sdl2_frt/src/events/SDL_gesture.c

/*
  Simple DirectMedia Layer
  Copyright (C) 1997-2020 Sam Lantinga <slouken@libsdl.org>

  This software is provided 'as-is', without any express or implied
  warranty.  In no event will the authors be held liable for any damages
  arising from the use of this software.

  Permission is granted to anyone to use this software for any purpose,
  including commercial applications, and to alter it and redistribute it
  freely, subject to the following restrictions:

  1. The origin of this software must not be misrepresented; you must not
     claim that you wrote the original software. If you use this software
     in a product, an acknowledgment in the product documentation would be
     appreciated but is not required.
  2. Altered source versions must be plainly marked as such, and must not be
     misrepresented as being the original software.
  3. This notice may not be removed or altered from any source distribution.
*/

#include "../SDL_internal.h"

/* General gesture handling code for SDL */

#include "SDL_events.h"
#include "SDL_endian.h"
#include "SDL_events_c.h"
#include "SDL_gesture_c.h"

/*
#include <stdio.h>
*/

/* TODO: Replace with malloc */

#define MAXPATHSIZE 1024

#define ENABLE_DOLLAR

#define DOLLARNPOINTS 64

#if defined(ENABLE_DOLLAR)
#  define DOLLARSIZE 256
#  define PHI 0.618033989
#endif

typedef struct {
    float x,y;
} SDL_FloatPoint;

typedef struct {
    float length;

    int numPoints;
    SDL_FloatPoint p[MAXPATHSIZE];
} SDL_DollarPath;

typedef struct {
    SDL_FloatPoint path[DOLLARNPOINTS];
    unsigned long hash;
} SDL_DollarTemplate;

typedef struct {
    SDL_TouchID id;
    SDL_FloatPoint centroid;
    SDL_DollarPath dollarPath;
    Uint16 numDownFingers;

    int numDollarTemplates;
    SDL_DollarTemplate *dollarTemplate;

    SDL_bool recording;
} SDL_GestureTouch;

static SDL_GestureTouch *SDL_gestureTouch;
static int SDL_numGestureTouches = 0;
static SDL_bool recordAll;

#if 0
static void PrintPath(SDL_FloatPoint *path)
{
    int i;
    printf("Path:");
    for (i=0; i<DOLLARNPOINTS; i++) {
        printf(" (%f,%f)",path[i].x,path[i].y);
    }
    printf("\n");
}
#endif

int SDL_RecordGesture(SDL_TouchID touchId)
{
    int i;
    if (touchId < 0) recordAll = SDL_TRUE;
    for (i = 0; i < SDL_numGestureTouches; i++) {
        if ((touchId < 0) || (SDL_gestureTouch[i].id == touchId)) {
            SDL_gestureTouch[i].recording = SDL_TRUE;
            if (touchId >= 0)
                return 1;
        }
    }
    return (touchId < 0);
}

void SDL_GestureQuit()
{
    SDL_free(SDL_gestureTouch);
    SDL_gestureTouch = NULL;
}

static unsigned long SDL_HashDollar(SDL_FloatPoint* points)
{
    unsigned long hash = 5381;
    int i;
    for (i = 0; i < DOLLARNPOINTS; i++) {
        hash = ((hash<<5) + hash) + (unsigned long)points[i].x;
        hash = ((hash<<5) + hash) + (unsigned long)points[i].y;
    }
    return hash;
}


static int SaveTemplate(SDL_DollarTemplate *templ, SDL_RWops *dst)
{
    if (dst == NULL) {
        return 0;
    }

    /* No Longer storing the Hash, rehash on load */
    /* if (SDL_RWops.write(dst, &(templ->hash), sizeof(templ->hash), 1) != 1) return 0; */

#if SDL_BYTEORDER == SDL_LIL_ENDIAN
    if (SDL_RWwrite(dst, templ->path,
                    sizeof(templ->path[0]),DOLLARNPOINTS) != DOLLARNPOINTS) {
        return 0;
    }
#else
    {
        SDL_DollarTemplate copy = *templ;
        SDL_FloatPoint *p = copy.path;
        int i;
        for (i = 0; i < DOLLARNPOINTS; i++, p++) {
            p->x = SDL_SwapFloatLE(p->x);
            p->y = SDL_SwapFloatLE(p->y);
        }

