CALLBACK functions in cvi

Question

hi,
Need a simple clarification on working with callback function.
i have 3 different callback buttons function as start test, stop test, quit.
Whenever Start test button is pressed by EVENT_COMMIT, it calls some functions and executes the same. in the middle of this function execution i need to stop the test by pressing stop test button or i need to quit the interface. How can i do this?
i am facing problem like once i press the start button i am not getting controls to other button until the all functions available inside start button gets completed.
Thanks in advance
Solved!
Go to Solution.

Answer 1

The sleep (1000) and not calling ProcessSystemEvents () are the reasons!
Sleep () completely blocks the program until the time has expired. It is advisable that you dont call it for long intervals!
If you don't call ProcessSystemEvents () you cannot get stop button press
Try modifying the code this way:
int    requestToStop;    // Define this at module level
int CVICALLBACK Btn_Start_Test (int panel, int control, int event,
  void *callbackData, int eventData1, int eventData2)
switch (event)  {
 case EVENT_COMMIT:
   requestToStop = 0;    // Clear stop flag and start the test
   if (Tree_getselectedChilditems())
       MessagePopup ("Info", "Operator stopped the test!");
   else
       MessagePopup("Info","TEST COMPLETED SUCCESSFULLY");
   break;
 return 0;
int CVICALLBACK btn_stop_test (int panel, int control, int event,
  void *callbackData, int eventData1, int eventData2)
 switch (event)  {
  case EVENT_COMMIT:
    requestToStop = 1;
//  XL_KillWindowsProcess("EXCEL.EXE");//not exactly excel file,it may be any file which is running 
    break;
 return 0;
int Tree_getselectedChilditems (void)     //double testcaseno)
 int noOfItems;int val,i;  //int index;
 int noOfChild,index=1;
 char treelabel[500]={0};
 char charval;char TCno[100];
 int select;  char testno[100]={0};
 double tini;
  for(error = GetTreeItem (panelHandle, PANEL_TREE, VAL_CHILD, 0, VAL_FIRST, VAL_NEXT_PLUS_SELF, VAL_MARKED, &index);
          index >= 0&&error<=0;error = GetTreeItem(panelHandle, PANEL_TREE, VAL_ALL, 0,
                index, VAL_NEXT, VAL_MARKED, &index))
         GetTreeCellAttribute(panelHandle, PANEL_TREE,
            index, 0, ATTR_LABEL_TEXT, treelabel);
   Scan(treelabel,"%s",TCno);
   strcpy(testcaseno,TCno);
//   Sleep(1000);     // Substitute this line with the following code
     tini = Timer ();
     while (Timer () - tini < 1.0) {
        ProcessSystemEvents ();
        if (RequestToStop) break;     // Operator stoo
   readTestcasesheet(ExcelWorkbookHandle, ExcelWorksheetHandle,testcaseno);
   Fmt(treelabel,"%s",""); 
   if (RequestToStop) break;     // Operator stop
  return requestToStop;
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