Errors of Porting to OpenGL 1.2 for Managed C++ coding in VC++.NET (2002)

Scott_Chang · August 4, 2003, 4:57am

Hi all,
I tried to use Managed C++ coding of VC++.NET (2002)and
OpenGL version 1.2 to draw a hexagon shape of benzene.
My OpenGLdrawBenzene.cpp is the following:
// This is the main project file for VC++ application
project
// generated using an Application Wizard.

#include “stdafx.h”
#include
#include
#include // OpenGL Graphics Utility
Library
#using
#include

using namespace System;

// These variables set the dimensions of the
rectanglar region we wish to view.
const double Xmin = 0.0, Xmax = 3.0;
const double Ymin = 0.0, Ymax = 3.0;

// Clear the rendering window
glClear(GL_COLOR_BUFFER_BIT |
GL_DEPTH_BUFFER_BIT);

// Set drawing color to white
glColor3f( 1.0, 1.0, 1.0 );

// Draw six points on xy plane with z=0.0
glBegin(GL_POINTS);
glVertex3f( 0.0, 0.0, 0.0 );
glVertex3f( 0.9, 1.0, 0.0 );
glVertex3f( 1.9, 1.0, 0.0 );
glVertex3f( 2.8, 0.0, 0.0 );
glVertex3f( 1.9,-1.0, 0.0 );
glVertex3f( 0.9,-1.0, 0.0 );
glEnd();
// Flush the pipeline. (Not usually necessary.)
glFlush();
}
// Initialize OpenGL’s rendering modes
void initRendering()
{
// Called when the window is resized
// w, h - width and height of the window in
pixels.
void resizeWindow(int w, int h)
{
double scale, center;
double windowXmin, windowXmax, windowYmin,
windowYmax;

// Define the portion of the window used for OpenGL

rendering.
glViewport( 0, 0, w, h ); // View port uses
whole
window

// Set up the projection view matrix: orthographic

projection
// Determine the min and max values for x and y
that
should appear in the window.
// The complication is that the aspect ratio of the
window may not match the
// aspect ratio of the scene we want
to view.
w = (w==0) ? 1 : w;
h = (h==0) ? 1 : h;
if ( (Xmax-Xmin)/w < (Ymax-Ymin)/h ) {
scale = ((Ymax-Ymin)/h)/((Xmax-Xmin)/w);
center = (Xmax+Xmin)/2;
windowXmin = center - (center-Xmin)*scale;
windowXmax = center + (Xmax-center)*scale;
windowYmin = Ymin;
windowYmax = Ymax;
}
else {
scale = ((Xmax-Xmin)/w)/((Ymax-Ymin)/h);
center = (Ymax+Ymin)/2;
windowYmin = center - (center-Ymin)*scale;
windowYmax = center + (Ymax-center)*scale;
windowXmin = Xmin;
windowXmax = Xmax;
}

// Now that we know the max & min values for x & y

that should be visible in the window,
// we set up the orthographic
projection.
glMatrixMode( GL_PROJECTION );
glLoadIdentity();
glOrtho( windowXmin, windowXmax, windowYmin,
windowYmax, -1, 1 );

}

// This is the entry point for this application
int _tmain(int argc, char** argv)
{
// TODO: Please replace the sample code below with
your own.
Console::WriteLine(S"OpenGLdrawBenzene");

///////////int main( int argc, char** argv )

glutInit(&argc,argv);

// The image is not animated so single buffering is

OK.
glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB |
GLUT_DEPTH );

// Window position (from top corner), and size

(width
and hieght)
glutInitWindowPosition( 20, 60 );
glutInitWindowSize( 360, 360 );
glutCreateWindow( “SimpleDraw - Press space bar to
toggle images” );

// Initialize OpenGL as we like it..
initRendering();

// Set up callback functions for key presses
glutKeyboardFunc( myKeyboardFunc );		
// Handles

“normal” ascii symbols
// glutSpecialFunc( mySpecialKeyFunc ); //
Handles
“special” keyboard keys

// Set up the callback function for resizing

windows
glutReshapeFunc( resizeWindow );

// Call this for background processing
// glutIdleFunc( myIdleFunction );

