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1991-09-01
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Using Borland C++ IDE with
the Microsoft Visual BASIC Control Development Kit (CDK)
I wrote this description to help anyone using Borland's C++
compiler and Integrated Development Environment (IDE) to create
custom controls for use with Microsoft's Visual BASIC. The MS
CDK (Control Development Kit) has a series of example programs
that were written to work with Microsoft C version 6 or later.
This document should help you get them to work using Borland's
development products.
This document assumes that you have purchased the MS CDK product.
I make reference to specific line numbers within the files that
were shipped to me with version 1.0 of that product. When
working with Borland's IDE, you can tell what line that you are
currently editing by referencing the numbers in the bottom left-
hand corner of the active edit window. The numbers shown there
appear in the format:
<line number> : <column position>
for example:
25:32
which says that your cursor is on the 32nd character of line 25.
In this document, I also assume that you have installed your
Borland C++ product in the drive\subdirectory C:\BORLANDC. Also
that after installing the CDK, you have copied the file VBAPI.LIB
to C:\BORLANDC\LIB and the file VBAPI.H to C:\BORLANDC\INCLUDE.
While experimenting with this code, I created a subdirectory
called TEMP under the directory for each control, copied all
files for that control there, and edited the copies. It is NEVER
advisable to edit your original copies of anything. Also
remember that whenever you are coding at a systems-level, you
should save your code frequently.
If you have any comments, suggestions, or neat VBX files, please
feel free to drop me a line in my Compuserve mailbox, or at my
humble homestead at 1188 Morgan Ave, Williamsport, PA 17701.
Throughout this document, I mention products and programs that
are protected by some sort of legal nonsense or another, and I
hope I can appease all legal-eagles by saying that any Borland
product mentioned is trademarked and legally protected by Borland
International Inc. of Scotts Valley, CA. Any Microsoft product
is trademarked and legally protected by Microsoft Corporation of
Redmond, WA. Anything done by you using the descriptions here
should make neither them (nor me) liable for any silliness that
might prevail.
Brent K. Langley Compuserve Userid 70312,2142 Page 1
Using Borland C++ IDE with
the Microsoft Visual BASIC Control Development Kit (CDK)
GETTING THE CDK TO WORK:
I have found that in getting the CDK code to work with the IDE
there are 8 steps that I had to follow:
1) Change WINDOWS.H
2) Copy and Rename LibInit.Obj to C:\BORLANDC\LIB\C0VBINIT.OBJ
3) Create a Project file (.PRJ) to create the VBX/DLL file
4) Change CCINIT.C to take advantage of changes in WINDOWS.H
5) Handle any syntax errors in demo code
6) Handle any language incompatibilities in code
7) "Make" Project from IDE
8) Rename (or Copy) xxxxxxxx.DLL to xxxxxxxx.VBX
Steps 1 and 2 from above only need to be done once. Steps 3 and
4 need to be done for every project, but follow the same steps.
Steps 5 and 6 will be addressed separatly for each of the three
example programs that need fixing. Steps 7 and 8 let you put all
of the pieces together.
STEP ONE: CHANGE WINDOWS.H
The normal startup code for a DLL does a little processing and
then calls your function called LibMain. In a .VBX file, we have
to replace the normal startup code with a modified routine that
passes some extra information to our control's LibMain. This
means that the format for calling a VBX's LibMain is different
from a normal DLL's LibMain. This causes no real hassle to
MSC/SDK developers because Microsoft doesn't include a function
prototype in their version of WINDOWS.H for LibMain, however,
Borland does. And when Borland's compiler sees the CDK version
of the LibMain function, it stops compiling with an error.
We could just remove the function prototype for LibMain from
Borland's WINDOWS.H, but it will help us with our syntax checking
if we leave it there. My solution is to define a constant called
_CDK before the #include of WINDOWS.H. Then have WINDOWS.H
determine the existance of this defined constant to decide
whether to use the CDK or normal version of LibMain.
To do this, load C:\BORLANDC\INCLUDE\WINDOWS.H and then press
Ctrl-PgDn to go to the bottom of the file. Move your cursor up
to about line 3473, and you should see Borland's function
prototype for LibMain. I changed this part of the code to be:
#ifndef _CDK
int FAR PASCAL LibMain ( HANDLE, WORD, WORD, LPSTR );
#else
BOOL FAR PASCAL LibMain( HANDLE, HANDLE, unsigned short );
#endif
I used "unsigned short" instead of USHORT for the third parameter
of the CDK version of LibMain because USHORT isn't seen in a
typedef statement until the file VBAPI.H is #include'd later.
