The LA Fox DeveloDer Newsletter

September 1997

Drag and Drop (Con’t from page 3)

object.

do case

case nState = 0 && Entering this object

oSource.Draglcon=this.parent.CanTargetlcon

case nState = 1 && Leaving this object

oSource. Dragicon = this. parent.NoDroplcon

endcase

Keep in mind that oSource is “lstSource”, our Drag source. We

change the cursor from the circle and slash (NODROP.CUR) to

a page with “YES” on it whenever the cursor is over our drop

target. Since both our targets are images and behave in the

same way, this code is identical for either target.

2. The DragDrop method is what gets executed when the ‘drop”

portion occurs. For these two targets the code is nearly identi-

cal:

For the Screen Picture object, the code reads:

LPARAMETERS oSource, nXcoord, nYCoord

FOR ncnt = I to ThisForm.IstSource.ListCount

if ThisFor.1stSource.selected(nCnt)

?? chr(7)

if messagebox(’View Report Now?', +32,’Vlew’)==l

&&OK

cRptNametrim(aReports(nCntj)

report form (cRptName) preview

endif

endf

endfor

and for the Printer Picture Object, the code looks like:

LPARAMETERS oSource, nXCoord, nYCoord

for nCnt = I to ThisForm.IstSource.ListCount

if ThisForm.IstSource.selected(nCnt)

?? chr(7)

if

messagebox(’Print Report Now?’,1+32,’Print’)==1 &&OK

cRptNametrim(aReports(nCnt])

report form (cRptName) noconsole to print

endif

endif

endfor

No rocket science here, just very little code to produce a feature

that can impress our clients and make for stimulating conversa-

tion at cocktail parties.

Files for this demo were all contained in a single directory.

They have been zipped and are available as VFP_DRAG.ZIP on

the LA Fox Website at http://www.mesllc.com/lafox.html.

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LA Fox

Implementation of ActiveX

Controls in Visual FoxPro

Part 2

by Michael W Thomas, Rocky Mountain FUG

Licensing and Distribution

Licensing of ActiveX controls varies greatly. Some charge the

developer a one time fee, sometimes as low as a few hundred

dollars, while others may charge a “per-seat” fee. Some OCX’s

also require a license file (generally have a .LIC extension) to be

distributed with the OCX.

When distributing, you must also make sure that the support

libraries are also available. For ActiveX, you must have the OLE

2.2 libraries installed. Microsoft packages these files into a

self-extracting executable called AXDIST.EXE and is available

from their web site. If using an older OLE-compliant control, the

MFC libraries are required, the latest being version 4.2. Note

that the MFC’s have 16-bit and 32-bit versions with the same file

names. Controls created with Visual Basic also require the

1.3MB VB Virtual Machihe DLL(MSVBVM5O.DLL).

ActiveX controls must be registered on each computer running

the application in order to be used. Fortunately, ActiveX con-

trols, if written property, are self-registering using regsvr32.exe.

In your VFP application, you should check to make sure that

die control is registered bekirz. trying to instantiate it or you will

receive an error (which may notbe trapable within VFP). Each

class has a unique ID that looks like this: {8996B0A1-D7BE-

101 B-8650-00AA003A5593}. All of the classes are registered in

the Windows Registry under HKEY_CLASSES_ROOT\CLSID.

OCX’s are generally installed to the \Windows\System directory.

Documentation

The most difficult part of developing applications using ActiveX is

finding proper documentation. In short, I have not found ad-

equate documentation on any aspect of ActiveX. Even the

Word Basic and VBA command language, used in ActiveX

automation, is difficult to find. Finding documentation for

Exchange client is nearly impossible. Third-party ActiveX

controls will probably offer the most comprehensive documenta-

tion, but it is still insufficient, in my experience. Just a warn-

ing...

ActiveX Controls in Visual FoxPro

Visual FoxPro is an excellent language in which to work with

ActiveX controls. In VFP, ActiveX controls are imbedded in

OLEContainer controls. This provides a feature that is unique to

VFP: the ability to subclass ActiveX controls. Once the

OLEContainer class is defined, it can be instantiated and

subclassed as any other VFP class. In the class designer,

when you select to create a class based on OLEContainer, you

will be prompted with a list of ActiveX controls to choose from.

(Con’t. page 5)

Page 4