flightgear/Simulator/Autopilot/autopilot.cxx

// autopilot.cxx -- autopilot subsystem
//
// Written by Jeff Goeke-Smith, started April 1998.
//
// Copyright (C) 1998  Jeff Goeke-Smith, jgoeke@voyager.net
//
// 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., 675 Mass Ave, Cambridge, MA 02139, USA.
//
// $Id$


#ifdef HAVE_CONFIG_H
#  include <config.h>
#endif

#include <assert.h>
#include <stdlib.h>

#include <Scenery/scenery.hxx>

#include "autopilot.hxx"

#include <Include/fg_constants.h>
#include <Debug/logstream.hxx>
#include <Main/options.hxx>
#include <GUI/gui.h>


// The below routines were copied right from hud.c ( I hate reinventing
// the wheel more than necessary)

// The following routines obtain information concerntin the aircraft's
// current state and return it to calling instrument display routines.
// They should eventually be member functions of the aircraft.
//


static double get_speed( void ) {
    return( current_aircraft.fdm_state->get_V_equiv_kts() );
}

static double get_aoa( void )
{
    return( current_aircraft.fdm_state->get_Gamma_vert_rad() * RAD_TO_DEG );
}

static double fgAPget_roll( void )
{
    return( current_aircraft.fdm_state->get_Phi() * RAD_TO_DEG );
}

static double get_pitch( void )
{
    return( current_aircraft.fdm_state->get_Theta() );
}

double fgAPget_heading( void )
{
    return( current_aircraft.fdm_state->get_Psi() * RAD_TO_DEG );
}

static double fgAPget_altitude( void )
{
    return( current_aircraft.fdm_state->get_Altitude() * FEET_TO_METER );
}

static double fgAPget_climb( void )
{
    // return in meters per minute
    return( current_aircraft.fdm_state->get_Climb_Rate() * FEET_TO_METER * 60 );
}

static double get_sideslip( void )
{
    return( current_aircraft.fdm_state->get_Beta() );
}

static double fgAPget_agl( void )
{
    double agl;

    agl = current_aircraft.fdm_state->get_Altitude() * FEET_TO_METER
	- scenery.cur_elev;

    return( agl );
}

// End of copied section.  ( thanks for the wheel :-)

// Local Prototype section

double LinearExtrapolate( double x, double x1, double y1, double x2, double y2);
double NormalizeDegrees( double Input);

// End Local ProtoTypes

fgAPDataPtr APDataGlobal;       // global variable holding the AP info
// I want this gone.  Data should be in aircraft structure


bool fgAPHeadingEnabled( void )
{
    fgAPDataPtr APData;
    
    APData = APDataGlobal;
    
    // heading hold enabled?
    return APData->heading_hold;
}

bool fgAPAltitudeEnabled( void )
{
    fgAPDataPtr APData;
    
    APData = APDataGlobal;
    
    // altitude hold or terrain follow enabled?
    return APData->altitude_hold;
}

bool fgAPTerrainFollowEnabled( void )
{
    fgAPDataPtr APData;
    
    APData = APDataGlobal;
            
    // altitude hold or terrain follow enabled?
    return APData->terrain_follow ;
}

bool fgAPAutoThrottleEnabled( void )
{
    fgAPDataPtr APData;
    
    APData = APDataGlobal;

    // autothrottle enabled?
    return APData->auto_throttle;
}

void fgAPAltitudeAdjust( double inc )
{
    // Remove at a later date
    fgAPDataPtr APData = APDataGlobal;
    // end section

    double target_alt, target_agl;

    if ( current_options.get_units() == fgOPTIONS::FG_UNITS_FEET ) {
	target_alt = APData->TargetAltitude * METER_TO_FEET;
	target_agl = APData->TargetAGL * METER_TO_FEET;
    } else {
	target_alt = APData->TargetAltitude;
	target_agl = APData->TargetAGL;
    }

    target_alt = (int)(target_alt / inc) * inc + inc;
    target_agl = (int)(target_agl / inc) * inc + inc;

    if ( current_options.get_units() == fgOPTIONS::FG_UNITS_FEET ) {
	target_alt *= FEET_TO_METER;
	target_agl *= FEET_TO_METER;
    }

    APData->TargetAltitude = target_alt;
    APData->TargetAGL = target_agl;
}

void fgAPAltitudeSet( double new_altitude ) {
    // Remove at a later date
    fgAPDataPtr APData = APDataGlobal;
    // end section
    double target_alt = new_altitude;
    
    if ( current_options.get_units() == fgOPTIONS::FG_UNITS_FEET )
        target_alt = new_altitude * FEET_TO_METER;

    if( target_alt < scenery.cur_elev )
        target_alt = scenery.cur_elev;
        
    APData->TargetAltitude = target_alt;
}

void fgAPHeadingAdjust( double inc )
{
    fgAPDataPtr APData;
    APData = APDataGlobal;

    double target = (int)(APData->TargetHeading / inc) * inc + inc;

