KnowledgeBase Archive

An Archive of Early Microsoft KnowledgeBase Articles

View on GitHub

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

Article: Q184386
Product(s): Microsoft FoxPro
Version(s): WINDOWS:6.0
Operating System(s): 
Keyword(s): 
Last Modified: 13-AUG-1999

-------------------------------------------------------------------------------
The information in this article applies to:

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

SUMMARY
=======

In Visual FoxPro version 5.0, Drag and Drop could be used to move Visual FoxPro
controls around on a form. This feature is still available in Visual FoxPro 6.0;
however, the new OLE Drag and Drop features may be used to accomplish this. This
article provides the steps to set up the OLE Drag and Drop properties and
methods to help a programmer get started using OLE Drag and Drop to move
controls around on a form.

The article does not cover the background for OLE Drag and Drop. For more
information on OLE Drag and Drop, see Chapter 31, "Interoperability and the
Internet" in the Microsoft Visual FoxPro "Programmer's Guide," version 6.0.

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

Follow the steps below to create a form with some Visual FoxPro controls that
can be moved around the form using the OLE Drag and Drop feature.

1. Create a new form.

2. Add a command button, label and a text box to the form.

3. Set the OLEDropMode property of the form to 1 - Enabled.

4. Add the following code to the OLEDragOver event of the form. Note that the
  LPARAMETERS line should already be in the event code by default.

        LPARAMETERS oDataObject,nEffect,nButton,nShift,nXCoord,nYCoord,nState
        IF nState=0
           IF oDataObject.GetFormat('VFP Source Object')
              This.OLEDropHasData=1
              This.OLEDropEffects=2
            ENDIF
        ENDIF

5. Add the following code to the OLDDragDrop event of the form. Note that the
  LPARAMETERS line should already be in the event code by default.

        LPARAMETERS oDataObject,nEffect,nButton,nShift,nXCoord,nYCoord
        NODEFAULT
        LOCAL oSource
        IF oDataObject.GetFormat('VFP Source Object')
           oSource=oDataObject.GetData('VFP Source Object')
           oSource.Left=nXCoord
           oSource.Top=nYCoord
        ENDIF

6. Set the following property of the command button, text box and the label:

        OLEDragMode = 1 - Automatic

7. Set the Caption properties of the label and command button and the Value
  property of the text box as desired.

8. Save and run the form.

9. Drag the controls around by clicking them with the left or right mouse
  button, holding the mouse button down and dragging. Notice that the tip of
  the mouse pointer is where the top, left corner of the control will be placed
  when the mouse button is released. In order to move the text box, drag the
  mouse to select blank space or select some text that has been entered. Then
  drag with the highlighted selection.

10. Once the form is successfully run and the dragging and dropping of the
  controls is working, try making this change. Remark out the NODEFAULT
  command in the OLEDragDrop event code of the form as entered in step 5
  above.

11. Save and run the form again. Drag one of the controls with the right mouse
  button. When the control is dropped in the new location, a short- cut
  context menu appears with the options of Move Here and Cancel. Choose either
  one as it makes no difference at this point.

12. Now try changing the This.OLEDropEffects=2 line in the OLEDragOver event of
  the form as shown in step 4 above. Try the different values listed below.
  For each setting, run the form and drag a control with the right mouse.
  Notice how the menu changes. Try holding down the control key while
  dragging.

     This.OLEDropEffects=1       Copy Here and Cancel menu
     This.OLEDropEffects=2       Move Here and Cancel menu
     This.OLEDropEffects=3       Copy Here, Move Here and Cancel menu
     This.OLEDropEffects=4       Link Here and Cancel menu
     This.OLEDropEffects=6       Move Here, Link Here and Cancel menu
     This.OLEDropEffects=7       Move Here, Copy Here, Link Here and
                                    Cancel menu

  OLEDropEffects of 1 (copy), 2 (move) and 4 (link) along with 0 (none) are the
  base drop effect values. The base values can be added together to produce
  combinations - 3, 6 and 7. The NODEFAULT keyword in the OLEDragDrop event
  code is used to suppress the menu when right dragging.

  Further use of OLEDropEffects and the default menu that appears when right
  dragging is beyond the scope of this article. The information above is
  intended to be an introduction.

A brief explanation of the code in the steps above follows. For more in- depth
information, please refer to the articles listed in the REFERENCES section.

First, the OLEDragMode properties of the controls on the form were set to 1 -
Automatic. This allows the different data types that each control supports to be
placed into the Data Object automatically. When the controls were dragged over
the form, the Data Object was queried to see if the 'VFP Source Object' data
format was in the Data Object. The 'VFP Source Object' data type was needed to
move the controls on the form. Once this data type was found with the
OLEDragOver event, the form was told that there was matching data in the Data
Object (This.OLEDropHasData=1) and what different drop effects were supported
(This.OLEDropEffects=2). Then when the mouse button was released, the
OLEDragDrop event checked the Data Object again for the desired format. Once
found, the data in the matching format was obtained from the Data Object
(oSource=oDataObject.GetData()) by creating an object reference to the control
that was stored in the oSource variable in the OLEDragDrop event. The
coordinates of the mouse that were passed to the OLEDragDrop event were used to
set the Top and Left properties of the control.

REFERENCES
==========

Microsoft Visual FoxPro Programmer's Guide, version 6.0, Chapter 31,
"Interoperability and the Internet".

Visual FoxPro Help, 6.0; search on "OLE Drag and Drop"

Additional query words: FxprgClassoop kbvfp600

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

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

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.