path: root/ldmicro/circuit.cpp

//-----------------------------------------------------------------------------
// Copyright 2007 Jonathan Westhues
//
// This file is part of LDmicro.
// 
// LDmicro 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 3 of the License, or
// (at your option) any later version.
// 
// LDmicro 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 LDmicro.  If not, see <http://www.gnu.org/licenses/>.
//------
//
// Routines for modifying the circuit: add a particular element at a
// particular point, delete the selected element, etc. 
// Jonathan Westhues, Oct 2004
//-----------------------------------------------------------------------------
#include <linuxUI.h>
#include <stdio.h>
#include <stdlib.h>
#include <iostream>

#include "ldmicro.h"

static ElemSubcktSeries *LoadSeriesFromFile(FILE *f);

//-----------------------------------------------------------------------------
// Convenience routines for allocating frequently-used data structures.
//-----------------------------------------------------------------------------
ElemLeaf *AllocLeaf(void)
{
    return (ElemLeaf *)CheckMalloc(sizeof(ElemLeaf));
}
ElemSubcktSeries *AllocSubcktSeries(void)
{
    return (ElemSubcktSeries *)CheckMalloc(sizeof(ElemSubcktSeries));
}
ElemSubcktParallel *AllocSubcktParallel(void)
{
    return (ElemSubcktParallel *)CheckMalloc(sizeof(ElemSubcktParallel));
}

//-----------------------------------------------------------------------------
// Routine that does the actual work of adding a leaf element to the left/
// right of or above/below the selected element. If we are adding left/right
// in a series circuit then it's easy; just increase length of that
// subcircuit and stick it in. Same goes for above/below in a parallel
// subcircuit. If we are adding above/below in a series circuit or left/right
// in a parallel circuit then we must create a new parallel (for series) or
// series (for parallel) subcircuit with 2 elements, one for the previously
// selected element and one for the new element. Calls itself recursively on
// all subcircuits. Returns TRUE if it or a child made the addition.
//-----------------------------------------------------------------------------
static BOOL AddLeafWorker(int which, void *any, int newWhich, ElemLeaf *newElem)
{
    int i;

    switch(which) {
        case ELEM_SERIES_SUBCKT: {
            ElemSubcktSeries *s = (ElemSubcktSeries *)any;
            for(i = 0; i < s->count; i++) {
                if(s->contents[i].d.any == Selected) {
                    break;
                }
                if(s->contents[i].which == ELEM_PARALLEL_SUBCKT) {
                    if(AddLeafWorker(ELEM_PARALLEL_SUBCKT, s->contents[i].d.any,
                        newWhich, newElem))
                    {
                        return TRUE;
                    }
                }
            }
            if(i == s->count) break;
            if(s->contents[i].which == ELEM_PLACEHOLDER) {
                // Special case--placeholders are replaced. They only appear
                // in the empty series subcircuit that I generate for them,
                // so there is no need to consider them anywhere but here.
                // If we copy instead of replacing then the DisplayMatrix
                // tables don't get all messed up.
                memcpy(s->contents[i].d.leaf, newElem, sizeof(ElemLeaf));
                s->contents[i].d.leaf->selectedState = SELECTED_LEFT;
                CheckFree(newElem);
                s->contents[i].which = newWhich;
                SelectedWhich = newWhich;
                return TRUE;
            }
            if(s->count >= (MAX_ELEMENTS_IN_SUBCKT-1)) {
                Error(_("Too many elements in subcircuit!"));
                return TRUE;
            }
            switch(Selected->selectedState) {
                case SELECTED_LEFT:
                    memmove(&s->contents[i+1], &s->contents[i],
                        (s->count - i)*sizeof(s->contents[0]));
                    s->contents[i].d.leaf = newElem;
                    s->contents[i].which = newWhich;
                    (s->count)++;
                    break;

                case SELECTED_RIGHT:
                    memmove(&s->contents[i+2], &s->contents[i+1],
                        (s->count - i - 1)*sizeof(s->contents[0]));
                    s->contents[i+1].d.leaf = newElem;
                    s->contents[i+1].which = newWhich;
                    (s->count)++;
                    break;

