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NucleA

OpenGL Opengl Basic

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Hey guys, am trying to set opengl to a window using Dev cpp

here is my code:


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

LRESULT CALLBACK WindowHandler(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam){
switch(msg){
case WM_CLOSE:
DestroyWindow(hwnd);
break;
case WM_DESTROY:
PostQuitMessage(0);
break;
default: return DefWindowProc(hwnd, msg, wParam, lParam);
}
}

int WINAPI WinMain(HINSTANCE hThisInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow){
WNDCLASSEX wincl;

wincl.cbSize = sizeof(WNDCLASSEX);
wincl.style = CS_OWNDC;
wincl.hIcon = LoadIcon(NULL, IDI_APPLICATION);
wincl.hCursor = LoadCursor(NULL, IDC_ARROW);
wincl.hbrBackground = (HBRUSH) GetStockObject(BLACK_BRUSH);
wincl.cbClsExtra = 0;
wincl.cbWndExtra = 0;
wincl.hInstance = hThisInstance;
wincl.lpszMenuName = NULL;
wincl.lpszClassName = "MyWindowClass";
wincl.lpfnWndProc = WindowHandler;

RegisterClassEx(&wincl);

HWND hwnd;

hwnd = CreateWindow(
"MyWindowClass",
"OpenGl",
WS_POPUPWINDOW | WS_VISIBLE,
70, 70,
700,
510,
NULL,
NULL,
hThisInstance,
NULL
);

HDC hDc;
HGLRC hRc;
PIXELFORMATDESCRIPTOR pfd;
int iFormat;

hDc = GetDC(hwnd);

ZeroMemory(&pfd, sizeof(pfd));
pfd.nSize = sizeof(pfd);
pfd.nVersion = 1;
pfd.dwFlags = PFD_DRAW_TO_WINDOW | PFD_DOUBLEBUFFER | PFD_SUPPORT_OPENGL;
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 & enable rendering context*/
hRc = wglCreateContext(hDc);
wglMakeCurrent(hDc, hRc);

BOOL bQuit = false;
MSG msg;

while(!bQuit){
if(PeekMessage(&msg, NULL, 0, 0, PM_REMOVE)){
if(msg.message == WM_QUIT){
bQuit = true;
}
else{
TranslateMessage(&msg);
DispatchMessage(&msg);
}

}
else{
/*Drawing scene goes here*/
glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
glClear(GL_COLOR_BUFFER_BIT);
glBegin(GL_POINTS);
glVertex2f(0.2f, 0.2f);
glEnd();
SwapBuffers(hDc);


}

}

wglMakeCurrent(NULL, NULL);
wglDeleteContext(hRc);
ReleaseDC(hwnd, hDc);

DestroyWindow(hwnd);

}



But when i compile and run the code, nothing happens, no window appear but the program itself is running on the system.

Where did i make an error in the code?? Please helpp

Thanks and have a nice day! :p

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While I'm sorry I don't know the answer to your question, I'll give you two pieces of advice, which you're free to ignore if you want to:

1) Don't use Dev C++, I believe it is quite old and I hear nothing but bad things about it. (has cryptic error messages, poor intellisense, random bugs, etc) MSVC++ 2010 Express is a better option IMO, and you'll get much more support for it if you have problems (almost everyone uses it).

2) Unless you really want to dig into the nuts and bolts of windows API, let a library take care of the windowing code and you can focus on the OpenGL, it's much simpler. I'll recommend SFML, with which you can replace your entire windowing code with:


main(){
sf::Window App(sf::VideoMode(800,600,32));
App.SetActive();

bool quit = false;
while(!quit) {
glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
glClear(GL_COLOR_BUFFER_BIT);
glBegin(GL_POINTS);
glVertex2f(0.2f, 0.2f);
glEnd();
App.Display();
}
return;
}



Plus it has lots of other useful utilities you may find yourself needing along the way (support for image loading, audio, input handling, etc). It's a nice piece of software.

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The reason am using opengl is that in the future i will need to develop multi threaded applications(like autocad) where there are several windows and view points. Also opengl is cross platform, thats my choice..:p

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I didn't say you should not use OpenGL, you can use OpenGL with SFML to replace the platform specific windowing code.

SFML handles multiple windows and is also cross platform, but that's the last I'll say about that :)

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Thanks very much. But i want to learn it the low level way since i have learned assembly and am a student at a university!

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Hello,

Be sure to clear WNDCLASSEX if you are not going to be setting all of the data members in it (you are messing hIconSm). Invalid values can cause RegisterClassEx to fail. Also, because you are using the *Ex routines, I would recommend using CreateWindowEx over CreateWindow.

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Quote:
Original post by NucleA
Thanks very much. But i want to learn it the low level way since i have learned assembly and am a student at a university!


SFML/SDL mainly lets you avoid the platform specific details (Win32/X11/etc) , if you intend to target multiple platforms its quite a good idea to use it, (The alternative is to rewrite a reasonably large chunk of code for each platform you wish to support), assembly has absolutely nothing to do with the Win32 API btw and most good universities tend to focus on the concepts rather than platform specific details.

In the code you posted 5 of the code lines are cross platform, the rest are windows specific and would have to be rewritten for Linux and Mac.

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"2) Unless you really want to dig into the nuts and bolts of windows API, let a library take care of the windowing code and you can focus on the OpenGL, it's much simpler."

Or you can take what karwosts said to the extreme and use Basic4gl:
http://basic4gl.net/

Although it runs off a VM, its pretty sweet when it comes to just trying something out/experimenting without getting into the specifics of c++... Thats just about as close to "Opengl Basic" as I can think of.

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