    APData->TargetHeading = NormalizeDegrees(target);
}

void fgAPHeadingSet( double new_heading ) {
    fgAPDataPtr APData = APDataGlobal;

    new_heading = NormalizeDegrees( new_heading );
    APData->TargetHeading = new_heading;
}

void fgAPAutoThrottleAdjust( double inc )
{
    fgAPDataPtr APData;
    APData = APDataGlobal;

    double target = (int)(APData->TargetSpeed / inc) * inc + inc;

    APData->TargetSpeed = target;
}

void fgAPReset(void)
{
    fgAPDataPtr APData = APDataGlobal;
    
    if( fgAPTerrainFollowEnabled() )
	fgAPToggleTerrainFollow( );

    if( fgAPAltitudeEnabled() )
	fgAPToggleAltitude();
		
    if( fgAPHeadingEnabled() )
	fgAPToggleHeading();
		
    if( fgAPAutoThrottleEnabled() )
	fgAPToggleAutoThrottle();
    
    APData->TargetHeading = 0.0;     // default direction, due north
    APData->TargetAltitude = 3000;   // default altitude in meters
    APData->alt_error_accum = 0.0;
}

#define mySlider puSlider

/// These statics will eventually go into the class
/// they are just here while I am experimenting -- NHV :-)

static double MaxRollAdjust;       // MaxRollAdjust       = 2 * APData->MaxRoll;
static double RollOutAdjust;       // RollOutAdjust       = 2 * APData->RollOut;
static double MaxAileronAdjust;    // MaxAileronAdjust    = 2 * APData->MaxAileron;
static double RollOutSmoothAdjust; // RollOutSmoothAdjust = 2 * APData->RollOutSmooth;

static float MaxRollValue;         // 0.1 -> 1.0
static float RollOutValue;
static float MaxAileronValue;
static float RollOutSmoothValue;

static float TmpMaxRollValue;      // for cancel operation
static float TmpRollOutValue;
static float TmpMaxAileronValue;
static float TmpRollOutSmoothValue;

static puDialogBox     *APAdjustDialog;
static puFrame         *APAdjustFrame;
static puText          *APAdjustDialogMessage;
static puFont          APAdjustLegendFont;
static puFont          APAdjustLabelFont;

static puOneShot       *APAdjustOkButton;
static puOneShot       *APAdjustResetButton;
static puOneShot       *APAdjustCancelButton;

//static puButton        *APAdjustDragButton;

static puText          *APAdjustMaxRollTitle;
static puText          *APAdjustRollOutTitle;
static puText          *APAdjustMaxAileronTitle;
static puText          *APAdjustRollOutSmoothTitle;

static puText          *APAdjustMaxAileronText;
static puText          *APAdjustMaxRollText;
static puText          *APAdjustRollOutText;
static puText          *APAdjustRollOutSmoothText;

static mySlider        *APAdjustHS0;
static mySlider        *APAdjustHS1;
static mySlider        *APAdjustHS2;
static mySlider        *APAdjustHS3;

static char SliderText[4][8];

// THIS NEEDS IMPROVEMENT !!!!!!!!!!!!!
static int scan_number(char *s, double *new_value)
{
    int ret = 0;
    char WordBuf[64];
    char *cptr = s;
    char *WordBufPtr = WordBuf;

    if (*cptr == '+')
        cptr++;
    if (*cptr == '-') {
        *WordBufPtr++ = *cptr++;
    }
    while (isdigit(*cptr) ) {
        *WordBufPtr++ = *cptr++;
        ret = 1;
    }
    if (*cptr == '.') 
        *WordBufPtr++ = *cptr++;  // put the '.' into the string
    while (isdigit(*cptr)) {
        *WordBufPtr++ = *cptr++;
        ret = 1;
    }
    if( ret == 1 ) {
        *WordBufPtr = '\0';
        sscanf(WordBuf, "%lf", new_value);
    }
    
    return(ret);
} // scan_number


///////// AutoPilot New Heading Dialog

static puDialogBox     *ApHeadingDialog;
static puFrame         *ApHeadingDialogFrame;
static puText          *ApHeadingDialogMessage;
static puInput         *ApHeadingDialogInput;
static puOneShot       *ApHeadingDialogOkButton;
static puOneShot       *ApHeadingDialogCancelButton;

void ApHeadingDialog_Cancel(puObject *)
{
    ApHeadingDialogInput->rejectInput();
    FG_POP_PUI_DIALOG( ApHeadingDialog );
}

void ApHeadingDialog_OK (puObject *me)
{
    int error = 0;
    char *c;
    string s;
    ApHeadingDialogInput -> getValue( &c );
    
    if( strlen(c) ) {
        double NewHeading;
        if( scan_number( c, &NewHeading ) )
	    {
		if(!fgAPHeadingEnabled())
		    fgAPToggleHeading();
		fgAPHeadingSet( NewHeading );
	    } else {
		error = 1;
		s = c;
		s += " is not a valid number.";
	    }
    }
    ApHeadingDialog_Cancel(me);
    if( error )  mkDialog(s.c_str());
}

void NewHeading(puObject *cb)
{
    //  string ApHeadingLabel( "Enter New Heading" );
    //  ApHeadingDialogMessage  -> setLabel(ApHeadingLabel.c_str());
    ApHeadingDialogInput    -> acceptInput();
    FG_PUSH_PUI_DIALOG( ApHeadingDialog );
}

void NewHeadingInit(void)
{
    //  printf("NewHeadingInit\n");
    char NewHeadingLabel[] = "Enter New Heading";
    char *s;

    float heading = fgAPget_heading();
    int len = 260/2 -
	(puGetStringWidth( puGetDefaultLabelFont(), NewHeadingLabel ) /2 );
    