        if (SDL_RWwrite(dst, copy.path,
                        sizeof(copy.path[0]),DOLLARNPOINTS) != DOLLARNPOINTS) {
            return 0;
        }
    }
#endif

    return 1;
}


int SDL_SaveAllDollarTemplates(SDL_RWops *dst)
{
    int i,j,rtrn = 0;
    for (i = 0; i < SDL_numGestureTouches; i++) {
        SDL_GestureTouch* touch = &SDL_gestureTouch[i];
        for (j = 0; j < touch->numDollarTemplates; j++) {
            rtrn += SaveTemplate(&touch->dollarTemplate[j], dst);
        }
    }
    return rtrn;
}

int SDL_SaveDollarTemplate(SDL_GestureID gestureId, SDL_RWops *dst)
{
    int i,j;
    for (i = 0; i < SDL_numGestureTouches; i++) {
        SDL_GestureTouch* touch = &SDL_gestureTouch[i];
        for (j = 0; j < touch->numDollarTemplates; j++) {
            if (touch->dollarTemplate[j].hash == gestureId) {
                return SaveTemplate(&touch->dollarTemplate[j], dst);
            }
        }
    }
    return SDL_SetError("Unknown gestureId");
}

/* path is an already sampled set of points
Returns the index of the gesture on success, or -1 */
static int SDL_AddDollarGesture_one(SDL_GestureTouch* inTouch, SDL_FloatPoint* path)
{
    SDL_DollarTemplate* dollarTemplate;
    SDL_DollarTemplate *templ;
    int index;

    index = inTouch->numDollarTemplates;
    dollarTemplate =
        (SDL_DollarTemplate *)SDL_realloc(inTouch->dollarTemplate,
                                          (index + 1) *
                                          sizeof(SDL_DollarTemplate));
    if (!dollarTemplate) {
        return SDL_OutOfMemory();
    }
    inTouch->dollarTemplate = dollarTemplate;

    templ = &inTouch->dollarTemplate[index];
    SDL_memcpy(templ->path, path, DOLLARNPOINTS*sizeof(SDL_FloatPoint));
    templ->hash = SDL_HashDollar(templ->path);
    inTouch->numDollarTemplates++;

    return index;
}

static int SDL_AddDollarGesture(SDL_GestureTouch* inTouch, SDL_FloatPoint* path)
{
    int index = -1;
    int i = 0;
    if (inTouch == NULL) {
        if (SDL_numGestureTouches == 0) return SDL_SetError("no gesture touch devices registered");
        for (i = 0; i < SDL_numGestureTouches; i++) {
            inTouch = &SDL_gestureTouch[i];
            index = SDL_AddDollarGesture_one(inTouch, path);
            if (index < 0)
                return -1;
        }
        /* Use the index of the last one added. */
        return index;
    }
    return SDL_AddDollarGesture_one(inTouch, path);
}

int SDL_LoadDollarTemplates(SDL_TouchID touchId, SDL_RWops *src)
{
    int i,loaded = 0;
    SDL_GestureTouch *touch = NULL;
    if (src == NULL) return 0;
    if (touchId >= 0) {
        for (i = 0; i < SDL_numGestureTouches; i++) {
            if (SDL_gestureTouch[i].id == touchId) {
                touch = &SDL_gestureTouch[i];
            }
        }
        if (touch == NULL) {
            return SDL_SetError("given touch id not found");
        }
    }

    while (1) {
        SDL_DollarTemplate templ;

        if (SDL_RWread(src,templ.path,sizeof(templ.path[0]),DOLLARNPOINTS) < DOLLARNPOINTS) {
            if (loaded == 0) {
                return SDL_SetError("could not read any dollar gesture from rwops");
            }
            break;
        }

#if SDL_BYTEORDER != SDL_LIL_ENDIAN
        for (i = 0; i < DOLLARNPOINTS; i++) {
            SDL_FloatPoint *p = &templ.path[i];
            p->x = SDL_SwapFloatLE(p->x);
            p->y = SDL_SwapFloatLE(p->y);
        }
#endif

        if (touchId >= 0) {
            /* printf("Adding loaded gesture to 1 touch\n"); */
            if (SDL_AddDollarGesture(touch, templ.path) >= 0)
                loaded++;
        }
        else {
            /* printf("Adding to: %i touches\n",SDL_numGestureTouches); */
            for (i = 0; i < SDL_numGestureTouches; i++) {
                touch = &SDL_gestureTouch[i];
                /* printf("Adding loaded gesture to + touches\n"); */
                /* TODO: What if this fails? */
                SDL_AddDollarGesture(touch,templ.path);
            }
            loaded++;
        }
    }

