wcmTouchFilter.c

/*
 * Copyright 2009 - 2013 by Ping Cheng, Wacom. <pingc@wacom.com>
 * Copyright 2011 by Alexey Osipov. <simba@lerlan.ru>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 */

#include <config.h>

#include "xf86Wacom.h"
#include "wcmTouchFilter.h"
#include <math.h>

/* Defines for 2FC Gesture */
#define WACOM_HORIZ_ALLOWED           1
#define WACOM_VERT_ALLOWED            2
#define WACOM_GESTURE_LAG_TIME       10

#define GESTURE_NONE_MODE             0
#define GESTURE_TAP_MODE              1
#define GESTURE_SCROLL_MODE           2
#define GESTURE_ZOOM_MODE             4
#define GESTURE_LAG_MODE              8
#define GESTURE_PREDRAG_MODE         16
#define GESTURE_DRAG_MODE            32
#define GESTURE_CANCEL_MODE          64
#define GESTURE_MULTITOUCH_MODE     128

#define WCM_SCROLL_UP                 5	/* vertical up */
#define WCM_SCROLL_DOWN               4	/* vertical down */
#define WCM_SCROLL_LEFT               6	/* horizontal left */
#define WCM_SCROLL_RIGHT              7	/* horizontal right */

static void wcmSendButtonClick(WacomDevicePtr priv, int button, int state);
static void wcmFingerScroll(WacomDevicePtr priv);
static void wcmFingerZoom(WacomDevicePtr priv);

/**
 * Returns a pointer to the channel associated with the given contact
 * number. The first contact made in a gesture will be number zero,
 * the second number one, and so on.
 *
 * @param[in] common
 * @param[in] num     Contact number to search for
 * @return            Pointer to the associated channel, or NULL if none found
 */
static WacomChannelPtr getContactNumber(WacomCommonPtr common, unsigned int num)
{
	for (size_t i = 0; i < MAX_CHANNELS; i++)
	{
		WacomChannelPtr channel = common->wcmChannel+i;
		WacomDeviceState state  = channel->valid.state;
		if (state.device_type == TOUCH_ID && state.serial_num == num + 1)
			return channel;
	}

	DBG(10, common, "Channel for contact number %u not found.\n", num);
	return NULL;
}

/**
 * Returns the device state for the first num contacts with specified
 * age.
 *
 * @param[in]  common
 * @param[out] states  List of device states to fill with history
 * @param[in]  num     Length of states list
 * @param[in]  age     Age of state information, zero being the most-current
 */
static void getStateHistory(WacomCommonPtr common, WacomDeviceState states[], unsigned int num, unsigned int age)
{
	for (unsigned int i = 0; i < num; i++)
	{
		WacomChannelPtr channel = getContactNumber(common, i);
		if (channel == NULL || i > ARRAY_SIZE(channel->valid.states))
		{
			DBG(7, common, "Could not get state history for contact %u, age %u.\n", i, age);
			continue;
		}
		states[i] = channel->valid.states[age];
	}
}

/**
 * Send a touch event for the provided contact ID. This makes use of
 * the multitouch API available in XI2.2.
 *
 * @param[in] priv
 * @param[in] channel    Channel to send a touch event for
 * @param[in] no_update  If 'true', TouchUpdate events will not be created.
 * This should be used when entering multitouch mode to ensure TouchBegin
 * events are sent for already-in-prox contacts.
 */
static void
wcmSendTouchEvent(WacomDevicePtr priv, WacomChannelPtr channel, Bool no_update)
{
	WacomDeviceState state = channel->valid.state;
	WacomDeviceState oldstate = channel->valid.states[1];
	int type = -1;

	wcmRotateAndScaleCoordinates (priv, &state.x, &state.y);

	if (!state.proximity) {
		DBG(6, priv->common, "This is a touch end event\n");
		type = XI_TouchEnd;
	}
	else if (!oldstate.proximity || no_update) {
		DBG(6, priv->common, "This is a touch begin event\n");
		type = XI_TouchBegin;
	}
	else {
		DBG(6, priv->common, "This is a touch update event\n");
		type = XI_TouchUpdate;
	}

