
    <<DisplayControllers.Mesa>>
        <<Mike Spreitzer August 26, 1986 8:52:23 pm PDT>>

    DIRECTORY CharDisplays, IO, Rope;

    DisplayControllers: CEDAR DEFINITIONS = {

        REFTEXT: TYPE = REF TEXT;
        ROPE: TYPE = Rope.ROPE;
        CharDisplay: TYPE = CharDisplays.CharDisplay;
        BoolDefaultsFalse: TYPE = CharDisplays.BoolDefaultsFalse;

        DisplayController: TYPE = REF DisplayControllerRep;
        DisplayControllerRep: TYPE = RECORD [
            cd: CharDisplay,
            cp: ControlProgram,
            cps: ControlProgramState,
            toDisplay, fromDisplay: IO.STREAM,
                <<Destruction of the display, and hence the controller, closes these streams.>>
            driver: IO.STREAM _ NIL
                <<Here for only one purpose: driver.CharsAvail[] tells whether more coming soon.>>
            ];

        Create: PROC [cd: CharDisplay, cp: ControlProgram] RETURNS [dc: DisplayController];

        SetDriver: PROC [dc: DisplayController, driver: IO.STREAM];

        ControlProgram: TYPE = REF ControlProgramRep;
        ControlProgramRep: TYPE = RECORD [
            bits: [7 .. 8],
            start: Vertex,
            Init: PROC [dc: DisplayController],
            clientData: REF ANY
            ];

        Vertex: TYPE = REF VertexRep;
        VertexRep: TYPE = RECORD [
            repStyle: VertexRepStyle,
            t: Transition _ [[NIL, NIL], NIL],
            edgeList: EdgeList _ NIL,
            edgeArray: TransitionArray _ NIL];

        VertexRepStyle: TYPE = {epsilon, list, array};

        TransitionArray: TYPE = REF TransitionArrayRep;
        TransitionArrayRep: TYPE = ARRAY CHAR OF Transition;

        EdgeList: TYPE = LIST OF Edge;
        Edge: TYPE = RECORD [
            char: CHAR,
            transition: Transition
            ];

        Transition: TYPE = RECORD [
            action: Action,
            newVertex: Vertex];

        Action: TYPE = RECORD [proc: ActionProc, clientData: REF ANY _ NIL, overrideable: BOOL _ FALSE];
        ActionProc: TYPE = PROC [dc: DisplayController, clientData: REF ANY];

        ControlProgramState: TYPE = REF ControlProgramStateRep;
        ControlProgramStateRep: TYPE = RECORD [
            curVertex: Vertex _ NIL,
            regs: ARRAY RegID OF INTEGER _ ALL[0],
            modes: Modes _ ALL[FALSE],
            chars--since last in start state--: REFTEXT,
            clientData: REF ANY _ NIL
            ];

        RegID: TYPE = {line, col, aux1, aux2, aux3, aux4};

        Mode: TYPE = {insert, delete};
        Modes: TYPE = ARRAY Mode OF BoolDefaultsFalse;

        NewControlProgram: PROC [Init: PROC [dc: DisplayController] _ NIL, clientData: REF ANY _ NIL, bits: [7 .. 8] _ 8] RETURNS [cp: 
        ControlProgram];

        AddInstruction: PROC [cp: ControlProgram, steps: StepList, final: Action];

        StepList: TYPE = LIST OF Step;
        Step: TYPE = REF ANY --actually UNION [ROPE, REFTEXT, Decode]--;

        Decode: TYPE = REF DecodeRep;
        DecodeRep: TYPE = RECORD [
            reg: RegID,
            base: NAT _ 10,
            org: CHAR _ '0,
            offset: INT _ 0,
            xor: INTEGER _ 0,
            len: NAT _ 0 --=0 means variable length, #0 means fixed--];
            <<decodes ((char XOR xor) - org) by base, then adds offset>>

        NumChars: NAT = (LAST[CHAR] - FIRST[CHAR]) + 1;

        Naught: ActionProc;
        Print: ActionProc;

        }.