    ApHeadingDialog = new puDialogBox (150, 50);
    {
        ApHeadingDialogFrame   = new puFrame (0, 0, 260, 150);
        
        ApHeadingDialogMessage = new puText   (len, 110);
        ApHeadingDialogMessage    -> setDefaultValue (NewHeadingLabel);
        ApHeadingDialogMessage    -> getDefaultValue (&s);
        ApHeadingDialogMessage    -> setLabel        (s);
    
        ApHeadingDialogInput   = new puInput  ( 50, 70, 210, 100 );
        ApHeadingDialogInput   ->    setValue ( heading );

        ApHeadingDialogOkButton     =  new puOneShot         (50, 10, 110, 50);
        ApHeadingDialogOkButton     ->     setLegend         (gui_msg_OK);
        ApHeadingDialogOkButton     ->     makeReturnDefault (TRUE);
        ApHeadingDialogOkButton     ->     setCallback       (ApHeadingDialog_OK);
        
        ApHeadingDialogCancelButton =  new puOneShot         (140, 10, 210, 50);
        ApHeadingDialogCancelButton ->     setLegend         (gui_msg_CANCEL);
        ApHeadingDialogCancelButton ->     setCallback       (ApHeadingDialog_Cancel);
        
    }
    FG_FINALIZE_PUI_DIALOG( ApHeadingDialog );
}

///////// AutoPilot New Altitude Dialog

static puDialogBox     *ApAltitudeDialog = 0;
static puFrame         *ApAltitudeDialogFrame = 0;
static puText          *ApAltitudeDialogMessage = 0;
static puInput         *ApAltitudeDialogInput = 0;

static puOneShot       *ApAltitudeDialogOkButton = 0;
static puOneShot       *ApAltitudeDialogCancelButton = 0;

void ApAltitudeDialog_Cancel(puObject *)
{
    ApAltitudeDialogInput -> rejectInput();
    FG_POP_PUI_DIALOG( ApAltitudeDialog );
}

void ApAltitudeDialog_OK (puObject *me)
{
    int error = 0;
    string s;
    char *c;
    ApAltitudeDialogInput->getValue( &c );

    if( strlen( c ) ) {
        double NewAltitude;
        if( scan_number( c, &NewAltitude) )
	    {
		if(!(fgAPAltitudeEnabled()))
		    fgAPToggleAltitude();
		fgAPAltitudeSet( NewAltitude );
	    } else {
		error = 1;
		s = c;
		s += " is not a valid number.";
	    }
    }
    ApAltitudeDialog_Cancel(me);
    if( error )  mkDialog(s.c_str());
}

void NewAltitude(puObject *cb)
{
    ApAltitudeDialogInput -> acceptInput();
    FG_PUSH_PUI_DIALOG( ApAltitudeDialog );
}

void NewAltitudeInit(void)
{
    //  printf("NewAltitudeInit\n");
    char NewAltitudeLabel[] = "Enter New Altitude";
    char *s;

    float alt = current_aircraft.fdm_state->get_Altitude();
    int len = 260/2 -
	(puGetStringWidth( puGetDefaultLabelFont(), NewAltitudeLabel )/2);
    
    ApAltitudeDialog = new puDialogBox (150, 50);
    {
        ApAltitudeDialogFrame   = new puFrame  (0, 0, 260, 150);
        ApAltitudeDialogMessage = new puText   (len, 110);
        ApAltitudeDialogMessage    -> setDefaultValue (NewAltitudeLabel);
        ApAltitudeDialogMessage    -> getDefaultValue (&s);
        ApAltitudeDialogMessage    -> setLabel (s);
        
        ApAltitudeDialogInput   = new puInput  ( 50, 70, 210, 100 );
        ApAltitudeDialogInput      -> setValue ( alt );
        // Uncomment the next line to have input active on startup
        // ApAltitudeDialogInput   ->    acceptInput       ( );
        // cursor at begining or end of line ?
        //len = strlen(s);
	//      len = 0;
	//      ApAltitudeDialogInput   ->    setCursor         ( len );
	//      ApAltitudeDialogInput   ->    setSelectRegion   ( 5, 9 );

        ApAltitudeDialogOkButton     =  new puOneShot         (50, 10, 110, 50);
        ApAltitudeDialogOkButton     ->     setLegend         (gui_msg_OK);
        ApAltitudeDialogOkButton     ->     makeReturnDefault (TRUE);
        ApAltitudeDialogOkButton     ->     setCallback       (ApAltitudeDialog_OK);
        
