HOWTO: Manual Mode OLE Drag and Drop Mouse Pointer Changes

• Microsoft Visual FoxPro for Windows, version 6.0

SUMMARY

This article provides the steps for implementing OLE Drag and Drop in manual mode to drag the caption of a command button to a text box. The article also features the Data Object methods ClearData, SetData and the changing of mouse cursors. This article is a more extensive version of the Microsoft Knowledge Base article Q185654, "HOWTO: Starting OLE Drag & Drop In Manual Mode". The steps and the information in this article are the same as those in Q185654. However, there are many enhancements in this article. If you are new to OLE Drag and Drop, we recommend that you start with Q185654.

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

MORE INFORMATION

The steps below illustrate how to implement OLE Drag and Drop in manual mode to drag the caption of a Command button to a Text box. In the steps where you add code to the various events and methods, the LPARAMETERS lines shown are already there by default. Do not add the lines a second time.

1. Create a new form and save the form. Be sure the default directory is set to the folder where the form is saved.



2. Add two command buttons and a text box.



3. Select the command button with the caption of "Command2" and change the caption to "Reset Controls".



4. Place the following code in the Click event of Command2:

   
         Thisform.Text1.Value=SPACE(10)
         Thisform.Command1.Caption="Text To Drag" 




5. Copy the following files from the Visual Studio\Common\Graphics folders specified to the folder where the form is saved:

   
         \Icons\Misc\Eye.ico
         \Cursors\H_move.cur
         \Cursors\H_we.cur 




6. Set the following properties of Command1:

   
         Caption="Text To Drag"
         OLEDragPicture="eye.ico" 




7. Add the following code to the Click event of Command1:

   
         WAIT WINDOW "Hello" 




8. Add the following code to the MouseDown event of Command1:

   
         LPARAMETERS nButton, nShift, nXCoord, nYCoord
   
         IF nButton=2
            *This.OLEDrag(.F.)
            This.OLEDrag(.T.)
         ENDIF 

   This code checks to see if the right mouse button is down. If the right mouse button is down, the code calls the OLEDrag method. You can call the OLEDrag method with either true or false. The difference is shown later in this article.



9. Add the following code to the OLEDrag method of Command1:

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

   The code above changes the color of the caption text of the command button. It is included here as a visual confirmation that the method is firing.



10. Add the following code to the OLEStartDrag event of Command1:

    
          LPARAMETERS oDataObject, nEffect
    
          nEffect=3
          oDataObject.ClearData
          oDataObject.SetData("Hello",1) 

    In this event code, you clear the data in the Data Object, which in this case means that you clear the caption of the command button is from the Data Object. Next, it sets the caption to the word "Hello." for illustration purposes only. If you need to drop the actual command button caption into the text box, you would not use this code. The nEffect parameter is set to 3, which is the sum of 1 (for copy) and 2 (for move). The nEffect parameter is an output parameter that you pass to the OLEDragOver event of the drop target. By default, it would be 7 (copy+move+link). Since this specific code example does not support linking, nEffect is set to 3.
    
    When using OLE Drag and Drop in automatic mode, the OLEStartDrag event is the first event to fire. In manual mode, the MouseDown and OLEDrag methods have to run first to start OLEStartDrag.



11. Add the following code to the OLEGiveFeedback event of Command1:

    
          LPARAMETERS nEffect, eMouseCursor
            DO CASE
             CASE nEffect=1
                eMouseCursor="H_we.cur"
             CASE nEffect=2
                eMouseCursor="H_move.cur"
            ENDCASE 

    The code in this method checks the nEffect parameter. Visual FoxPro automatically sets the nEffect parameter to either 1 or 2, depending on whether or not the control key is depressed. The mouse cursor is then set appropriately. Note that the use of these cursors are for illustration purposes only.



12. Add the following code to the OLECompleteDrag event of Command1:

    
          LPARAMETERS nEffect
    
          DO CASE
          CASE nEffect=2
             This.Caption="You Moved Me"
          CASE nEffect=1
             This.Caption="You Copied Me"
          CASE nEffect=0
             This.Caption="You Didn't Drop Me"
          ENDCASE
          This.ResetToDefault("ForeColor")
          Thisform.Text1.BackColor=RGB(200,224,216) 

    This code checks to see if you should copy or move the text from the command button. The OLEDragDrop event of the drop target (the text box) sets the nEffect parameter and then passes it to the OLECompleteDrag of the drag source (the command button). The programmer then needs to take appropriate action in the OLECompleteDrag.