                case SELECTED_BELOW:
                case SELECTED_ABOVE: {
                    ElemSubcktParallel *p = AllocSubcktParallel();
                    p->count = 2;
    
                    int t;
                    t = (Selected->selectedState == SELECTED_ABOVE) ? 0 : 1;
                    p->contents[t].which = newWhich;
                    p->contents[t].d.leaf = newElem;
                    t = (Selected->selectedState == SELECTED_ABOVE) ? 1 : 0;
                    p->contents[t].which = s->contents[i].which;
                    p->contents[t].d.any = s->contents[i].d.any;
                    
                    s->contents[i].which = ELEM_PARALLEL_SUBCKT;
                    s->contents[i].d.parallel = p;
                    break;
                }
                default:
                    oops();
                    break;
            }
            return TRUE;
            break;
        }
        case ELEM_PARALLEL_SUBCKT: {
            ElemSubcktParallel *p = (ElemSubcktParallel *)any;
            for(i = 0; i < p->count; i++) {
                if(p->contents[i].d.any == Selected) {
                    break;
                }
                if(p->contents[i].which == ELEM_SERIES_SUBCKT) {
                    if(AddLeafWorker(ELEM_SERIES_SUBCKT, p->contents[i].d.any,
                        newWhich, newElem))
                    {
                        return TRUE;
                    }
                }
            }
            if(i == p->count) break;
            if(p->count >= (MAX_ELEMENTS_IN_SUBCKT-1)) {
                Error(_("Too many elements in subcircuit!"));
                return TRUE;
            }
            switch(Selected->selectedState) {
                case SELECTED_ABOVE:
                    memmove(&p->contents[i+1], &p->contents[i],
                        (p->count - i)*sizeof(p->contents[0]));
                    p->contents[i].d.leaf = newElem;
                    p->contents[i].which = newWhich;
                    (p->count)++;
                    break;

                case SELECTED_BELOW:
                    memmove(&p->contents[i+2], &p->contents[i+1],
                        (p->count - i - 1)*sizeof(p->contents[0]));
                    p->contents[i+1].d.leaf = newElem;
                    p->contents[i+1].which = newWhich;
                    (p->count)++;
                    break;

                case SELECTED_LEFT:
                case SELECTED_RIGHT: {
                    ElemSubcktSeries *s = AllocSubcktSeries();
                    s->count = 2;
    
                    int t;
                    t = (Selected->selectedState == SELECTED_LEFT) ? 0 : 1;
                    s->contents[t].which = newWhich;
                    s->contents[t].d.leaf = newElem;
                    t = (Selected->selectedState == SELECTED_LEFT) ? 1 : 0;
                    s->contents[t].which = p->contents[i].which;
                    s->contents[t].d.any = p->contents[i].d.any;
                    
                    p->contents[i].which = ELEM_SERIES_SUBCKT;
                    p->contents[i].d.series = s;
                    break;
                }
                default:
                    oops();
                    break;
            }
            return TRUE;
            break;
        }
    }

    return FALSE;
}

//-----------------------------------------------------------------------------
// Add the specified leaf node in the position indicated by the cursor. We
// will search through the entire program using AddLeafWorker to find the
// insertion point, and AddLeafWorker will stick it in at the requested
// location and return TRUE. We return TRUE if it worked, else FALSE.
//-----------------------------------------------------------------------------
static BOOL AddLeaf(int newWhich, ElemLeaf *newElem)
{
    if(!Selected || Selected->selectedState == SELECTED_NONE) return FALSE;

    int i;
    for(i = 0; i < Prog.numRungs; i++) {
        if(AddLeafWorker(ELEM_SERIES_SUBCKT, Prog.rungs[i], newWhich, newElem))
        {
            WhatCanWeDoFromCursorAndTopology();
            return TRUE;
        }
    }
    return FALSE;
}

//-----------------------------------------------------------------------------
// Routines to allocate memory for a new circuit element (contact, coil, etc.)
// and insert it into the current program with AddLeaf. Fill in some default
// parameters, name etc. when we create the leaf; user can change them later.
//-----------------------------------------------------------------------------
void AddComment(char *str)
{
    if(!CanInsertComment) return;