	wcmEmitTouch(priv, type, state.serial_num - 1, state.x, state.y);
}

/**
 * Send multitouch events. If entering multitouch mode (indicated by
 * GESTURE_LAG_MODE), then touch events are sent for all in-prox
 * contacts. Otherwise, only the specified contact has a touch event
 * generated.
 *
 * @param[in] priv
 * @param[in] contact_id  ID of the contact to send event for (at minimum)
 */
static void
wcmFingerMultitouch(WacomDevicePtr priv, unsigned int contact_id) {
	Bool lag_mode = priv->common->wcmGestureMode == GESTURE_LAG_MODE;
	Bool prox = FALSE;

	for (size_t i = 0; i < MAX_CHANNELS; i++) {
		WacomChannelPtr channel = priv->common->wcmChannel+i;
		WacomDeviceState state  = channel->valid.state;
		if (state.device_type != TOUCH_ID)
			continue;

		if (lag_mode || state.serial_num == contact_id + 1) {
			wcmSendTouchEvent(priv, channel, lag_mode);
		}

		prox |= state.proximity;
	}

	if (!prox)
		priv->common->wcmGestureMode = GESTURE_NONE_MODE;
	else if (lag_mode)
		priv->common->wcmGestureMode = GESTURE_MULTITOUCH_MODE;
}

static double touchDistance(WacomDeviceState ds0, WacomDeviceState ds1)
{
	int xDelta = ds0.x - ds1.x;
	int yDelta = ds0.y - ds1.y;
	double distance = sqrt((double)(xDelta*xDelta + yDelta*yDelta));
	return distance;
}

static Bool vectorsSameDirection(WacomCommonPtr common, WacomDeviceState ds00,
		WacomDeviceState ds01, WacomDeviceState ds10, WacomDeviceState ds11)
{
	float dx0 = ds01.x - ds00.x;
	float dy0 = ds01.y - ds00.y;
	float m0 = sqrt(dx0*dx0 + dy0*dy0);
	float dx1 = ds11.x - ds10.x;
	float dy1 = ds11.y - ds10.y;
	float m1 = sqrt(dx1*dx1 + dy1*dy1);

	float dot = (dx0/m0 * dx1/m1) + (dy0/m0 * dy1/m1);
	float angle = acos(dot);

	return angle < (3.141592f / 2);
}

static Bool pointsInLine(WacomCommonPtr common, WacomDeviceState ds0,
		WacomDeviceState ds1)
{
	Bool ret = FALSE;
	Bool rotated = common->wcmRotate == ROTATE_CW ||
			common->wcmRotate == ROTATE_CCW;
	unsigned int horizon_rotated = (rotated) ?
			WACOM_HORIZ_ALLOWED : WACOM_VERT_ALLOWED;
	unsigned int vertical_rotated = (rotated) ?
			WACOM_VERT_ALLOWED : WACOM_HORIZ_ALLOWED;
	unsigned int scroll_threshold = common->wcmGestureParameters.wcmScrollDistance;
	unsigned int dx = abs(ds0.x - ds1.x);
	unsigned int dy = abs(ds0.y - ds1.y);

	if (!common->wcmGestureParameters.wcmScrollDirection)
	{
		if (dx < scroll_threshold && dy > scroll_threshold)
		{
			common->wcmGestureParameters.wcmScrollDirection = horizon_rotated;
			ret = TRUE;
		}
		if (dy < scroll_threshold && dx > scroll_threshold)
		{
			common->wcmGestureParameters.wcmScrollDirection = vertical_rotated;
			ret = TRUE;
		}
	}
	else if (common->wcmGestureParameters.wcmScrollDirection == vertical_rotated)
	{
		if (dy < scroll_threshold)
			ret = TRUE;
	}
	else if (common->wcmGestureParameters.wcmScrollDirection == horizon_rotated)
	{
		if (dx < scroll_threshold)
			ret = TRUE;
	}
	return ret;
}

/* send a button event */
static void wcmSendButtonClick(WacomDevicePtr priv, int button, int state)
{
	int mode = is_absolute(priv);
	WacomAxisData axes = {0};

