更改 Qt OpenGL 窗口示例以使用 OpenGL 3.3

我正在尝试更改 Qt OpenGL 示例以使用更现代的 opengl，版本 330 似乎合适。

所以我做了：

• 在 main.cpp 上设置版本和配置文件
• 设置着色器版本
• 更改着色器以使用统一

它现在构建没有任何错误，但我只看到一个空白窗口。

我错了什么？也许有多种事情？

main.cpp

#include <QGuiApplication>

#include "openglwindow.h"

int main(int argc, char** argv)
{
    QSurfaceFormat fmt;
    fmt.setSamples(16);

    fmt.setDepthBufferSize(24);

    fmt.setVersion(3, 3);
    fmt.setProfile(QSurfaceFormat::CoreProfile);

    QGuiApplication app(argc, argv);
    OpenGLWindow window;

    window.setFormat(fmt);
    window.resize(640, 480);
    window.show();

    window.setAnimating(true);

    return app.exec();
}

openglwindow.h

#include <QWindow>
#include <QOpenGLFunctions>

class QPainter;
class QOpenGLContext;
class QOpenGLPaintDevice;

#include <QOpenGLShaderProgram>
#include <QKeyEvent>

class OpenGLWindow : public QWindow, protected QOpenGLFunctions
{
    Q_OBJECT

    bool m_animating = false;

    QOpenGLContext* m_context = nullptr;
    QOpenGLPaintDevice* m_device = nullptr;

    GLint m_posAttr = 0;
    GLint m_colAttr = 0;
    GLint m_matrixUniform = 0;

    QOpenGLShaderProgram* m_program = nullptr;
    int m_frame = 0;

public:
    explicit OpenGLWindow(QWindow* parent = nullptr);

    virtual void render();

    virtual void initialize();

    void setAnimating(bool animating);

public slots:
    void renderNow();

protected:
    bool event(QEvent* event) override;
    void exposeEvent(QExposeEvent*) override;

    void keyPressEvent(QKeyEvent* event) override
    {
        switch (event->key())
        {
        case Qt::Key_Escape:
            close();
            break;
        }
    }
};

openglwindow.cpp

#include "openglwindow.h"

#include <QOpenGLContext>
#include <QOpenGLPaintDevice>
#include <QPainter>

#include <QGuiApplication>
#include <QMatrix4x4>
#include <QScreen>
#include <QtMath>

const char* vertexShaderSource = R"(
    # version 330 core

    uniform vec4 posAttr;
    uniform vec4 colAttr;

    out vec4 col;

    uniform mat4 matrix;
    void main() {

       col = colAttr;

       gl_Position = matrix * posAttr;
    }
)";

const char* fragmentShaderSource = R"(
    # version 330 core

    out vec4 FragColor;

    in vec4 col;

    void main() {
       FragColor = col;
    }
)";

OpenGLWindow::OpenGLWindow(QWindow* parent)
    : QWindow(parent)
{
    setSurfaceType(QWindow::OpenGLSurface);
}

void OpenGLWindow::initialize()
{
    m_program = new QOpenGLShaderProgram(this);
    m_program->addShaderFromSourceCode(QOpenGLShader::Vertex, vertexShaderSource);
    m_program->addShaderFromSourceCode(QOpenGLShader::Fragment, fragmentShaderSource);
    m_program->link();

    m_posAttr = m_program->uniformLocation("posAttr");

    m_colAttr = m_program->uniformLocation("colAttr");

    m_matrixUniform = m_program->uniformLocation("matrix");

}

void OpenGLWindow::render()
{
    const qreal retinaScale = devicePixelRatio();
    glViewport(0, 0, width() * retinaScale, height() * retinaScale);

    glClear(GL_COLOR_BUFFER_BIT);

    glClearColor(1.0, 1.0, 1.0, 1.0);

    m_program->bind();