    ElemLeaf *c = AllocLeaf();
    strcpy(c->d.comment.str, str);

    AddLeaf(ELEM_COMMENT, c);
}
void AddContact(void)
{
    if(!CanInsertOther) return;

    ElemLeaf *c = AllocLeaf();
    strcpy(c->d.contacts.name, "Xnew");
    c->d.contacts.negated = FALSE;

    AddLeaf(ELEM_CONTACTS, c);
}
void AddContactNeg(void)
{
    if(!CanInsertOther) return;

    ElemLeaf *c = AllocLeaf();
    strcpy(c->d.contacts.name, "Xnew");
    c->d.contacts.negated = TRUE;

    AddLeaf(ELEM_CONTACTS, c);
}
void AddCoil(void)
{
    if(!CanInsertEnd) return;

    ElemLeaf *c = AllocLeaf();
    strcpy(c->d.coil.name, "Ynew");
    c->d.coil.negated = FALSE;
    c->d.coil.setOnly = FALSE;
    c->d.coil.resetOnly = FALSE;

    AddLeaf(ELEM_COIL, c);
}
void AddCoilNeg(void)
{
    if(!CanInsertEnd) return;

    ElemLeaf *c = AllocLeaf();
    strcpy(c->d.coil.name, "Ynew");
    c->d.coil.negated = TRUE;
    c->d.coil.setOnly = FALSE;
    c->d.coil.resetOnly = FALSE;

    AddLeaf(ELEM_COIL, c);
}
void AddCoilSet(void)
{
    if(!CanInsertEnd) return;

    ElemLeaf *c = AllocLeaf();
    strcpy(c->d.coil.name, "Ynew");
    c->d.coil.negated = FALSE;
    c->d.coil.setOnly = TRUE;
    c->d.coil.resetOnly = FALSE;

    AddLeaf(ELEM_COIL, c);
}
void AddCoilRes(void)
{
    if(!CanInsertEnd) return;

    ElemLeaf *c = AllocLeaf();
    strcpy(c->d.coil.name, "Ynew");
    c->d.coil.negated = FALSE;
    c->d.coil.setOnly = FALSE;
    c->d.coil.resetOnly = TRUE;

    AddLeaf(ELEM_COIL, c);
}
void AddTimer(int which)
{
    if(!CanInsertOther) return;

    ElemLeaf *t = AllocLeaf();
    strcpy(t->d.timer.name, "Tnew");
    t->d.timer.delay = 100000;

    AddLeaf(which, t);
}
void AddEmpty(int which)
{
    if(!CanInsertOther) return;

    ElemLeaf *t = AllocLeaf();
    AddLeaf(which, t);
}
void AddReset(void)
{
    if(!CanInsertEnd) return;

    ElemLeaf *t = AllocLeaf();
    strcpy(t->d.reset.name, "Tnew");
    AddLeaf(ELEM_RES, t);
}
void AddMasterRelay(void)
{
    if(!CanInsertEnd) return;

    ElemLeaf *t = AllocLeaf();
    AddLeaf(ELEM_MASTER_RELAY, t);
}
void AddShiftRegister(void)
{
    if(!CanInsertEnd) return;

    ElemLeaf *t = AllocLeaf();
    strcpy(t->d.shiftRegister.name, "reg");
    t->d.shiftRegister.stages = 7;
    AddLeaf(ELEM_SHIFT_REGISTER, t);
}
void AddFormattedString(void)
{
    if(!CanInsertOther) return;

    ElemLeaf *t = AllocLeaf();
    strcpy(t->d.fmtdStr.var, "var");
    strcpy(t->d.fmtdStr.string, "value: \\3\\r\\n");
    AddLeaf(ELEM_FORMATTED_STRING, t);
}
void AddLookUpTable(void)
{
    if(!CanInsertEnd) return;

    ElemLeaf *t = AllocLeaf();
    strcpy(t->d.lookUpTable.dest, "dest");
    strcpy(t->d.lookUpTable.index, "index");
    t->d.lookUpTable.count = 0;
    t->d.lookUpTable.editAsString = 0;
    AddLeaf(ELEM_LOOK_UP_TABLE, t);
}
void AddPiecewiseLinear(void)
{
    if(!CanInsertEnd) return;