Brent K. Langley Compuserve Userid 70312,2142 Page 2
Using Borland C++ IDE with
the Microsoft Visual BASIC Control Development Kit (CDK)
STEP TWO: RENAME LIBINIT.OBJ TO C0VBINIT.OBJ
Page 20 of the CDK Guide explains that LIBINIT.OBJ contains
initialization code to replace the code from the file
LIBENTRY.OBJ that is normally linked into DLL projects first. So
we must ensure that the code from LIBINIT.OBJ is linked before
any other code in our projects.
On page 141 of Borland's C++ User Guide, we find the section of
the project manager chapter titled "Overriding Libraries" states
that we can have our own startup file linked first, if:
1) its name starts with C0 (the letter C followed by zero)
2) it is placed as the first file in the project.
We'll worry about making a project file in a minute, but for now,
lets give LibInit.OBJ a new name to conform with step one from
above. While we're at it, lets also move it to a standard
location (since the CDK manual says that this code would seldom
need to change.) If LibInit.OBJ is in your current directory,
type:
COPY LIBINIT.OBJ C:\BORLANDC\LIB\C0VBINIT.OBJ
You could call it anything you want (so long as it starts with
"C0") but since it contains the Visual Basic INITialization code,
I thought that this name was appropriate.
STEP THREE: CREATE A PROJECT FILE
For each control, you will make a project file that looks similar
to the following:
C:\BORLANDC\LIB\C0VBINIT.OBJ
C:\BORLANDC\LIB\C0DC.OBJ
C:\BORLANDC\LIB\VBAPI.LIB
CCINIT.C
program.DEF
program.RC
program.C
.
. (any other program files or libraries)
.
For example, the project for the CNTR control would look like:
C:\BORLANDC\LIB\C0VBINIT.OBJ
C:\BORLANDC\LIB\C0DC.OBJ
C:\BORLANDC\LIB\VBAPI.LIB
CCINIT.C
CNTR.DEF
CNTR.RC
CNTR.C
Brent K. Langley Compuserve Userid 70312,2142 Page 3
Using Borland C++ IDE with
the Microsoft Visual BASIC Control Development Kit (CDK)
STEP THREE: CREATE A PROJECT FILE (continued)
The file C:\BORLANDC\LIB\C0DC.OBJ listed in the above projects is
the normal startup code file for Borland C (that has been
superseded by C0VBINIT.OBJ) and should appear immediately after
C0VBINIT.OBJ in your project file. This file should actually be
C0Dx.OBJ where "x" indicates your memory model that you are
compiling with. Since I used the "Compact" memory model for
compiling my projects, this is C0Dc.OBJ in my code examples.
Since a VBX file is a type of DLL, you should let the project
manager know that you will be creating a DLL. You can do this by
typing Alt-O to activate the Options menu. Type A to select your
Application type, and then type D to select DLL. Now when you
save your project, this information will be stored with it.
Besides the interactive way of building a project, you could make
a batch file to create your project files, or you could copy this
text to a .PRJ file, but then remember to run PRJCNVT to change
the old-style text project file to Borland's new project file
format.
An example .BAT file called MAKEPRJ.BAT might contain:
@ECHO OFF
IF "%1"=="" GOTO ERROR
ECHO C:\BORLANDC\LIB\C0VBINIT.OBJ > %1.PRJ
ECHO C:\BORLANDC\LIB\C0DC.OBJ >> %1.PRJ
ECHO C:\BORLANDC\LIB\VBAPI.LIB >> %1.PRJ
ECHO CCINIT.C >> %1.PRJ
ECHO %1.DEF >> %1.PRJ
ECHO %1.RC >> %1.PRJ
ECHO %1.C >> %1.PRJ
PRJCNVT %1.PRJ
GOTO END
:ERROR
ECHO You must specify a project name
:END
This uses the program PRJCNVT.EXE in your C:\BORLANDC\BIN
subdirectory (probably in you PATH) to convert from a text .PRJ
file to Borland's new project file format. The first ECHO
statement creates a new .PRJ file, and the rest of the ECHO
statements append their line of text to this file. The file is
named using whatever you specify on the command line after the
word MAKEPRJ. For Example:
MAKEPRJ CNTR
Would make the project example shown on the previous page and
name it CNTR.PRJ. Remember then to set the Alt-O-A-D options
when you load this into the IDE.