	/* send button event in state */
	wcmEmitButton(priv, mode, button, state, &axes);

	/* We have changed the button state (from down to up) for the device
	 * so we need to update the record */
	if (button == 1)
		priv->oldState.buttons = 0;
}

/*****************************************************************************
 *   translate second finger tap to right click
 ****************************************************************************/

static void wcmFingerTapToClick(WacomDevicePtr priv)
{
	WacomCommonPtr common = priv->common;
	WacomDeviceState ds[2] = {}, dsLast[2] = {};

	if (!common->wcmGesture)
		return;

	getStateHistory(common, ds, ARRAY_SIZE(ds), 0);
	getStateHistory(common, dsLast, ARRAY_SIZE(dsLast), 1);

	DBG(10, priv, "\n");

	/* process second finger tap if matched */
	if ((ds[0].sample < ds[1].sample) &&
	    ((wcmTimeInMillis() -
	    dsLast[1].sample) <= common->wcmGestureParameters.wcmTapTime) &&
	    !ds[1].proximity && dsLast[1].proximity)
	{
		/* send left up before sending right down */
		wcmSendButtonClick(priv, 1, 0);
		common->wcmGestureMode = GESTURE_TAP_MODE;

		/* right button down */
		wcmSendButtonClick(priv, 3, 1);

		/* right button up */
		wcmSendButtonClick(priv, 3, 0);
	}
}

static uint32_t wcmSingleFingerTapTimer(WacomTimerPtr timer, uint32_t time, pointer arg)
{
	WacomDevicePtr priv = (WacomDevicePtr)arg;
	WacomCommonPtr common = priv->common;

	if (common->wcmGestureMode == GESTURE_PREDRAG_MODE)
	{
		/* left button down */
		wcmSendButtonClick(priv, 1, 1);

		/* left button up */
		wcmSendButtonClick(priv, 1, 0);
		common->wcmGestureMode = GESTURE_NONE_MODE;
	}

	return 0;
}

/* A single finger tap is defined as 1 finger tap that lasts less than
 * wcmTapTime.  It results in a left button press.
 *
 * Some work must be done to make sure two fingers were not touching
 * during this gesture. This is easy if first finger is released
 * first.  To handle case of second finger released first, require
 * second finger to have been released before first finger ever touched.
 *
 * Function relies on ds[0/1].sample to be updated only when entering or
 * exiting proximity so no storage is needed when initial touch occurs.
 */
static void wcmSingleFingerTap(WacomDevicePtr priv)
{
	WacomCommonPtr common = priv->common;
	WacomDeviceState ds[2] = {}, dsLast[2] = {};

	getStateHistory(common, ds, ARRAY_SIZE(ds), 0);
	getStateHistory(common, dsLast, ARRAY_SIZE(dsLast), 1);

	DBG(10, priv, "\n");

	/* This gesture is only valid on touchpads. */
	if (TabletHasFeature(priv->common, WCM_LCD))
		return;

	if (!ds[0].proximity && dsLast[0].proximity && !ds[1].proximity)
	{
		/* Single Tap must have lasted less than wcmTapTime
		 * and second finger must not have released after
		 * first finger touched.
		 */
		if (ds[0].sample - dsLast[0].sample <=
		    common->wcmGestureParameters.wcmTapTime &&
		    ds[1].sample < dsLast[0].sample)
		{
			common->wcmGestureMode = GESTURE_PREDRAG_MODE;

			/* Delay to detect possible drag operation */
			wcmTimerSet(priv->tap_timer, common->wcmGestureParameters.wcmTapTime,
				    wcmSingleFingerTapTimer, priv);
		}
	}
}

/* Monitors for 1 finger touch and forces left button press or 1 finger
 * release and will remove left button press.
 *
 * This function relies on wcmGestureMode will only be zero if
 * WACOM_GESTURE_LAG_TIME has passed and still ony 1 finger on screen.
 */
static void wcmSingleFingerPress(WacomDevicePtr priv)
{
	WacomCommonPtr common = priv->common;
	WacomChannelPtr firstChannel = getContactNumber(common, 0);
	WacomChannelPtr secondChannel = getContactNumber(common, 1);
	Bool firstInProx = firstChannel && firstChannel->valid.states[0].proximity;
	Bool secondInProx = secondChannel && secondChannel->valid.states[0].proximity;