    ElemLeaf *t = AllocLeaf();
    strcpy(t->d.piecewiseLinear.dest, "yvar");
    strcpy(t->d.piecewiseLinear.index, "xvar");
    t->d.piecewiseLinear.count = 0;
    AddLeaf(ELEM_PIECEWISE_LINEAR, t);
}
void AddMove(void)
{
    if(!CanInsertEnd) return;

    ElemLeaf *t = AllocLeaf();
    strcpy(t->d.move.dest, "dest");
    strcpy(t->d.move.src, "src");
    AddLeaf(ELEM_MOVE, t);
}
void AddMath(int which)
{
    if(!CanInsertEnd) return;

    ElemLeaf *t = AllocLeaf();
    strcpy(t->d.math.dest, "dest");
    strcpy(t->d.math.op1, "src");
    strcpy(t->d.math.op2, "1");
    AddLeaf(which, t);
}
void AddCmp(int which)
{
    if(!CanInsertOther) return;

    ElemLeaf *t = AllocLeaf();
    strcpy(t->d.cmp.op1, "var");
    strcpy(t->d.cmp.op2, "1");
    AddLeaf(which, t);
}
void AddCounter(int which)
{
    if(which == ELEM_CTC) {    
        if(!CanInsertEnd) return;
    } else {
        if(!CanInsertOther) return;
    }

    ElemLeaf *t = AllocLeaf();
    strcpy(t->d.counter.name, "Cnew");
    t->d.counter.max = 0;
    AddLeaf(which, t);
}
void AddReadAdc(void)
{
    if(!CanInsertEnd) return;

    ElemLeaf *t = AllocLeaf();
    strcpy(t->d.readAdc.name, "Anew");
    AddLeaf(ELEM_READ_ADC, t);
}
void AddSetPwm(void)
{
    if(!CanInsertEnd) return;

    ElemLeaf *t = AllocLeaf();
    strcpy(t->d.setPwm.name, "duty_cycle");
    t->d.setPwm.targetFreq = 1000;
    AddLeaf(ELEM_SET_PWM, t);
}
void AddUart(int which)
{
    if(!CanInsertOther) return;

    ElemLeaf *t = AllocLeaf();
    strcpy(t->d.uart.name, "char");
    AddLeaf(which, t);
}
void AddPersist(void)
{
    if(!CanInsertEnd) return;

    ElemLeaf *t = AllocLeaf();
    strcpy(t->d.persist.var, "saved");
    AddLeaf(ELEM_PERSIST, t);
}

//-----------------------------------------------------------------------------
// Any subcircuit containing only one element should be collapsed into its
// parent. Call ourselves recursively to do this on every child of the passed
// subcircuit. The passed subcircuit will not be collapsed itself, so that
// the rung subcircuit may contain only one element as a special case. Returns
// TRUE if it or a child made any changes, and for completeness must be
// called iteratively on the root till it doesn't do anything.
//-----------------------------------------------------------------------------
static BOOL CollapseUnnecessarySubckts(int which, void *any)
{
    BOOL modified = FALSE;

