Flushing keyboard buffer

[Paul Marsh]

I have a program for testing circuit boards. A test is performed when the operator clicks the appropriate button or presses the space bar when the button has focus.

My problem is that whilst the test is running I want to prevent further, accidental key presses from causing the routine from running again. Disabling the button doesn't work because I guess subsequent keystrokes are being held in the buffer. In the PB Console Compiler I could flush the keyboard buffer using "Input Flush". I haven't been able to find an equivalent way of doing this in Firefly/PBwin.

Any ideas or pointers please?

- Paul

[paulDiagnos]

I would just disable the button to prevent any keyboard presses, or clicks.

so if they push a button the first command executed for the button call back would be...

FF_Control_Disable (hWndControl) 

then when the test is completed, re-enable the control again ...

FF_Control_Enable (hWndControl )

hope this helps.

PAul

[Paul Marsh]

Thanks Paul.

I tried this but the routine still fires twice. I also tried shifting the focus immediately after it's clicked but I still get the same effect. I guess this is because the key press remains in the buffer and when the control is re-enabled after the test is completed the button picks it up. My reasoning is that if I can flush the buffer before re-enabling the button my troubles will be over ...  but we are talking Windows here!

[TechSupport]

Hi Paul,

I have tried to replicate your result with a simple sample project but I can not get it to receive any more clicks once the button is disabled. Windows is not supposed to sent BN_CLICKED notifications to windows that are disabled. It is in the BN_CLICKED handler that you are disabling the button, right?

Here is the code that I used (Form with two command buttons and a label)

Code Select Expand




'------------------------------------------------------------------------------------------------------------------------
Function FORM1_COMMAND1_BN_CLICKED ( _
                                   ControlIndex     As Long,  _  ' index in Control Array
                                   hWndForm         As Dword, _  ' handle of Form
                                   hWndControl      As Dword, _  ' handle of Control
                                   idButtonControl  As Long   _  ' identifier of button
                                   ) As Long

   Static p As Long
   
   Incr p
   FF_Control_SetText HWND_FORM1_LABEL1, Str$(p)
   
   FF_Control_Disable HWND_FORM1_COMMAND1 
   
   ' Call function that will do the processing. Keystrokes may continue to
   ' be pressed during this time.
   Sleep 5000

End Function


'------------------------------------------------------------------------------------------------------------------------
Function FORM1_COMMAND2_BN_CLICKED ( _
                                   ControlIndex     As Long,  _  ' index in Control Array
                                   hWndForm         As Dword, _  ' handle of Form
                                   hWndControl      As Dword, _  ' handle of Control
                                   idButtonControl  As Long   _  ' identifier of button
                                   ) As Long

   FF_Control_Enable HWND_FORM1_COMMAND1
   SetFocus HWND_FORM1_COMMAND1

End Function


[Paul Marsh]

Hi Paul -

Thanks for the usual excellent support.

Essentially the only difference between your code and mine seems to be that for each routine I've re-enabled the control from inside its own BN_CLICKED handler after the test routine has finished thus -

Code Select Expand


Function FORM1_COMMAND1_BN_CLICKED ( _
                                   ControlIndex     As Long,  _  ' index in Control Array
                                   hWndForm         As Dword, _  ' handle of Form
                                   hWndControl      As Dword, _  ' handle of Control
                                   idButtonControl  As Long   _  ' identifier of button
                                   ) As Long

   Static p As Long
   
   Incr p
   FF_Control_SetText HWND_FORM1_LABEL1, Str$(p)
   
   FF_Control_Disable HWND_FORM1_COMMAND1 
   
   ' Call function that will do the processing. Keystrokes may continue to
   ' be pressed during this time.
   Sleep 5000

   FF_Control_Enable HWND_FORM1_COMMAND1
   SetFocus HWND_FORM1_COMMAND1

End Function


This seems to be what's causing my problem. Maybe I'm doing something fundamentally silly here?

Now that I know your code works I'll re-consider my interface so that I use a second control to re-enable the first.

- Paul

[TechSupport]

I wonder if you Postmessage a user defined message rather than re-enabling from inside BN_CLICKED. The theory would be that it would allow BN_CLICKED to fully finish prior to re-enabling the control. I haven't tested it but maybe it's worth a try.

Code Select Expand


%MSG_USER_ENABLE = %WM_USER + 100

Function FORM1_COMMAND1_BN_CLICKED ( _
                                   ControlIndex     As Long,  _  ' index in Control Array
                                   hWndForm         As Dword, _  ' handle of Form
                                   hWndControl      As Dword, _  ' handle of Control
                                   idButtonControl  As Long   _  ' identifier of button
                                   ) As Long

   Static p As Long
   
   Incr p
   FF_Control_SetText HWND_FORM1_LABEL1, Str$(p)
   
   FF_Control_Disable HWND_FORM1_COMMAND1 
   
   ' Call function that will do the processing. Keystrokes may continue to
   ' be pressed during this time.
   Sleep 5000

   ' Post a message to re-enable the command button
   PostMessage hWndForm, %MSG_USER_ENABLE, 0, 0

End Function


Function FORM1_CUSTOM ( _
                      hWndForm      As Dword, _  ' handle of Form
                      wMsg          As Long,  _  ' type of message
                      wParam        As Dword, _  ' first message parameter
                      lParam        As Long   _  ' second message parameter
                      ) As Long

   Select Case wMsg
      Case %MSG_USER_ENABLE
         FF_Control_Enable HWND_FORM1_COMMAND1
         SetFocus HWND_FORM1_COMMAND1
   End Select
   
End Function


[Paul Marsh]

Hi Paul -

Alas this doesn't work 

- Paul