,7 @@
     std::list<NotifyArgs> out;
     std::vector<PointerCoords> coords;
     std::vector<PointerProperties> properties;
-    std::map<size_t, size_t> coordsIndexForSlotNumber;
+    std::map<size_t /*slotNumber*/, size_t /*coordsIndex*/> coordsIndexForSlotNumber;
 
     // For all the touches that were already down, send a MOVE event with their updated coordinates.
     // A convention of the MotionEvent API is that pointer coordinates in UP events match the
@@ -175,11 +208,19 @@
             // to stay perfectly still between frames, and if it does the worst that can happen is
             // an extra MOVE event, so it's not worth the overhead of checking for changes.
             coordsIndexForSlotNumber[slotNumber] = coords.size();
-            coords.push_back(makePointerCoordsForSlot(mMotionAccumulator.getSlot(slotNumber)));
+            coords.push_back(makePointerCoordsForSlot(slotNumber));
             properties.push_back({.id = pointerId, .toolType = ToolType::FINGER});
         }
         out.push_back(
                 makeMotionArgs(when, readTime, AMOTION_EVENT_ACTION_MOVE, coords, properties));
+        if (input_flags::include_relative_axis_values_for_captured_touchpads()) {
+            // For any further events we send from this sync, the pointers won't have moved relative
+            // to the positions we just reported in this MOVE event, so zero out the relative axes.
+            for (PointerCoords& pointer : coords) {
+                pointer.setAxisValue(AMOTION_EVENT_AXIS_RELATIVE_X, 0);
+                pointer.setAxisValue(AMOTION_EVENT_AXIS_RELATIVE_Y, 0);
+            }
+        }
     }
 
     std::vector<size_t> upSlots, downSlots;
@@ -234,6 +275,9 @@
                                      /*flags=*/cancel ? AMOTION_EVENT_FLAG_CANCELED : 0));
 
         freePointerIdForSlot(slotNumber);
+        if (input_flags::include_relative_axis_values_for_captured_touchpads()) {
+            mPreviousCoordsForSlotNumber.erase(slotNumber);
+        }
         coords.erase(coords.begin() + indexToRemove);
         properties.erase(properties.begin() + indexToRemove);
         // Now that we've removed some coords and properties, we might have to update the slot
@@ -254,7 +298,7 @@
                 : actionWithIndex(AMOTION_EVENT_ACTION_POINTER_DOWN, coordsIndex);
 
         coordsIndexForSlotNumber[slotNumber] = coordsIndex;
-        coords.push_back(makePointerCoordsForSlot(mMotionAccumulator.getSlot(slotNumber)));
+        coords.push_back(makePointerCoordsForSlot(slotNumber));
         properties.push_back(
                 {.id = allocatePointerIdToSlot(slotNumber), .toolType = ToolType::FINGER});
 
@@ -286,12 +330,22 @@
                             AMOTION_EVENT_INVALID_CURSOR_POSITION, mDownTime, /*videoFrames=*/{});
 }
 
-PointerCoords CapturedTouchpadEventConverter::makePointerCoordsForSlot(
-        const MultiTouchMotionAccumulator::Slot& slot) const {
+PointerCoords CapturedTouchpadEventConverter::makePointerCoordsForSlot(size_t slotNumber) {
+    const MultiTouchMotionAccumulator::Slot& slot = mMotionAccumulator.getSlot(slotNumber);
     PointerCoords coords;
     coords.clear();
     coords.setAxisValue(AMOTION_EVENT_AXIS_X, slot.getX());
     coords.setAxisValue(AMOTION_EVENT_AXIS_Y, slot.getY());
+    if (input_flags::include_relative_axis_values_for_captured_touchpads()) {
+        if (auto it = mPreviousCoordsForSlotNumber.find(slotNumber);
+            it != mPreviousCoordsForSlotNumber.end()) {
+            auto [oldX, oldY] = it->second;
+            coords.setAxisValue(AMOTION_EVENT_AXIS_RELATIVE_X, slot.getX() - oldX);
+            coords.setAxisValue(AMOTION_EVENT_AXIS_RELATIVE_Y, slot.getY() - oldY);
+        }
+        mPreviousCoordsForSlotNumber[slotNumber] = std::make_pair(slot.getX(), slot.getY());
+    }
+
     coords.setAxisValue(AMOTION_EVENT_AXIS_TOUCH_MAJOR, slot.getTouchMajor());
     coords.setAxisValue(AMOTION_EVENT_AXIS_TOUCH_MINOR, slot.getTouchMinor());
     coords.setAxisValue(AMOTION_EVENT_AXIS_TOOL_MAJOR, slot.getToolMajor());
diff --git a/services/inputflinger/reader/mapper/CapturedTouchpadEventConverter.h b/services/inputflinger/reader/mapper/CapturedTouchpadEventConverter.h
index 9b6df7a..d6c0708 100644
--- a/services/inputflinger/reader/mapper/CapturedTouchpadEventConverter.h
+++ b/services/inputflinger/reader/mapper/CapturedTouchpadEventConverter.h
@@ -21,6 +21,7 @@
 #include <map>
 #include <set>
 #include <string>
+#include <utility>
 #include <vector>
 
 #include <android/input.h>
@@ -49,12 +50,14 @@
 private:
     void tryAddRawMotionRange(InputDeviceInfo& deviceInfo, int32_t androidAxis,
                               int32_t evdevAxis) const;
+    void tryAddRawMotionRangeWithRelative(InputDeviceInfo& deviceInfo, int32_t androidAxis,
+                                          int32_t androidRelativeAxis, int32_t evdevAxis) const;
     [[nodiscard]] std::list<NotifyArgs> sync(nsecs_t when, nsecs_t readTime);
     [[nodiscard]] NotifyMotionArgs makeMotionArgs(nsecs_t when, nsecs_t readTime, int32_t action,
                                                   const std::vector<PointerCoords>& coords,
                                                   const std::vector<PointerProperties>& properties,
                                                   int32_t actionButton = 0, int32_t flags = 0);
-    PointerCoords makePointerCoordsForSlot(const MultiTouchMotionAccumulator::Slot& slot) const;
+    PointerCoords makePointerCoordsForSlot(size_t slotNumber);
     int32_t allocatePointerIdToSlot(size_t slotNumber);
     void freePointerIdForSlot(size_t slotNumber);
 
@@ -76,8 +79,7 @@
 
     std::bitset<MAX_POINTER_ID + 1> mPointerIdsInUse;
     std::map<size_t, int32_t> mPointerIdForSlotNumber;
-
-    static constexpr uint32_t SOURCE = AINPUT_SOURCE_TOUCHPAD;
+    std::map<size_t, std::pair<float, float>> mPreviousCoordsForSlotNumber;
 };
 
 } // namespace android