forms - How to render an openGL frame in C++ builder?

Question

I want to initialize an openGL frame inside a form in C++ builder. I tried copying the contents of this given openGL startup code provided here: http://edn.embarcadero.com/article/10528
I tried replacing TForm1 with TFrame1 and then put it in the form design, but it didn't work. How to do this properly, any experience with this?

Answer 1

easy, just use TForm::Handle as window handle ...

Here some ancient example of mine in BCB5 ported to BDS2006:

//---------------------------------------------------------------------------

#include <vcl.h>
#pragma hdrstop

#include "Unit1.h"
#include <gl/gl.h>
#include <gl/glu.h>
//---------------------------------------------------------------------------
#pragma package(smart_init)
#pragma resource "*.dfm"
TForm1 *Form1;
//---------------------------------------------------------------------------
int TForm1::ogl_init()
    {
    if (ogl_inicialized) return 1;
    hdc = GetDC(Form1->Handle);             // get device context
    PIXELFORMATDESCRIPTOR pfd;
    ZeroMemory( &pfd, sizeof( pfd ) );      // set the pixel format for the DC
    pfd.nSize = sizeof( pfd );
    pfd.nVersion = 1;
    pfd.dwFlags = PFD_DRAW_TO_WINDOW | PFD_SUPPORT_OPENGL | PFD_DOUBLEBUFFER;
    pfd.iPixelType = PFD_TYPE_RGBA;
    pfd.cColorBits = 24;
    pfd.cDepthBits = 24;
    pfd.iLayerType = PFD_MAIN_PLANE;
    SetPixelFormat(hdc,ChoosePixelFormat(hdc, &pfd),&pfd);
    hrc = wglCreateContext(hdc);            // create current rendering context
    if(hrc == NULL)
            {
            ShowMessage("Could not initialize OpenGL Rendering context !!!");
            ogl_inicialized=0;
            return 0;
            }
    if(wglMakeCurrent(hdc, hrc) == false)
            {
            ShowMessage("Could not make current OpenGL Rendering context !!!");
            wglDeleteContext(hrc);          // destroy rendering context
            ogl_inicialized=0;
            return 0;
            }
    ogl_resize();
    glEnable(GL_DEPTH_TEST);                // Zbuf
    glDisable(GL_CULL_FACE);                // vynechavaj odvratene steny
    glDisable(GL_TEXTURE_2D);               // pouzivaj textury, farbu pouzivaj z textury
    glDisable(GL_BLEND);                    // priehladnost
    glShadeModel(GL_SMOOTH);                // gourard shading
    glClearColor(0.0f, 0.0f, 0.0f, 1.0f);   // background color
    ogl_inicialized=1;
    return 1;
    }
//---------------------------------------------------------------------------
void TForm1::ogl_exit()
    {
    if (!ogl_inicialized) return;
    wglMakeCurrent(NULL, NULL);     // release current rendering context
    wglDeleteContext(hrc);          // destroy rendering context
    ogl_inicialized=0;
    }
//---------------------------------------------------------------------------
void TForm1::ogl_draw()
    {
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    float x=0.5,y=0.5,z=20.0;
    glBegin(GL_QUADS);

    glColor3f(0.0f, 1.0f, 0.0f);
    glVertex3f(-x,-y,-z);
    glVertex3f(-x,+y,-z);
    glVertex3f(+x,+y,-z);
    glVertex3f(+x,-y,-z);
    glColor3f(0.0f, 0.0f, 1.0f);
    glVertex3f(-x,-y,+z);
    glVertex3f(-x,+y,+z);
    glVertex3f(+x,+y,+z);
    glVertex3f(+x,-y,+z);

    glEnd();



    glFlush();
    SwapBuffers(hdc);
    }
//---------------------------------------------------------------------------
void TForm1::ogl_resize()
    {
    xs=ClientWidth;
    ys=ClientHeight;
    if (xs<=0) xs = 1;                  // Prevent a divide by zero
    if (ys<=0) ys = 1;
    if (!ogl_inicialized) return;
    glViewport(0,0,xs,ys);              // Set Viewport to window dimensions
    glMatrixMode(GL_PROJECTION);        // operacie s projekcnou maticou
    glLoadIdentity();                   // jednotkova matica projekcie
    gluPerspective(30,float(xs)/float(ys),0.1,100.0); // matica=perspektiva,120 stupnov premieta z viewsize do 0.1
    glMatrixMode(GL_TEXTURE);           // operacie s texturovou maticou
    glLoadIdentity();                   // jednotkova matica textury
    glMatrixMode(GL_MODELVIEW);         // operacie s modelovou maticou
    glLoadIdentity();                   // jednotkova matica modelu (objektu)
    ogl_draw();
    }
//---------------------------------------------------------------------------
__fastcall TForm1::TForm1(TComponent* Owner)
    : TForm(Owner)
    {
    ogl_inicialized=0;
    hdc=NULL;
    hrc=NULL;
    ogl_init();
    }
//---------------------------------------------------------------------------
void __fastcall TForm1::FormDestroy(TObject *Sender)
    {
    ogl_exit();
    }
//---------------------------------------------------------------------------
void __fastcall TForm1::FormResize(TObject *Sender)
    {
    ogl_resize();
    }
//---------------------------------------------------------------------------
void __fastcall TForm1::FormPaint(TObject *Sender)
    {
    ogl_draw();
    }
//---------------------------------------------------------------------------
void __fastcall TForm1::Timer1Timer(TObject *Sender)
    {
    ogl_draw();
    }
//---------------------------------------------------------------------------
void __fastcall TForm1::FormMouseWheelDown(TObject *Sender, TShiftState Shift,
      TPoint &MousePos, bool &Handled)
    {
    glMatrixMode(GL_PROJECTION);
    glTranslatef(0,0,+2.0);
    ogl_draw();
    }
//---------------------------------------------------------------------------
void __fastcall TForm1::FormMouseWheelUp(TObject *Sender, TShiftState Shift,
      TPoint &MousePos, bool &Handled)
    {
    glMatrixMode(GL_PROJECTION);
    glTranslatef(0,0,-2.0);
    ogl_draw();
    }
//---------------------------------------------------------------------------

1. create empty 1-Form project

2. add this to form class header as its user defined members

       int     xs,ys;
       HDC     hdc;            // device context
       HGLRC   hrc;            // rendering context
       int  ogl_inicialized;
       int  ogl_init();
       void ogl_exit();
       void ogl_draw();
       void ogl_resize();
   

3. add timer ~ 20-40 ms

4. create events and copy bodies for resize,repaint,ontimer,... to match above source code
5. compile and run

Notes

• it is not required that all OpenGL stuff is member of form class
• timer can have any interval
• OpenGL can be also just a part of a window not only the whole thing
• can combine with VCL components (use panels for buttons etc and resize OpenGL to area outside)
• If you cannot get it to work comment me, but i do not see anything difficult to do ...
• Do not forget to include gl.h !!!
• if all work then you should see green quad in the center of form
• mouse wheel moves camera forward/backward ('zoom')

When you're ready to go beond OpenGL 1.0 take a look at:

• complete GL+GLSL+VAO/VBO C++ example

Have fun ...