	DBG(10, priv, "\n");

	/* This gesture is only valid on touchscreens. */
	if (!TabletHasFeature(priv->common, WCM_LCD))
		return;

	if (!firstChannel)
		return;

	if (firstInProx && !secondInProx) {
		firstChannel->valid.states[0].buttons |= 1;
		common->wcmGestureMode = GESTURE_DRAG_MODE;
	}
	else {
		firstChannel->valid.states[0].buttons &= ~1;
		common->wcmGestureMode = GESTURE_NONE_MODE;
	}
}


/**
 * Cancel any in-progress gesture, returning to GESTURE_NONE_MODE until new
 * fingers enter proximity.
 */
void wcmCancelGesture(WacomDevicePtr priv)
{
	WacomCommonPtr common = priv->common;

	if (!IsTouch(priv))
		return;

	if (common->wcmGestureMode == GESTURE_DRAG_MODE)
		wcmSendButtonClick(priv, 1, 0);
	common->wcmGestureMode = GESTURE_CANCEL_MODE;
}

/* parsing gesture mode according to 2FGT data */
void wcmGestureFilter(WacomDevicePtr priv, unsigned int touch_id)
{
	WacomCommonPtr common = priv->common;
	WacomDeviceState ds[2] = {}, dsLast[2] = {};

	getStateHistory(common, ds, ARRAY_SIZE(ds), 0);
	getStateHistory(common, dsLast, ARRAY_SIZE(dsLast), 1);

	DBG(10, priv, "\n");

	if (!IsTouch(priv))
	{
		/* this should never happen */
		wcmLogSafe(priv, W_ERROR, "WACOM: No touch device found for %s \n",
			 common->device_path);
		return;
	}

	/* Send multitouch data to X if appropriate */
	if (!common->wcmGesture) {
		switch (common->wcmGestureMode) {
		case GESTURE_CANCEL_MODE:
			break;
		case GESTURE_NONE_MODE:
			if (TabletHasFeature(common, WCM_LCD))
				common->wcmGestureMode = GESTURE_MULTITOUCH_MODE;
			else if (ds[1].proximity)
				common->wcmGestureMode = GESTURE_LAG_MODE;
			_fallthrough_;
		case GESTURE_LAG_MODE:
		case GESTURE_MULTITOUCH_MODE:
			if (common->wcmGestureMode != GESTURE_NONE_MODE)
				wcmFingerMultitouch(priv, touch_id);
			break;
		default:
			wcmCancelGesture(priv);
			break;
		}
	}
	if (common->wcmGestureMode == GESTURE_MULTITOUCH_MODE)
		return;

	/* Do not process gestures while in CANCEL mode. Only reset back to
	 * NONE mode once all fingers have left the screen.
	 */
	if (common->wcmGestureMode == GESTURE_CANCEL_MODE)
	{
		if (ds[0].proximity || ds[1].proximity)
			return;
		else
			common->wcmGestureMode = GESTURE_NONE_MODE;
	}