// call this whenever window needs redrawing
glutDisplayFunc( drawScene );

fprintf(stdout, "Press space bar to toggle images;

escape button to quit.
");

// Start the main loop.  glutMainLoop never

returns.
glutMainLoop( );
return 0;
}
///////////////////////////////////////
When I built it, I got many errors:
------ Build started: Project: OpenGLdrawBenzene,
Configuration: Debug Win32 ------

Compiling…
OpenGLdrawBenzene.cpp
OpenGLdrawBenzene.cpp(18) : error C2501: ‘glClear’ :
missing storage-class or type specifiers
OpenGLdrawBenzene.cpp(18) : error C2365: ‘glClear’ :
redefinition; previous definition was a ‘function’
C:\Program Files\Microsoft Visual Studio
…NET\Vc7\PlatformSDK\Include\gl\GL.h(1162) : see
declaration of ‘glClear’
OpenGLdrawBenzene.cpp(21) : error C2501: ‘glColor3f’ :
missing storage-class or type specifiers
OpenGLdrawBenzene.cpp(21) : error C2365: ‘glColor3f’ :
redefinition; previous definition was a ‘function’
C:\Program Files\Microsoft Visual Studio
…NET\Vc7\PlatformSDK\Include\gl\GL.h(1173) : see
declaration of ‘glColor3f’
OpenGLdrawBenzene.cpp(21) : error C2078: too many
initializers
OpenGLdrawBenzene.cpp(23) : error C2501: ‘glBegin’ :
missing storage-class or type specifiers
OpenGLdrawBenzene.cpp(23) : error C2365: ‘glBegin’ :
redefinition; previous definition was a ‘function’
C:\Program Files\Microsoft Visual Studio
…NET\Vc7\PlatformSDK\Include\gl\GL.h(1156) : see
declaration of ‘glBegin’
OpenGLdrawBenzene.cpp(24) : error C2501: ‘glVertex3f’
: missing storage-class or type specifiers
OpenGLdrawBenzene.cpp(24) : error C2365: ‘glVertex3f’
: redefinition; previous definition was a ‘function’
C:\Program Files\Microsoft Visual Studio
…NET\Vc7\PlatformSDK\Include\gl\GL.h(1472) : see
declaration of ‘glVertex3f’
OpenGLdrawBenzene.cpp(24) : error C2078: too many
initializers
OpenGLdrawBenzene.cpp(25) : error C2501: ‘glVertex3f’
: missing storage-class or type specifiers
OpenGLdrawBenzene.cpp(25) : error C2365: ‘glVertex3f’
: redefinition; previous definition was a ‘function’
C:\Program Files\Microsoft Visual Studio
…NET\Vc7\PlatformSDK\Include\gl\GL.h(1472) : see
declaration of ‘glVertex3f’
OpenGLdrawBenzene.cpp(25) : error C2078: too many
initializers
OpenGLdrawBenzene.cpp(26) : error C2501: ‘glVertex3f’
: missing storage-class or type specifiers
OpenGLdrawBenzene.cpp(26) : error C2365: ‘glVertex3f’
: redefinition; previous definition was a ‘function’
C:\Program Files\Microsoft Visual Studio
…NET\Vc7\PlatformSDK\Include\gl\GL.h(1472) : see
declaration of ‘glVertex3f’
OpenGLdrawBenzene.cpp(26) : error C2078: too many
initializers
OpenGLdrawBenzene.cpp(27) : error C2501: ‘glVertex3f’
: missing storage-class or type specifiers
OpenGLdrawBenzene.cpp(27) : error C2365: ‘glVertex3f’
: redefinition; previous definition was a ‘function’
C:\Program Files\Microsoft Visual Studio
…NET\Vc7\PlatformSDK\Include\gl\GL.h(1472) : see
declaration of ‘glVertex3f’
OpenGLdrawBenzene.cpp(27) : error C2078: too many
initializers
OpenGLdrawBenzene.cpp(28) : error C2501: ‘glVertex3f’
: missing storage-class or type specifiers
OpenGLdrawBenzene.cpp(28) : error C2365: ‘glVertex3f’
: redefinition; previous definition was a ‘function’
C:\Program Files\Microsoft Visual Studio
…NET\Vc7\PlatformSDK\Include\gl\GL.h(1472) : see
declaration of ‘glVertex3f’
OpenGLdrawBenzene.cpp(28) : error C2078: too many
initializers
OpenGLdrawBenzene.cpp(29) : error C2501: ‘glVertex3f’
: missing storage-class or type specifiers
OpenGLdrawBenzene.cpp(29) : error C2365: ‘glVertex3f’
: redefinition; previous definition was a ‘function’
C:\Program Files\Microsoft Visual Studio
…NET\Vc7\PlatformSDK\Include\gl\GL.h(1472) : see
declaration of ‘glVertex3f’
OpenGLdrawBenzene.cpp(29) : error C2078: too many
initializers
OpenGLdrawBenzene.cpp(30) : error C2556: ‘int
glEnd(void)’ : overloaded function differs only by
return type from ‘void glEnd(void)’
C:\Program Files\Microsoft Visual Studio
…NET\Vc7\PlatformSDK\Include\gl\GL.h(1226) : see
declaration of ‘glEnd’
OpenGLdrawBenzene.cpp(30) : error C2373: ‘glEnd’ :
redefinition; different type modifiers
C:\Program Files\Microsoft Visual Studio
…NET\Vc7\PlatformSDK\Include\gl\GL.h(1226) : see
declaration of ‘glEnd’
OpenGLdrawBenzene.cpp(32) : error C2556: ‘int
glFlush(void)’ : overloaded function differs only by
return type from ‘void glFlush(void)’
C:\Program Files\Microsoft Visual Studio
…NET\Vc7\PlatformSDK\Include\gl\GL.h(1242) : see
declaration of ‘glFlush’
OpenGLdrawBenzene.cpp(32) : error C2373: ‘glFlush’ :
redefinition; different type modifiers
C:\Program Files\Microsoft Visual Studio
…NET\Vc7\PlatformSDK\Include\gl\GL.h(1242) : see
declaration of ‘glFlush’
OpenGLdrawBenzene.cpp(33) : error C2059: syntax error
: ‘}’
OpenGLdrawBenzene.cpp(33) : error C2143: syntax error
: missing ‘;’ before ‘}’
OpenGLdrawBenzene.cpp(33) : error C2059: syntax error
: ‘}’
OpenGLdrawBenzene.cpp(36) : error C2143: syntax error
: missing ‘;’ before ‘{’
OpenGLdrawBenzene.cpp(36) : error C2447: ‘{’ : missing
function header (old-style formal list?)
OpenGLdrawBenzene.cpp(119) : fatal error C1004:
unexpected end of file found

