clock pointer C using GL.

clock_pointer.c

#include <windows.h>
#include <gl/gl.h>

LRESULT CALLBACK WndProc(HWND hWnd,
			 UINT message,
			 WPARAM wParam,
			 LPARAM lParam);
void EnableOpenGL(HWND hWnd, HDC *hDC, HGLRC *hRC);
void DisableOpenGL(HWND hWnd, HDC hDC, HGLRC hRC);


// --- WinMain --- The main guy.
int WINAPI WinMain(HINSTANCE hInstance,
                   HINSTANCE hPrevInstance,
                   LPSTR lpCmdLine,
                   int iCmdShow)
{
	WNDCLASS wc;
	HWND     hWnd;
	HDC      hDC;
	HGLRC    hRC;        
	MSG      msg;
	BOOL     bQuit = FALSE;
	float    theta = 0.0f,
		 i     = 0.0f,
		 j     = 0.0f;

	// register window class
	wc.style         = CS_OWNDC;
	wc.lpfnWndProc   = WndProc;
	wc.cbClsExtra    = 0;
	wc.cbWndExtra    = 0;
	wc.hInstance     = hInstance;
	wc.hIcon         = LoadIcon(NULL, IDI_APPLICATION);
	wc.hCursor       = LoadCursor(NULL, IDC_ARROW);
	wc.hbrBackground = (HBRUSH) GetStockObject(BLACK_BRUSH);
	wc.lpszMenuName  = NULL;
	wc.lpszClassName = "GLSample";

	RegisterClass(&wc);

	// create main window
	hWnd = CreateWindow("GLSample",
			    "OpenGL Sample", 
			    WS_CAPTION | WS_POPUPWINDOW | WS_VISIBLE,
			    500, 150, 400, 400,
			    NULL,
			    NULL,
			    hInstance,
			    NULL);

	// enable OpenGL for the window
	EnableOpenGL(hWnd, &hDC, &hRC);

	// program main loop
	while (!bQuit) {
		// check for messages
		if (PeekMessage(&msg, NULL, 0, 0, PM_REMOVE)) {
			// handle or dispatch messages
			if (msg.message == WM_QUIT) {
				bQuit = TRUE;
			} else {
				TranslateMessage(&msg);
				DispatchMessage(&msg);
			}
		} else {
			// OpenGL animation code goes here
			glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
			glClear(GL_COLOR_BUFFER_BIT);
			
			glPushMatrix();
			glRotatef(theta, 1.0f, 0.0f, 1.0f);
			
			glBegin(GL_LINE_LOOP);
			
			glColor3f(1.0f, 1.0f, 1.0f);
		
			for (i = 0.0f; i < 1.0f; i += 0.15f) {
				for (j = 0.0f; i < 1.0f; i += 0.15f) {
					glVertex2f(j, i);
				}
			}
			
			glEnd();
			glPopMatrix();
			
			SwapBuffers(hDC);
			
			theta -= 6.0f;
			Sleep(1000);
		}
	}

	// shutdown OpenGL
	DisableOpenGL(hWnd, hDC, hRC);
	
	// destroy the window explicitly
	DestroyWindow(hWnd);
	
	return msg.wParam;
}


// --- Window Procedure ---
LRESULT CALLBACK WndProc(HWND hWnd,
			 UINT message,
                         WPARAM wParam,
			 LPARAM lParam)
{
	switch (message) {
		case WM_CREATE:
			return 0;
		
		case WM_CLOSE:
			PostQuitMessage (0);
			return 0;
		
		case WM_DESTROY:
			return 0;

		case WM_KEYDOWN:
			switch (wParam) {
				case VK_ESCAPE:
					PostQuitMessage(0);
					return 0;
			}
		return 0;
		
		default:
			return DefWindowProc(hWnd, message, wParam, lParam);
	}
}


// --- Enable OpenGL ---
void EnableOpenGL(HWND hWnd, HDC *hDC, HGLRC *hRC)
{
	PIXELFORMATDESCRIPTOR pfd;
	int iFormat;
	
	// get the device context (DC)
	*hDC = GetDC(hWnd);
	
	// set the pixel format for the DC
	ZeroMemory(&pfd, sizeof(pfd));
	
	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 = 16;
	pfd.iLayerType = PFD_MAIN_PLANE;
	
	iFormat = ChoosePixelFormat(*hDC, &pfd);
	SetPixelFormat(*hDC, iFormat, &pfd);
	
	// create and enable the render context (RC)
	*hRC = wglCreateContext(*hDC);
	wglMakeCurrent(*hDC, *hRC);
}

// --- Disable OpenGL ---
void DisableOpenGL(HWND hWnd, HDC hDC, HGLRC hRC)
{
	wglMakeCurrent(NULL, NULL);
	wglDeleteContext(hRC);
	ReleaseDC(hWnd, hDC);
}