	/* When 2 fingers are in proximity, it must always be in one of
	 * the valid 2 fingers modes: LAG, SCROLL, or ZOOM.
	 * LAG mode is used while deciding between SCROLL and ZOOM and
	 * prevents cursor movement.  Force to LAG mode if ever in NONE
	 * mode to stop cursor movement.
	 */
	if (ds[0].proximity && ds[1].proximity)
	{
		if (common->wcmGestureMode == GESTURE_NONE_MODE)
			common->wcmGestureMode = GESTURE_LAG_MODE;
	}
	/* If we're in a multitouch mode but two fingers aren't in proximity
	 * we should directly head to CANCEL mode and wait for both fingers
	 * to leave the screen.
	 */
	else if (common->wcmGestureMode & (GESTURE_SCROLL_MODE | GESTURE_ZOOM_MODE))
	{
		common->wcmGestureMode = GESTURE_CANCEL_MODE;
	}
	/* When only 1 finger is in proximity, it can be in either LAG mode,
	 * NONE mode or DRAG mode.
	 * 1 finger LAG mode is a very short time period mainly to debounce
	 * initial touch.
	 * NONE and DRAG mode means cursor is allowed to move around.
	 * DRAG mode in addition means that left button pressed.
	 * There is no need to bother about LAG_TIME while in DRAG mode.
	 * TODO: This has to use dsLast[0] because of later logic that
	 * wants mode to be NONE still when 1st entering proximity.
	 * That could use some re-arranging/cleanup.
	 *
	 */
	else if (dsLast[0].proximity && common->wcmGestureMode != GESTURE_DRAG_MODE)
	{
		CARD32 ms = wcmTimeInMillis();

		if ((ms - ds[0].sample) < WACOM_GESTURE_LAG_TIME)
		{
			/* Must have recently come into proximity.  Change
			 * into LAG mode.
			 */
			if (common->wcmGestureMode == GESTURE_NONE_MODE)
				common->wcmGestureMode = GESTURE_LAG_MODE;
		}
		else
		{
			/* Been in LAG mode long enough. Force to NONE mode. */
			common->wcmGestureMode = GESTURE_NONE_MODE;
		}
	}

	if  (ds[1].proximity && !dsLast[1].proximity)
	{
		/* keep the initial states for gesture mode */
		common->wcmGestureState[1] = ds[1];

		/* reset the initial count for a new getsure */
		common->wcmGestureParameters.wcmGestureUsed  = 0;
	}

	if (ds[0].proximity && !dsLast[0].proximity)
	{
		/* keep the initial states for gesture mode */
		common->wcmGestureState[0] = ds[0];

		/* reset the initial count for a new getsure */
		common->wcmGestureParameters.wcmGestureUsed  = 0;

		/* initialize the cursor position */
		if (common->wcmGestureMode == GESTURE_NONE_MODE && touch_id == 0)
			goto ret;

		/* got second touch in TapTime interval after first one,
		 * switch to DRAG mode */
		if (common->wcmGestureMode == GESTURE_PREDRAG_MODE)
		{
			/* left button down */
			wcmSendButtonClick(priv, 1, 1);
			common->wcmGestureMode = GESTURE_DRAG_MODE;
			goto ret;
		}
	}

	if (!ds[0].proximity && !ds[1].proximity)
	{
		/* first finger was out-prox when GestureMode was still on */
		if (!dsLast[0].proximity &&
		    common->wcmGestureMode != GESTURE_NONE_MODE)
			/* send first finger out prox */
			wcmSoftOutEvent(priv);

		/* if were in DRAG mode, send left button up now */
		if (common->wcmGestureMode == GESTURE_DRAG_MODE)
			wcmSendButtonClick(priv, 1, 0);

		/* exit gesture mode when both fingers are out */
		common->wcmGestureMode = GESTURE_NONE_MODE;
		common->wcmGestureParameters.wcmScrollDirection = 0;

		goto ret;
	}

	if (!(common->wcmGestureMode & (GESTURE_SCROLL_MODE | GESTURE_ZOOM_MODE)) && touch_id == 1)
		wcmFingerTapToClick(priv);

	/* Change mode happens only when both fingers are out */
	if (common->wcmGestureMode & GESTURE_TAP_MODE)
		goto ret;

	/* continue zooming if already in zoom mode */
	if ((common->wcmGestureMode & GESTURE_ZOOM_MODE))
		wcmFingerZoom(priv);

	/* continue scrollling if already in scroll mode */
	else if (common->wcmGestureMode & GESTURE_SCROLL_MODE)
		wcmFingerScroll(priv);

