Using EXIT Command

[C.M. Rouleau]

Is it possible to use the exit command to sense a DDT button
press or Escape key press? I'd like to exit a block structure
such as FOR/NEXT or DO/LOOP if one of these events occurs but I'm
not sure how to do it. Are there any other simple ways to interrupt
a block structure if one has an impatient user?

Thanks

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[Sven Blumenstein]

Youy can run your Loop in a THREAD and Terminate / Stop the THREAD
if the User wants to interrupt it.

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[C.M. Rouleau]

Originally posted by Sven Blumenstein:
Youy can run your Loop in a THREAD and Terminate / Stop the THREAD
if the User wants to interrupt it.

Ok, I've looked at the thread command and it looks rather straight
forward to run my loop in a thread. THREAD CLOSE seems to be the
closest thing to terminating or stopping a thread as you noted above,
but the command description says it won't stop a thread if it is still
running - it simply releases its handle. Thus, I'm still confused
as to how you kill a loop for impatient users - could you provide
a snippet of code?

Thanks

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[Lance Edmonds]

The easiest way is to use a GLOBAL LONG and periodically test it's value from within the thread.


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Lance
PowerBASIC Support
mailto:[email protected][email protected]</A>

[Semen Matusovski]

I do something like this

   #Compile Exe
   #Dim All
   #Register None
   #Include "Win32Api.INC"

   Sub DOGUIMessage(hDlg As Long)
      Dim Msg As tagMsg
      While PeekMessage(Msg, %NULL, %NULL, %NULL, %PM_REMOVE)
         If IsFalse(IsDialogMessage(hDlg, Msg)) Then
            TranslateMessage Msg
            DispatchMessage Msg
         End If
      Wend
   End Sub

   CallBack Function DlgProc
      Static Terminate As Long
      Local i As Long, j As Long
      Select Case CbMsg
         Case %WM_INITDIALOG
            Control Add Label,  CbHndl, 101, "",      10, 10, 50, 15
            Control Add Button, CbHndl, 102, "Start", 10, 30, 50, 15
            Control Add Button, CbHndl, 103, "Stop",  10, 50, 50, 15
         Case %WM_COMMAND
            If CbCtl = 102 Then
               Terminate = 0
               Do
                  If Terminate Then MsgBox "Terminated": Exit Do
                  For i = 1 To 1000000: Next: Incr j
                  Control Set Text CbHndl, 101, Format$(j)
                  DoGUIMessage CbHndl
               Loop
           ElseIf CbCtl = 103 Then
              Terminate = 1
           End If

      End Select
   End Function

   Function PbMain
      Dim hDlg As Long
      Dialog New 0, "Test", ,, 100, 100, %WS_CAPTION Or %WS_SYSMENU Or %WS_MINIMIZEBOX To hDlg
      Dialog Show Modal hDlg Call DlgProc
   End Function

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E-MAIL: [email protected]

[C.M. Rouleau]

Originally posted by Semen Matusovski:
I do something like this

   Sub DOGUIMessage(hDlg As Long)
      Dim Msg As tagMsg
      While PeekMessage(Msg, %NULL, %NULL, %NULL, %PM_REMOVE)
         If IsFalse(IsDialogMessage(hDlg, Msg)) Then
            TranslateMessage Msg
            DispatchMessage Msg
         End If
      Wend
   End Sub

Thanks Semen. I used a combination of your code above and Lance's
suggestion about going global to do what I wanted to do without using
threads. My success seems to be a result of your code snippet above -
what does the sub do? Is it some sort of message eater?

Just curious


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[Semen Matusovski]

> Is it some sort of message eater?

Correctly to say - a processor, because this block does exactly the same work as DDT message pump and equal Dialog Doevents upto the "end of query".
Forgot to mention. In sample above it's necessary to prevent double enterance for WM_COMMAND, CbCtl = 102.
(special static variable, which indicates that process already running).

[This message has been edited by Semen Matusovski (edited July 27, 2001).]

[C.M. Rouleau]

Semen,

The following code is based on your example and the idea of a message
processor to free up time slices. I tried DIALOG DOEVENTS instead
of your sub program and everything seems to work fine - the user is
able to start and interrupt the process at will. I was wondering,
however, if I'm overlooking something or have I found another way
to do what I originally wanted to do.

