Rewrite touch navigation dpad synthesis.

The new implementation more accurately tracks the velocity
of flings and takes care to avoid obvious discontinuities.
The main goal is for a fling to appear to be a linear
extension of the movement already in progress.  The minimum
fling velocity is set to ensure that flings appear to be
fairly smooth despite being discretized.

Use sequences of repeated key events instead of individual
down/up events to represent continuous motions in one
direction which can be helpful for stopping flings at boundaries
such as when flinging the cursor position within a text view.

Compute the movement thresholds based on the physical
size of the touch pad, if known.  If not known, we assume a
nominal size.

Support stopping flings with a tap just like we do for
normal touch events elsewhere in the framework.

Moved the detection of ASSIST swipes into the InputReader
where it belongs.  These swipes must be detected globally
to ensure consistent behavior across the all applications.

Added a custom protocol in EventHub to enable input device
drivers to override the timestamp of the following events
in a packet.  This change enables input device drivers
that have a better idea of when an input event was actually
generated to pass this information to the input system.
Particularly useful with uinput.

Bug: 8583760
Change-Id: I8ef4e827804786d549cfaa00793a2b9dd0fda465
diff --git a/services/input/EventHub.h b/services/input/EventHub.h
index afc12ef..c93fc7a 100644
--- a/services/input/EventHub.h
+++ b/services/input/EventHub.h
@@ -42,6 +42,20 @@
 #define BTN_FIRST 0x100  // first button code
 #define BTN_LAST 0x15f   // last button code
 
+/*
+ * These constants are used privately in Android to pass raw timestamps
+ * through evdev from uinput device drivers because there is currently no
+ * other way to transfer this information.  The evdev driver automatically
+ * timestamps all input events with the time they were posted and clobbers
+ * whatever information was passed in.
+ *
+ * For the purposes of this hack, the timestamp is specified in the
+ * CLOCK_MONOTONIC timebase and is split into two EV_MSC events specifying
+ * seconds and microseconds.
+ */
+#define MSC_ANDROID_TIME_SEC 0x6
+#define MSC_ANDROID_TIME_USEC 0x7
+
 namespace android {
 
 enum {
@@ -329,6 +343,9 @@
         bool ffEffectPlaying;
         int16_t ffEffectId; // initially -1
 
+        int32_t timestampOverrideSec;
+        int32_t timestampOverrideUsec;
+
         Device(int fd, int32_t id, const String8& path, const InputDeviceIdentifier& identifier);
         ~Device();