	/* process complex two finger gestures */
	else if (ds[0].proximity && ds[1].proximity)
	{
		if (dsLast[0].proximity && dsLast[1].proximity) {
			/* scroll should be considered first since it requires
			 * a finger distance check */
			wcmFingerScroll(priv);

			if (!(common->wcmGestureMode & GESTURE_SCROLL_MODE))
				wcmFingerZoom(priv);
		}
	}
ret:
	if ((common->wcmGestureMode == GESTURE_NONE_MODE || common->wcmGestureMode == GESTURE_DRAG_MODE) &&
	    touch_id == 0)
	{
		wcmSingleFingerTap(priv);
		wcmSingleFingerPress(priv);
	}
}

static void wcmSendScrollEvent(WacomDevicePtr priv, int dist,
			 int buttonUp, int buttonDn)
{
	int button = (dist > 0) ? buttonUp : buttonDn;
	WacomCommonPtr common = priv->common;
	unsigned int count = (unsigned int)((1.0 * abs(dist)/
		common->wcmGestureParameters.wcmScrollDistance));
	WacomDeviceState ds[2] = {};

	getStateHistory(common, ds, ARRAY_SIZE(ds), 0);

	/* user might have changed from up to down or vice versa */
	if (count < common->wcmGestureParameters.wcmGestureUsed)
	{
		common->wcmGestureState[0] = ds[0];
		common->wcmGestureState[1] = ds[1];
		common->wcmGestureParameters.wcmGestureUsed  = 0;
		return;
	}

	count -= common->wcmGestureParameters.wcmGestureUsed;
	common->wcmGestureParameters.wcmGestureUsed += count;
	while (count--)
	{
		wcmSendButtonClick(priv, button, 1);
		wcmSendButtonClick(priv, button, 0);
		DBG(10, priv, "loop count = %u \n", count);
	}
}

static void wcmFingerScroll(WacomDevicePtr priv)
{
	WacomCommonPtr common = priv->common;
	WacomDeviceState ds[2] = {};
	WacomDeviceState *start = common->wcmGestureState;
	int midPoint_new = 0;
	int midPoint_old = 0;
	int dist = 0;
	WacomFilterState filterd;  /* borrow this struct */
	int max_spread = common->wcmGestureParameters.wcmZoomDistance;
	int spread;

	if (!common->wcmGesture)
		return;

	getStateHistory(common, ds, ARRAY_SIZE(ds), 0);

	DBG(10, priv, "\n");

	spread = fabs(touchDistance(ds[0], ds[1]) - touchDistance(start[0], start[1]));

	if (common->wcmGestureMode != GESTURE_SCROLL_MODE)
	{
		if (spread < max_spread)
		{
			/* two fingers stay close to each other all the time and
			 * move in vertical or horizontal direction together
			 */
			if (pointsInLine(common, ds[0], start[0])
			    && pointsInLine(common, ds[1], start[1])
			    && common->wcmGestureParameters.wcmScrollDirection
			    && vectorsSameDirection(common, ds[0], start[0], ds[1], start[1]))
			{
				/* left button might be down. Send it up first */
				wcmSendButtonClick(priv, 1, 0);
				common->wcmGestureMode = GESTURE_SCROLL_MODE;
			}
		}
	}

	/* still not a scroll event yet? */
	if (common->wcmGestureMode != GESTURE_SCROLL_MODE)
		return;

	/* initialize the points so we can rotate them */
	filterd.x[0] = ds[0].x;
	filterd.y[0] = ds[0].y;
	filterd.x[1] = ds[1].x;
	filterd.y[1] = ds[1].y;
	filterd.x[2] = common->wcmGestureState[0].x;
	filterd.y[2] = common->wcmGestureState[0].y;
	filterd.x[3] = common->wcmGestureState[1].x;
	filterd.y[3] = common->wcmGestureState[1].y;

	/* scrolling has directions so rotation has to be considered first */
	for (unsigned int i = 0; i < 6; i++) {
		wcmRotateAndScaleCoordinates(priv, &filterd.x[i], &filterd.y[i]);
	}

	/* check vertical direction */
	if (common->wcmGestureParameters.wcmScrollDirection == WACOM_VERT_ALLOWED)
	{
		midPoint_old = (((double)filterd.y[2] + (double)filterd.y[3]) / 2.);
		midPoint_new = (((double)filterd.y[0] + (double)filterd.y[1]) / 2.);