13. Set the OLEDropMode property of the text box to 1 - Enabled.



14. Add the following code to the OLEDragOver event of the text box:

    
          LPARAMETERS oDataObject, nEffect, nButton, nShift, ;
             nXCoord, nYCoord, nState
    
          DO CASE
          CASE nState=0
             This.BackColor=RGB(10,255,10)
             IF oDataObject.GetFormat(1)    && CF_TEXT
                    This.OLEDropHasData=1
                    This.OLEDropEffects=3     && Copy and Move
             ELSE
                    This.OLEDropHasData=0
                    This.OLEDropEffects=0
             ENDIF
          CASE nState=1
          CASE nState=2
          ENDCASE 

    This code fires when you drag data over the text box. This sets the nState parameter to zero. The event checks the Data Object to see if there is text data in the object. If so, it sets the OLEDropHasData and OLEDropEffects properties. The other cases for nState without any code are for illustration purposes only.



15. Add the following code to the OLEDragDrop event of the text box:

    
          LPARAMETERS oDataObject, nEffect, nButton, nShift, nXCoord, nYCoord
          LOCAL nOperation
    
          IF nShift=2        && Control is down
              nOperation=1   && DropEffect_Copy
          ELSE
              nOperation=2   && DropEffect_Move
          ENDIF
    
          DO CASE
          CASE oDataObject.GetFormat(1)    && CF_TEXT
              This.Value=oDataObject.GetData(1)
              NODEFAULT
          ENDCASE
          nEffect=nOperation 

    This code fires when you drop data onto the text box. The first check that takes place is for the nShift parameter. If the Control key is down, the nEffect parameter sets to 1 for copy, otherwise it is 2 for move. The nEffect parameter is an output parameter so it passes to the OLECompleteDrag event of the drag source, Command1. After the check of the nShift parameter, a check for the Data Object for text data with the oDataObject.GetFormat(1) code occurs. If the check finds text, the Value property of the text box changes to text data. The inclusion of the NODEFAULT keyword here has two purposes. First, if it is not, a shortcut menu appears when you drop the data. Based on the settings in the code above, the menu has options for Copy Here, Move Here and Cancel. This menu essentially does nothing as there has been no allowances made for it in the OLECompleteDrag event of the drag source. Second, if you do not include NODEFAULT, and select either Copy Here or Move Here from the shortcut menu, the text you are dropping into the text box, appears twice. "Hello Hello" is what displays. This is because you set the Value property to "Hello" in the code and then the default drop behavior of the text box adds the second "Hello" to the Value property.



16. Save and run the form. Right-click the "Text To Drag" command button and drag and drop into the text box. Use the Reset Controls command button to reset. Try holding down the Control key while right dragging.
    
    The key program code in the example created above for starting OLE Drag and Drop in manual mode is the code shown in step 8 for the MouseDown event of the drag source. Also note that the OLEDragMode property of the "Text To Drag" command button is set to 0 - Manual.
    
    As stated in step 8, you can call the OLEDrag method with either True (.T.) or False (.F.). If you call OLEDrag with False, the OLEStartDrag event fires immediately. If you call OLEDrag with True, there is a slight delay before the OLEStartDrag event fires. Follow these steps to see the difference.



17. Starting with the OLEDrag method being True, which is how it should be set after step 16 above, right-click the "Text To Drag" command button. There should be a slight delay before the eye icon appears. Try this a few times. It should not be necessary to reset the controls.



18. Modify the form. Open the MouseDown event of the "Text To Drag" command button. Remark out the This.OLEDrag(.T.) and unremark the This.OLEDrag(.F.) lines of code. Save and run the form.



19. Right-click the "Text To Drag" command button. Notice that the eye icon appears immediately. If you move the mouse, the No Drop mouse pointer also appears.

1. As discussed in step 15 above, remark out the NODEFAULT keyword in the OLEDragDrop event of the text box. Run the form and drag the "Text To Drag" command button over the text box. Experiment.



2. Try not clearing and setting the data in the OLEStartDrag event of the "Text To Drag" command button. See step 10 above. Also, try not setting nEffect in the OLEStartDrag event.



3. Try setting the OLEDropEffects for the text box to 1 or 2. See step 14 above for the code. Try this in conjunction with removing the NODEFAULT keyword from the OLEDragDrop event of the text box. Try setting OLEDropEffects to 4 and 7. OLEDropEffect of 4 is Link. Seven is Copy, Move or Link.

REFERENCES

Visual FoxPro Books Online: Programmer's Guide; Chapter 31 - Interoperability and the Internet; OLE Drag and Drop topic.

For additional information, 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

Q185497 HOWTO: Using GridHitTest() with OLE Drag and Drop

Additional query words: kbvfp600

Keywords :
Version : WINDOWS:6.0
Platform : WINDOWS
Issue type : kbhowto