    QMatrix4x4 matrix;
    matrix.perspective(60.0f, 4.0f / 3.0f, 0.1f, 100.0f);
    matrix.translate(0, 0, -2);
    matrix.rotate(100.0f * m_frame / screen()->refreshRate(), 0, 1, 0);

    m_program->setUniformValue(m_matrixUniform, matrix);

    static const GLfloat vertices[] = {
         0.0f,  0.707f,
        -0.5f, -0.5f,
         0.5f, -0.5f
    };

    static const GLfloat colors[] = {
        1.0f, 0.0f, 0.0f,
        0.0f, 1.0f, 0.0f,
        0.0f, 0.0f, 1.0f
    };

    glVertexAttribPointer(m_posAttr, 2, GL_FLOAT, GL_FALSE, 0, vertices);
    glVertexAttribPointer(m_colAttr, 3, GL_FLOAT, GL_FALSE, 0, colors);

    glEnableVertexAttribArray(m_posAttr);
    glEnableVertexAttribArray(m_colAttr);

    glDrawArrays(GL_TRIANGLES, 0, 3);

    glDisableVertexAttribArray(m_colAttr);
    glDisableVertexAttribArray(m_posAttr);

    m_program->release();

    ++m_frame;
}

bool OpenGLWindow::event(QEvent* event)
{
    switch (event->type()) {
    case QEvent::UpdateRequest:
        renderNow();
        return true;
    default:
        return QWindow::event(event);
    }
}

void OpenGLWindow::exposeEvent(QExposeEvent*)
{
    if (isExposed())
        renderNow();
}

void OpenGLWindow::renderNow()
{
    if (!isExposed())
        return;

    bool needsInitialize = false;

    if (!m_context) {
        m_context = new QOpenGLContext(this);
        m_context->setFormat(requestedFormat());
        m_context->create();

        needsInitialize = true;
    }

    m_context->makeCurrent(this);

    if (needsInitialize) {
        initializeOpenGLFunctions();
        initialize();
    }

    render();

    m_context->swapBuffers(this);

    if (m_animating)
        requestUpdate();
}

void OpenGLWindow::setAnimating(bool animating)
{
    m_animating = animating;
}

尝试了 J. M. Arnold 的建议，但结果是：

QOpenGLFunctions created with non-current context
QOpenGLShaderProgram::uniformLocation(posAttr): shader program is not linked
QOpenGLShaderProgram::uniformLocation(colAttr): shader program is not linked
QOpenGLShaderProgram::uniformLocation(matrix): shader program is not linked
ASSERT: "QOpenGLFunctions::isInitialized(d_ptr)" in file /Users/user/Qt/5.15.2/clang_64/lib/QtGui.framework/Headers/qopenglfunctions.h, line 1092

我检查了 OpenGL 版本

    unsigned int major = glfwGetWindowAttrib(window, GLFW_CONTEXT_VERSION_MAJOR);
    unsigned int minor = glfwGetWindowAttrib(window, GLFW_CONTEXT_VERSION_MINOR);
    cout << "oepngl shader version: " << major << "." << minor << endl;

