如果这不准确，我深表歉意。我正在尽我所能将代码从一台计算机手动复制到另一台计算机，而目标计算机没有编译器（不要问）。
头文件
#ifndef MYOPENGLWIDGET_H
#define MYOPENGLWIDGET_H
#include <qopenglwidget.h>
class MyOpenGlWidget : public QOpenGLWidget
{
Q_OBJECT
public:
explicit MyOpenGlWidget(QWidget *parent = 0, Qt::WindowFlags f = Qt::WindowFlags());
virtual ~MyOpenGlWidget();
protected:
// these are supposed to be overridden, so use the "override" keyword to compiler check yourself
virtual void initializeGL() override;
virtual void resizeGL(int w, int h) override;
virtual void paintGL() override;
private:
QPixmap *_foregroundPixmap;
}
#endif
源文件
QOpenGLFunctions_2_1 *f = 0;
MyOpenGlWidget::MyOpenGlWidget(QWidget *parent, Qt::WindowFlags f) :
QOpenGLWidget(parent, f)
{
_foregroundPixmap = 0;
QPixmap *p = new QPixmap("beveled_texture.tiff");
if (!p->isNull())
{
_foregroundPixmap = p;
}
}
MyOpenGlWidget::~MyOpenGlWidget()
{
delete _foregroundPixmap;
}
void MyOpenGlWidget::initializeGL()
{
// getting a deprecated set of functions because such is my work environment
// Note: Also, QOpenGLWidget doesn't support these natively.
f = QOpenGLContext::currentContext()->versionFunctions<QOpenGLFunctions_2_1>();
f->glClearColor(0.0f, 1.0f, 0.0f, 1.0f); // clearing to green
f->glEnable(GL_DEPTH_TEST);
f->glEnable(GL_CULL_FACE); // implicitly culling front face
f->glEnable(GL_SCISSOR_TEST);
// it is either copy the matrix and viewport code from resizeGL or just call the method
this->resizeGL(this->width(), this->height());
}
void MyOpenGlWidget::resizeGL(int w, int h)
{
// make the viewport square
int sideLen = qMin(w, h);
int x = (w - side) / 2;
int y = (h - side) / 2;
// the widget is 400x400, so this random demonstration square will show up inside it
f->glViewport(50, 50, 100, 100);
f->glMatrixMode(GL_PROJECTION);
f->glLoadIdentity();
f->glOrtho(-2.0f, +2.0f, -2.0f, +2.0f, 1.0f, 15.0f); // magic numbers left over from a demo
f->glMatrixMode(GL_MODELVIEW);
// queue up a paint event
// Note: QGLWidget used updateGL(), but QOpenGLWidget uses update().
this->update();
}
void MyOpenGlWidget::paintGL()
{
f->glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
// I want to draw a texture with beveled edges the size of this widget, so I can't
// have the background clearing all the way to the edges
f->glScissor(50, 50, 200, 200); // more magic numbers just for demonstration
// clears to green in just scissored area (unless QPainter is created)
f->glClearColor(0.0f, 1.0f, 0.0f, 1.0f);
// loading identity matrix, doing f->glTranslatef(...) and f->glRotatef(...)
// pixmap loaded earlier in another function
if (_foregroundPixmap != 0)
{
// QPixmap apparently draws such that culling the back face will cull the entire
// pixmap, so have to switch culling for duration of pixmap drawing
f->glCullFace(GL_FRONT);
QPainter(this);
painter.drawPixmap(0, 0, _foregroundPixmap->scaled(this->size()));
// done, so switch back to culling the front face
f->glCullFace(GL_BACK);
}
QOpenGLFunctions_2_1 *f = 0;
void MyOpenGlWidget::initializeGL()
{
// getting a deprecated set of functions because such is my work environment
// Note: Also, QOpenGLWidget doesn't support these natively.
f = QOpenGLContext::currentContext()->versionFunctions<QOpenGLFunctions_2_1>();
f->glClearColor(0.0f, 1.0f, 0.0f, 1.0f); // clearing to green
f->glEnable(GL_DEPTH_TEST);
f->glEnable(GL_CULL_FACE); // implicitly culling front face
f->glEnable(GL_SCISSOR_TEST);
// it is either copy the matrix and viewport code from resizeGL or just call it directly
this->resizeGL(this->width(), this->height());
}
void MyOpenGlWidget::resizeGL(int w, int h)
{
// make the viewport square
int sideLen = qMin(w, h);
int x = (w - side) / 2;
int y = (h - side) / 2;
// the widget is 400x400, so this random demonstration square will show up inside it
f->glViewport(50, 50, 100, 100);
f->glMatrixMode(GL_PROJECTION);
f->glLoadIdentity();
f->glOrtho(-2.0f, +2.0f, -2.0f, +2.0f, 1.0f, 15.0f); // magic numbers left over from a demo
f->glMatrixMode(GL_MODELVIEW);
// queue up a paint event
// Note: QGLWidget used updateGL(), but QOpenGLWidget uses update().
this->update();
}
void MyOpenGlWidget::paintGL()
{
f->glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
// I want to draw a texture with beveled edges the size of this widget, so I can't
// have the background clearing all the way to the edges
f->glScissor(50, 50, 200, 200); // more magic numbers just for demonstration
// clears to green in just scissored area (unless QPainter is created)
f->glClearColor(0.0f, 1.0f, 0.0f, 1.0f);
// loading identity matrix, doing f->glTranslatef(...) and f->glRotatef(...), drawing triangles
// done drawing, so now draw the beveled foreground
if (_foregroundPixmap != 0)
{
// QPixmap apparently draws such that culling the back face will cull the entire
// pixmap, so have to switch culling for duration of pixmap drawing
f->glCullFace(GL_FRONT);
QPainter(this);
painter.drawPixmap(0, 0, _foregroundPixmap->scaled(this->size()));
// done, so switch back to culling the front face
f->glCullFace(GL_BACK);
}
}
问题是这段代码来自paintGL()：
QPainter(this);
一旦创建了 QPainter 对象glScissor(...)，我之前在函数中所做的调用就会溢出，并且会进行某种glClearColor(...)调用（可能来自 QPainter 的构造函数），将整个视口清除为我刚刚设置的背景颜色glScissor(...)。然后像素图可以很好地绘制我的斜面纹理。
我不希望 QPainter 超出我的剪裁范围。
我得到的最接近解释的是两个 QPainter 方法，beginNativePainting()和endNativePainting(). 根据文档，这两者之间禁用了剪刀测试，但在他们的示例中，他们重新启用了它。我尝试使用这个“原生绘画”代码，但我无法阻止 QPainter 的存在，因为它忽略了 GL 的剪裁和清除我的整个视口。
为什么会发生这种情况，我该如何阻止这种情况？
注意：这台工作电脑有网络政策，禁止我去imgur之类的娱乐网站上传“我想要的”和“我得到的”图片，所以我必须用文字说明。