        ApAltitudeDialogCancelButton =  new puOneShot         (140, 10, 210, 50);
        ApAltitudeDialogCancelButton ->     setLegend         (gui_msg_CANCEL);
        ApAltitudeDialogCancelButton ->     setCallback       (ApAltitudeDialog_Cancel);
        
    }
    FG_FINALIZE_PUI_DIALOG( ApAltitudeDialog );
}

/////// simple AutoPilot GAIN / LIMITS ADJUSTER

   
#define fgAP_CLAMP(val,min,max) \
( (val) = (val) > (max) ? (max) : (val) < (min) ? (min) : (val) )

    static void maxroll_adj(puObject *hs)
{
    float val ;
    fgAPDataPtr APData;
    APData = APDataGlobal;
    
    hs -> getValue ( &val ) ;
    fgAP_CLAMP ( val, 0.1, 1.0 ) ;
    //    printf ( "maxroll_adj( %p ) %f %f\n", hs, val, MaxRollAdjust * val ) ;
    APData->MaxRoll = MaxRollAdjust * val;
    sprintf(SliderText[0],"%05.2f", APData->MaxRoll );
    APAdjustMaxRollText -> setLabel ( SliderText[0] ) ;
}

static void rollout_adj(puObject *hs)
{
    float val ;
    fgAPDataPtr APData;
    APData = APDataGlobal;
    
    hs -> getValue ( &val ) ;
    fgAP_CLAMP ( val, 0.1, 1.0 ) ;
    //    printf ( "rollout_adj( %p ) %f %f\n", hs, val, RollOutAdjust * val ) ;
    APData->RollOut = RollOutAdjust * val;
    sprintf(SliderText[1],"%05.2f", APData->RollOut );
    APAdjustRollOutText -> setLabel ( SliderText[1] );
}

static void maxaileron_adj( puObject *hs )
{
    float val ;
    fgAPDataPtr APData;
    APData = APDataGlobal;
    
    hs -> getValue ( &val ) ;
    fgAP_CLAMP ( val, 0.1, 1.0 ) ;
    //    printf ( "maxaileron_adj( %p ) %f %f\n", hs, val, MaxAileronAdjust * val ) ;
    APData->MaxAileron = MaxAileronAdjust * val;
    sprintf(SliderText[3],"%05.2f", APData->MaxAileron );
    APAdjustMaxAileronText -> setLabel ( SliderText[3] );
}

static void rolloutsmooth_adj( puObject *hs )
{
    float val ;
    fgAPDataPtr APData;
    APData = APDataGlobal;
    
    hs -> getValue ( &val ) ;
    fgAP_CLAMP ( val, 0.1, 1.0 ) ;
    //    printf ( "rolloutsmooth_adj( %p ) %f %f\n", hs, val, RollOutSmoothAdjust * val ) ;
    APData->RollOutSmooth = RollOutSmoothAdjust * val;
    sprintf(SliderText[2],"%5.2f", APData->RollOutSmooth );
    APAdjustRollOutSmoothText -> setLabel ( SliderText[2] );
	
}

static void goAwayAPAdjust (puObject *)
{
    FG_POP_PUI_DIALOG( APAdjustDialog );
}

void cancelAPAdjust(puObject *self)
{
    fgAPDataPtr APData  = APDataGlobal;
	
    APData->MaxRoll       = TmpMaxRollValue;
    APData->RollOut       = TmpRollOutValue;
    APData->MaxAileron    = TmpMaxAileronValue;
    APData->RollOutSmooth = TmpRollOutSmoothValue;
    
    goAwayAPAdjust(self);
}

void resetAPAdjust(puObject *self)
{
    fgAPDataPtr APData  = APDataGlobal;
	
    APData->MaxRoll       = MaxRollAdjust / 2;
    APData->RollOut       = RollOutAdjust / 2;
    APData->MaxAileron    = MaxAileronAdjust / 2;
    APData->RollOutSmooth = RollOutSmoothAdjust / 2;
    
    FG_POP_PUI_DIALOG( APAdjustDialog );
    
    fgAPAdjust( self );
}

void fgAPAdjust( puObject * )
{
    fgAPDataPtr APData  = APDataGlobal;
	
    TmpMaxRollValue        = APData->MaxRoll;
    TmpRollOutValue        = APData->RollOut;
    TmpMaxAileronValue     = APData->MaxAileron;
    TmpRollOutSmoothValue  = APData->RollOutSmooth;

    MaxRollValue        = APData->MaxRoll       / MaxRollAdjust;
    RollOutValue        = APData->RollOut       / RollOutAdjust;
    MaxAileronValue     = APData->MaxAileron    / MaxAileronAdjust;
    RollOutSmoothValue  = APData->RollOutSmooth / RollOutSmoothAdjust;

