How to Render an OpenGL Frame Within a C Builder Form?

Rendering an OpenGL Frame in C Builder

While customizing a C Builder form with OpenGL, it's common to encounter issues when directly copying OpenGL startup code from online resources. For those using C Builder, here's a detailed guide to render an OpenGL frame within a form:

Initialization

1. In the form class header, define user-defined members as follows:

<code class="cpp">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();</code>

2. Create a timer with an interval of 20-40 milliseconds.
3. In the form's events (e.g., resize, repaint, timer), add code similar to the following:

<code class="cpp">void __fastcall TForm1::FormResize(TObject* Sender)
{
    ogl_resize();
}

void __fastcall TForm1::FormPaint(TObject* Sender)
{
    ogl_draw();
}

void __fastcall TForm1::Timer1Timer(TObject* Sender)
{
    ogl_draw();
}</code>

OpenGL Initialization

4. Within the ogl_init() function, perform the following steps:

<code class="cpp">hdc = GetDC(Form1->Handle);             // get device context

PIXELFORMATDESCRIPTOR pfd;
ZeroMemory(&pfd, sizeof(pfd));      // set the pixel format for the DC
...

if(wglMakeCurrent(hdc, hrc) == false)
{
    ShowMessage("Could not make current OpenGL Rendering context !!!");
    wglDeleteContext(hrc);          // destroy rendering context
    ogl_inicialized=0;
    return 0;
}
...</code>

OpenGL Rendering

5. In the ogl_draw() function, create and draw a primitive object (e.g., a quad):

<code class="cpp">glBegin(GL_QUADS);
...
glEnd();</code>

Additional Notes

• Remember to include header file.
• You can use TForm::Handle as the window handle when initializing OpenGL.
• This example demonstrates a simple green quad in the center of the form.
• For more advanced OpenGL functionality (e.g., GLSL, VAO/VBO), refer to additional resources online.

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