Developer CD Series 1998 November: Tool Chest/Dev.CD Nov 98 TC.toast/Sample Code/Snippets/Development Tools & Languages/DTSCPlusLibrary/Sources/UserTermination.cp

Text File | 1993-01-14 | 5.0 KB | 166 lines | [TEXT/MPS ]

/* _________________________________________________________________________________________________________ //
  Copyright © 1992 Apple Computer, Inc. All rights reserved.
  Macintosh Developer Technical Support.C++ Macintosh Toolbox Framework.
  Programmer: Kent Sandvik
  Date: 9/26/92
  Revision comments are at the end of this file.
  ---
  TUserTermination is a command dot tracking class, used for finding out if the end user wants to stop
  an action. Most of the code is based on earlier snippet by Dave Radcliffe/DTS.
  TUserTermination.cp contains class body information for the TUserTermination class.
  _________________________________________________________________________________________________________ */

#ifndef _USERTERMINATION_
#include "UserTermination.h"
#endif


// _________________________________________________________________________________________________________ //
// TGDevice class member function implementations

//    CONSTRUCTORS & DESTRUCTORS
#pragma segment UserTermination
TUserTermination::TUserTermination(char ASCIIValue)
// The default constructor wants an ASCII char, such as '.' as value (that is default).
// It will call the initialize function that will map the ASCII value to a virtual key code.
{
    long auxVersion = 0;

    // Initialize fields to known values
    fChar = ASCIIValue;
    fKeyCode = 0;

    // Test if A/UX is present or not, needed later for the event handling code
    OSErr anErr = Gestalt(gestaltAUXVersion, &auxVersion);
    if (anErr == gestaltUnknownErr || auxVersion == 0)
        fAUX = false;
    else
        fAUX = true;

    // Do any other dynamic initialization
    this->Initialize();
}


#pragma segment UserTermination
TUserTermination::~TUserTermination()
// Default constructor, nothing just now.
{
}


//    INITIALIZATION ROUTINES
#pragma segment UserTermination
void TUserTermination::Initialize()
// Initialize will fetch the KCHR handle, and convert the ASCII character to
// a real virtual key code.
{
    Handle hKCHR = NULL;
    Ptr pKCHR;
    short KCHRId;
    Boolean notDone;
    long state;
    long ktResult;

    pKCHR = (Ptr)GetEnvirons(smKCHRCache);        // try to get the pointer directly
    if (!pKCHR)                                    // maybe pre-System7
    {
        KCHRId = (short)GetScript(short(GetEnvirons(smKeyScript)), smScriptKeys);
        hKCHR = GetResource('KCHR', KCHRId);    // get the KCHR resource
        pKCHR = *hKCHR;                            // get the pointer
    }
    notDone = true;

    if (pKCHR)
    {
        state = 0;

        while ((fKeyCode <= 0x7F) && notDone)
            // loop through all possible keycodes
            {
                ktResult = KeyTrans((pKCHR), fKeyCode, &state);// get the ASCII value
                if (((ktResult & ktAscii1Mask) == fChar) || ((ktResult & ktAscii2Mask) == fChar))// check result for desited real char
                    notDone = false;
                else
                    fKeyCode++;                    // keep looking
            }
    }
    // Clean up
    if (hKCHR)
        ReleaseResource(hKCHR);

    if (notDone)
        fKeyCode = -1;                            // set an insane value

    return;                                        // job done
}


//    MAIN INTERFACE

#pragma segment UserTermination
Boolean TUserTermination::Abort()
//    Abort returns true if the user has pressed Command-Period.
//    It does this by walking the event queue.  Walking the event queue is not
//    recommended, but since we want a Command-Period event to take priority over
//    any other events in the queue, looking ahead in the queue is the only way.
//
//    Note that for A/UX, this technique does not work as A/UX does not support
//    the Macintosh event queue structure.  In that case, we will call CheckAUXEventQueue
//    to find the result.
{
    Boolean foundEvent = false;
    EvQElPtr eventQPtr;
    QHdrPtr eventQHdr;

    if (fAUX)                                    // we are running A/UX
        foundEvent = this->CheckAUXEventQueue(fKeyCode, cmdKey);
    else
    {
        eventQHdr = GetEvQHdr();                // get the event queue
        eventQPtr = (EvQElPtr)eventQHdr->qHead;    // get the first element

        while (eventQPtr &&!foundEvent)
        {
            foundEvent = (((eventQPtr->evtQMessage & keyCodeMask) >> 8) == fKeyCode && (eventQPtr->evtQModifiers & cmdKey));// the event we want + cmd key?

            if (!foundEvent)
                eventQPtr = (EvQElPtr)eventQPtr->qLink;// get the next element in the queue
        }
    }
    return foundEvent;
}


//    PRIVATE INTERNAL FUNCTIONS

#pragma segment UserTermination
Boolean TUserTermination::CheckAUXEventQueue(char keyCode,
                                             short modifiers)
{
    struct
    {
        EventRecord mask;
        EventRecord value;
    } eventFilter;

    eventFilter.mask.what = everyEvent;
    eventFilter.value.what = keyDown;            // look for a keydown event
    eventFilter.mask.message = keyCodeMask;
    eventFilter.value.message = keyCode << 8;    // Set keyCode
    eventFilter.mask.modifiers = modifiers;
    eventFilter.value.modifiers = modifiers;    // Set modifiers
    eventFilter.mask.when = 0;
    eventFilter.mask.where.v = 0;                // Zero out other stuff
    eventFilter.mask.where.h = 0;
    return ((AUXDispatch(kAUXFindEvent, (char*) & eventFilter) > 0) && (eventFilter.value.what != nullEvent));// Have A/UX look for us
}


// _________________________________________________________________________________________________________ //

/*    Change History (most recent last):
  No        Init.    Date        Comment
  1            khs        9/26/92        New file
*/