LstDrawList() Crashes!

[Jimi Malcolm]

This probably has an easy answer.  It's probably something simple I'm
overlooking but I thought I'd give you all the source to see the problem in
context.

Here's the new code that I'm working with.  The call to LstDrawList crashes
it saying it's reading from low memory and jibberish appears on the screen.
It uses SysFormPointerArrayToStrings() so watch out when looking through
this for the string pointers to pointers.  It might get a little confusing
but it compiles fine.

Here's the calling code from the MainForm's event handler routine.  This is
where the offending MemHandle and character pointer are defined.  It warned
me to initialize them before using them in MainFormInit().  frmCloseEvent
releases the handle we've been using.  This occurs after the user selects an
item in the list.

<<<CODE>>>
 MemHandle hStrings = 0;
 char  *pStrings = 0;
    ...
  case frmOpenEvent:
   FrmDrawForm(frmPMain);
   MainFormInit(frmPMain, &hStrings, pStrings);
   handled = true;
   break;

  case frmCloseEvent:
   MemHandleFree(hStrings);
   handled = true;
   break;
<<<END>>>

The MainFormInit() is passed the handle and string pointer to store the data
in.

<<<CODE>>>
void MainFormInit(FormPtr frmPMain, MemHandle *hStrings, char *pStrings) {
 UInt8    stringCnt;
 UInt16    topRecordInList = 0;
 UInt32    stringLength,
      offset = 0;  // Offset from start of pStrings to where we are
currently copying
           // Start at neg one because we initiate MemPtrNew with 1
 char    *pTempString;
 MemHandle   hRecord;
 PackedPatientType *pPatient;
 ListPtr    lstPPatients = GetObjectPtr(MainPatientsList);

 *hStrings = MemHandleNew(1); // Just get a pointer and put a dummy size in
it

 for (stringCnt = topRecordInList; stringCnt < topRecordInList +
MAX_HIST_VIEWABLE_ITEMS; stringCnt++) {
  if ((hRecord = DmQueryRecord(gDB, stringCnt)) == NULL)
   break; // No more records to display
  // Lock down that patient's record so we can read from it without the Data
Manager moving it around on us
  pPatient = MemHandleLock(hRecord);

  pTempString = &pPatient->firstField + pPatient->offsetLastName;

  stringLength = StrLen(pTempString) + 1;

  MemHandleResize(*hStrings, offset + stringLength);
  pStrings = MemHandleLock(*hStrings);
  StrCopy(pStrings + offset, pTempString);
  *(pStrings + stringLength - 1) = '\0';
  MemHandleUnlock(*hStrings);
  MemHandleUnlock(hRecord);
  offset += stringLength;
 }

 pStrings = MemHandleLock(*hStrings);
 if ((*hStrings = SysFormPointerArrayToStrings(pStrings, stringCnt)) == 0) {
  FrmCustomAlert(ErrorAlert, "Memory: Unable to convert strings to pointer
array to strings.", "", "");
  return;
 }
 pStrings = MemHandleLock(*hStrings);
 LstSetListChoices(lstPPatients, &pStrings, stringCnt);
 LstDrawList(lstPPatients);
}
<<<END>>>

Thanks a ton.  I've now gone through this for just over four hours straight.

--
Jimi Malcolm
Web Content Manager
inburst Internet Media
inburst.com
jimi.malcolm@inburst



-- 
For information on using the Palm Developer Forums, or to unsubscribe, please see 
http://www.palmos.com/dev/tech/support/forums/