在QAbstractScrollArea中使用QOpenGLWidget作为视口

时间：2015-05-05 06:48:50

标签： opengl qt5

我在QOpenGLWidget中实现滚动时遇到了麻烦。要清楚，我希望滚动条能够更改opengl小部件中呈现的内容，而不是滚动小部件本身。根据{{​​3}}论坛答案，我一直在尝试实现QAbstractScrollArea的子类。我发现当opengl小部件被设置为qabstractscrollarea的视口时，没有任何东西被渲染，只有黑屏。

为了说明这一点，我基于Qt中分发的hellogl2示例项目创建了一个基本示例。

在mainwindow.cpp中，当glwidget设置为画布的视口时，不会进行渲染。 

m_scrollCanvas->setViewport(m_glWidget);

但是，当这一行被注释掉时，会显示opengl小部件。

是否有人知道为何将opengl widet设置为QAbstractScrollArea的视口时未显示？

的main.cpp 

#include "mainwindow.h"
#include <QApplication>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;
    w.show();

    return a.exec();
}

mainwindow.cpp 

#include "mainwindow.h"
#include "scrollcanvas.h"
#include "glwidget.h"

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
{
    m_scrollCanvas = new ScrollCanvas(this);
    m_glWidget = new GLWidget(m_scrollCanvas);
    m_scrollCanvas->setViewport(m_glWidget);
    setCentralWidget(m_scrollCanvas);
}

MainWindow::~MainWindow()
{

}

mainwindow.h 

#include <QMainWindow>
#include "glwidget.h"
#include "scrollcanvas.h"

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    MainWindow(QWidget *parent = 0);
    ~MainWindow();

private:
    ScrollCanvas * m_scrollCanvas;
    GLWidget * m_glWidget;

};

glwidget.h 

#include <QOpenGLWidget>
#include <QOpenGLVertexArrayObject>
#include <QOpenGLBuffer>
#include <QOpenGLShaderProgram>
#include <QMatrix4x4>
#include <qopengl.h>
#include <QVector>
#include <QVector3D>

class Logo
{
public:
    Logo();
    const GLfloat *constData() const { return m_data.constData(); }
    int count() const { return m_count; }
    int vertexCount() const { return m_count / 6; }

private:
    void quad(GLfloat x1, GLfloat y1, GLfloat x2, GLfloat y2, GLfloat x3, GLfloat y3, GLfloat x4, GLfloat y4);
    void extrude(GLfloat x1, GLfloat y1, GLfloat x2, GLfloat y2);
    void add(const QVector3D &v, const QVector3D &n);

    QVector<GLfloat> m_data;
    int m_count;
};

class GLWidget : public QOpenGLWidget
{
public:
    GLWidget(QWidget * parent);
    ~GLWidget();

protected:
    void resizeGL(int w, int h);
    void paintGL();
    void initializeGL();

private:
    void setupVertexAttribs();
    Logo m_logo;
    QOpenGLVertexArrayObject m_vao;
    QOpenGLBuffer m_logoVbo;
    QOpenGLShaderProgram *m_program;
    int m_projMatrixLoc;
    int m_mvMatrixLoc;
    int m_normalMatrixLoc;
    int m_lightPosLoc;
    QMatrix4x4 m_proj;
    QMatrix4x4 m_camera;
    QMatrix4x4 m_world;
};

glwidget.cpp 

#include "glwidget.h"



GLWidget::GLWidget(QWidget *parent) : QOpenGLWidget(parent), m_program(0)
{
}

GLWidget::~GLWidget()
{
    m_logoVbo.destroy();
    delete m_program;
    m_program = 0;
}

static const char *vertexShaderSourceCore =
    "#version 150\n"
    "in vec4 vertex;\n"
    "in vec3 normal;\n"
    "out vec3 vert;\n"
    "out vec3 vertNormal;\n"
    "uniform mat4 projMatrix;\n"
    "uniform mat4 mvMatrix;\n"
    "uniform mat3 normalMatrix;\n"
    "void main() {\n"
    "   vert = vertex.xyz;\n"
    "   vertNormal = normalMatrix * normal;\n"
    "   gl_Position = projMatrix * mvMatrix * vertex;\n"
    "}\n";

static const char *fragmentShaderSourceCore =
    "#version 150\n"
    "in highp vec3 vert;\n"
    "in highp vec3 vertNormal;\n"
    "out highp vec4 fragColor;\n"
    "uniform highp vec3 lightPos;\n"
    "void main() {\n"
    "   highp vec3 L = normalize(lightPos - vert);\n"
    "   highp float NL = max(dot(normalize(vertNormal), L), 0.0);\n"
    "   highp vec3 color = vec3(0.39, 1.0, 0.0);\n"
    "   highp vec3 col = clamp(color * 0.2 + color * 0.8 * NL, 0.0, 1.0);\n"
    "   fragColor = vec4(col, 1.0);\n"
    "}\n";