    ok();
    switch(which) {
        case ELEM_SERIES_SUBCKT: {
            ElemSubcktSeries *s = (ElemSubcktSeries *)any;
            int i;
            for(i = 0; i < s->count; i++) {
                if(s->contents[i].which == ELEM_PARALLEL_SUBCKT) {
                    ElemSubcktParallel *p = s->contents[i].d.parallel;
                    if(p->count == 1) {
                        if(p->contents[0].which == ELEM_SERIES_SUBCKT) {
                            // merge the two series subcircuits
                            ElemSubcktSeries *s2 = p->contents[0].d.series;
                            int makeSpaces = s2->count - 1;
                            memmove(&s->contents[i+makeSpaces+1],
                                &s->contents[i+1],
                                (s->count - i - 1)*sizeof(s->contents[0]));
                            memcpy(&s->contents[i], &s2->contents[0],
                                (s2->count)*sizeof(s->contents[0]));
                            s->count += makeSpaces;
                            CheckFree(s2);
                        } else {
                            s->contents[i].which = p->contents[0].which;
                            s->contents[i].d.any = p->contents[0].d.any;
                        }
                        CheckFree(p);
                        modified = TRUE;
                    } else {
                        if(CollapseUnnecessarySubckts(ELEM_PARALLEL_SUBCKT,
                            s->contents[i].d.parallel))
                        {
                            modified = TRUE;
                        }
                    }
                }
                // else a leaf, not a problem
            }
            break;
        }
        case ELEM_PARALLEL_SUBCKT: {
            ElemSubcktParallel *p = (ElemSubcktParallel *)any;
            int i;
            for(i = 0; i < p->count; i++) {
                if(p->contents[i].which == ELEM_SERIES_SUBCKT) {
                    ElemSubcktSeries *s = p->contents[i].d.series;
                    if(s->count == 1) {
                        if(s->contents[0].which == ELEM_PARALLEL_SUBCKT) {
                            // merge the two parallel subcircuits
                            ElemSubcktParallel *p2 = s->contents[0].d.parallel;
                            int makeSpaces = p2->count - 1;
                            memmove(&p->contents[i+makeSpaces+1],
                                &p->contents[i+1],
                                (p->count - i - 1)*sizeof(p->contents[0]));
                            memcpy(&p->contents[i], &p2->contents[0],
                                (p2->count)*sizeof(p->contents[0]));
                            p->count += makeSpaces;
                            CheckFree(p2);
                        } else {
                            p->contents[i].which = s->contents[0].which;
                            p->contents[i].d.any = s->contents[0].d.any;
                        }
                        CheckFree(s);
                        modified = TRUE;
                    } else {
                        if(CollapseUnnecessarySubckts(ELEM_SERIES_SUBCKT,
                            p->contents[i].d.series))
                        {
                            modified = TRUE;
                        }
                    }
                }
                // else a leaf, not a problem
            }
            break;
        }
        
        default:
            oops();
            break;
    }
    ok();
    return modified;
}

//-----------------------------------------------------------------------------
// Delete the selected leaf element from the circuit. Just pull it out of the
// subcircuit that it was in before, and don't worry about creating
// subcircuits with only one element; we will clean that up later in a second
// pass. Returns TRUE if it or a child (calls self recursively) found and
// removed the element.
//-----------------------------------------------------------------------------
static BOOL DeleteSelectedFromSubckt(int which, void *any)
{   
    ok();
    switch(which) {
        case ELEM_SERIES_SUBCKT: {
            ElemSubcktSeries *s = (ElemSubcktSeries *)any;
            int i;
            for(i = 0; i < s->count; i++) {
                if(s->contents[i].d.any == Selected) {
                    ForgetFromGrid(s->contents[i].d.any);
                    CheckFree(s->contents[i].d.any);
                    memmove(&s->contents[i], &s->contents[i+1],
                        (s->count - i - 1)*sizeof(s->contents[0]));
                    (s->count)--;
                    return TRUE;
                }
                if(s->contents[i].which == ELEM_PARALLEL_SUBCKT) {
                    if(DeleteSelectedFromSubckt(ELEM_PARALLEL_SUBCKT,
                        s->contents[i].d.any))
                    {
                        return TRUE;
                    }
                }
            }
            break;
        }
        case ELEM_PARALLEL_SUBCKT: {
            ElemSubcktParallel *p = (ElemSubcktParallel *)any;
            int i;
            for(i = 0; i < p->count; i++) {
                if(p->contents[i].d.any == Selected) {
                    ForgetFromGrid(p->contents[i].d.any);
                    CheckFree(p->contents[i].d.any);
                    memmove(&p->contents[i], &p->contents[i+1],
                        (p->count - i - 1)*sizeof(p->contents[0]));
                    (p->count)--;
                    return TRUE;
                }
                if(p->contents[i].which == ELEM_SERIES_SUBCKT) {
                    if(DeleteSelectedFromSubckt(ELEM_SERIES_SUBCKT,
                        p->contents[i].d.any))
                    {
                        return TRUE;
                    }
                }
            }
            break;
        }
        default:
            oops();
            break;
    }
    return FALSE;
}

