Question

我在屏幕上为渲染图像编写了OpenGL代码。我使用GLUT创建了一个窗口和回调，但我希望在win32窗口中呈现的图像不在GLUT中，基本上我们有一个CreateWindowEx() API来创建{ {1}}我们有一个win32（句柄），以便我们可以将此句柄传递给HWND，但我在HDC中找不到这样的内容，是否有可能发送句柄到GLUT？或其他方法？

下面是我的代码，它在屏幕上成功渲染图像。

GLUT

Answer 1

如果你想创建一个没有任何窗口库的win32 OpenGL窗口，你必须执行以下操作：

注册窗口类RegisterClassEx
创建一个窗口CreateWindow
创建一个OpneGL上下文wglCreateContext
将上下文设为当前上下文wglMakeCurrent
显示窗口ShowWindow

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

const std::wstring wnd_class( L"my_wnd_class" );
HWND hOGLWnd = NULL;
HGLRC hOGLRenderContext = NULL;

HWND createWindow( int width, int height )
{
    // Get module handle
    HMODULE hModule = ::GetModuleHandle( 0 );
    if (!hModule)
        return NULL;

    // Create window calss
    WNDCLASSEX wndClassData;
    memset( &wndClassData, 0, sizeof( WNDCLASSEX ) );
    wndClassData.cbSize         = sizeof( WNDCLASSEX );
    wndClassData.style          = CS_DBLCLKS;
    wndClassData.lpfnWndProc    = WindowProcedure;
    wndClassData.cbClsExtra     = 0;
    wndClassData.cbWndExtra     = 0;
    wndClassData.hInstance      = hModule;
    wndClassData.hIcon          = ::LoadIcon(0,IDI_APPLICATION);
    wndClassData.hCursor        = ::LoadCursor(0,IDC_ARROW);
    wndClassData.hbrBackground  = ::CreateSolidBrush(COLOR_WINDOW+1);
    wndClassData.lpszMenuName   = 0;
    wndClassData.lpszClassName  = wnd_class.c_str();
    wndClassData.hIconSm        = 0;
    if ( !::RegisterClassEx( &wndClassData ) )
        return false;

    // Creaate Window
    hOGLWnd = ::CreateWindow( wnd_class.c_str(), NULL, WS_OVERLAPPEDWINDOW, 0, 0, width, height, NULL, NULL, hModule, NULL);
    if ( hOGLWnd == NULL )
        return NULL;

    // Get device context
    HDC hDC = ::GetDC( hOGLWnd );

    // Create OpenGL context
    DWORD pixelFormatFlags = PFD_SUPPORT_OPENGL | PFD_SUPPORT_COMPOSITION | PFD_GENERIC_ACCELERATED | PFD_DRAW_TO_WINDOW | PFD_DOUBLEBUFFER;
    PIXELFORMATDESCRIPTOR pfd =
    {
      sizeof(PIXELFORMATDESCRIPTOR),
      1,
      pixelFormatFlags,         //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
    };
    int pixelFormat = ::ChoosePixelFormat( hDC, &pfd ); 
    ::SetPixelFormat( hDC, pixelFormat, &pfd );
    hOGLRenderContext = ::wglCreateContext( hDC );

    // make OpenGL context the current context
    ::wglMakeCurrent( hDC, hOGLRenderContext );

    // release device context
    ::ReleaseDC( hOGLWnd, hDC );

    // show the window
    ::ShowWindow( hOGLWnd, SW_SHOWDEFAULT );
    return hOGLWnd;
}

对于窗口，过程是neede，它处理窗口消息：

LRESULT CALLBACK WindowProcedure( HWND hWnd, unsigned int msg, WPARAM wparam, LPARAM lparam )
{
    switch(msg)
    {
    case WM_DESTROY:
        PostQuitMessage(0);
        break;

    case WM_ERASEBKGND: 
        display();
        break;
    }
    return DefWindowProc( hWnd, msg, wparam, lparam );
}

主循环必须调度窗口消息（消息循环）：

void mainloop( void )
{
    MSG msg;
    while( ::GetMessage( &msg, 0, 0, 0 ) )
        ::DispatchMessage( &msg );
}

窗口可以像这样被破坏：

void destroyWindow(void)
{
    if ( HDC currentDC = ::wglGetCurrentDC() )
        ::wglMakeCurrent( currentDC , NULL );
    ::DestroyWindow( hOGLWnd );
    ::wglDeleteContext( hOGLRenderContext );

    HMODULE hModule = ::GetModuleHandle( 0 );
    if (!hModule)
        return;
    ::UnregisterClass( wnd_class.c_str(), hModule );
}

为了完整性的一个简单的演示程序：

#include <GL/glew.h>
#include <vector>
#include <stdexcept>

int main()
{
    int w = 800;
    int h = 600;

    HWND hWnd = createWindow( w, h );
    if ( hWnd == 0 )
        throw std::runtime_error( "error initializing window" ); 

    if ( glewInit() != GLEW_OK )
        throw std::runtime_error( "error initializing glew" );

    static const std::vector<float> varray
    { 
      -0.707f, -0.75f,    1.0f, 0.0f, 0.0f, 1.0f, 
       0.707f, -0.75f,    1.0f, 1.0f, 0.0f, 1.0f,
       0.0f,    0.75f,    0.0f, 0.0f, 1.0f, 1.0f
    };

    GLuint vbo;
    glGenBuffers( 1, &vbo );
    glBindBuffer( GL_ARRAY_BUFFER, vbo );
    glBufferData( GL_ARRAY_BUFFER, varray.size()*sizeof(*varray.data()), varray.data(), GL_STATIC_DRAW );

    GLuint vao;
    glGenVertexArrays( 1, &vao );
    glBindVertexArray( vao );
    glVertexPointer( 2, GL_FLOAT, 6*sizeof(*varray.data()), 0 );
    glEnableClientState( GL_VERTEX_ARRAY );
    glColorPointer( 4, GL_FLOAT, 6*sizeof(*varray.data()), (void*)(2*sizeof(*varray.data())) ); 
    glEnableClientState( GL_COLOR_ARRAY );
    glBindBuffer( GL_ARRAY_BUFFER, 0 );

    mainloop();    
    destroyWindow();
    return 0;
}

void display( void )
{
    RECT clientRect;
      ::GetClientRect( hOGLWnd, &clientRect );
    glViewport( 0, 0, clientRect.right-clientRect.left, clientRect.bottom-clientRect.top );
    glClearColor(0.0f, 0.0f, 0.0f, 0.0f);    

    glDrawArrays( GL_TRIANGLES, 0, 3 );

    // swap buffers
    HDC hDC = ::GetDC( hOGLWnd );
    ::SwapBuffers( hDC );
    ::ReleaseDC( hOGLWnd, hDC );

    // create message WM_ERASEBKGND
    ::InvalidateRect( hOGLWnd, NULL, TRUE);
 }

请注意，如果您不显示窗口（跳过ShowWindow），则您有一个隐藏窗口，您可以在其中进行图像渲染。您可以通过glReadPixels从GPU读取渲染图像，或者您可以创建带有附加纹理的帧缓冲区，并按glGetTexImage读取纹理。

在win32窗口中使用OpenGL渲染图像

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