static const char *vertexShaderSource =
    "attribute vec4 vertex;\n"
    "attribute vec3 normal;\n"
    "varying vec3 vert;\n"
    "varying vec3 vertNormal;\n"
    "uniform mat4 projMatrix;\n"
    "uniform mat4 mvMatrix;\n"
    "uniform mat3 normalMatrix;\n"
    "void main() {\n"
    "   vert = vertex.xyz;\n"
    "   vertNormal = normalMatrix * normal;\n"
    "   gl_Position = projMatrix * mvMatrix * vertex;\n"
    "}\n";

static const char *fragmentShaderSource =
    "varying highp vec3 vert;\n"
    "varying highp vec3 vertNormal;\n"
    "uniform highp vec3 lightPos;\n"
    "void main() {\n"
    "   highp vec3 L = normalize(lightPos - vert);\n"
    "   highp float NL = max(dot(normalize(vertNormal), L), 0.0);\n"
    "   highp vec3 color = vec3(0.39, 1.0, 0.0);\n"
    "   highp vec3 col = clamp(color * 0.2 + color * 0.8 * NL, 0.0, 1.0);\n"
    "   gl_FragColor = vec4(col, 1.0);\n"
    "}\n";

void GLWidget::paintGL()
{
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glEnable(GL_DEPTH_TEST);
    glEnable(GL_CULL_FACE);

    m_world.setToIdentity();
    m_world.rotate(180.0f - (0 / 16.0f), 1, 0, 0);
    m_world.rotate(0 / 16.0f, 0, 1, 0);
    m_world.rotate(0 / 16.0f, 0, 0, 1);

    QOpenGLVertexArrayObject::Binder vaoBinder(&m_vao);
    m_program->bind();
    m_program->setUniformValue(m_projMatrixLoc, m_proj);
    m_program->setUniformValue(m_mvMatrixLoc, m_camera * m_world);
    QMatrix3x3 normalMatrix = m_world.normalMatrix();
    m_program->setUniformValue(m_normalMatrixLoc, normalMatrix);

    glDrawArrays(GL_TRIANGLES, 0, m_logo.vertexCount());

    m_program->release();
}
void GLWidget::initializeGL()
{
    glClearColor(0, 0, 0, 1);

    m_program = new QOpenGLShaderProgram;
    m_program->addShaderFromSourceCode(QOpenGLShader::Vertex, vertexShaderSource);
    m_program->addShaderFromSourceCode(QOpenGLShader::Fragment, fragmentShaderSource);
    m_program->bindAttributeLocation("vertex", 0);
    m_program->bindAttributeLocation("normal", 1);
    m_program->link();

    m_program->bind();
    m_projMatrixLoc = m_program->uniformLocation("projMatrix");
    m_mvMatrixLoc = m_program->uniformLocation("mvMatrix");
    m_normalMatrixLoc = m_program->uniformLocation("normalMatrix");
    m_lightPosLoc = m_program->uniformLocation("lightPos");

    // Create a vertex array object. In OpenGL ES 2.0 and OpenGL 2.x
    // implementations this is optional and support may not be present
    // at all. Nonetheless the below code works in all cases and makes
    // sure there is a VAO when one is needed.
    m_vao.create();
    QOpenGLVertexArrayObject::Binder vaoBinder(&m_vao);

    // Setup our vertex buffer object.
    m_logoVbo.create();
    m_logoVbo.bind();
    m_logoVbo.allocate(m_logo.constData(), m_logo.count() * sizeof(GLfloat));

    // Store the vertex attribute bindings for the program.
    setupVertexAttribs();

    // Our camera never changes in this example.
    m_camera.setToIdentity();
    m_camera.translate(0, 0, -1);

    // Light position is fixed.
    m_program->setUniformValue(m_lightPosLoc, QVector3D(0, 0, 70));

    m_program->release();
}
void GLWidget::resizeGL(int w, int h)
{
    m_proj.setToIdentity();
    m_proj.perspective(45.0f, GLfloat(w) / h, 0.01f, 100.0f);
}

void GLWidget::setupVertexAttribs()
{
    m_logoVbo.bind();
    glEnableVertexAttribArray(0);
    glEnableVertexAttribArray(1);
    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(GLfloat), 0);
    glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(GLfloat), reinterpret_cast<void *>(3 * sizeof(GLfloat)));
    m_logoVbo.release();
}