Build log was saved at “file://c:\Documents and
Settings\default\My
Documents\Programming\OpenGLdrawBenzene\Debug\BuildLog.htm”
OpenGLdrawBenzene - 35 error(s), 0 warning(s)

---------------------- Done ----------------------

Build: 0 succeeded, 1 failed, 0 skipped

///////////////////////////////////////////////
Please kindly tell me what caused the first error in
Line 18 of this .cpp

glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

and how to cure it. If you can help me more in
solving the rest of the errors, I will be greatly
appreciated.

Thanks in advance,
Scott Chang

imported_jwatte · August 4, 2003, 4:59am

Details of what error messages from your compiler mean, and what you can do to fix them, might be available in the documentation that came with your compiler.

Scott_Chang · August 4, 2003, 8:18am

I really do not know what storage-class is and explanation for the error C2501 in the compiler do not ring a bell to me. Please be specific and give me more details for solving the error.

Thanks,
Scott Chang

Korval · August 4, 2003, 9:09am

I tried to use Managed C++ coding of VC++.NET (2002)and OpenGL version 1.2 to draw a hexagon shape of benzene.

Managed C++ has limitations placed on it, compared to real C++. I don’t know what those limitations are, but it is not unreasonable to believe that GL violates them.

#include // OpenGL Graphics Utility Library

What is this, specifically? Your errors seem like you’re not really including the appropriate OpenGL headers.

roffe · August 4, 2003, 9:10am

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vccore98/html/c2501.asp

Compiler errors have nothing to do with OpenGL coding. I suggest you post these question in a VC or .NET forum in the future.