    APAdjustHS0 -> setValue ( MaxRollValue ) ;
    APAdjustHS1 -> setValue ( RollOutValue ) ;
    APAdjustHS2 -> setValue ( RollOutSmoothValue ) ;
    APAdjustHS3 -> setValue ( MaxAileronValue ) ;
    
    FG_PUSH_PUI_DIALOG( APAdjustDialog );
}


// Done once at system initialization
// Done once at system initialization
void fgAPAdjustInit( void ) {

    //  printf("fgAPAdjustInit\n");
#define HORIZONTAL  FALSE

    int DialogX = 40;
    int DialogY = 100;
    int DialogWidth = 230;

    char Label[] =  "AutoPilot Adjust";
    char *s;

    fgAPDataPtr APData = APDataGlobal;

    int labelX = (DialogWidth / 2) -
	(puGetStringWidth( puGetDefaultLabelFont(), Label ) / 2);
    labelX -= 30;  // KLUDGEY

    int nSliders = 4;
    int slider_x = 10;
    int slider_y = 55;
    int slider_width = 210;
    int slider_title_x = 15;
    int slider_value_x = 160;
    float slider_delta = 0.1f;
    
    TmpMaxRollValue       = APData-> MaxRoll;
    TmpRollOutValue       = APData-> RollOut;
    TmpMaxAileronValue    = APData-> MaxAileron;
    TmpRollOutSmoothValue = APData-> RollOutSmooth;

    MaxRollValue       = APData-> MaxRoll / MaxRollAdjust;
    RollOutValue       = APData-> RollOut / RollOutAdjust;
    MaxAileronValue    = APData-> MaxAileron / MaxAileronAdjust;
    RollOutSmoothValue = APData-> RollOutSmooth / RollOutSmoothAdjust;

    puGetDefaultFonts (  &APAdjustLegendFont,  &APAdjustLabelFont );
    APAdjustDialog = new puDialogBox ( DialogX, DialogY ); {
        int horiz_slider_height = puGetStringHeight (APAdjustLabelFont) +
	    puGetStringDescender (APAdjustLabelFont) +
	    PUSTR_TGAP + PUSTR_BGAP + 5;

        APAdjustFrame = new puFrame ( 0, 0,
                                      DialogWidth, 85 + nSliders * horiz_slider_height );

        APAdjustDialogMessage = new puText ( labelX, 52 + nSliders * horiz_slider_height );
        APAdjustDialogMessage -> setDefaultValue ( Label );
        APAdjustDialogMessage -> getDefaultValue ( &s );
        APAdjustDialogMessage -> setLabel        ( s );

        APAdjustHS0 = new mySlider ( slider_x, slider_y, slider_width, HORIZONTAL ) ;
        APAdjustHS0-> setDelta ( slider_delta ) ;
        APAdjustHS0-> setValue ( MaxRollValue ) ;
        APAdjustHS0-> setCBMode ( PUSLIDER_DELTA ) ;
        APAdjustHS0-> setCallback ( maxroll_adj ) ;

        sprintf( SliderText[ 0 ], "%05.2f", APData->MaxRoll );
        APAdjustMaxRollTitle = new puText ( slider_title_x, slider_y ) ;
        APAdjustMaxRollTitle-> setDefaultValue ( "MaxRoll" ) ;
        APAdjustMaxRollTitle-> getDefaultValue ( &s ) ;
        APAdjustMaxRollTitle-> setLabel ( s ) ;
        APAdjustMaxRollText = new puText ( slider_value_x, slider_y ) ;
        APAdjustMaxRollText-> setLabel ( SliderText[ 0 ] ) ;

        slider_y += horiz_slider_height;

        APAdjustHS1 = new mySlider ( slider_x, slider_y, slider_width, HORIZONTAL ) ;
        APAdjustHS1-> setDelta ( slider_delta ) ;
        APAdjustHS1-> setValue ( RollOutValue ) ;
        APAdjustHS1-> setCBMode ( PUSLIDER_DELTA ) ;
        APAdjustHS1-> setCallback ( rollout_adj ) ;

        sprintf( SliderText[ 1 ], "%05.2f", APData->RollOut );
        APAdjustRollOutTitle = new puText ( slider_title_x, slider_y ) ;
        APAdjustRollOutTitle-> setDefaultValue ( "AdjustRollOut" ) ;
        APAdjustRollOutTitle-> getDefaultValue ( &s ) ;
        APAdjustRollOutTitle-> setLabel ( s ) ;
        APAdjustRollOutText = new puText ( slider_value_x, slider_y ) ;
        APAdjustRollOutText-> setLabel ( SliderText[ 1 ] );

        slider_y += horiz_slider_height;

