MORE INFORMATION
Brief Description of Each Function
_FreeObject() - releases an object from the Visual FoxPro API data pool.
_GetObjectProperty() - returns a property value for an object.
_ObjectCmp() - compares the properties of two objects and returns 0 if
their properties and property values are identical.
_ObjectReference() - Increments the reference count of an object.
_ObjectRelease() - Decrements the reference count of an object.
_SetObjectProperty() - Sets a property for an object.
_WGetObjectClientWindow() - Returns the handle of the client window in
which the specified object is contained.
_WGetObjectWindow() - Returns the handle of the frame window in which
the specified object is contained.
Uses for the Functions
The use of some of these object functions may not be immediately apparent.
The _FreeObject(), _ObjectReference(), and _ObjectRelease() functions can
be thought of as similar to the memory locking functions.
To be sure that the object reference is valid between calls, you can call
ObjectReference(), like _HLock, to tell Visual FoxPro not to alter this
object in memory. Then when you're finished, you can call ObjectRelease()
as you can call HUnLock(). To get rid of the object reference entirely, you
can call FreeObject() in a comparable manner to FreeHand().
The following sample code demonstrates an FLL that uses all of these new
functions. There is a section of C code listed first that you can use to
build the FLL. That section is followed by a section of FoxPro code to test
the functionality of your new FLL.
C Source Code for FLL
Build the following code as you would for any other FLL. If you need help,
see the Professional Features Guide Chapter 11 and the Microsoft
Knowledge Base.
// Following is the C code to create a single FLL that
// showcases how to call each of the new object functions.
// include the library construction header file
#include <pro_ext.h>
far changeWTitle (ParamBlk FAR *parm)
{
WHandle wh;
if (parm->p[0].val.ev_type=='O')
{
wh=_WGetObjectWindow(&parm->p[0].val);
_WSetTitle(wh, "Changed Title");
}
return(0);
}
far getoTop(ParamBlk FAR *parm)
{
Value val;
_MemFill(&val, 0, sizeof(Value)); // Clear out our return value
val.ev_length = 0; // Assume a bad return.
if (parm->p[0].val.ev_type == 'O')
{
_GetObjectProperty(&val, &parm->p[0].val, "TOP");
}
_RetVal(&val);
return(0);
}
far changeoTop(ParamBlk FAR *parm)
{
Value val;
int status;
_MemFill(&val, 0, sizeof(Value)); // Clear out return value
val.ev_type = 'L';
val.ev_length = 0; // Assume a bad return
if (parm->p[0].val.ev_type == 'O')
{
if (!(status= _SetObjectProperty(&parm->p[0].val,
"TOP", &parm->p[1].val, 0)))
val.ev_length = 1; // succeeded
}
_RetVal(&val);
return(0);
}
far compare(ParamBlk FAR *parm)
{
if (parm->p[0].val.ev_type == 'O' && parm->p[1].val.ev_type == 'O')
{
_RetInt((long) _ObjectCmp(&parm->p[0].val, &parm->p[1].val),5);
}
return(0);
}
far changeCWTitle(ParamBlk FAR *parm)
{
WHandle wh;
if (parm->p[0].val.ev_type == 'O') // Check for 'O' as in Oscar
{
wh = _WGetObjectClientWindow(&parm->p[0].val);
_WSetTitle(wh, "Changed Title");
}
return(0);
}
far ofree(Value *val1)
{
if (val1->ev_type=='O')
{
_FreeObject(val1);
return(0);
}
return(1);
}
far objref(ParamBlk FAR *parm)
{
// This function shows how to keep an object reference around.
// You would call this with a child object. It gets a ref
// to the parent, increment the reference, change the
// value of a property, then release the ref and free the object.
Value setval,getval;
char returnstr[80];
_MemFill(&setval,0,sizeof(Value));
_MemFill(&getval,0,sizeof(Value));
setval.ev_type='I';
setval.ev_long=70;
if (parm->p[0].val.ev_type == 'O')
{
if (! _GetObjectProperty(&getval, &parm->p[0].val, "PARENT"))
{
_ObjectReference(&getval); //increment the Ref Count of the object
strcpy(returnstr,"Increment Refcount, ");
if (!(_SetObjectProperty(&getval, "TOP", &setval,0)))
{
strcat(returnstr,"Set the top to 70, ");
}
_ObjectRelease(&getval);
strcat(returnstr,"Release reference, ");
if (!ofree(&getval))
{
strcat(returnstr,"Freed the object\n");
}
_RetChar(returnstr);
}
}
return(0);
}
// The FoxInfo structure registers the function
FoxInfo myFoxInfo[] = {
{"CHANGEWTITLE",(FPFI) changeWTitle, 1, "O"},
{"OGETTOP", (FPFI) getoTop, 1, "O"},
{"OSETTOP", changeoTop, 2, "O?"},
{"CHANGECWTITLE", changeCWTitle, 1, "O"},
{"OCOMPARE", compare, 2, "OO"},
{"OMOVEPARENT",objref,1,"O"},
};
// the FoxTable structure
FoxTable _FoxTable = {
(FoxTable *) 0, sizeof(myFoxInfo)/sizeof(FoxInfo), myFoxInfo
};
FoxPro Code Component
When you have entered the code and successfully built it into a DLL, you
can save that file to your Visual FoxPro default directory as Newapi.fll.
Then use the following FoxPro code to call and test the function.
SET LIBRARY TO NEWAPI.FLL
PUBLIC x
x=CreateObject('myform')
x.Show
Define Class myform as form
add object command1 as commandbutton
add object command2 as commandbutton
add object command3 as commandbutton
add object command4 as commandbutton
add object command5 as commandbutton
add object spintop as spinner
command1.caption="Change FrameWindow Title of _screen"
command2.caption="Set .TOP of this button to this value:"
command3.caption="Display .TOP value of the form"
command4.caption="Move the form and test Obj Ref"
command5.caption="Change Window Title of this Form"
spintop.value=10
proc init
for i=1 to thisform.controlcount-1
with thisform.controls(i)
.visible=.t.
if pemstatus(thisform.controls(i),'autosize',5)
.autosize=.t.
.autosize=.f.
.width=260
.left=10
ENDIF
if i>1
.top=thisform.controls(i-1).height*(i-1)+10*(i-1)
ENDIF
endwith
endfor
with this
.spintop.top=.command2.top
.spintop.height=.command2.height
.spintop.width=50
.spintop.left=.command2.left+.command2.width+10
.spintop.value=.command2.top
endproc
proc command1.click
=changewtitle(_screen); // change the form title
endproc
proc command2.click
=OSetTop(this,this.parent.spintop.value)
endproc
proc command3.click
val=OGetTop(thisform)
=messagebox(str(val))
endproc
proc command4.click
=messagebox(OMOVEPARENT(this))
endproc
proc command5.click
=CHANGECWTITLE(thisform)
endproc
enddefine