SetPixel() function on windows.h . How to use it??

windows.h provides a function SetPixel() to print a pixel at specified location of a window. The general form of the function is

SetPixel(HDC hdc, int x, int y, COLORREF& color);

where, x and y are coordinates of pixel to be display and color is the color of pixel. The following program draws a horizontal line to a window.

Note: to run this code in your machine with Code::blocks IDE, add a link library libgdi32.a (it is usually inside MinGW\lib )  in linker setting.

#include <windows.h>
static HWND sHwnd;
static COLORREF redColor=RGB(255,0,0);
static COLORREF blueColor=RGB(0,0,255);
static COLORREF greenColor=RGB(0,255,0);
void SetWindowHandle(HWND hwnd){
    sHwnd=hwnd;
}
void setPixel(int x,int y,COLORREF& color=redColor){
    if(sHwnd==NULL){
        MessageBox(NULL,"sHwnd was not initialized !","Error",MB_OK|MB_ICONERROR);
        exit(0);
    }
    HDC hdc=GetDC(sHwnd);
    SetPixel(hdc,x,y,color);
    ReleaseDC(sHwnd,hdc);
    return;
}
void drawLine(){
    for(int i = 0; i < 100; i++)
        setPixel(10+i, 100, blueColor);
}
LRESULT CALLBACK WndProc(HWND hwnd,UINT message,WPARAM wParam,LPARAM lParam){
    switch(message){
        case WM_PAINT:
            SetWindowHandle(hwnd);
            drawLine();
            break;
        case WM_CLOSE: // FAIL THROUGH to call DefWindowProc
            break;
        case WM_DESTROY:
            PostQuitMessage(0);
            return 0;
        default:
        break; // FAIL to call DefWindowProc //
    }
    return DefWindowProc(hwnd,message,wParam,lParam);
}
int WINAPI WinMain(HINSTANCE hInstance,HINSTANCE hPrevInstance,LPSTR lpCmdLine,int iCmdShow){
    static TCHAR szAppName[] = TEXT("Test");
    WNDCLASS wndclass;
    wndclass.style         = CS_HREDRAW|CS_VREDRAW ;
    wndclass.lpfnWndProc   = WndProc ;
    wndclass.cbClsExtra    = 0 ;
    wndclass.cbWndExtra    = 0 ;
    wndclass.hInstance     = hInstance ;
    wndclass.hIcon         = LoadIcon (NULL, IDI_APPLICATION) ;
    wndclass.hCursor       = LoadCursor (NULL, IDC_ARROW) ;
    wndclass.hbrBackground = (HBRUSH) GetStockObject (WHITE_BRUSH) ;
    wndclass.lpszMenuName  = NULL ;
    wndclass.lpszClassName = szAppName ;
    // Register the window //
    if(!RegisterClass(&wndclass)){
        MessageBox(NULL,"Registering the class failled","Error",MB_OK|MB_ICONERROR);
        exit(0);
    }
    // CreateWindow //
    HWND hwnd=CreateWindow(szAppName,"SetPixel example - programming-technique.blogspot.com",
                WS_OVERLAPPEDWINDOW,
                 CW_USEDEFAULT,
                 CW_USEDEFAULT,
                 CW_USEDEFAULT,
                 CW_USEDEFAULT,
                 NULL,
                 NULL,
                 hInstance,
                 NULL);
    if(!hwnd){
        MessageBox(NULL,"Window Creation Failed!","Error",MB_OK);
        exit(0);
    }
    // ShowWindow and UpdateWindow //
    ShowWindow(hwnd,iCmdShow);
    UpdateWindow(hwnd);
    // Message Loop //
    MSG msg;
    while(GetMessage(&msg,NULL,0,0)){
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }
    return 0;
}