        APAdjustHS2 = new mySlider ( slider_x, slider_y, slider_width, HORIZONTAL ) ;
        APAdjustHS2-> setDelta ( slider_delta ) ;
        APAdjustHS2-> setValue ( RollOutSmoothValue ) ;
        APAdjustHS2-> setCBMode ( PUSLIDER_DELTA ) ;
        APAdjustHS2-> setCallback ( rolloutsmooth_adj ) ;

        sprintf( SliderText[ 2 ], "%5.2f", APData->RollOutSmooth );
        APAdjustRollOutSmoothTitle = new puText ( slider_title_x, slider_y ) ;
        APAdjustRollOutSmoothTitle-> setDefaultValue ( "RollOutSmooth" ) ;
        APAdjustRollOutSmoothTitle-> getDefaultValue ( &s ) ;
        APAdjustRollOutSmoothTitle-> setLabel ( s ) ;
        APAdjustRollOutSmoothText = new puText ( slider_value_x, slider_y ) ;
        APAdjustRollOutSmoothText-> setLabel ( SliderText[ 2 ] );

        slider_y += horiz_slider_height;

        APAdjustHS3 = new mySlider ( slider_x, slider_y, slider_width, HORIZONTAL ) ;
        APAdjustHS3-> setDelta ( slider_delta ) ;
        APAdjustHS3-> setValue ( MaxAileronValue ) ;
        APAdjustHS3-> setCBMode ( PUSLIDER_DELTA ) ;
        APAdjustHS3-> setCallback ( maxaileron_adj ) ;

        sprintf( SliderText[ 3 ], "%05.2f", APData->MaxAileron );
        APAdjustMaxAileronTitle = new puText ( slider_title_x, slider_y ) ;
        APAdjustMaxAileronTitle-> setDefaultValue ( "MaxAileron" ) ;
        APAdjustMaxAileronTitle-> getDefaultValue ( &s ) ;
        APAdjustMaxAileronTitle-> setLabel ( s ) ;
        APAdjustMaxAileronText = new puText ( slider_value_x, slider_y ) ;
        APAdjustMaxAileronText-> setLabel ( SliderText[ 3 ] );

        APAdjustOkButton = new puOneShot ( 10, 10, 60, 50 );
        APAdjustOkButton-> setLegend ( gui_msg_OK );
        APAdjustOkButton-> makeReturnDefault ( TRUE );
        APAdjustOkButton-> setCallback ( goAwayAPAdjust );

        APAdjustCancelButton = new puOneShot ( 70, 10, 150, 50 );
        APAdjustCancelButton-> setLegend ( gui_msg_CANCEL );
        APAdjustCancelButton-> setCallback ( cancelAPAdjust );

        APAdjustResetButton = new puOneShot ( 160, 10, 220, 50 );
        APAdjustResetButton-> setLegend ( gui_msg_RESET );
        APAdjustResetButton-> setCallback ( resetAPAdjust );
    }
    FG_FINALIZE_PUI_DIALOG( APAdjustDialog );
    
#undef HORIZONTAL
}

void fgAPInit( fgAIRCRAFT *current_aircraft )
{
    fgAPDataPtr APData ;

    FG_LOG( FG_AUTOPILOT, FG_INFO, "Init AutoPilot Subsystem" );

    APData  = (fgAPDataPtr)calloc(sizeof(fgAPData),1);
    
    if (APData == NULL) {
	// I couldn't get the mem.  Dying
	FG_LOG( FG_AUTOPILOT, FG_ALERT, "No ram for Autopilot. Dying.");
	exit(-1);
    }
    
    APData->heading_hold = false ;     // turn the heading hold off
    APData->altitude_hold = false ;    // turn the altitude hold off

    APData->TargetHeading = 0.0;    // default direction, due north
    APData->TargetAltitude = 3000;  // default altitude in meters
    APData->alt_error_accum = 0.0;

    // These eventually need to be read from current_aircaft somehow.

#if 0
    // Original values
    // the maximum roll, in Deg
    APData->MaxRoll = 7;
    // the deg from heading to start rolling out at, in Deg
    APData->RollOut = 30;
    // how far can I move the aleron from center.
    APData->MaxAileron= .1;
    // Smoothing distance for alerion control
    APData->RollOutSmooth = 10;
#endif

    // the maximum roll, in Deg
    APData->MaxRoll = 20;

    // the deg from heading to start rolling out at, in Deg
    APData->RollOut = 20;

    // how far can I move the aleron from center.
    APData->MaxAileron= .2;

    // Smoothing distance for alerion control
    APData->RollOutSmooth = 10;

    //Remove at a later date
    APDataGlobal = APData;
    
#if !defined( USING_SLIDER_CLASS )
    MaxRollAdjust       = 2 * APData->MaxRoll;
    RollOutAdjust       = 2 * APData->RollOut;
    MaxAileronAdjust    = 2 * APData->MaxAileron;
    RollOutSmoothAdjust = 2 * APData->RollOutSmooth;
#endif // !defined( USING_SLIDER_CLASS )

    fgAPAdjustInit( ) ;
    NewHeadingInit();
    NewAltitudeInit();
};

int fgAPRun( void )
{
    // Remove the following lines when the calling funcitons start
    // passing in the data pointer

    fgAPDataPtr APData;
    
    APData = APDataGlobal;
    // end section
    
    // heading hold enabled?
    if ( APData->heading_hold == true ) {
	double RelHeading;
	double TargetRoll;
	double RelRoll;
	double AileronSet;
	
