MotionEvent: Simplify logic around transformations

This is a refactor that simplifies logic around Transforms applied to
MotionEvents.

PointerCoords should only contain raw values that are unmodified by
MotionEven transformations. The MotionEvent's Transform should only be
applied when getting these values through MotionEvent's getAxisValue
APIs.

Bug: 179274888
Test: atest libinput_tests
Test: manual with test app
Change-Id: If60d98ade84d481afd655a3abc921e50697071b3

1 files changed, 94 insertions, 96 deletions

diff --git a/libs/input/Input.cpp b/libs/input/Input.cpp
index 649a14087e..70ed438112 100644
--- a/libs/input/Input.cpp
+++ b/libs/input/Input.cpp
@@ -39,6 +39,60 @@ using android::base::StringPrintf;
 
 namespace android {
 
+namespace {
+
+float transformAngle(const ui::Transform& transform, float angleRadians) {
+    // Construct and transform a vector oriented at the specified clockwise angle from vertical.
+    // Coordinate system: down is increasing Y, right is increasing X.
+    float x = sinf(angleRadians);
+    float y = -cosf(angleRadians);
+    vec2 transformedPoint = transform.transform(x, y);
+
+    // Determine how the origin is transformed by the matrix so that we
+    // can transform orientation vectors.
+    const vec2 origin = transform.transform(0, 0);
+
+    transformedPoint.x -= origin.x;
+    transformedPoint.y -= origin.y;
+
+    // Derive the transformed vector's clockwise angle from vertical.
+    float result = atan2f(transformedPoint.x, -transformedPoint.y);
+    if (result < -M_PI_2) {
+        result += M_PI;
+    } else if (result > M_PI_2) {
+        result -= M_PI;
+    }
+    return result;
+}
+
+// Rotates the given point to the transform's orientation. If the display width and height are
+// provided, the point is rotated in the screen space. Otherwise, the point is rotated about the
+// origin. This helper is used to avoid the extra overhead of creating new Transforms.
+vec2 rotatePoint(const ui::Transform& transform, float x, float y, int32_t displayWidth = 0,
+                 int32_t displayHeight = 0) {
+    // 0x7 encapsulates all 3 rotations (see ui::Transform::RotationFlags)
+    static const int ALL_ROTATIONS_MASK = 0x7;
+    const uint32_t orientation = (transform.getOrientation() & ALL_ROTATIONS_MASK);
+    if (orientation == ui::Transform::ROT_0) {
+        return {x, y};
+    }
+
+    vec2 xy(x, y);
+    if (orientation == ui::Transform::ROT_90) {
+        xy.x = displayHeight - y;
+        xy.y = x;
+    } else if (orientation == ui::Transform::ROT_180) {
+        xy.x = displayWidth - x;
+        xy.y = displayHeight - y;
+    } else if (orientation == ui::Transform::ROT_270) {
+        xy.x = y;
+        xy.y = displayWidth - x;
+    }
+    return xy;
+}
+
+} // namespace
+
 const char* motionClassificationToString(MotionClassification classification) {
     switch (classification) {
         case MotionClassification::NONE:
@@ -315,9 +369,14 @@ void PointerCoords::copyFrom(const PointerCoords& other) {
 }
 
 void PointerCoords::transform(const ui::Transform& transform) {
-    vec2 newCoords = transform.transform(getX(), getY());
-    setAxisValue(AMOTION_EVENT_AXIS_X, newCoords.x);
-    setAxisValue(AMOTION_EVENT_AXIS_Y, newCoords.y);
+    const vec2 xy = transform.transform(getXYValue());
+    setAxisValue(AMOTION_EVENT_AXIS_X, xy.x);
+    setAxisValue(AMOTION_EVENT_AXIS_Y, xy.y);
+
+    if (BitSet64::hasBit(bits, AMOTION_EVENT_AXIS_ORIENTATION)) {
+        const float val = getAxisValue(AMOTION_EVENT_AXIS_ORIENTATION);
+        setAxisValue(AMOTION_EVENT_AXIS_ORIENTATION, transformAngle(transform, val));
+    }
 }
 