    return loaded;
}


#if defined(ENABLE_DOLLAR)
static float dollarDifference(SDL_FloatPoint* points,SDL_FloatPoint* templ,float ang)
{
    /*  SDL_FloatPoint p[DOLLARNPOINTS]; */
    float dist = 0;
    SDL_FloatPoint p;
    int i;
    for (i = 0; i < DOLLARNPOINTS; i++) {
        p.x = (float)(points[i].x * SDL_cos(ang) - points[i].y * SDL_sin(ang));
        p.y = (float)(points[i].x * SDL_sin(ang) + points[i].y * SDL_cos(ang));
        dist += (float)(SDL_sqrt((p.x-templ[i].x)*(p.x-templ[i].x)+
                                 (p.y-templ[i].y)*(p.y-templ[i].y)));
    }
    return dist/DOLLARNPOINTS;

}

static float bestDollarDifference(SDL_FloatPoint* points,SDL_FloatPoint* templ)
{
    /*------------BEGIN DOLLAR BLACKBOX------------------
      -TRANSLATED DIRECTLY FROM PSUDEO-CODE AVAILABLE AT-
      -"http://depts.washington.edu/aimgroup/proj/dollar/"
    */
    double ta = -M_PI/4;
    double tb = M_PI/4;
    double dt = M_PI/90;
    float x1 = (float)(PHI*ta + (1-PHI)*tb);
    float f1 = dollarDifference(points,templ,x1);
    float x2 = (float)((1-PHI)*ta + PHI*tb);
    float f2 = dollarDifference(points,templ,x2);
    while (SDL_fabs(ta-tb) > dt) {
        if (f1 < f2) {
            tb = x2;
            x2 = x1;
            f2 = f1;
            x1 = (float)(PHI*ta + (1-PHI)*tb);
            f1 = dollarDifference(points,templ,x1);
        }
        else {
            ta = x1;
            x1 = x2;
            f1 = f2;
            x2 = (float)((1-PHI)*ta + PHI*tb);
            f2 = dollarDifference(points,templ,x2);
        }
    }
    /*
      if (f1 <= f2)
          printf("Min angle (x1): %f\n",x1);
      else if (f1 >  f2)
          printf("Min angle (x2): %f\n",x2);
    */
    return SDL_min(f1,f2);
}

/* DollarPath contains raw points, plus (possibly) the calculated length */
static int dollarNormalize(const SDL_DollarPath *path,SDL_FloatPoint *points, SDL_bool is_recording)
{
    int i;
    float interval;
    float dist;
    int numPoints = 0;
    SDL_FloatPoint centroid;
    float xmin,xmax,ymin,ymax;
    float ang;
    float w,h;
    float length = path->length;

    /* Calculate length if it hasn't already been done */
    if (length <= 0) {
        for (i=1;i < path->numPoints; i++) {
            float dx = path->p[i  ].x - path->p[i-1].x;
            float dy = path->p[i  ].y - path->p[i-1].y;
            length += (float)(SDL_sqrt(dx*dx+dy*dy));
        }
    }

    /* Resample */
    interval = length/(DOLLARNPOINTS - 1);
    dist = interval;

    centroid.x = 0;centroid.y = 0;

    /* printf("(%f,%f)\n",path->p[path->numPoints-1].x,path->p[path->numPoints-1].y); */
    for (i = 1; i < path->numPoints; i++) {
        float d = (float)(SDL_sqrt((path->p[i-1].x-path->p[i].x)*(path->p[i-1].x-path->p[i].x)+
                                   (path->p[i-1].y-path->p[i].y)*(path->p[i-1].y-path->p[i].y)));
        /* printf("d = %f dist = %f/%f\n",d,dist,interval); */
        while (dist + d > interval) {
            points[numPoints].x = path->p[i-1].x +
                ((interval-dist)/d)*(path->p[i].x-path->p[i-1].x);
            points[numPoints].y = path->p[i-1].y +
                ((interval-dist)/d)*(path->p[i].y-path->p[i-1].y);
            centroid.x += points[numPoints].x;
            centroid.y += points[numPoints].y;
            numPoints++;

            dist -= interval;
        }
        dist += d;
    }
    if (numPoints < DOLLARNPOINTS-1) {
        if (is_recording) {
            SDL_SetError("ERROR: NumPoints = %i", numPoints);
        }
        return 0;
    }
    /* copy the last point */
    points[DOLLARNPOINTS-1] = path->p[path->numPoints-1];
    numPoints = DOLLARNPOINTS;

    centroid.x /= numPoints;
    centroid.y /= numPoints;