	RelHeading =  
	    NormalizeDegrees( APData->TargetHeading - fgAPget_heading());
	// figure out how far off we are from desired heading
	
	// Now it is time to deterime how far we should be rolled.
	FG_LOG( FG_AUTOPILOT, FG_DEBUG, "RelHeading: " << RelHeading );
	
	
	// Check if we are further from heading than the roll out point
	if ( fabs(RelHeading) > APData->RollOut ) {
	    // set Target Roll to Max in desired direction
	    if (RelHeading < 0 ) {
		TargetRoll = 0-APData->MaxRoll;
	    } else {
		TargetRoll = APData->MaxRoll;
	    }
	} else {
	    // We have to calculate the Target roll

	    // This calculation engine thinks that the Target roll
	    // should be a line from (RollOut,MaxRoll) to (-RollOut,
	    // -MaxRoll) I hope this works well.  If I get ambitious
	    // some day this might become a fancier curve or
	    // something.

	    TargetRoll = LinearExtrapolate( RelHeading, -APData->RollOut,
					    -APData->MaxRoll, APData->RollOut,
					    APData->MaxRoll );
	}
	
	// Target Roll has now been Found.

	// Compare Target roll to Current Roll, Generate Rel Roll

	FG_LOG( FG_COCKPIT, FG_BULK, "TargetRoll: " << TargetRoll );
	
	RelRoll = NormalizeDegrees(TargetRoll - fgAPget_roll());

	// Check if we are further from heading than the roll out smooth point
	if ( fabs(RelRoll) > APData->RollOutSmooth ) {
	    // set Target Roll to Max in desired direction
	    if (RelRoll < 0 ) {
		AileronSet = 0-APData->MaxAileron;
	    } else {
		AileronSet = APData->MaxAileron;
	    }
	} else {
	    AileronSet = LinearExtrapolate( RelRoll, -APData->RollOutSmooth,
					    -APData->MaxAileron,
					    APData->RollOutSmooth,
					    APData->MaxAileron );
	}
	
	controls.set_aileron( AileronSet );
	controls.set_rudder( 0.0 );
    }

    // altitude hold or terrain follow enabled?
    if ( APData->altitude_hold || APData->terrain_follow ) {
	double speed, max_climb, error;
	double prop_error, int_error;
	double prop_adj, int_adj, total_adj;

	if ( APData->altitude_hold ) {
	    // normal altitude hold
	    APData->TargetClimbRate = 
		(APData->TargetAltitude - fgAPget_altitude()) * 8.0;
	} else if ( APData->terrain_follow ) {
	    // brain dead ground hugging with no look ahead
	    APData->TargetClimbRate = 
		( APData->TargetAGL - fgAPget_agl() ) * 16.0;
	} else {
	    // just try to zero out rate of climb ...
	    APData->TargetClimbRate = 0.0;
	}

	speed = get_speed();

	if ( speed < 90.0 ) {
	    max_climb = 0.0;
	} else if ( speed < 100.0 ) {
	    max_climb = (speed - 90.0) * 20;
	} else {
	    max_climb = ( speed - 100.0 ) * 4.0 + 200.0;
	}

	if ( APData->TargetClimbRate > max_climb ) {
	    APData->TargetClimbRate = max_climb;
	}

	if ( APData->TargetClimbRate < -400.0 ) {
	    APData->TargetClimbRate = -400.0;
	}

	error = fgAPget_climb() - APData->TargetClimbRate;

	// accumulate the error under the curve ... this really should
	// be *= delta t
	APData->alt_error_accum += error;

	// calculate integral error, and adjustment amount
	int_error = APData->alt_error_accum;
	// printf("error = %.2f  int_error = %.2f\n", error, int_error);
	int_adj = int_error / 8000.0;
	
	// caclulate proportional error
	prop_error = error;
	prop_adj = prop_error / 2000.0;

	total_adj = 0.9 * prop_adj + 0.1 * int_adj;
	if ( total_adj >  0.6 ) { total_adj =  0.6; }
	if ( total_adj < -0.2 ) { total_adj = -0.2; }

	controls.set_elevator( total_adj );
    }

    // auto throttle enabled?
    if ( APData->auto_throttle ) {
	double error;
	double prop_error, int_error;
	double prop_adj, int_adj, total_adj;

	error = APData->TargetSpeed - get_speed();

	// accumulate the error under the curve ... this really should
	// be *= delta t
	APData->speed_error_accum += error;
	if ( APData->speed_error_accum > 2000.0 ) {
	    APData->speed_error_accum = 2000.0;
	}
	if ( APData->speed_error_accum < -2000.0 ) {
	    APData->speed_error_accum = -2000.0;
	}

	// calculate integral error, and adjustment amount
	int_error = APData->speed_error_accum;

	// printf("error = %.2f  int_error = %.2f\n", error, int_error);
	int_adj = int_error / 200.0;
	
