CursorInputMapper: share acceleration curves with touchpad
The new touchpad mapper implemented in Android 14 replaced our simple
cursor movement acceleration curves (where the acceleration factor
increased linearly with speed between minimum and maximum values) with
more sophisticated multi-segment curves. However, cursor movement using
mice remained on the old curves. For consistency and to improve pointing
accuracy, use the same curves for mice, too.
This is also a good opportunity to improve the documentation comments
and naming now that I've wrapped my head around the maths a bit better.
Bug: 315313622
Test: atest inputflinger_tests
Test: check pointer movement with a mouse, including changing the
pointer speed setting and checking that the movement speed changes
Change-Id: Ifcf43f4de6017f06b66f37d5e03a13cc257d92d5
diff --git a/include/input/AccelerationCurve.h b/include/input/AccelerationCurve.h
new file mode 100644
index 0000000..0cf648a
--- /dev/null
+++ b/include/input/AccelerationCurve.h
@@ -0,0 +1,49 @@
+/*
+ * Copyright 2024 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 once
+
+#include <cstdint>
+#include <vector>
+
+namespace android {
+
+/**
+ * Describes a section of an acceleration curve as a function which outputs a scaling factor (gain)
+ * for the pointer movement, given the speed of the mouse or finger (in mm/s):
+ *
+ * gain(input_speed_mm_per_s) = baseGain + reciprocal / input_speed_mm_per_s
+ */
+struct AccelerationCurveSegment {
+ /**
+ * The maximum pointer speed at which this segment should apply, in mm/s. The last segment in a
+ * curve should always set this to infinity.
+ */
+ double maxPointerSpeedMmPerS;
+ /** The gain for this segment before the reciprocal is taken into account. */
+ double baseGain;
+ /** The reciprocal part of the formula, which should be divided by the input speed. */
+ double reciprocal;
+};
+
+/**
+ * Creates an acceleration curve for the given pointer sensitivity value. The sensitivity value
+ * should be between -7 (for the lowest sensitivity) and 7, inclusive.
+ */
+std::vector<AccelerationCurveSegment> createAccelerationCurveForPointerSensitivity(
+ int32_t sensitivity);
+
+} // namespace android