    /* printf("Centroid (%f,%f)",centroid.x,centroid.y); */
    /* Rotate Points so point 0 is left of centroid and solve for the bounding box */
    xmin = centroid.x;
    xmax = centroid.x;
    ymin = centroid.y;
    ymax = centroid.y;

    ang = (float)(SDL_atan2(centroid.y - points[0].y,
                            centroid.x - points[0].x));

    for (i = 0; i<numPoints; i++) {
        float px = points[i].x;
        float py = points[i].y;
        points[i].x = (float)((px - centroid.x)*SDL_cos(ang) -
                              (py - centroid.y)*SDL_sin(ang) + centroid.x);
        points[i].y = (float)((px - centroid.x)*SDL_sin(ang) +
                              (py - centroid.y)*SDL_cos(ang) + centroid.y);


        if (points[i].x < xmin) xmin = points[i].x;
        if (points[i].x > xmax) xmax = points[i].x;
        if (points[i].y < ymin) ymin = points[i].y;
        if (points[i].y > ymax) ymax = points[i].y;
    }

    /* Scale points to DOLLARSIZE, and translate to the origin */
    w = xmax-xmin;
    h = ymax-ymin;

    for (i=0; i<numPoints; i++) {
        points[i].x = (points[i].x - centroid.x)*DOLLARSIZE/w;
        points[i].y = (points[i].y - centroid.y)*DOLLARSIZE/h;
    }
    return numPoints;
}

static float dollarRecognize(const SDL_DollarPath *path,int *bestTempl,SDL_GestureTouch* touch)
{
    SDL_FloatPoint points[DOLLARNPOINTS];
    int i;
    float bestDiff = 10000;

    SDL_memset(points, 0, sizeof(points));

    dollarNormalize(path, points, SDL_FALSE);

    /* PrintPath(points); */
    *bestTempl = -1;
    for (i = 0; i < touch->numDollarTemplates; i++) {
        float diff = bestDollarDifference(points,touch->dollarTemplate[i].path);
        if (diff < bestDiff) {bestDiff = diff; *bestTempl = i;}
    }
    return bestDiff;
}
#endif

int SDL_GestureAddTouch(SDL_TouchID touchId)
{
    SDL_GestureTouch *gestureTouch = (SDL_GestureTouch *)SDL_realloc(SDL_gestureTouch,
                                                                     (SDL_numGestureTouches + 1) *
                                                                     sizeof(SDL_GestureTouch));

    if (!gestureTouch) {
        return SDL_OutOfMemory();
    }

    SDL_gestureTouch = gestureTouch;

    SDL_zero(SDL_gestureTouch[SDL_numGestureTouches]);
    SDL_gestureTouch[SDL_numGestureTouches].id = touchId;
    SDL_numGestureTouches++;
    return 0;
}

int SDL_GestureDelTouch(SDL_TouchID touchId)
{
    int i;
    for (i = 0; i < SDL_numGestureTouches; i++) {
        if (SDL_gestureTouch[i].id == touchId) {
            break;
        }
    }

    if (i == SDL_numGestureTouches) {
        /* not found */
        return -1;
    }

    SDL_free(SDL_gestureTouch[i].dollarTemplate);
    SDL_zero(SDL_gestureTouch[i]);

    SDL_numGestureTouches--;
    SDL_memcpy(&SDL_gestureTouch[i], &SDL_gestureTouch[SDL_numGestureTouches], sizeof(SDL_gestureTouch[i]));
    return 0;
}

static SDL_GestureTouch * SDL_GetGestureTouch(SDL_TouchID id)
{
    int i;
    for (i = 0; i < SDL_numGestureTouches; i++) {
        /* printf("%i ?= %i\n",SDL_gestureTouch[i].id,id); */
        if (SDL_gestureTouch[i].id == id)
            return &SDL_gestureTouch[i];
    }
    return NULL;
}

static void SDL_SendGestureMulti(SDL_GestureTouch* touch,float dTheta,float dDist)
{
    if (SDL_GetEventState(SDL_MULTIGESTURE) == SDL_ENABLE) {
        SDL_Event event;
        event.mgesture.type = SDL_MULTIGESTURE;
        event.mgesture.touchId = touch->id;
        event.mgesture.x = touch->centroid.x;
        event.mgesture.y = touch->centroid.y;
        event.mgesture.dTheta = dTheta;
        event.mgesture.dDist = dDist;
        event.mgesture.numFingers = touch->numDownFingers;
        SDL_PushEvent(&event);
    }
}