	// caclulate proportional error
	prop_error = error;
	prop_adj = 0.5 + prop_error / 50.0;

	total_adj = 0.9 * prop_adj + 0.1 * int_adj;
	if ( total_adj > 1.0 ) { total_adj = 1.0; }
	if ( total_adj < 0.0 ) { total_adj = 0.0; }

	controls.set_throttle( FGControls::ALL_ENGINES, total_adj );
    }

    /*
    if (APData->Mode == 2) // Glide slope hold
    {
    double RelSlope;
    double RelElevator;
        
    // First, calculate Relative slope and normalize it
    RelSlope = NormalizeDegrees( APData->TargetSlope - get_pitch());
    
    // Now calculate the elevator offset from current angle
    if ( abs(RelSlope) > APData->SlopeSmooth )
    {
        if ( RelSlope < 0 )     //  set RelElevator to max in the correct direction
        RelElevator = -APData->MaxElevator;
        else
        RelElevator = APData->MaxElevator;
    }
        
    else
        RelElevator = LinearExtrapolate(RelSlope,-APData->SlopeSmooth,-APData->MaxElevator,APData->SlopeSmooth,APData->MaxElevator);
        
    // set the elevator
    fgElevMove(RelElevator);
        
    }
    */
    
    // Ok, we are done
    return 0;

}

/*
void fgAPSetMode( int mode)
{
    //Remove the following line when the calling funcitons start passing in the data pointer
    fgAPDataPtr APData;
    
    APData = APDataGlobal;
    // end section
    
    fgPrintf( FG_COCKPIT, FG_INFO, "APSetMode : %d\n", mode );
    
    APData->Mode = mode;  // set the new mode
}
*/

void fgAPToggleHeading( void )
{
    // Remove at a later date
    fgAPDataPtr APData;

    APData = APDataGlobal;
    // end section

    if ( APData->heading_hold ) {
	// turn off heading hold
	APData->heading_hold = false;
    } else {
	// turn on heading hold, lock at current heading
	APData->heading_hold = true;
	APData->TargetHeading = fgAPget_heading();
    }

    FG_LOG( FG_COCKPIT, FG_INFO, " fgAPSetHeading: (" 
	    << APData->heading_hold << ") " << APData->TargetHeading );
}


void fgAPToggleAltitude( void )
{
    // Remove at a later date
    fgAPDataPtr APData;

    APData = APDataGlobal;
    // end section

    if ( APData->altitude_hold ) {
	// turn off altitude hold
	APData->altitude_hold = false;
    } else {
	// turn on altitude hold, lock at current altitude
	APData->altitude_hold = true;
	APData->terrain_follow = false;
	APData->TargetAltitude = fgAPget_altitude();
	APData->alt_error_accum = 0.0;
	// alt_error_queue.erase( alt_error_queue.begin(), 
	//                        alt_error_queue.end() );
    }

    FG_LOG( FG_COCKPIT, FG_INFO, " fgAPSetAltitude: (" 
	    << APData->altitude_hold << ") " << APData->TargetAltitude );
}


void fgAPToggleAutoThrottle ( void )
{
    // Remove at a later date
    fgAPDataPtr APData;

    APData = APDataGlobal;
    // end section

    if ( APData->auto_throttle ) {
	// turn off altitude hold
	APData->auto_throttle = false;
    } else {
	// turn on terrain follow, lock at current agl
	APData->auto_throttle = true;
	APData->TargetSpeed = get_speed();
	APData->speed_error_accum = 0.0;
    }

    FG_LOG( FG_COCKPIT, FG_INFO, " fgAPSetAutoThrottle: (" 
	    << APData->auto_throttle << ") " << APData->TargetSpeed );
}

void fgAPToggleTerrainFollow( void )
{
    // Remove at a later date
    fgAPDataPtr APData;

    APData = APDataGlobal;
    // end section

    if ( APData->terrain_follow ) {
	// turn off altitude hold
	APData->terrain_follow = false;
    } else {
	// turn on terrain follow, lock at current agl
	APData->terrain_follow = true;
	APData->altitude_hold = false;
	APData->TargetAGL = fgAPget_agl();
	APData->alt_error_accum = 0.0;
    }

    FG_LOG( FG_COCKPIT, FG_INFO, " fgAPSetTerrainFollow: ("
	    << APData->terrain_follow << ") " << APData->TargetAGL );
}

double LinearExtrapolate( double x,double x1,double y1,double x2,double y2)
{
    // This procedure extrapolates the y value for the x posistion on a line defined by x1,y1; x2,y2
    //assert(x1 != x2); // Divide by zero error.  Cold abort for now
    
    double m, b, y;     // the constants to find in y=mx+b
    m=(y2-y1)/(x2-x1);  // calculate the m
    b= y1- m * x1;  // calculate the b
    y = m * x + b;  // the final calculation
    
    return y;
};

double NormalizeDegrees(double Input)
{
    // normalize the input to the range (-180,180]
    // Input should not be greater than -360 to 360.  Current rules send the output to an undefined state.
    if (Input > 180)
	Input -= 360;
    if (Input <= -180)
	Input += 360;
    
    return (Input);
};