MFC中的OpenGL在錯誤的Y位置控制繪製

我有使用OpenGL在派生的CWnd類的設備上下文中繪製矩形的代碼。有人可以告訴我爲什麼矩形沒有在我的控件的左上角位置繪製？ OpenGL用深藍填充整個控件，爲什麼我的矩形不能從相同的y位置繪製？ x位置很好，但y位移。MFC中的OpenGL在錯誤的Y位置控制繪製

void CMyImage::OnPaint() 
{ 
    CPaintDC dc(this); // device context for painting 
    HDC hdc; 

    hdc = ::GetDC(m_hWnd); 

    MySetPixelFormat(hdc); 

    HGLRC hglrc; 

    glClearColor(0,0,0,0); 
    glColor3f(1, 1, 1); 

    hglrc = wglCreateContext(hdc); 

    if(hglrc) 
    { 
    // try to make it the thread's current rendering context 
    if(wglMakeCurrent(hdc, hglrc)) 
    { 
     glViewport(0, 0, m_ScreenWidth, m_ScreenHeight);     // Reset The Current Viewport 

     glMatrixMode(GL_PROJECTION);      // Select The Projection Matrix 
     glLoadIdentity();       // Reset The Projection Matrix 

     glOrtho(0.0f, m_ScreenWidth, m_ScreenHeight, 0.0f, -1.0f, 1.0f); 

     glMatrixMode(GL_MODELVIEW);      // Select The Modelview Matrix 
     glLoadIdentity();       // Reset The Modelview Matrix 
     glTranslatef(0.5, 0.5, 0); 

     // Dark blue.. 
     glClearColor(0.0f, 0.0f, 0.3f, 1.0f); 

     glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);   

     glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA); 
     glAlphaFunc(GL_GREATER, 0.1f); 

     glEnable(GL_BLEND); 
     glEnable(GL_ALPHA_TEST); 

     glBindTexture(GL_TEXTURE_2D, 0); 

     glColor4f(1.0f, 1.0f, 0, 1); 
     DrawFilledRectangle(0, 0, 320, 200); 

     glColor4f(1.0f, 0, 0, 1); 
     DrawFilledRectangle(0, 0, 50, 50);

...

void DrawFilledRectangle(int nLeft, int nTop, int nWidth, int nHeight) 
{ 
    // Undo the glTranslatef(0.5, 0.5) thats needed for drawing lines.. 
    glLoadIdentity(); 

    float fLeft = (float) nLeft; 
    float fTop = (float) nTop; 

    float fRight = fLeft + (float) nWidth; 
    float fBottom = fTop + (float) nHeight; 

    GLfloat avRect[ 18 ]; 
    GLfloat *p = avRect;  

    p = AddVertex3(p, fLeft, fTop); 
    p = AddVertex3(p, fRight, fTop); 
    p = AddVertex3(p, fRight, fBottom); 

    p = AddVertex3(p, fLeft, fTop); 
    p = AddVertex3(p, fLeft, fBottom); 
    p = AddVertex3(p, fRight, fBottom); 

    glEnableClientState(GL_VERTEX_ARRAY); 
    glEnableClientState(GL_NORMAL_ARRAY); 

    glVertexPointer(3, GL_FLOAT, 0, avRect); 

    glDrawArrays(GL_TRIANGLES, 0, 6); 

    glDisableClientState(GL_VERTEX_ARRAY); 
} 

GLfloat *AddVertex3(GLfloat *pVertices, float fX, float fY) 
{ 
    GLfloat *p = pVertices; 

    *p = fX; p ++; 
    *p = fY; p ++; 
    *p = 0.0f; p ++; 

    return p; 
}

這裏是正在發生的事情的圖像。紅色和黃色的矩形應該在左上角。

enter image description here

來源

2015-06-13 SparkyNZ

我發現，通過設置我的控件的大小，以便它是一樣的視口的大小，它繪製矩形在正確的左上角位置。

來源

2015-06-13 07:09:48 SparkyNZ

MFC中的OpenGL在錯誤的Y位置控制繪製

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