		/* allow one finger scroll */
		if (!ds[0].proximity)
		{
			midPoint_old = filterd.y[3];
			midPoint_new = filterd.y[1];
		}

		if (!ds[1].proximity)
		{
			midPoint_old = filterd.y[2];
			midPoint_new = filterd.y[0];
		}

		dist = midPoint_old - midPoint_new;
		wcmSendScrollEvent(priv, dist, WCM_SCROLL_UP, WCM_SCROLL_DOWN);
	}

	if (common->wcmGestureParameters.wcmScrollDirection == WACOM_HORIZ_ALLOWED)
	{
		midPoint_old = (((double)filterd.x[2] + (double)filterd.x[3]) / 2.);
		midPoint_new = (((double)filterd.x[0] + (double)filterd.x[1]) / 2.);

		/* allow one finger scroll */
		if (!ds[0].proximity)
		{
			midPoint_old = filterd.x[3];
			midPoint_new = filterd.x[1];
		}

		if (!ds[1].proximity)
		{
			midPoint_old = filterd.x[2];
			midPoint_new = filterd.x[0];
		}

		dist = midPoint_old - midPoint_new;
		wcmSendScrollEvent(priv, dist, WCM_SCROLL_RIGHT, WCM_SCROLL_LEFT);
	}
}

static void wcmFingerZoom(WacomDevicePtr priv)
{
	WacomCommonPtr common = priv->common;
	WacomDeviceState ds[2] = {};
	WacomDeviceState *start = common->wcmGestureState;
	unsigned int count, button;
	int dist = touchDistance(common->wcmGestureState[0],
			common->wcmGestureState[1]);
	int max_spread = common->wcmGestureParameters.wcmZoomDistance;
	int spread;

	if (!common->wcmGesture)
		return;

	getStateHistory(common, ds, ARRAY_SIZE(ds), 0);

	DBG(10, priv, "\n");

	spread = fabs(touchDistance(ds[0], ds[1]) - touchDistance(start[0], start[1]));

	if (common->wcmGestureMode != GESTURE_ZOOM_MODE)
	{
		/* two fingers moved apart from each other */
		if (spread > max_spread)
		{
			/* left button might be down, send it up first */
			wcmSendButtonClick(priv, 1, 0);
			common->wcmGestureMode = GESTURE_ZOOM_MODE;
		}
	}

	if (common->wcmGestureMode != GESTURE_ZOOM_MODE)
		return;

	dist = touchDistance(ds[0], ds[1]) - dist;
	count = (unsigned int)((1.0 * abs(dist)/common->wcmGestureParameters.wcmZoomDistance));

	/* user might have changed from left to right or vice versa */
	if (count < common->wcmGestureParameters.wcmGestureUsed)
	{
		/* reset the initial states for the new getsure */
		common->wcmGestureState[0] = ds[0];
		common->wcmGestureState[1] = ds[1];
		common->wcmGestureParameters.wcmGestureUsed  = 0;
		return;
	}

	/* zooming? Send ctrl + scroll up/down event.
	FIXME: this hardcodes the positions of ctrl and assumes that ctrl is
	actually a modifier. Tough luck. The alternative is to run through
	the XKB table and figure out where the key for the ctrl modifier is
	hiding. Good luck.
	Gesture support is not supposed to be in the driver...
	 */
	button = (dist > 0) ? 4 : 5;

	count -= common->wcmGestureParameters.wcmGestureUsed;
	common->wcmGestureParameters.wcmGestureUsed += count;
	while (count--)
	{
		wcmEmitKeycode (priv, 37 /*XK_Control_L*/, 1);
		wcmSendButtonClick (priv, button, 1);
		wcmSendButtonClick (priv, button, 0);
		wcmEmitKeycode (priv, 37 /*XK_Control_L*/, 0);
	}
}

Bool wcmTouchNeedSendEvents(WacomCommonPtr common)
{
	return !(common->wcmGestureMode & ~GESTURE_DRAG_MODE);
}

/* vim: set noexpandtab tabstop=8 shiftwidth=8: */