#include <qmath.h>

Logo::Logo()
    : m_count(0)
{
    m_data.resize(2500 * 6);

    const GLfloat x1 = +0.06f;
    const GLfloat y1 = -0.14f;
    const GLfloat x2 = +0.14f;
    const GLfloat y2 = -0.06f;
    const GLfloat x3 = +0.08f;
    const GLfloat y3 = +0.00f;
    const GLfloat x4 = +0.30f;
    const GLfloat y4 = +0.22f;

    quad(x1, y1, x2, y2, y2, x2, y1, x1);
    quad(x3, y3, x4, y4, y4, x4, y3, x3);

    extrude(x1, y1, x2, y2);
    extrude(x2, y2, y2, x2);
    extrude(y2, x2, y1, x1);
    extrude(y1, x1, x1, y1);
    extrude(x3, y3, x4, y4);
    extrude(x4, y4, y4, x4);
    extrude(y4, x4, y3, x3);

    const int NumSectors = 100;

    for (int i = 0; i < NumSectors; ++i) {
        GLfloat angle = (i * 2 * M_PI) / NumSectors;
        GLfloat angleSin = qSin(angle);
        GLfloat angleCos = qCos(angle);
        const GLfloat x5 = 0.30f * angleSin;
        const GLfloat y5 = 0.30f * angleCos;
        const GLfloat x6 = 0.20f * angleSin;
        const GLfloat y6 = 0.20f * angleCos;

        angle = ((i + 1) * 2 * M_PI) / NumSectors;
        angleSin = qSin(angle);
        angleCos = qCos(angle);
        const GLfloat x7 = 0.20f * angleSin;
        const GLfloat y7 = 0.20f * angleCos;
        const GLfloat x8 = 0.30f * angleSin;
        const GLfloat y8 = 0.30f * angleCos;

        quad(x5, y5, x6, y6, x7, y7, x8, y8);

        extrude(x6, y6, x7, y7);
        extrude(x8, y8, x5, y5);
    }
}

void Logo::add(const QVector3D &v, const QVector3D &n)
{
    GLfloat *p = m_data.data() + m_count;
    *p++ = v.x();
    *p++ = v.y();
    *p++ = v.z();
    *p++ = n.x();
    *p++ = n.y();
    *p++ = n.z();
    m_count += 6;
}

void Logo::quad(GLfloat x1, GLfloat y1, GLfloat x2, GLfloat y2, GLfloat x3, GLfloat y3, GLfloat x4, GLfloat y4)
{
    QVector3D n = QVector3D::normal(QVector3D(x4 - x1, y4 - y1, 0.0f), QVector3D(x2 - x1, y2 - y1, 0.0f));

    add(QVector3D(x1, y1, -0.05f), n);
    add(QVector3D(x4, y4, -0.05f), n);
    add(QVector3D(x2, y2, -0.05f), n);

    add(QVector3D(x3, y3, -0.05f), n);
    add(QVector3D(x2, y2, -0.05f), n);
    add(QVector3D(x4, y4, -0.05f), n);

    n = QVector3D::normal(QVector3D(x1 - x4, y1 - y4, 0.0f), QVector3D(x2 - x4, y2 - y4, 0.0f));

    add(QVector3D(x4, y4, 0.05f), n);
    add(QVector3D(x1, y1, 0.05f), n);
    add(QVector3D(x2, y2, 0.05f), n);

    add(QVector3D(x2, y2, 0.05f), n);
    add(QVector3D(x3, y3, 0.05f), n);
    add(QVector3D(x4, y4, 0.05f), n);
}

void Logo::extrude(GLfloat x1, GLfloat y1, GLfloat x2, GLfloat y2)
{
    QVector3D n = QVector3D::normal(QVector3D(0.0f, 0.0f, -0.1f), QVector3D(x2 - x1, y2 - y1, 0.0f));

    add(QVector3D(x1, y1, +0.05f), n);
    add(QVector3D(x1, y1, -0.05f), n);
    add(QVector3D(x2, y2, +0.05f), n);

    add(QVector3D(x2, y2, -0.05f), n);
    add(QVector3D(x2, y2, +0.05f), n);
    add(QVector3D(x1, y1, -0.05f), n);
}

scrollcanvas.h 

#include <QAbstractScrollArea>
class ScrollCanvas : public QAbstractScrollArea
{
public:
    ScrollCanvas(QWidget * parent) : QAbstractScrollArea(parent){}
    ~ScrollCanvas(){}
};

1 个答案:

答案 0 :(得分：1)

解决方案最终变得非常简单。首先，我将ScrollCanvas作为GLWidget的友元类，以允许我访问受保护的函数。然后在ScrollCanvas的实现中我重载了paintEvent和resizeEvent，如下所示：

void ScrollCanvas::resizeEvent(QResizeEvent * event)
{
    GLWidget * glw = dynamic_cast<GLWidget *>(viewport());
    glw->resizeEvent(event);
}

void ScrollCanvas::paintEvent(QPaintEvent *event)
{
    GLWidget * glw = dynamic_cast<GLWidget *>(viewport());
    glw->paintEvent(event);
}
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