diff mbox

[2/2] input: appletouch: use better cursor movement smoothing algorithm

Message ID 52CF38A2.3020103@gmail.com (mailing list archive)
State New, archived
Headers show

Commit Message

Clinton Sprain Jan. 10, 2014, 12:02 a.m. UTC 
From: Clinton Sprain <clintonsprain@gmail.com>

Implements a new algorithm used to smooth cursor movement, using the inertia
of the cursor's prior movements to modulate the next cursor movement. This
further mitigates the 'stepping' users see when moving the cursor diagonally.
A 'legacy' module parameter has been added in case the older devices do not
like the new algorithm.

Signed-Off-By: Clinton Sprain <clintonsprain@gmail.com>
---
 drivers/input/mouse/appletouch.c |  118 ++++++++++++++++++++++++++++++++------
 1 file changed, 100 insertions(+), 18 deletions(-)

--
1.7.9.5

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diff mbox

Patch

diff --git a/drivers/input/mouse/appletouch.c b/drivers/input/mouse/appletouch.c
index ba6bbd7..7a33188 100644
--- a/drivers/input/mouse/appletouch.c
+++ b/drivers/input/mouse/appletouch.c
@@ -209,13 +209,16 @@  struct atp {
 	bool			overflow_warned;
 	int			x_old;		/* last reported x/y, */
 	int			y_old;		/* used for smoothing */
+	int			x_older;	/* 2nd to last reported x/y,*/
+	int			y_older;	/* used for smoothing */
+	int			x_oldest;       /* 3rd to last reported x/y,*/
+	int			y_oldest;       /* used for smoothing */
 	signed char		xy_cur[ATP_XSENSORS + ATP_YSENSORS];
 	signed char		xy_old[ATP_XSENSORS + ATP_YSENSORS];
 	int			xy_acc[ATP_XSENSORS + ATP_YSENSORS];
 	int			idlecount;	/* number of empty packets */
 	struct work_struct	work;
 };
-
 #define dbg_dump(msg, tab)						\
 {									\
 	if (debug > 1) {						\
@@ -260,6 +263,13 @@  static int debug;
 module_param(debug, int, 0644);
 MODULE_PARM_DESC(debug, "Activate debugging output");

+static int legacy;
+module_param(legacy, int, 0644);
+MODULE_PARM_DESC(legacy, "1 = Use old cursor movement smoothing."
+			 " Older behavior averages current with"
+			 " last cursor position. New behavior"
+			 " uses cursor movement inertia.");
+
 /*
  * By default newer Geyser devices send standard USB HID mouse
  * packets (Report ID 2). This code changes device mode, so it
@@ -338,6 +348,59 @@  static void atp_reinit(struct work_struct *work)
 			retval);
 }

+static int atp_smooth_legacy(int curr, int old)
+{
+	return ((old * 3) + curr) >> 2;
+}
+
+static int atp_smooth(int curr, int old, int older, int oldest)
+{
+	int diff, projected, olderprojected, smooth;
+
+	diff = old - older;
+	projected = old + diff;
+
+	diff = older - oldest;
+	olderprojected = older + diff;
+
+	smooth = (projected * 7 + olderprojected * 8 + curr) >> 4;
+
+	return smooth;
+}
+
+static void atp_refresh_old_xy(int x, int y, struct atp *dev)
+{
+	if (legacy != true) {
+		dev->x_oldest = dev->x_older;
+		dev->y_oldest = dev->y_older;
+		dev->x_older = dev->x_old;
+		dev->y_older = dev->y_old;
+	}
+	dev->x_old = x;
+	dev->y_old = y;
+}
+
+static void atp_reset_old_xy(struct atp *dev)
+{
+	if (legacy != true) {
+		dev->x_oldest = dev->y_oldest = -1;
+		dev->x_older = dev->y_older = -1;
+	}
+	dev->x_old = dev->y_old = -1;
+}
+
+static void atp_default_old_xy(struct atp *dev)
+{
+	if (dev->x_older == -1)
+		dev->x_older = dev->x_old;
+	if (dev->y_older == -1)
+		dev->y_older = dev->y_old;
+	if (dev->x_oldest == -1)
+		dev->x_oldest = dev->x_older;
+	if (dev->y_oldest == -1)
+		dev->y_oldest = dev->y_older;
+}
+
 static int atp_calculate_abs(int *xy_sensors, int nb_sensors, int fact,
 			     int *z, int *fingers)
 {
@@ -386,8 +449,13 @@  static int atp_calculate_abs(int *xy_sensors, int nb_sensors, int fact,
 		 * occasionally jump a number of pixels (slowly moving the
 		 * finger makes this issue most apparent.)
 		 */
-		pcum += (xy_sensors[i] - threshold) * i;
-		psum += (xy_sensors[i] - threshold);
+		if (legacy == true) {
+			pcum += (xy_sensors[i] - threshold) * i;
+			psum += (xy_sensors[i] - threshold);
+		} else {
+			pcum += (xy_sensors[i]) * i;
+			psum += (xy_sensors[i]);
+		}
 	}

