c++ - QPainter 和 QOpenGLWidget 类中的 OpenGL native 代码

Question

我正在准备一个桌面应用程序来绘制一些二维图。我正在使用 C++:Qt 5 和 visual studio 2013。我创建了一个简单的 GUI 并将 myQOpenGLWidget 放入其中。我已经在使用我自己的 openGl 着色器绘制绘图、坐标轴和刻度线。一切正常，现在我想将描述添加到我的轴和刻度中，以使图表可以进行分析。由于在 OpenGL 本身中没有专门的函数来渲染文本，我想出了使用 QPainter 对象只是为了将所需的描述添加到已经创建的绘图中。这里有问题开始......

这是我的 QopenGLWidget 实现的功能:

void GLWidget::initializeGL() {
initializeOpenGLFunctions();
glEnable(GL_POINT_SPRITE);
glEnable(GL_VERTEX_PROGRAM_POINT_SIZE);
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

vertexShad = new QOpenGLShader(QOpenGLShader::Vertex);
fragmentShad = new QOpenGLShader(QOpenGLShader::Fragment);

bool flag = vertexShad->compileSourceFile(QString("vs.glsl"));
if (flag) printf("compiled vertex Shader\n");
flag = fragmentShad->compileSourceFile(QString("fs.glsl"));
if (flag) printf("compiled fragment Shader\n");
flag = program.addShader(vertexShad);
if (flag) printf("linked vertex Shader\n");
flag = false;
flag =program.addShader(fragmentShad);
if (flag) printf("linked fragment Shader\n");

program.link();
program.bind();
}

绘制GL:

void GLWidget::paintGL() {
painter = new QPainter(this);

painter->beginNativePainting();
glViewport(0, 0, this->width(), this->height());
glClearColor(1.0f, 1.0f, 1.0f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
drawAxes();
glViewport(MARGIN, MARGIN, this->width() - MARGIN * 2, this->height() - MARGIN * 2);
glScissor(MARGIN, MARGIN, this->width() - MARGIN * 2, this->height() - MARGIN * 2);
glEnable(GL_SCISSOR_TEST);
  // here are the functions which use native openGL code
  // ...
  // disabling openGL settings
glDisable(GL_SCISSOR_TEST);
glDisable(GL_POINT_SPRITE);
glDisable(GL_VERTEX_PROGRAM_POINT_SIZE);
glDisable(GL_BLEND);
painter->endNativePainting();

drawTicksValues(); // function that uses QPainter
painter->end();
 }

drawTicksValues:

void GLWidget::drawTicksValues() {
char * maxText = new char[4];
sprintf(maxText, "%d", maxY);
char * minText = new char[4];
sprintf(minText, "%d", minY);
painter->drawText(0, MARGIN, QString(maxText));
painter->drawText(0, height() - MARGIN, QString(minText));
painter->drawText(MARGIN, height() - MARGIN + 20, QString("0"));
painter->drawText(width() - MARGIN, height() - MARGIN + 20, QString(100));
}

主要内容:

int main(int argc, char *argv[])
{
 QApplication a(argc, argv);
 QSurfaceFormat  format;
 format.setSamples(4);
 format.setDepthBufferSize(24);
 format.setStencilBufferSize(8);

 QSurfaceFormat::setDefaultFormat(format);
 SymmGaitModels w;
 w.show();
 return a.exec();
}

不幸的是，当我运行代码时，对于未注释的 QPainter 部分，轴和图被清除，只显示我用 QPainter 绘制的数字。但是如果我评论 QPainter 部分，绘图和轴就会正常绘制。关于如何使用 QPainter 将文本添加到我的绘图而不是清除它，有什么建议吗？

Answer 1

我终于成功了。

首先，我必须更改并设置格式(您必须在显示小部件之前更改它)，例如在 main 函数中，在我的应用程序显示之前

主要内容:

int main(int argc, char *argv[])
{
 QApplication a(argc, argv);

 SymmGaitModels w;
   // GLWidget is my implemantation of QOpenGLWidget
 GLWidget* gl = w.findChild<GLWidget*>("OpenGLWidget");
 QSurfaceFormat  format;
 //format.setSamples(4);
 //format.setDepthBufferSize(24);
 //format.setStencilBufferSize(8);
   format.setProfile(QSurfaceFormat::OpenGLContextProfile::CompatibilityProfile);
 QSurfaceFormat::setDefaultFormat(format);

 gl->setFormat(format);
 w.show();
 return a.exec();
}

此外，我不得不在

QPainter-> beginNativePainting()
 ...
QPainter->endNativePainting();

而且我必须实现 paintEvent 函数。我只是把 paintGL() 表达式放在那里。现在我的函数看起来像这样:

void GLWidget::initializeGL() {
 printf("autoFILL: %d\n",this->autoFillBackground());
 initializeOpenGLFunctions(); // this function has to stay in initializeGL
 // commented functions below has to be removed and put after beginNativePainting
     //glEnable(GL_POINT_SPRITE);
 //glEnable(GL_VERTEX_PROGRAM_POINT_SIZE);
 //glEnable(GL_BLEND);
 //glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

   // shaders may be compiled and added here, but program has to be linked and built after beginNativePainting()
 vertexShad = new QOpenGLShader(QOpenGLShader::Vertex);
 fragmentShad = new QOpenGLShader(QOpenGLShader::Fragment);

 bool flag = vertexShad->compileSourceFile(QString("vs.glsl"));
 //bool flag = vertexShad->compileSourceCode(vertexShadSrc);
 if (flag) printf("compiled vertex Shader\n");
 flag = fragmentShad->compileSourceFile(QString("fs.glsl"));
 //flag = fragmentShad->compileSourceCode(fragmentShadSrc);
 if (flag) printf("compiled fragment Shader\n");
 flag = program.addShader(vertexShad);
 if (flag) printf("linked vertex Shader\n");
 flag = false;
 flag =program.addShader(fragmentShad);
 if (flag) printf("linked fragment Shader\n");
}

void GLWidget::paintEvent(QPaintEvent *e) {
 paintGL(); // still this, widget has to be now refreshed by widget->update()
 }

void GLWidget::paintGL() {
 painter = new QPainter(this);
 painter->beginNativePainting();
 //
 glEnable(GL_POINT_SPRITE);
 glEnable(GL_VERTEX_PROGRAM_POINT_SIZE);
 glEnable(GL_BLEND);
 glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

 program.link();
 program.bind();
 //
 glViewport(0, 0, this->width(), this->height());
 glClearColor(1.0f, 1.0f, 1.0f, 1.0f);
 glClear(GL_COLOR_BUFFER_BIT);
 drawAxes();
 glViewport(MARGIN, MARGIN, this->width() - MARGIN * 2, this->height() - MARGIN * 2);
 glScissor(MARGIN, MARGIN, this->width() - MARGIN * 2, this->height() - MARGIN * 2);
 glEnable(GL_SCISSOR_TEST);
 // methods using native openGL functions here
 glDisable(GL_SCISSOR_TEST);
 glDisable(GL_POINT_SPRITE);
 glDisable(GL_VERTEX_PROGRAM_POINT_SIZE);
 glDisable(GL_BLEND);
 program.disconnect();
 painter->endNativePainting();
 drawTicksValues();
 painter->end();
}

添加 paintEvent 实现后，现在必须使用 widget->update() 刷新 openGL 小部件。

希望它对其他正在努力使用 QPainter 和 native openGL 函数的人有所帮助，因为 Qt 文档在这个主题上似乎有点肤浅。

谢谢!亚当