它打印

oepngl shader version: 4.1

我使用的是 M1 macOS。

在调试模式下运行我看到：

got fallback qt version 0x50f02
2022-12-04 20:11:35.615922+0800 openglwindow[61955:13089400] SecTaskLoadEntitlements failed error=22 cs_flags=20, pid=61955
2022-12-04 20:11:35.616020+0800 openglwindow[61955:13089400] SecTaskCopyDebugDescription: openglwindow[61955]/0#-1 LF=0
2022-12-04 20:11:37.052719+0800 openglwindow[61955:13089400] [] CurrentVBLDelta returned 0 for display 2 -- ignoring unreasonable value
2022-12-04 20:11:37.052744+0800 openglwindow[61955:13089400] [] [0x10c868c20] Bad CurrentVBLDelta for display 2 is zero. defaulting to 60Hz.
2022-12-04 20:11:37.053344+0800 openglwindow[61955:13089476] [] CurrentVBLDelta returned 0 for display 2 -- ignoring unreasonable value
2022-12-04 20:11:37.053354+0800 openglwindow[61955:13089476] [] [0x10c868c20] Bad CurrentVBLDelta for display 2 is zero. defaulting to 60Hz.
2022-12-04 20:11:37.194804+0800 openglwindow[61955:13089476] [] CurrentVBLDelta returned 0 for display 2 -- ignoring unreasonable value
2022-12-04 20:11:37.194832+0800 openglwindow[61955:13089476] [] [0x10c868c20] Bad CurrentVBLDelta for display 2 is zero. defaulting to 60Hz.
2022-12-04 20:11:37.212722+0800 openglwindow[61955:13089476] [] CurrentVBLDelta returned 0 for display 2 -- ignoring unreasonable value
2022-12-04 20:11:37.212748+0800 openglwindow[61955
:13089476] [] [0x10c868c20] Bad CurrentVBLDelta for display 2 is zero. defaulting to 60Hz.
2022-12-04 20:11:37.229195+0800 openglwindow[61955:13089476] [] CurrentVBLDelta returned 0 for display 2 -- ignoring unreasonable value
2022-12-04 20:11:37.229226+0800 openglwindow[61955:13089476] [] [0x10c868c20] Bad CurrentVBLDelta for display 2 is zero. defaulting to 60Hz.
2022-12-04 20:11:37.245219+0800 openglwindow[61955:13089476] [] CurrentVBLDelta returned 0 for display 2 -- ignoring unreasonable value
2022-12-04 20:11:37.245244+0800 openglwindow[61955:13089476] [] [0x10c868c20] Bad CurrentVBLDelta for display 2 is zero. defaulting to 60Hz.
2022-12-04 20:11:37.262730+0800 openglwindow[61955:13089476] [] CurrentVBLDelta returned 0 for display 2 -- ignoring unreasonable value
2022-12-04 20:11:37.262760+0800 openglwindow[61955:13089476] [] [0x10c868c20] Bad CurrentVBLDelta for display 2 is zero. defaulting to 60Hz.
2022-12-04 20:11:37.279399+0800 openglwindow[61955:13089476] [] CurrentVBLDelta returned 0 for display 2 -- ignoring unreasonable value
2022-12-04 20:11:37.279446+0800 openglwindow[61955:13089476] [] [0x10c868c20] Bad CurrentVBLDelta for display 2 is zero. defaulting to 60Hz.
2022-12-04 20:11:37.296006+0800 openglwindow[61955:13089476] [] CurrentVBLDelta returned 0 for display 2 -- ignoring unreasonable value
2022-12-04 20:11:37.296045+0800 openglwindow[61955:13089476] [] [0x10c868c20] Bad CurrentVBLDelta for display 2 is zero. defaulting to 60Hz.
2022-12-04 20:11:37.312713+0800 openglwindow[61955:13089476] [] CurrentVBLDelta returned 0 for display 2 -- ignoring unreasonable value
2022-12-04 20:11:37.312746+0800 openglwindow[61955:13089476] [] [0x10c868c20] Bad CurrentVBLDelta for display 2 is zero. defaulting to 60Hz.
2022-12-04 20:11:37.329405+0800 openglwindow[61955:13089476] [] CurrentVBLDelta returned 0 for display 2 -- ignoring unreasonable value
2022-12-04 20:11:37.329449+0800 openglwindow[61955

错误在你的内心eposeEvent:

void OpenGLWindow::exposeEvent(QExposeEvent*)
{
    if (isExposed())
        renderNow();
}

您忘记初始化 OpenGL 上下文：调用initialize(); and render();而不是你的renderNow();!

这应该是working最后：

void OpenGLWindow::exposeEvent(QExposeEvent*)
{
    if (isExposed()) {
        initialize();
        render();
    }
}

顺便一提：renderNow()初始化方法OpenGLWindow::render()但它不会初始化该方法OpenGLWindow::initialize() (-> OpenGLWindow::initialize()只会被调用一次OpenGLWindow首先创建对象，但是OpenGLWindow::render()每当renderNow()叫做）