Brent K. Langley Compuserve Userid 70312,2142 Page 4
Using Borland C++ IDE with
the Microsoft Visual BASIC Control Development Kit (CDK)
STEP FOUR: CHANGE CCINIT.C
In step one, we modified WINDOWS.H to allow correct function
prototyping of the LibMain function. In the file CCINIT.C we
will take advantage of this change. This is the file where our
version of LibMain is declared, so we want WINDOWS.H to use the
CDK version of the prototype.
This is pretty simple, all you need to do is to include the line:
#define _CDK
before the #include <windows.h> statement in the file CCINIT.C.
I suggest that you type over line 6 in this file which is
currently blank. This will preserve the line numbers for the
rest of the code. CCINIT.C is very similar for each of the
example programs in the CDK, but each does vary slightly. Please
make this change for every sample control project in the CDK.
STEP FIVE: HANDLE SYNTAX ERRORS
STEP SIX: HANDLE ANY LANGUAGE INCOMPATIBILITIES
CIRCLE1, CIRCLE2, and PUSH have no further problems so you can
continue with steps seven and eight for them.
However, there is still some work that needs to be done with the
files for CIRCLE3, CNTR, and PIX. I prefer to address the
problems for each of these programs separately, so please see
their individual descriptions on the following pages.
STEP SEVEN: MAKE PROJECT
You're just about done! Press F9 and the IDE will create your
DLL file. If you prefer to use Borland's MAKE utility, you can
convert your .PRJ file from step three (above) to a .MAK file
with the Borland utility PRJ2MAK and then edit this make file to
tailor it to your own specifications.
STEP EIGHT: RENAME .DLL FILE TO .VBX
The IDE's project manager will create a file with the same
filename as that of your .PRJ file. The resulting file's
extension will be .DLL but the Visual BASIC system will be
expecting a Visual Basic eXtension file. To accomodate Visual
BASIC, just RENAME (I prefer to COPY) name.DLL to name.VBX
That's all there is (as if it isn't enough!) Now you can load
Visual BASIC and select Alt F D for File Add-file and specify
your .VBX file.
Brent K. Langley Compuserve Userid 70312,2142 Page 5
Using Borland C++ IDE with
the Microsoft Visual BASIC Control Development Kit (CDK)
CIRCLE3
In addition to following the steps described above (such as
putting the #define _CDK in CCINIT.C) CIRCLE3 has some
compatibility problems:
CIRCLE3 PROBLEM 1:
On line 114 of CIRCLE.C there is a call to VBCreateHsz that uses
the new MS C v6 type keyword "_segment". My info on this keyword
comes from an article in the March 1990 issue of Microsoft
Systems Journal by Noel J. Bergman. While describing the new (at
that time) version 6 of MS C, he describes briefly, on page 58,
the concept of "based pointers" and the function of _segement.
He says: "When _segment is used to cast a near address, the
result is the current value in DS" which can be obtained in BC++
by specifying _DS or FP_SEG( (void far *) addr ). He continues:
"If the address is a far address, the result is the segment for
that far address." You can use the FP_SEG( addr ) macro in dos.h
to get this value.
A consistent way to handle both cases would be to use the FP_SEG
macro and cast (void far *) on the pointer. For example:
FP_SEG( (void far *) addr )
Or, since the macro does this casting for you internally, you can
abbreviate this as just:
FP_SEG( addr )
A side note: when looking in the include file dos.h I found that
FP_SEG is using a cast operation with the word _seg !?! What is
that?? Is it the same as _segment ?? It doesn't seem so. Since
I couldn't find it in the documentation, lets play it safe and
stick with FP_SEG. Although, if you are converting a MAJOR
project, you could speed up the conversion by doing a global
search and replace: changing all
(_segment)
to
(void _seg *)(void far *)
Using FP_SEG is easier to read (I think), and a little more
portable. The choice is up to you, but for this example, lets
change line 114 of CIRCLE.C to read:
hsz = VBCreateHsz( FP_SEG(hctl), (LPSTR)lp);
and then put the #include <dos.h> on the blank line between the
includes for <windows.h> and <vbapi.h> (this will preserve line
numbers for the further editing that we have to do...)