//-----------------------------------------------------------------------------
// Delete the selected item from the program. Just call
// DeleteSelectedFromSubckt on every rung till we find it.
//-----------------------------------------------------------------------------
void DeleteSelectedFromProgram(void)
{
    if(!Selected || Selected->selectedState == SELECTED_NONE) return;
    int i = RungContainingSelected();
    if(i < 0) return;

    if(Prog.rungs[i]->count == 1 && 
        Prog.rungs[i]->contents[0].which != ELEM_PARALLEL_SUBCKT)
    {
        Prog.rungs[i]->contents[0].which = ELEM_PLACEHOLDER;
        SelectedWhich = ELEM_PLACEHOLDER;
        Selected->selectedState = SELECTED_LEFT;
        WhatCanWeDoFromCursorAndTopology();
        return;
    }

    int gx, gy;
    if(!FindSelected(&gx, &gy)) {
        gx = 0;
        gy = 0;
    }

    if(DeleteSelectedFromSubckt(ELEM_SERIES_SUBCKT, Prog.rungs[i])) {
        while(CollapseUnnecessarySubckts(ELEM_SERIES_SUBCKT, Prog.rungs[i]))
            ;
        WhatCanWeDoFromCursorAndTopology();
        MoveCursorNear(gx, gy);
        return;
    }
}

//-----------------------------------------------------------------------------
// Free a circuit and all of its subcircuits. Calls self recursively to do
// so.
//-----------------------------------------------------------------------------
void FreeCircuit(int which, void *any)
{
    ok();
    switch(which) {
        case ELEM_SERIES_SUBCKT: {
            ElemSubcktSeries *s = (ElemSubcktSeries *)any;
            int i;
            for(i = 0; i < s->count; i++) {
                FreeCircuit(s->contents[i].which, s->contents[i].d.any);
            }
            CheckFree(s);
            break;
        }
        case ELEM_PARALLEL_SUBCKT: {
            ElemSubcktParallel *p = (ElemSubcktParallel *)any;
            int i;
            for(i = 0; i < p->count; i++) {
                FreeCircuit(p->contents[i].which, p->contents[i].d.any);
            }
            CheckFree(p);
            break;
        }
        CASE_LEAF
            ForgetFromGrid(any);
            CheckFree(any);
            break;

        default:
            oops();
            break;
    }
    ok();
}

//-----------------------------------------------------------------------------
// Free the entire program.
//-----------------------------------------------------------------------------
void FreeEntireProgram(void)
{
    ForgetEverything();   //Uncommented code

    int i;
    for(i = 0; i < Prog.numRungs; i++) {
        FreeCircuit(ELEM_SERIES_SUBCKT, Prog.rungs[i]);
    }
    Prog.numRungs = 0;
    Prog.cycleTime = 10000;
    Prog.mcuClock = 4000000;
    Prog.baudRate = 2400;
    Prog.io.count = 0;
    Prog.mcu = NULL;
}

//-----------------------------------------------------------------------------
// Returns true if the given subcircuit contains the given leaf.
//-----------------------------------------------------------------------------
static BOOL ContainsElem(int which, void *any, ElemLeaf *seek)
{
    switch(which) {
        case ELEM_SERIES_SUBCKT: {
            ElemSubcktSeries *s = (ElemSubcktSeries *)any;
            int i;
            for(i = 0; i < s->count; i++) {
                if(ContainsElem(s->contents[i].which, s->contents[i].d.any,
                    seek))
                {
                    return TRUE;
                }
            }
            break;
        }
        case ELEM_PARALLEL_SUBCKT: {
            ElemSubcktParallel *p = (ElemSubcktParallel *)any;
            int i;
            for(i = 0; i < p->count; i++) {
                if(ContainsElem(p->contents[i].which, p->contents[i].d.any, 
                    seek))
                {
                    return TRUE;
                }
            }
            break;
        }
        CASE_LEAF
            if(any == seek)
                return TRUE;
            break;

