gl_init_winapi.cpp

#include <windows.h>
#include <gl/gl.h>  //toto mozes mozna mat ako GL/gl.h keby daco

//forward deklaracie
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);

//main funkcia
int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
                   LPSTR lpCmdLine, int iCmdShow)
{
    WNDCLASS wc;    //window class
    HWND hWnd;  //handle na window
    HDC hDC;    //handle na device context
    HGLRC hRC;  //handle na GL rendering context
    MSG msg;    //WinApi je message based paradigma, troska sa zda byt za vlasy pritiahnuta, ale je to okej
    BOOL quit = FALSE;
    float theta = 0.0f; //premenna na zmenu stavu

    //zaregistrujeme window clasu
    wc.style = CS_OWNDC;
    wc.lpfnWndProc = WndProc;   //window procedura, ktoru sme zadefinovali nizsie
    wc.cbClsExtra = 0;
    wc.cbWndExtra = 0;
    wc.hInstance = hInstance;   //handle instancu programu, ktoru namapujeme na samotny window
    wc.hCursor = LoadCursor( NULL, IDC_ARROW );
    wc.hbrBackground = (HBRUSH)GetStockObject( BLACK_BRUSH );
    wc.lpszMenuName = NULL;
    wc.lpszClassName = "OpenGL";    //class name windowu co spravime
    RegisterClass( &wc );       //zaregistrujeme na dalsie pouzivanie

    // vytvorime samotne okno
    hWnd = CreateWindow(
        "OpenGL", "Opengl is great but DirectX rocks!!!",   //class name a window title v tomto poradi to je
                                    //definovane
        WS_CAPTION | WS_POPUPWINDOW | WS_VISIBLE,
        0, 0, 256, 256,     //sirka a vyska windowu tych 256, 256
        NULL, NULL, hInstance, NULL );

    //namapujeme OpenGL na okno a na render/device context
    EnableOpenGL( hWnd, &hDC, &hRC );

    //tu prebieha hlavny uzol programu
    while ( !quit )
    {
        //zistime, ci su nejake messages v message loope, ak su, tak handle them, if not tak vykreslujeme
        if ( PeekMessage( &msg, NULL, 0, 0, PM_REMOVE )  )
        {
            //ak doslo quit message, tak vypne aplikaciu, ak nie, posunie message dalej
            if ( msg.message == WM_QUIT )
            {
                quit = TRUE;
            }
            else
            {
                TranslateMessage( &msg );
                DispatchMessage( &msg );
            }
        }
        else
        {
            //
            //sem ide veskery rendrovaci loop, toto vsetko z else mozes aj vymazat ak chces
            //a nahradit vlastnym :) (az na glClearColor a glClear, tie treba hocijak...a SwapBuffers)
            //
            glClearColor( 0.0f, 0.0f, 0.0f, 0.0f ); //vymaz celeho framebufferu na nejaku solid farbu
                                //vo formate RGBA...nemusi byt cierne, odporucam
                                //vyskusat aj cornflower blue na debugovacie ucely
                                //R: 0.258824f G: 0.258824f B: 0.435294f A: 1.0f
            glClear( GL_COLOR_BUFFER_BIT ); //vymazeme color buffer (cize vsetko co sme nakreslili vo frame
                            //neskor sa ti tu objavia aj ine parametre ako depth a stencil buffer
                            //az budes robit normal a shadow mapping

            glPushMatrix(); //ulozime stav projekcnej matice
            glRotatef( theta, 0.0f, 0.0f, 1.0f );   //pootocime po X ovej osi o theta obrazec
            glBegin( GL_TRIANGLES );    //tymto prikazom povies OpenGL ze chces zacat vykreslovanie
            {               //trojuholnikov...existuje viacero typov, ako GL_LINES alebo
                            //GL_POINTS alebo GL_TRIANDGLE_STRIP/GL_TRIANGLE_FAN
                            //ale v ziadnom pripade nepouzi GL_QUAD...je to uz deprecated davno
                glColor3f( 1.0f, 0.0f, 0.0f );  //v OpenGL nastavujes vzdy dany stav, nez sa to vykona
                                //cize tu mas nastavenu farbu pre dany vertex, ak robis
                                //per vertex lighting ako v tomto pripade
                glVertex2f( 0.0f, 1.0f );   //tu si das vykreslit dany vertex s poziciami udanymi X a Y
                glColor3f( 0.0f, 1.0f, 0.0f );
                glVertex2f( 0.87f, -0.5f );
                glColor3f( 0.0f, 0.0f, 1.0f );
                glVertex2f( -0.87f, -0.5f );
            }
            glEnd();    //touto funkciou povies OpenGL ze si dokoncila vykreslovanie pre dany utvar
            glPopMatrix();  //obnovis stav projekcnej matice

            SwapBuffers( hDC ); //zamenis frontbuffer za backbuffer, kde sa ti zatial vsetko vykreslilo v pozadi

            theta += 1.0f;  //inkrementujes tetu :D
        }
    }

    //vycistis OpenGL a vypnes
    DisableOpenGL( hWnd, hDC, hRC );

    //explicitne zavres okno
    DestroyWindow( hWnd );

    return msg.wParam;

}

//window procedura
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 )
        {
            //tu mozes definovat vstupy z klavesnice, napr VK_ENTER tusim na stlacenie entra
        case VK_ESCAPE:
            PostQuitMessage(0); //tu sa posle message na vypnutie okna
            return 0;

        }
        return 0;

    default:
        return DefWindowProc( hWnd, message, wParam, lParam );

    }

}

//funkcia na nastavenie opengl
void EnableOpenGL(HWND hWnd, HDC * hDC, HGLRC * hRC)
{
    PIXELFORMATDESCRIPTOR pfd;  //pixel format descriptor nam udava hlbku farieb a udava paletu
    int format;

    //ziskame device context z handlu na window
    *hDC = GetDC( hWnd );

    //tu sa nastavuje pixel format pre OpenGL
    ZeroMemory( &pfd, sizeof( pfd ) );
    pfd.nSize = sizeof( pfd );
    pfd.nVersion = 1;
    pfd.dwFlags = PFD_DRAW_TO_WINDOW | PFD_SUPPORT_OPENGL | PFD_DOUBLEBUFFER;   //doublebuffered pre znizenie flickeringu
                                            //support pre opengl
                                            //support pre priame kreslenie na window
    pfd.iPixelType = PFD_TYPE_RGBA;     //RGBA format farby, tusim tu si mozes dat aj ARGB32 a ine formaty, ako HSV a tak
    pfd.cColorBits = 24;        //kolko bitov chces na uchovavanie farieb...24 bity mas dost na zopar milionov farieb
    pfd.cDepthBits = 16;        //hlbka farby v bitoch per pixel
    pfd.iLayerType = PFD_MAIN_PLANE;    //netusim popravde co to robi, ale treba to
    format = ChoosePixelFormat( *hDC, &pfd );   //tu nam priradi system potrebny pixel format
    SetPixelFormat( *hDC, format, &pfd );       //ktory potom nastavime na ten window

    *hRC = wglCreateContext( *hDC ); //tu sa nam vytvori render context
    wglMakeCurrent( *hDC, *hRC );   //ktory hned priradime a zapneme

}

//Funkcia na uvolnenie contextu, a vypnutie okna
void DisableOpenGL(HWND hWnd, HDC hDC, HGLRC hRC)
{
    wglMakeCurrent( NULL, NULL );
    wglDeleteContext( hRC );
    ReleaseDC( hWnd, hDC );
}