1 files changed, 110 insertions, 0 deletions
diff --git a/widget/gonk/libui/VelocityControl.cpp b/widget/gonk/libui/VelocityControl.cpp
new file mode 100644
index 000000000..31365a220
--- /dev/null
+++ b/widget/gonk/libui/VelocityControl.cpp
@@ -0,0 +1,110 @@
+/*
+ * Copyright (C) 2012 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 "VelocityControl"
+//#define LOG_NDEBUG 0
+
+// Log debug messages about acceleration.
+#define DEBUG_ACCELERATION 0
+
+#include <math.h>
+#include <limits.h>
+
+#include "VelocityControl.h"
+#include <utils/BitSet.h>
+#include <utils/Timers.h>
+
+namespace android {
+
+// --- VelocityControl ---
+
+const nsecs_t VelocityControl::STOP_TIME;
+
+VelocityControl::VelocityControl() {
+    reset();
+}
+
+void VelocityControl::setParameters(const VelocityControlParameters& parameters) {
+    mParameters = parameters;
+    reset();
+}
+
+void VelocityControl::reset() {
+    mLastMovementTime = LLONG_MIN;
+    mRawPosition.x = 0;
+    mRawPosition.y = 0;
+    mVelocityTracker.clear();
+}
+
+void VelocityControl::move(nsecs_t eventTime, float* deltaX, float* deltaY) {
+    if ((deltaX && *deltaX) || (deltaY && *deltaY)) {
+        if (eventTime >= mLastMovementTime + STOP_TIME) {
+#if DEBUG_ACCELERATION
+            ALOGD("VelocityControl: stopped, last movement was %0.3fms ago",
+                    (eventTime - mLastMovementTime) * 0.000001f);
+#endif
+            reset();
+        }
+
+        mLastMovementTime = eventTime;
+        if (deltaX) {
+            mRawPosition.x += *deltaX;
+        }
+        if (deltaY) {
+            mRawPosition.y += *deltaY;
+        }
+        mVelocityTracker.addMovement(eventTime, BitSet32(BitSet32::valueForBit(0)), &mRawPosition);
+
+        float vx, vy;
+        float scale = mParameters.scale;
+        if (mVelocityTracker.getVelocity(0, &vx, &vy)) {
+            float speed = hypotf(vx, vy) * scale;
+            if (speed >= mParameters.highThreshold) {
+                // Apply full acceleration above the high speed threshold.
+                scale *= mParameters.acceleration;
+            } else if (speed > mParameters.lowThreshold) {
+                // Linearly interpolate the acceleration to apply between the low and high
+                // speed thresholds.
+                scale *= 1 + (speed - mParameters.lowThreshold)
+                        / (mParameters.highThreshold - mParameters.lowThreshold)
+                        * (mParameters.acceleration - 1);
+            }
+
+#if DEBUG_ACCELERATION
+            ALOGD("VelocityControl(%0.3f, %0.3f, %0.3f, %0.3f): "
+                    "vx=%0.3f, vy=%0.3f, speed=%0.3f, accel=%0.3f",
+                    mParameters.scale, mParameters.lowThreshold, mParameters.highThreshold,
+                    mParameters.acceleration,
+                    vx, vy, speed, scale / mParameters.scale);
+#endif
+        } else {
+#if DEBUG_ACCELERATION
+            ALOGD("VelocityControl(%0.3f, %0.3f, %0.3f, %0.3f): unknown velocity",
+                    mParameters.scale, mParameters.lowThreshold, mParameters.highThreshold,
+                    mParameters.acceleration);
+#endif
+        }
+
+        if (deltaX) {
+            *deltaX *= scale;
+        }
+        if (deltaY) {
+            *deltaY *= scale;
+        }
+    }
+}
+
+} // namespace android