#if defined(ENABLE_DOLLAR)
static void SDL_SendGestureDollar(SDL_GestureTouch* touch,
                          SDL_GestureID gestureId,float error)
{
    if (SDL_GetEventState(SDL_DOLLARGESTURE) == SDL_ENABLE) {
        SDL_Event event;
        event.dgesture.type = SDL_DOLLARGESTURE;
        event.dgesture.touchId = touch->id;
        event.dgesture.x = touch->centroid.x;
        event.dgesture.y = touch->centroid.y;
        event.dgesture.gestureId = gestureId;
        event.dgesture.error = error;
        /* A finger came up to trigger this event. */
        event.dgesture.numFingers = touch->numDownFingers + 1;
        SDL_PushEvent(&event);
    }
}

static void SDL_SendDollarRecord(SDL_GestureTouch* touch,SDL_GestureID gestureId)
{
    if (SDL_GetEventState(SDL_DOLLARRECORD) == SDL_ENABLE) {
        SDL_Event event;
        event.dgesture.type = SDL_DOLLARRECORD;
        event.dgesture.touchId = touch->id;
        event.dgesture.gestureId = gestureId;
        SDL_PushEvent(&event);
    }
}
#endif


void SDL_GestureProcessEvent(SDL_Event* event)
{
    float x,y;
#if defined(ENABLE_DOLLAR)
    int index;
    int i;
    float pathDx, pathDy;
#endif
    SDL_FloatPoint lastP;
    SDL_FloatPoint lastCentroid;
    float lDist;
    float Dist;
    float dtheta;
    float dDist;

    if (event->type == SDL_FINGERMOTION ||
        event->type == SDL_FINGERDOWN ||
        event->type == SDL_FINGERUP) {
        SDL_GestureTouch* inTouch = SDL_GetGestureTouch(event->tfinger.touchId);

        /* Shouldn't be possible */
        if (inTouch == NULL) return;

        x = event->tfinger.x;
        y = event->tfinger.y;

        /* Finger Up */
        if (event->type == SDL_FINGERUP) {
#if defined(ENABLE_DOLLAR)
            SDL_FloatPoint path[DOLLARNPOINTS];
#endif

            inTouch->numDownFingers--;

#if defined(ENABLE_DOLLAR)
            if (inTouch->recording) {
                inTouch->recording = SDL_FALSE;
                dollarNormalize(&inTouch->dollarPath, path, SDL_TRUE);
                /* PrintPath(path); */
                if (recordAll) {
                    index = SDL_AddDollarGesture(NULL,path);
                    for (i = 0; i < SDL_numGestureTouches; i++)
                        SDL_gestureTouch[i].recording = SDL_FALSE;
                }
                else {
                    index = SDL_AddDollarGesture(inTouch,path);
                }

                if (index >= 0) {
                    SDL_SendDollarRecord(inTouch,inTouch->dollarTemplate[index].hash);
                }
                else {
                    SDL_SendDollarRecord(inTouch,-1);
                }
            }
            else {
                int bestTempl;
                float error;
                error = dollarRecognize(&inTouch->dollarPath,
                                        &bestTempl,inTouch);
                if (bestTempl >= 0){
                    /* Send Event */
                    unsigned long gestureId = inTouch->dollarTemplate[bestTempl].hash;
                    SDL_SendGestureDollar(inTouch,gestureId,error);
                    /* printf ("%s\n",);("Dollar error: %f\n",error); */
                }
            }
#endif
            /* inTouch->gestureLast[j] = inTouch->gestureLast[inTouch->numDownFingers]; */
            if (inTouch->numDownFingers > 0) {
                inTouch->centroid.x = (inTouch->centroid.x*(inTouch->numDownFingers+1)-
                                       x)/inTouch->numDownFingers;
                inTouch->centroid.y = (inTouch->centroid.y*(inTouch->numDownFingers+1)-
                                       y)/inTouch->numDownFingers;
            }
        }
        else if (event->type == SDL_FINGERMOTION) {
            float dx = event->tfinger.dx;
            float dy = event->tfinger.dy;
#if defined(ENABLE_DOLLAR)
            SDL_DollarPath* path = &inTouch->dollarPath;
            if (path->numPoints < MAXPATHSIZE) {
                path->p[path->numPoints].x = inTouch->centroid.x;
                path->p[path->numPoints].y = inTouch->centroid.y;
                pathDx =
                    (path->p[path->numPoints].x-path->p[path->numPoints-1].x);
                pathDy =
                    (path->p[path->numPoints].y-path->p[path->numPoints-1].y);
                path->length += (float)SDL_sqrt(pathDx*pathDx + pathDy*pathDy);
                path->numPoints++;
            }
#endif
            lastP.x = x - dx;
            lastP.y = y - dy;
            lastCentroid = inTouch->centroid;

