Replace ChromeOS pointer ballistics with Android-specific ones
This are the initial curve suggested by UX research, and is still
subject to tweaks and changes if I understand correctly.
Bug: 265798483
Test: manual
Change-Id: Ie45379f8d2340311b1e2f10b1cc04f61efefb0bd
(cherry picked from commit 4f18a6e2a6c49ea56a5fd7d4a373ddd7c766ed6f)
Merged-In: Ie45379f8d2340311b1e2f10b1cc04f61efefb0bd
diff --git a/services/inputflinger/reader/mapper/TouchpadInputMapper.cpp b/services/inputflinger/reader/mapper/TouchpadInputMapper.cpp
index 9f32311..8ab6748 100644
--- a/services/inputflinger/reader/mapper/TouchpadInputMapper.cpp
+++ b/services/inputflinger/reader/mapper/TouchpadInputMapper.cpp
@@ -16,6 +16,7 @@
#include "../Macros.h"
+#include <limits>
#include <optional>
#include <android/input.h>
@@ -30,6 +31,76 @@
namespace {
+// Describes a segment of the acceleration curve.
+struct CurveSegment {
+ // The maximum pointer speed which this segment should apply. The last segment in a curve should
+ // always set this to infinity.
+ double maxPointerSpeedMmPerS;
+ double slope;
+ double intercept;
+};
+
+const std::vector<CurveSegment> segments = {
+ {10.922, 3.19, 0},
+ {31.750, 4.79, -17.526},
+ {98.044, 7.28, -96.52},
+ {std::numeric_limits<double>::infinity(), 15.04, -857.758},
+};
+
+const std::vector<double> sensitivityFactors = {1, 2, 4, 5, 6, 7, 8, 9, 10, 11, 12, 14, 16, 18, 20};
+
+std::vector<double> createAccelerationCurveForSensitivity(int32_t sensitivity,
+ size_t propertySize) {
+ LOG_ALWAYS_FATAL_IF(propertySize < 4 * segments.size());
+ std::vector<double> output(propertySize, 0);
+
+ // The Gestures library uses functions of the following form to define curve segments, where a,
+ // b, and c can be specified by us:
+ // output_speed(input_speed_mm) = a * input_speed_mm ^ 2 + b * input_speed_mm + c
+ //
+ // (a, b, and c are also called sqr_, mul_, and int_ in the Gestures library code.)
+ //
+ // We are trying to implement the following function, where slope and intercept are the
+ // parameters specified in the `segments` array above:
+ // gain(input_speed_mm) =
+ // 0.64 * (sensitivityFactor / 10) * (slope + intercept / input_speed_mm)
+ // Where "gain" is a multiplier applied to the input speed to produce the output speed:
+ // output_speed(input_speed_mm) = input_speed_mm * gain(input_speed_mm)
+ //
+ // To put our function in the library's form, we substitute it into the function above:
+ // output_speed(input_speed_mm) =
+ // input_speed_mm * (0.64 * (sensitivityFactor / 10) *
+ // (slope + 25.4 * intercept / input_speed_mm))
+ // then expand the brackets so that input_speed_mm cancels out for the intercept term:
+ // gain(input_speed_mm) =
+ // 0.64 * (sensitivityFactor / 10) * slope * input_speed_mm +
+ // 0.64 * (sensitivityFactor / 10) * intercept
+ //
+ // This gives us the following parameters for the Gestures library function form:
+ // a = 0
+ // b = 0.64 * (sensitivityFactor / 10) * slope
+ // c = 0.64 * (sensitivityFactor / 10) * intercept
+
+ double commonFactor = 0.64 * sensitivityFactors[sensitivity + 7] / 10;
+
+ size_t i = 0;
+ for (CurveSegment seg : segments) {
+ // The library's curve format consists of four doubles per segment:
+ // * maximum pointer speed for the segment (mm/s)
+ // * multiplier for the x² term (a.k.a. "a" or "sqr")
+ // * multiplier for the x term (a.k.a. "b" or "mul")
+ // * the intercept (a.k.a. "c" or "int")
+ // (see struct CurveSegment in the library's AccelFilterInterpreter)
+ output[i + 0] = seg.maxPointerSpeedMmPerS;
+ output[i + 1] = 0;
+ output[i + 2] = commonFactor * seg.slope;
+ output[i + 3] = commonFactor * seg.intercept;
+ i += 4;
+ }
+
+ return output;
+}
+
short getMaxTouchCount(const InputDeviceContext& context) {
if (context.hasScanCode(BTN_TOOL_QUINTTAP)) return 5;
if (context.hasScanCode(BTN_TOOL_QUADTAP)) return 4;
@@ -147,10 +218,12 @@
mGestureConverter.setOrientation(orientation);
}
if (!changes || (changes & InputReaderConfiguration::CHANGE_TOUCHPAD_SETTINGS)) {
- // TODO(b/265798483): load an Android-specific acceleration curve instead of mapping to one
- // of five ChromeOS curves.
- const int pointerSensitivity = (config->touchpadPointerSpeed + 7) / 3 + 1;
- mPropertyProvider.getProperty("Pointer Sensitivity").setIntValues({pointerSensitivity});
+ mPropertyProvider.getProperty("Use Custom Touchpad Pointer Accel Curve")
+ .setBoolValues({true});
+ GesturesProp accelCurveProp = mPropertyProvider.getProperty("Pointer Accel Curve");
+ accelCurveProp.setRealValues(
+ createAccelerationCurveForSensitivity(config->touchpadPointerSpeed,
+ accelCurveProp.getCount()));
mPropertyProvider.getProperty("Invert Scrolling")
.setBoolValues({config->touchpadNaturalScrollingEnabled});
mPropertyProvider.getProperty("Tap Enable")