<<>>
<<PreemptablePaintProcsImpl.mesa>>
<<Copyright Ó 1992 by Xerox Corporation.  All rights reserved.>>
<<Greene, June 14, 1990 7:29 pm PDT>>
<<Chauser, June 4, 1992 10:00 am PDT>>
<<Christian Jacobi, April 21, 1993 11:53 am PDT>>


    DIRECTORY
    Draw2d,
    ForkOps,
    Imager,
    PreemptablePaintProcs,
    Process,
    ViewerClasses,
    ViewerOps;

    PreemptablePaintProcsImpl: CEDAR MONITOR LOCKS lc USING lc: LockedContext
    IMPORTS ForkOps, Process, ViewerOps, Draw2d
    EXPORTS PreemptablePaintProcs =


    BEGIN OPEN PreemptablePaintProcs;

    nilLockedContext: LockedContext = NEW[LockedContextRec];

    NilLockedContext: PUBLIC PROC [] RETURNS [LockedContext] ~ {RETURN[nilLockedContext]};

    AbortContext: PUBLIC ENTRY PROC [lc: LockedContext] ~ {
        ENABLE UNWIND => NULL;
        lc.abort ¬ TRUE; lc.suspend ¬ FALSE; NOTIFY lc.stateHasChanged;
        };

    SuspendContext: PUBLIC ENTRY PROC [lc: LockedContext] ~ {
        ENABLE UNWIND => NULL;
        IF NOT lc.abort THEN lc.suspend ¬ TRUE;
        };

    RestartContext: PUBLIC ENTRY PROC [lc: LockedContext] ~ {
        ENABLE UNWIND => NULL;
        lc.suspend ¬ FALSE; NOTIFY lc.stateHasChanged;
        };

    DoUnderLock: PUBLIC ENTRY PROC [lc: LockedContext, Action: LockedContextActionProc] ~ {
        ENABLE UNWIND => NULL;
        WHILE lc.suspend DO WAIT lc.stateHasChanged ENDLOOP;
        IF lc.abort THEN ERROR ABORTED;
        Action[lc.context, lc.zip];
        };

    PaintWithoutLocks: PUBLIC PROC [self: ViewerClasses.Viewer, context: Imager.Context, whatChanged: REF, clear: BOOL, UnlockedPaint: 
    UnlockedPaintProc, PauseWhilePaint: PauseProc ¬ DefaultPauseWhilePaint, PauseWhileIdle: PauseProc ¬ DefaultPauseWhileIdle] 
    RETURNS [lc: LockedContext]
    ~ 
    {
        {
            WITH whatChanged SELECT FROM
                lockedContext: LockedContext => {
                    lc ¬ lockedContext;
                    IF lc.abort THEN RETURN;
                    lc.context ¬ context;
                    lc.zip ¬ Draw2d.GetZip[context, lc.zip];
                    RestartContext[lc];
                    PauseWhilePaint[];
                    GOTO Suspend;
                    }; 
                ENDCASE => {
                    lc ¬ NEW[LockedContextRec ¬ [
                        context: context,
                        zip: Draw2d.GetZip[context],
                        pauseWhileIdle: PauseWhileIdle,
                        viewer: self
                        ]];
                    TRUSTED{Process.Detach[FORK UnlockedPaint[self, lc, whatChanged, clear]]};
                    PauseWhilePaint[];
                    GOTO Suspend;
                    };
            EXITS
                Suspend =>  {
                    SuspendContext[lc];
                ForkOps.Fork[DelayThenContinuePaint, lc];
                    };
            }
        };


    DelayThenContinuePaint: PROC [data: REF] ~ {
        lc: LockedContext ~ NARROW[data];
        IF lc.abort THEN RETURN;
        lc.pauseWhileIdle[];
        IF lc.abort THEN RETURN;
        ViewerOps.PaintViewer[
            viewer: lc.viewer,
            hint: client,
            clearClient: FALSE,
            whatChanged: lc
            ];
        };

    DefaultPauseWhilePaint: PUBLIC PROC[] ~ {Process.PauseMsec[1000]};  --1 seconds of paint

    DefaultPauseWhileIdle: PUBLIC PROC[] ~ {Process.PauseMsec[50]};  --1/25 second idle


    END.