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Q187743: PRB: Right Mouse with Manual OLE D&D Disables Left Mouse

Article: Q187743
Product(s): Microsoft FoxPro
Version(s): WINDOWS:6.0
Operating System(s): 
Keyword(s): 
Last Modified: 26-AUG-1999

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The information in this article applies to:

- Microsoft Visual FoxPro for Windows, version 6.0 
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SYMPTOMS
========

When OLE Drag and Drop is started in manual mode by trapping for the right mouse
button (right-click) on the drag source object, the left mouse button seems to
be disabled until the right mouse button is clicked again.

CAUSE
=====

This is caused by setting the nEffect parameter in the OLEStartDrag() event.

RESOLUTION
==========

Here are two workarounds for this behavior:

- Place the NODEFAULT keyword in the method that calls the OLEDrag() method of
  the drag source. Normally, this is either the MouseDown or the MouseMove
  event.

  -or-

- Do not set the nEffect parameter in the OLEStartDrag() event.

STATUS
======

This behavior is by design.

MORE INFORMATION
================

Steps to Reproduce Behavior
---------------------------

1. Place the following code in a new program file and save it as Test.prg:

        PUBLIC oform1

        oform1=NEWOBJECT("form1")
        oform1.Show
        RETURN

        **************************************************
        *-- Form:         form1
        *-- ParentClass:  form
        *-- BaseClass:    form
        *
        DEFINE CLASS form1 AS form

           Top = 1
           Left = 2
           Height = 350
           Width = 474
           DoCreate = .T.
           OLEDropMode = 1
           Caption = "Try to move the form by dragging after right "+ ;
             "clicking the button"
           WindowState = 0
           BackColor = RGB(0,128,128)
           Name = "Form1"

           ADD OBJECT command1 AS commandbutton WITH ;
              Top = 120, ;
              Left = 240, ;
              Height = 73, ;
              Width = 97, ;
              Caption = "Right Click Me", ;
              Name = "Command1"

           PROCEDURE command1.MouseDown
              LPARAMETERS nButton, nShift, nXCoord, nYCoord
              IF nButton=2
              *   NODEFAULT
                  This.OLEDrag(.T.)
              ENDIF
           ENDPROC

           PROCEDURE command1.OLEDrag
              LPARAMETERS lDetectDrag
              IF lDetectDrag
                 This.ForeColor=RGB(0,255,64)
              ELSE
                 This.ForeColor=RGB(255,0,255)
              ENDIF
           ENDPROC

           PROCEDURE command1.OLECompleteDrag
              LPARAMETERS nEffect
              This.ResetToDefault("ForeColor")
           ENDPROC

           PROCEDURE command1.OLEStartDrag
              LPARAMETERS oDataObject, nEffect
              nEffect=3
           ENDPROC

        ENDDEFINE

2. Run the Test.prg program.

3. Right-click the command button. The caption text should change color when you
  click the button. This is just for visual confirmation.

4. Try to move the form by dragging the title bar with the left mouse. The left
  mouse button should act disabled, or in other words, you should not be able
  to move the form. You may have to right-click the command button more than
  once, because this behavior does not always occur.

5. Right-clicking anywhere on the form enables the left mouse button allowing
  you to move or close the form.

6. Edit the Test.prg file and remove the remark on the NODEFAULT keyword in the
  command1.MouseDown procedure. Save and rerun the form. Note that the left
  mouse button is not disabled.

REFERENCES
==========

For additional information on OLE Drag and Drop in manual mode and the nEffects
parameter, please see the following articles in the Microsoft Knowledge Base:

  Q185654 HOWTO: Starting OLE Drag and Drop In Manual Mode

  Q184386 HOWTO: Using OLE Drag & Drop to Move Controls on a Form

  Q186919 HOWTO: Manual Mode OLE Drag & Drop & Mouse Pointer Changes

Additional query words: kbFVp600 FxprgClassoop

======================================================================
Keywords          :  
Technology        : kbVFPsearch kbAudDeveloper kbVFP600
Version           : WINDOWS:6.0
Issue type        : kbprb

=============================================================================

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