Brent K. Langley Compuserve Userid 70312,2142 Page 6
Using Borland C++ IDE with
the Microsoft Visual BASIC Control Development Kit (CDK)
CIRCLE3 PROBLEM 2:
In line 406 of CIRCLE.C, the reference to FlashDlgProc is meant
to pass the address of a certain type of function to the function
VBDialogBoxParam. It's function prototype on line 423 is:
BOOL FAR PASCAL _export FlashDlgProc(HWND, USHORT, USHORT, LONG)
but what is required for VBDialogBoxParam (on line 309 of
VBAPI.H) is the type FARPROC that is defined on line 151 of
WINDOWS.H as:
typedef int (FAR PASCAL * FARPROC)();
OK, so all we need to do is cast this FARPROC type on the
function FlashDlgProc. Change line 406 of CIRCLE.C to read:
VBDialogBoxParam(hmodDLL, "FlashDlg", (FARPROC)FlashDlgProc, 0L);
Now your CIRCLE3.PRJ should compile cleanly. Remember to rename
(or copy) CIRCLE3.DLL to CIRCLE3.VBX then fire up Visual BASIC
and try it out!
Brent K. Langley Compuserve Userid 70312,2142 Page 7
Using Borland C++ IDE with
the Microsoft Visual BASIC Control Development Kit (CDK)
CNTR
CNTR, the counter control uses "based pointers" in a couple of
its modules so there is some conversion that needs to be done,
but there is an error (BUG??) in CCINIT.C that we must fix first.
In CCINIT.C on line 45, the function modifier "PASCAL" is
missing from the definition of the function LibMain, so change
this line from:
BOOL FAR LibMain
To:
BOOL FAR PASCAL LibMain
Also, at the top of CCINIT.C (line 6, for example) remember to
place the statement:
#define _CDK
In CNTR.H and CNTR.C we need to remove the based pointer
references and replace them with their equivalents in terms of
far pointers. I'm not sure why Microsoft added this based
pointer complexity to this program, unless its that they felt
that it would make the code run faster (using 16 bit pointers
rather than 32 bit.) But I don't think that this is the type of
application that would benefit from the added complication.
In CNTR.H we have some stuff to clean up. Lines 26 through 34
and also line 54 should be commented out as shown below:
// _segment segCntr;
// #define BP _based(segCntr) * // based pointer
// #define BH BP BP // based handle
// typedef VOID BH BHVOID; // void handle
// typedef CHAR BH BHSTR; // handle to a string
// #define CNTRDEREF(hctl) ((PCNTR)(VOID *) ...
and then change line 52 from:
typedef CNTR BP PCNTR;
to:
typedef CNTR far * PCNTR;
In CNTR.C comment-out line 53 as shown below:
// segCntr = (_segment) hctl;
and change line 54 from:
pcntr = CNTRDEREF(hctl);
to:
pcntr = VBDerefControl(hctl);
Now CNTR should compile ok. Rename CNTR.DLL to CNTR.VBX an go!
Brent K. Langley Compuserve Userid 70312,2142 Page 8
Using Borland C++ IDE with
the Microsoft Visual BASIC Control Development Kit (CDK)
PIX
Remember to put the line:
#define _CDK
on line 6 (the blank line above #include <windows.h>) in the file
CCINIT.C as described in step 4 (above).
Lines 81, 85, and 109 of PIX.C use the non-Borland _segment type
for casting as described for CIRCLE3 (above). On each of these
lines modify reference in the code for
(_segment) hctl
to appear like:
FP_SEG( hctl )
and place the line
#include <dos.h>
at the top of the file PIX.C.
Now this control should compile and link cleanly. Remember to
rename the resultant .DLL file to a .VBX file before you load
Visual BASIC and try it out.
--------------------------------------------------------------
Well, I hope this made enough sense to get you going. I tried to
not only tell you what to do, but to also tell you where in the
various references that I found my information. I hope it helps.
Also, I can't emphasize enough, for you to save your programs
often. A small mistake in your code can cause a Windows
Unexpected Application Error (UAE) and either kick you completely
out of Visual BASIC, kick you out of Windows, reboot your
machine, or freeze your machine. I have encountered all of these
battle scars, but I survived and you will too! Have fun....Brent
Brent K. Langley Compuserve Userid 70312,2142 Page 9