        default:
            oops();
    }
    return FALSE;
}

//-----------------------------------------------------------------------------
// Use ContainsElem to find the rung containing the cursor.
//-----------------------------------------------------------------------------
int RungContainingSelected(void)
{
    int i;
    for(i = 0; i < Prog.numRungs; i++) {
        if(ContainsElem(ELEM_SERIES_SUBCKT, Prog.rungs[i], Selected)) {
            return i;
        }
    }

    return -1;
}

//-----------------------------------------------------------------------------
// Delete the rung that contains the cursor.
//-----------------------------------------------------------------------------
void DeleteSelectedRung(void)
{
    if(Prog.numRungs == 1) {
        Error(_("Cannot delete rung; program must have at least one rung."));
        return;
    }

    int gx, gy;
    BOOL foundCursor;
    foundCursor = FindSelected(&gx, &gy);

    int i = RungContainingSelected();
    if(i < 0) return;

    FreeCircuit(ELEM_SERIES_SUBCKT, Prog.rungs[i]);
    Prog.numRungs--;
    memmove(&Prog.rungs[i], &Prog.rungs[i+1], 
        (Prog.numRungs - i)*sizeof(Prog.rungs[0]));

    if(foundCursor) MoveCursorNear(gx, gy);

    WhatCanWeDoFromCursorAndTopology();
}

//-----------------------------------------------------------------------------
// Allocate a new `empty' rung, with only a single relay coil at the end. All
// the UI code assumes that rungs always have a coil in them, so it would
// add a lot of nasty special cases to create rungs totally empty.
//-----------------------------------------------------------------------------
static ElemSubcktSeries *AllocEmptyRung(void)
{
    ElemSubcktSeries *s = AllocSubcktSeries();
    s->count = 1;
    s->contents[0].which = ELEM_PLACEHOLDER;
    ElemLeaf *l = AllocLeaf();
    s->contents[0].d.leaf = l;

    return s;
}

//-----------------------------------------------------------------------------
// Insert a rung either before or after the rung that contains the cursor.
//-----------------------------------------------------------------------------
void InsertRung(BOOL afterCursor)
{
    if(Prog.numRungs >= (MAX_RUNGS - 1)) {
        Error(_("Too many rungs!"));
        return;
    }
    
    int i = RungContainingSelected();
    if(i < 0) return;

    if(afterCursor) i++;
    memmove(&Prog.rungs[i+1], &Prog.rungs[i],
        (Prog.numRungs - i)*sizeof(Prog.rungs[0]));
    Prog.rungs[i] = AllocEmptyRung();
    (Prog.numRungs)++;

    WhatCanWeDoFromCursorAndTopology();
}

//-----------------------------------------------------------------------------
// Swap the row containing the selected element with the one under it, or do
// nothing if the rung is the last in the program.
//-----------------------------------------------------------------------------
void PushRungDown(void)
{
    int i = RungContainingSelected();
    if(i == (Prog.numRungs-1)) return;

    ElemSubcktSeries *temp = Prog.rungs[i];
    Prog.rungs[i] = Prog.rungs[i+1];
    Prog.rungs[i+1] = temp;

    WhatCanWeDoFromCursorAndTopology();
    ScrollSelectedIntoViewAfterNextPaint = TRUE;
}

//-----------------------------------------------------------------------------
// Swap the row containing the selected element with the one above it, or do
// nothing if the rung is the last in the program.
//-----------------------------------------------------------------------------
void PushRungUp(void)
{
    int i = RungContainingSelected();
    if(i == 0) return;

    ElemSubcktSeries *temp = Prog.rungs[i];
    Prog.rungs[i] = Prog.rungs[i-1];
    Prog.rungs[i-1] = temp;

    WhatCanWeDoFromCursorAndTopology();
    ScrollSelectedIntoViewAfterNextPaint = TRUE;
}

//-----------------------------------------------------------------------------
// Start a new project. Give them one rung, with a coil (that they can
// never delete) and nothing else.
//-----------------------------------------------------------------------------
void NewProgram(void)
{
    UndoFlush();
    FreeEntireProgram();
    
