OpenGL和QtQuick纹理问题

我正在C++中基于Qt附带的"openglunderqml"示例开发一个简单的QQuickItem实现。我做了一些修改，使用了不同的着色器和我加载的两个纹理。想法是着色器将在两个纹理之间交叉渐变（本质上只是我加载到纹理中的图像）。

当我把这个QQuickItem单独放在QML文件中并运行它时，一切都很好。图像相互交叉（我已经设置了一个属性动画来保持它们交叉），一切看起来都很好。然而，如果我放置其他元素（如文本），文本就不会正确呈现——只是一些形状奇怪的小块。如果我放了一张照片，事情就会变得很奇怪。QQuickItem不是渲染它应该在其中渲染的框，而是渲染全屏和倒置。据我所知，其他图像从未加载。

我想我一定没有做我应该做的事情，但我不知道是什么。请注意，第一个代码块包含着色器和渲染内容，第二个包含函数loadNewTexture（），该函数将新图像加载到纹理中（每个纹理只调用一次，而不是每次渲染），第三个包含QtQuick.qml文件。

以下是opengl代码（在QQuckItem:：Paint方法中）：

// Builds the OpenGL shaders that handle the crossfade
if (!m_program) {
    m_program = new QOpenGLShaderProgram();
    // Shader loads coordinate positions
    m_program->addShaderFromSourceCode(QOpenGLShader::Vertex,
                                       "attribute vec2 position;"
                                       "varying vec2 texcoord;"
                                       "void main() {"
                                       "    gl_Position = vec4(position, 0.0, 1.0);"
                                       "    texcoord = position * vec2(0.5) + vec2(0.5);"
                                       "}");
    // Shader does the crossfade
    m_program->addShaderFromSourceCode(QOpenGLShader::Fragment,
                                       "uniform lowp float xfade;"
                                       "uniform sampler2D textures[2];"
                                       "varying vec2 texcoord;"
                                       "void main() {"
                                       "    gl_FragColor = mix("
                                       "        texture2D(textures[0], texcoord),"
                                       "        texture2D(textures[1], texcoord),"
                                       "        xfade"
                                       "    );"
                                       "}");
    m_program->bindAttributeLocation("vertices", 0);
    m_program->link();
    connect(window()->openglContext(), SIGNAL(aboutToBeDestroyed()),
            this, SLOT(cleanup()), Qt::DirectConnection);
}
m_program->bind();
// Loads corner vertices as triangle strip
m_program->enableAttributeArray(0);
float values[] = {
    -1, -1,
     1, -1,
    -1,  1,
     1,  1
};
m_program->setAttributeArray(0, GL_FLOAT, values, 2);
// Loads the fade value
m_program->setUniformValue("xfade", (float) m_thread_xfade);
glEnable(GL_TEXTURE_2D);
// Check if a new texture needs to be loaded
if (!new_source_loaded && !m_adSource.isEmpty())
    new_source_loaded = loadNewTexture(m_adSource);
// Loads texture 0 into the shader
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, textures[0]);
m_program->setUniformValue("textures[0]", 0);
// Loads texture 1 into the shader
glActiveTexture(GL_TEXTURE1);
glBindTexture(GL_TEXTURE_2D, textures[1]);
m_program->setUniformValue("textures[1]", 1);
// Sets the OpenGL render area to the space given to this components
glViewport((GLint) this->x(), (GLint) this->y(), (GLint) this->width(), (GLint) this->height());
// Sets some parameters
glDisable(GL_DEPTH_TEST);
// Sets the clear color (backround color) to black
glClearColor(0, 0, 0, 1);
glClear(GL_COLOR_BUFFER_BIT);
// Draws triangle strip
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE);
glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
glDisable(GL_BLEND);
glDisable(GL_TEXTURE_2D);
// Cleans up vertices
m_program->disableAttributeArray(0);
m_program->release();

loadNewTexture（）函数：

bool AdRotator::loadNewTexture(QUrl source) {
    // Load the image from source url
    QImage image(source.path());
    // Check that the image was loaded properly
    if (image.isNull()) {
        qDebug() << QString("AdRotator::loadTexture: Loading image from source: ") << source.toString() << QString(" failed.");
        return false;
    }
    // Update this as the active texture
    active_texture = !active_texture;
    // Convert into GL-friendly format
    QImage GL_formatted_image = QGLWidget::convertToGLFormat(image);
    // Check that the image was converted properly
    if (image.isNull()) {
        qDebug() << QString("AdRotator::loadTexture: Converting image from source: ") << source.toString() << QString(" failed.");
        return false;
    }
    // Generate the texture base
    glGenTextures(1, &textures[active_texture]);
    glBindTexture(GL_TEXTURE_2D, textures[active_texture]);
    // Give texture parameters (scaling and edging options)
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S,     GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T,     GL_CLAMP_TO_EDGE);
    // Load pixels from image into texture
    glTexImage2D(
        GL_TEXTURE_2D, 0,           /* target, level of detail */
        GL_RGBA,                    /* internal format */
        GL_formatted_image.width(), GL_formatted_image.height(), 0,           /* width, height, border */
        GL_RGBA, GL_UNSIGNED_BYTE,   /* external format, type */
        GL_formatted_image.bits()   /* pixels */
    );
    if (textures[active_texture] == 0) qDebug() << QString("New Texture post-load failed.");
    return true;
}

.qml文件：

import QtQuick 2.0
Item {
    width: 1920
    height: 1080
    /* Image{} element breaks things
    Image {
        id: image1
        x: 0
        y: 0
        anchors.rightMargin: 0
        anchors.bottomMargin: 0
        anchors.leftMargin: 0
        anchors.topMargin: 0
        sourceSize.height: 1080
        sourceSize.width: 1920
        anchors.fill: parent
        fillMode: Image.PreserveAspectCrop
        source: "images/background.png"
    }*/
    /* The QQuickItem */
    ImageCrossfader {
        x: 753
        y: 107
        width: 1150
        height: 865
    }
}