            inTouch->centroid.x += dx/inTouch->numDownFingers;
            inTouch->centroid.y += dy/inTouch->numDownFingers;
            /* printf("Centrid : (%f,%f)\n",inTouch->centroid.x,inTouch->centroid.y); */
            if (inTouch->numDownFingers > 1) {
                SDL_FloatPoint lv; /* Vector from centroid to last x,y position */
                SDL_FloatPoint v; /* Vector from centroid to current x,y position */
                /* lv = inTouch->gestureLast[j].cv; */
                lv.x = lastP.x - lastCentroid.x;
                lv.y = lastP.y - lastCentroid.y;
                lDist = (float)SDL_sqrt(lv.x*lv.x + lv.y*lv.y);
                /* printf("lDist = %f\n",lDist); */
                v.x = x - inTouch->centroid.x;
                v.y = y - inTouch->centroid.y;
                /* inTouch->gestureLast[j].cv = v; */
                Dist = (float)SDL_sqrt(v.x*v.x+v.y*v.y);
                /* SDL_cos(dTheta) = (v . lv)/(|v| * |lv|) */

                /* Normalize Vectors to simplify angle calculation */
                lv.x/=lDist;
                lv.y/=lDist;
                v.x/=Dist;
                v.y/=Dist;
                dtheta = (float)SDL_atan2(lv.x*v.y - lv.y*v.x,lv.x*v.x + lv.y*v.y);

                dDist = (Dist - lDist);
                if (lDist == 0) {dDist = 0;dtheta = 0;} /* To avoid impossible values */

                /* inTouch->gestureLast[j].dDist = dDist;
                inTouch->gestureLast[j].dtheta = dtheta;

                printf("dDist = %f, dTheta = %f\n",dDist,dtheta);
                gdtheta = gdtheta*.9 + dtheta*.1;
                gdDist  =  gdDist*.9 +  dDist*.1
                knob.r += dDist/numDownFingers;
                knob.ang += dtheta;
                printf("thetaSum = %f, distSum = %f\n",gdtheta,gdDist);
                printf("id: %i dTheta = %f, dDist = %f\n",j,dtheta,dDist); */
                SDL_SendGestureMulti(inTouch,dtheta,dDist);
            }
            else {
                /* inTouch->gestureLast[j].dDist = 0;
                inTouch->gestureLast[j].dtheta = 0;
                inTouch->gestureLast[j].cv.x = 0;
                inTouch->gestureLast[j].cv.y = 0; */
            }
            /* inTouch->gestureLast[j].f.p.x = x;
            inTouch->gestureLast[j].f.p.y = y;
            break;
            pressure? */
        }
        else if (event->type == SDL_FINGERDOWN) {

            inTouch->numDownFingers++;
            inTouch->centroid.x = (inTouch->centroid.x*(inTouch->numDownFingers - 1)+
                                   x)/inTouch->numDownFingers;
            inTouch->centroid.y = (inTouch->centroid.y*(inTouch->numDownFingers - 1)+
                                   y)/inTouch->numDownFingers;
            /* printf("Finger Down: (%f,%f). Centroid: (%f,%f\n",x,y,
                 inTouch->centroid.x,inTouch->centroid.y); */

#if defined(ENABLE_DOLLAR)
            inTouch->dollarPath.length = 0;
            inTouch->dollarPath.p[0].x = x;
            inTouch->dollarPath.p[0].y = y;
            inTouch->dollarPath.numPoints = 1;
#endif
        }
    }
}

/* vi: set ts=4 sw=4 expandtab: */