    Prog.numRungs = 1;
    Prog.rungs[0] = AllocEmptyRung();
}

//-----------------------------------------------------------------------------
// Worker for ItemIsLastInCircuit. Basically we look for seek in the given
// circuit, trying to see whether it occupies the last position in a series
// subcircuit (which may be in a parallel subcircuit that is in the last
// position of a series subcircuit that may be in a parallel subcircuit that
// etc.)
//-----------------------------------------------------------------------------
static void LastInCircuit(int which, void *any, ElemLeaf *seek,
    BOOL *found, BOOL *andItemAfter)
{
    switch(which) {
        case ELEM_PARALLEL_SUBCKT: {
            ElemSubcktParallel *p = (ElemSubcktParallel *)any;
            int i;
            for(i = 0; i < p->count; i++) {
                LastInCircuit(p->contents[i].which, p->contents[i].d.any, seek,
                    found, andItemAfter);
                if(*found) return;
            }
            break;
        }
        case ELEM_SERIES_SUBCKT: {
            ElemSubcktSeries *s = (ElemSubcktSeries *)any;
            LastInCircuit(s->contents[s->count-1].which,
                s->contents[s->count-1].d.any, seek, found, andItemAfter);
            break;
        }
        default:
            if(*found) *andItemAfter = TRUE;
            if(any == seek) *found = TRUE;
            break;
    }
}

//-----------------------------------------------------------------------------
// Is an item the last one in the circuit (i.e. does one of its terminals go
// to the rightmost bus bar)? We need to know this because that is the only
// circumstance in which it is okay to insert a coil, RES, etc. after
// something
//-----------------------------------------------------------------------------
BOOL ItemIsLastInCircuit(ElemLeaf *item)
{
    int i = RungContainingSelected();
    if(i < 0) return FALSE;

    BOOL found = FALSE;
    BOOL andItemAfter = FALSE;

    LastInCircuit(ELEM_SERIES_SUBCKT, Prog.rungs[i], item, &found,
        &andItemAfter);

    if(found) return !andItemAfter;
    return FALSE;
}

//-----------------------------------------------------------------------------
// Returns TRUE if the subcircuit contains any of the given instruction
// types (ELEM_....), else FALSE.
//-----------------------------------------------------------------------------
static BOOL ContainsWhich(int which, void *any, int seek1, int seek2, int seek3)
{
    switch(which) {
        case ELEM_PARALLEL_SUBCKT: {
            ElemSubcktParallel *p = (ElemSubcktParallel *)any;
            int i;
            for(i = 0; i < p->count; i++) {
                if(ContainsWhich(p->contents[i].which, p->contents[i].d.any,
                    seek1, seek2, seek3))
                {
                    return TRUE;
                }
            }
            break;
        }
        case ELEM_SERIES_SUBCKT: {
            ElemSubcktSeries *s = (ElemSubcktSeries *)any;
            int i;
            for(i = 0; i < s->count; i++) {
                if(ContainsWhich(s->contents[i].which, s->contents[i].d.any,
                    seek1, seek2, seek3))
                {
                    return TRUE;
                }
            }
            break;
        }
        default:
            if(which == seek1 || which == seek2 || which == seek3) {
                return TRUE;
            }
            break;
    }
    return FALSE;
}

//-----------------------------------------------------------------------------
// Are either of the UART functions (send or recv) used? Need to know this
// to know whether we must receive their pins.
//-----------------------------------------------------------------------------
BOOL UartFunctionUsed(void)
{
    int i;
    for(i = 0; i < Prog.numRungs; i++) {
        if(ContainsWhich(ELEM_SERIES_SUBCKT, Prog.rungs[i],
            ELEM_UART_RECV, ELEM_UART_SEND, ELEM_FORMATTED_STRING))
        {
            return TRUE;
        }
    }
    return FALSE;
}

//-----------------------------------------------------------------------------
// Is the PWM function used? Need to know this to know whether we must reserve
// the pin.
//-----------------------------------------------------------------------------
BOOL PwmFunctionUsed(void)
{
    int i;
    for(i = 0; i < Prog.numRungs; i++) {
        if(ContainsWhich(ELEM_SERIES_SUBCKT, Prog.rungs[i], ELEM_SET_PWM, 
            -1, -1))
        {
            return TRUE;
        }
    }
    return FALSE;
}