 	if (psum > 0) {
@@ -570,10 +638,18 @@  static void atp_complete_geyser_1_2(struct urb *urb)

 	if (x && y) {
 		if (dev->x_old != -1) {
-			x = (dev->x_old * 3 + x) >> 2;
-			y = (dev->y_old * 3 + y) >> 2;
-			dev->x_old = x;
-			dev->y_old = y;
+			if (legacy == true) {
+				x = atp_smooth_legacy(x, dev->x_old);
+				y = atp_smooth_legacy(y, dev->y_old);
+			} else {
+
+				atp_default_old_xy(dev);
+
+				x = atp_smooth(x, dev->x_old,
+					dev->x_older, dev->x_oldest);
+				y = atp_smooth(y, dev->y_old,
+					dev->y_older, dev->y_oldest);
+			}

 			if (debug > 1)
 				printk(KERN_DEBUG "appletouch: "
@@ -587,12 +663,11 @@  static void atp_complete_geyser_1_2(struct urb *urb)
 					 min(ATP_PRESSURE, x_z + y_z));
 			atp_report_fingers(dev->input, max(x_f, y_f));
 		}
-		dev->x_old = x;
-		dev->y_old = y;
+		atp_refresh_old_xy(x, y, dev);

 	} else if (!x && !y) {

-		dev->x_old = dev->y_old = -1;
+		atp_reset_old_xy(dev);
 		input_report_key(dev->input, BTN_TOUCH, 0);
 		input_report_abs(dev->input, ABS_PRESSURE, 0);
 		atp_report_fingers(dev->input, 0);
@@ -682,10 +757,18 @@  static void atp_complete_geyser_3_4(struct urb *urb)

 	if (x && y) {
 		if (dev->x_old != -1) {
-			x = (dev->x_old * 3 + x) >> 2;
-			y = (dev->y_old * 3 + y) >> 2;
-			dev->x_old = x;
-			dev->y_old = y;
+			if (legacy == true) {
+				x = atp_smooth_legacy(x, dev->x_old);
+				y = atp_smooth_legacy(y, dev->y_old);
+			} else {
+
+				atp_default_old_xy(dev);
+
+				x = atp_smooth(x, dev->x_old,
+					dev->x_older, dev->x_oldest);
+				y = atp_smooth(y, dev->y_old,
+					dev->y_older, dev->y_oldest);
+			}

 			if (debug > 1)
 				printk(KERN_DEBUG "appletouch: X: %3d Y: %3d "
@@ -699,12 +782,11 @@  static void atp_complete_geyser_3_4(struct urb *urb)
 					 min(ATP_PRESSURE, x_z + y_z));
 			atp_report_fingers(dev->input, max(x_f, y_f));
 		}
-		dev->x_old = x;
-		dev->y_old = y;
+		atp_refresh_old_xy(x, y, dev);

 	} else if (!x && !y) {

-		dev->x_old = dev->y_old = -1;
+		atp_reset_old_xy(dev);
 		input_report_key(dev->input, BTN_TOUCH, 0);
 		input_report_abs(dev->input, ABS_PRESSURE, 0);
 		atp_report_fingers(dev->input, 0);
@@ -730,7 +812,7 @@  static void atp_complete_geyser_3_4(struct urb *urb)
 	if (!x && !y && !key) {
 		dev->idlecount++;
 		if (dev->idlecount == 10) {
-			dev->x_old = dev->y_old = -1;
+			atp_reset_old_xy(dev);
 			dev->idlecount = 0;
 			schedule_work(&dev->work);
 			/* Don't resubmit urb here, wait for reinit */