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我正在尝试通过以下示例与 OpenGL 取得联系：

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

#pragma comment (lib, "opengl32.lib")

LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam);

int WinMain( __in HINSTANCE hInstance, __in_opt HINSTANCE hPrevInstance, __in_opt LPSTR lpCmdLine, __in int nShowCmd )
{
    MSG msg          = {0};
    WNDCLASS wc      = {0}; 
    wc.lpfnWndProc   = WndProc;
    wc.hInstance     = hInstance;
    wc.hbrBackground = (HBRUSH)(COLOR_BACKGROUND);
    wc.lpszClassName = L"oglversionchecksample";
    wc.style = CS_OWNDC;
    if( !RegisterClass(&wc) )
        return 1;
    CreateWindowW(wc.lpszClassName,L"openglversioncheck",WS_OVERLAPPEDWINDOW|WS_VISIBLE,0,0,640,480,0,0,hInstance,0);

    while( GetMessage( &msg, NULL, 0, 0 ) > 0 )
        DispatchMessage( &msg );

    return 0;
}

LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    switch(message)
    {
    case WM_CREATE:
        {
        PIXELFORMATDESCRIPTOR pfd =
        {
            sizeof(PIXELFORMATDESCRIPTOR),
            1,
            PFD_DRAW_TO_WINDOW | PFD_SUPPORT_OPENGL | PFD_DOUBLEBUFFER,    //Flags
            PFD_TYPE_RGBA,            //The kind of framebuffer. RGBA or palette.
            32,                        //Colordepth of the framebuffer.
            0, 0, 0, 0, 0, 0,
            0,
            0,
            0,
            0, 0, 0, 0,
            24,                        //Number of bits for the depthbuffer
            8,                        //Number of bits for the stencilbuffer
            0,                        //Number of Aux buffers in the framebuffer.
            PFD_MAIN_PLANE,
            0,
            0, 0, 0
        };

        HDC ourWindowHandleToDeviceContext = GetDC(hWnd);

        int  letWindowsChooseThisPixelFormat;
        letWindowsChooseThisPixelFormat = ChoosePixelFormat(ourWindowHandleToDeviceContext, &pfd); 
        SetPixelFormat(ourWindowHandleToDeviceContext,letWindowsChooseThisPixelFormat, &pfd);

        HGLRC ourOpenGLRenderingContext = wglCreateContext(ourWindowHandleToDeviceContext);
        wglMakeCurrent (ourWindowHandleToDeviceContext, ourOpenGLRenderingContext);

        MessageBoxA(0,(char*)glGetString(GL_VERSION), "OPENGL VERSION",0);

        wglDeleteContext(ourOpenGLRenderingContext);
        PostQuitMessage(0);
        }
        break;
    default:
        return DefWindowProc(hWnd, message, wParam, lParam);
    }
    return 0;

}

我正在使用最新版本的Code::Blocks (v13.12)和 MinGW-TDM-GCC-4.8.1
在链接器设置中我链接到libopengl32.a并使用windows.h和 GL-headers MinGW 分布。

但是我收到此错误：

main.cpp|4|warning: ignoring #pragma comment  [-Wunknown-pragmas]|
main.cpp|8|error: 'int WinMain' redeclared as different kind of symbol|
codeblocks\mingw\include\winbase.h|1251|error: previous declaration of 'int WinMain(HINSTANCE, HINSTANCE, LPSTR, int)'|
main.cpp|8|error: '__in' was not declared in this scope|
main.cpp|8|error: '__in_opt' was not declared in this scope|
main.cpp|8|error: '__in_opt' was not declared in this scope|
main.cpp|8|error: '__in' was not declared in this scope|

我错过了什么？还是此示例仅在使用 Visual Studio 时才有效（如编译指示所示）？

编辑

我把所有东西都删掉了（没有opengl的东西），只有win头和它的WinMain，但同样的错误。

然后我用它的标准 main 替换了 WinMain（见这里）

int main()
{
    HINSTANCE hInstance = GetModuleHandle( NULL );
    HINSTANCE hPrevInstance = 0;
    LPSTR lpCmdLine = NULL;
    int nShowCmd = 0;

    ...same as before

    return 0;
}

在我也链接到libgdi32.a之后它编译没有错误，但是它只显示一个空的命令提示符。

编辑 2

我删除了宽字符串（L""和CreateWindowW到CreateWindow），现在它可以工作了..

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1 回答 1

1

我猜 mingw 不喜欢所有的 MSVC 特定的东西，删除#pragma comment和所有的__in，等等。我认为，由于 mingw 无法解决那些它不能与WinMain它拥有的定义匹配并且失败的东西。基本上将开头重写为：

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

LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam);

int WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nShowCmd)
于 2015-07-09T15:29:51.740 回答