 // --- PointerProperties ---
@@ -444,45 +503,32 @@ const PointerCoords* MotionEvent::getHistoricalRawPointerCoords(
 }
 
 float MotionEvent::getHistoricalRawAxisValue(int32_t axis, size_t pointerIndex,
-        size_t historicalIndex) const {
-    if (axis != AMOTION_EVENT_AXIS_X && axis != AMOTION_EVENT_AXIS_Y) {
-        return getHistoricalRawPointerCoords(pointerIndex, historicalIndex)->getAxisValue(axis);
-    }
-    // 0x7 encapsulates all 3 rotations (see ui::Transform::RotationFlags)
-    static const int ALL_ROTATIONS_MASK = 0x7;
-    uint32_t orientation = (mTransform.getOrientation() & ALL_ROTATIONS_MASK);
-    if (orientation == ui::Transform::ROT_0) {
-        return getHistoricalRawPointerCoords(pointerIndex, historicalIndex)->getAxisValue(axis);
-    }
+                                             size_t historicalIndex) const {
+    const PointerCoords* coords = getHistoricalRawPointerCoords(pointerIndex, historicalIndex);
 
-    // For compatibility, convert raw coordinates into "oriented screen space". Once app developers
-    // are educated about getRaw, we can consider removing this.
-    vec2 xy = getHistoricalRawPointerCoords(pointerIndex, historicalIndex)->getXYValue();
-    const float unrotatedX = xy.x;
-    if (orientation == ui::Transform::ROT_90) {
-        xy.x = mDisplayHeight - xy.y;
-        xy.y = unrotatedX;
-    } else if (orientation == ui::Transform::ROT_180) {
-        xy.x = mDisplayWidth - xy.x;
-        xy.y = mDisplayHeight - xy.y;
-    } else if (orientation == ui::Transform::ROT_270) {
-        xy.x = xy.y;
-        xy.y = mDisplayWidth - unrotatedX;
+    if (axis == AMOTION_EVENT_AXIS_X || axis == AMOTION_EVENT_AXIS_Y) {
+        // For compatibility, convert raw coordinates into "oriented screen space". Once app
+        // developers are educated about getRaw, we can consider removing this.
+        const vec2 xy = rotatePoint(mTransform, coords->getX(), coords->getY(), mDisplayWidth,
+                                    mDisplayHeight);
+        static_assert(AMOTION_EVENT_AXIS_X == 0 && AMOTION_EVENT_AXIS_Y == 1);
+        return xy[axis];
     }
-    static_assert(AMOTION_EVENT_AXIS_X == 0 && AMOTION_EVENT_AXIS_Y == 1);
-    return xy[axis];
+
+    return coords->getAxisValue(axis);
 }
 
 float MotionEvent::getHistoricalAxisValue(int32_t axis, size_t pointerIndex,
         size_t historicalIndex) const {
-    if (axis != AMOTION_EVENT_AXIS_X && axis != AMOTION_EVENT_AXIS_Y) {
-        return getHistoricalRawPointerCoords(pointerIndex, historicalIndex)->getAxisValue(axis);
+    const PointerCoords* coords = getHistoricalRawPointerCoords(pointerIndex, historicalIndex);
+
+    if (axis == AMOTION_EVENT_AXIS_X || axis == AMOTION_EVENT_AXIS_Y) {
+        const vec2 xy = mTransform.transform(coords->getXYValue());
+        static_assert(AMOTION_EVENT_AXIS_X == 0 && AMOTION_EVENT_AXIS_Y == 1);
+        return xy[axis];
     }
 
-    vec2 vals = mTransform.transform(
-            getHistoricalRawPointerCoords(pointerIndex, historicalIndex)->getXYValue());
-    static_assert(AMOTION_EVENT_AXIS_X == 0 && AMOTION_EVENT_AXIS_Y == 1);
-    return vals[axis];
+    return coords->getAxisValue(axis);
 }
 
 ssize_t MotionEvent::findPointerIndex(int32_t pointerId) const {
@@ -513,78 +559,30 @@ void MotionEvent::scale(float globalScaleFactor) {
     }
 }
 
