如何在 Qt 应用程序中替换 'gluOrtho2d'

Question

我正在努力使我七年前编写的程序恢复生机。它全部用 Qt 编写，并使用一些 OpenGL 在应用程序显示的图像上绘制一些框线。问题是 'gluOrtho2D' 被使用但不再被发现。我想知道如何解决这个问题。这是代码：

void MSContext::ResizePaint(int width, int height)
{
    // setup viewport, projection etc.:
    glViewport(0, 0, (GLint)width, (GLint)height);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluOrtho2D(0.0, (GLdouble) width, 0.0, (GLdouble) height);
    glMatrixMode(GL_MODELVIEW); 

    glClearColor(0.5, 0.5, 0.5, 1.0);
    glShadeModel(GL_FLAT);
    glPixelStorei(GL_UNPACK_ALIGNMENT, 1);

    CreatePrintCropMarks();
}

void MSContext::CreatePrintCropMarks()
{
    GLuint print45CropId = openGLListMgr()->print45CropId();
    glNewList( print45CropId, GL_COMPILE);
    {
        qreal lineSize = 4.0;
        // Shrink down the canvas by 4 pixels so that the crop will show up
        const QRectF& viewPort = primaryCanvas()->imageView()->viewRectangle();
        QRectF shrunkingCanvas = viewPort.adjusted(lineSize, lineSize, -lineSize, -lineSize);

        QRectF print45Crop = GetCropRect(shrunkingCanvas, 5, 4);
        QRectF print57Crop = GetCropRect(print45Crop, 7, 5);

        glLineWidth(lineSize / 2);
        glLineStipple(1,0xFF00);
        DrawBox(print57Crop);
        glLineWidth(lineSize);
        glLineStipple(1,0xFFFF);
        DrawBox(print45Crop);
    }
    glEndList();
}

Answer 1

在我的脑海里，我想知道为什么我从来没有听说过这个功能......原来在（老式的）OpenGL 中有一个很好的选择。来自 SGI GLU implementation:

void GLAPIENTRY                                                   
gluOrtho2D(GLdouble left, GLdouble right, GLdouble bottom, GLdouble top)
{
    glOrtho(left, right, bottom, top, -1, 1); 
}

所以你可以这样写：

glOrtho(0.0, (GLdouble) width, 0.0, (GLdouble) height, -1, 1);

如何在 Qt 应用程序中替换 'gluOrtho2d'

How to replace 'gluOrtho2d' in a Qt app

c++

qt

opengl

opengl-2.0