-Just curious

#COMPILE EXE
#REGISTER NONE
#INCLUDE "Win32Api.INC"
 
GLOBAL terminate_flag AS INTEGER
 
CALLBACK FUNCTION do_something()
    'set the terminate flag to zero
    terminate_flag=0
    'run some process
    DO
    IF terminate_flag THEN EXIT DO
    '
    'code to do something in the loop
    '
    'make sure this process doesn't hog the cpu
    DIALOG DOEVENTS
    LOOP
END FUNCTION
 
CALLBACK FUNCTION terminate_process()
    IF MSGBOX ("Are you sure you want to terminate the count?", %MB_YESNO, "Title Bar") = 7 THEN EXIT FUNCTION
    'set the terminate flag if user chooses yes
    terminate_flag=1
END FUNCTION
 
CALLBACK FUNCTION exit_dialog()
    IF MSGBOX ("Are you sure you want to exit?", %MB_YESNO, "Title Bar") = 7 THEN EXIT FUNCTION
    terminate_flag=1
    DIALOG END CBHNDL
END FUNCTION
 
' the main program
FUNCTION PBMAIN
    DIM hDlg AS LONG
    'create a dialog
    DIALOG NEW 0, "Title",,, 100, 100, %WS_CAPTION OR %WS_SYSMENU OR %WS_MINIMIZEBOX TO hDlg
    'add a dynamic label
    CONTROL ADD LABEL,  hDlg, 101, "", 10, 10, 50, 15, %SS_SUNKEN
    'and some buttons
    CONTROL ADD BUTTON, hDlg, 102, "Start", 10, 30, 50, 15, CALL do_something
    CONTROL ADD BUTTON, hDlg, 103, "Stop", 10, 50, 50, 15, CALL terminate_process
    CONTROL ADD BUTTON, hDlg, 104, "Exit", 10, 70, 50, 15, CALL exit_dialog
    'now show it
    DIALOG SHOW MODAL hDlg
END FUNCTION

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[Lance Edmonds]

In this case, DIALOG DOEVENTS is not "freeing timeslices" as such, but is giving a helping hand to the message pump so UI interactions are handled smoothly while the time-consuming processing code is executing.

This is a common strategy, easy to implement, and works well.

If you actually want to release the current timeslice (say, to reduce the CPU loading), use SLEEP %NULL (or SLEEP 0).

Note that your INTEGER (GLOBAL var) should be a LONG rather than an INTEGER (LONG is more efficient then INTEGER in Win32, and it works best for inter-Thread signalling without the need to use Synchronization Objects).

------------------
Lance
PowerBASIC Support
mailto:[email protected][email protected]</A>

[C.M. Rouleau]

So would I replace DIALOG DOEVENTS with SLEEP 0 or would I simply
add SLEEP 0 to my code after DIALOG DOEVENTS?

Thanks for the advice on LONG vs INTEGER - I'll make the switch.

Originally posted by Lance Edmonds:
In this case, DIALOG DOEVENTS is not "freeing timeslices" as such, but is giving a helping hand to the message pump so UI interactions are handled smoothly while the time-consuming processing code is executing.

This is a common strategy, easy to implement, and works well.

If you actually want to release the current timeslice (say, to reduce the CPU loading), use SLEEP %NULL (or SLEEP 0).

Note that your INTEGER (GLOBAL var) should be a LONG rather than an INTEGER (LONG is more efficient then INTEGER in Win32, and it works best for inter-Thread signalling without the need to use Synchronization Objects).

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[Semen Matusovski]

> if I'm overlooking something or have I found another way

I think, first.
Dialog Doevents processes one message only and it's not clear how often you should execute it.
From one side, if to do Dialog DoEvebts too often, you will lose a lot of time, because Dialog Doevents (GetMessage ?) doesn't return control immediatelly, if there are no messages in query.
From another side, if to do Dialog DoEvents not very often, remains messages in query and will begin repaint and other problems. OS posts a waste of messages.

My sub (actually nothing new for patent ) allows periodically to process ALL events, which are currently in query.

About Sleep ...
I cut a fragment from real app not successful (here Sleep is present, but outside this sub - one Sleep per some DoGUIMessage - I have reasons).
In geberal case it's possible to add Sleep 0 after Wend.

[This message has been edited by Semen Matusovski (edited July 30, 2001).]