-static vec2 transformPoint(const std::array<float, 9>& matrix, float x, float y) {
-    // Apply perspective transform like Skia.
-    float newX = matrix[0] * x + matrix[1] * y + matrix[2];
-    float newY = matrix[3] * x + matrix[4] * y + matrix[5];
-    float newZ = matrix[6] * x + matrix[7] * y + matrix[8];
-    if (newZ) {
-        newZ = 1.0f / newZ;
-    }
-    vec2 transformedPoint;
-    transformedPoint.x = newX * newZ;
-    transformedPoint.y = newY * newZ;
-    return transformedPoint;
-}
-
-static float transformAngle(const std::array<float, 9>& matrix, float angleRadians, float originX,
-                            float originY) {
-    // Construct and transform a vector oriented at the specified clockwise angle from vertical.
-    // Coordinate system: down is increasing Y, right is increasing X.
-    float x = sinf(angleRadians);
-    float y = -cosf(angleRadians);
-    vec2 transformedPoint = transformPoint(matrix, x, y);
-
-    transformedPoint.x -= originX;
-    transformedPoint.y -= originY;
-
-    // Derive the transformed vector's clockwise angle from vertical.
-    float result = atan2f(transformedPoint.x, -transformedPoint.y);
-    if (result < - M_PI_2) {
-        result += M_PI;
-    } else if (result > M_PI_2) {
-        result -= M_PI;
-    }
-    return result;
-}
-
 void MotionEvent::transform(const std::array<float, 9>& matrix) {
-    // We want to preserve the rawX and rawY so we just update the transform
-    // using the values of the transform passed in
+    // We want to preserve the raw axes values stored in the PointerCoords, so we just update the
+    // transform using the values passed in.
     ui::Transform newTransform;
     newTransform.set(matrix);
     mTransform = newTransform * mTransform;
 
-    // Determine how the origin is transformed by the matrix so that we
-    // can transform orientation vectors.
-    vec2 origin = transformPoint(matrix, 0, 0);
-
-    // Apply the transformation to all samples.
-    size_t numSamples = mSamplePointerCoords.size();
-    for (size_t i = 0; i < numSamples; i++) {
-        PointerCoords& c = mSamplePointerCoords.editItemAt(i);
-        float orientation = c.getAxisValue(AMOTION_EVENT_AXIS_ORIENTATION);
-        c.setAxisValue(AMOTION_EVENT_AXIS_ORIENTATION,
-                       transformAngle(matrix, orientation, origin.x, origin.y));
-    }
+    // We need to update the AXIS_ORIENTATION value here to maintain the old behavior where the
+    // orientation angle is not affected by the initial transformation set in the MotionEvent.
+    std::for_each(mSamplePointerCoords.begin(), mSamplePointerCoords.end(),
+                  [&newTransform](PointerCoords& c) {
+                      float orientation = c.getAxisValue(AMOTION_EVENT_AXIS_ORIENTATION);
+                      c.setAxisValue(AMOTION_EVENT_AXIS_ORIENTATION,
+                                     transformAngle(newTransform, orientation));
+                  });
 }
 
 void MotionEvent::applyTransform(const std::array<float, 9>& matrix) {
-    // Determine how the origin is transformed by the matrix so that we
-    // can transform orientation vectors.
-    vec2 origin = transformPoint(matrix, 0, 0);
+    ui::Transform transform;
+    transform.set(matrix);
 
     // Apply the transformation to all samples.
-    size_t numSamples = mSamplePointerCoords.size();
-    for (size_t i = 0; i < numSamples; i++) {
-        PointerCoords& c = mSamplePointerCoords.editItemAt(i);
-        float orientation = c.getAxisValue(AMOTION_EVENT_AXIS_ORIENTATION);
-        c.setAxisValue(AMOTION_EVENT_AXIS_ORIENTATION,
-                       transformAngle(matrix, orientation, origin.x, origin.y));
-        vec2 xy = transformPoint(matrix, c.getX(), c.getY());
-        c.setAxisValue(AMOTION_EVENT_AXIS_X, xy.x);
-        c.setAxisValue(AMOTION_EVENT_AXIS_Y, xy.y);
-    }
+    std::for_each(mSamplePointerCoords.begin(), mSamplePointerCoords.end(),
+                  [&transform](PointerCoords& c) { c.transform(transform); });
 }
 
 #ifdef __linux__