qt - 如何使用QSGSimpleTextureNode？

Question

我试图了解如何使用 QSGSimpleTextureNode 但 Qt 文档非常模糊。我想在场景图上渲染文本，所以基本上我想要的是绘制包含所有字形的纹理，然后在 QSGSimpleTextureNode 上设置该纹理。我的想法是使用标准 OpenGL 代码创建纹理，并将纹理数据设置为我刚刚创建的数据。我找不到示例来展示如何实现这一目标。

Answer 1

我会使用 QSGGeometryNode 而不是 QSGSimpleTextureNode。如果我没记错的话，不可能在 QSGSimpleTextureNode 中设置纹理坐标。您可以为 SpriteText 编写自定义 QQuickItem 并覆盖 updatePaintNode:

QSGNode* SpriteText::updatePaintNode(QSGNode *old, UpdatePaintNodeData *data)
{
     QSGGeometryNode* node = static_cast<QSGGeometryNode*>(old);
     if (!node){
        node = new QSGGeometryNode();
     }
     QSGGeometry *geometry = NULL;
     if (!old){
        geometry = new QSGGeometry(QSGGeometry::defaultAttributes_TexturedPoint2D()
                      ,vertexCount);
        node->setFlag(QSGNode::OwnsGeometry);
        node->setMaterial(material);  // <-- Texture with your glyphs
        node->setFlag(QSGNode::OwnsMaterial);
        geometry->setDrawingMode(GL_TRIANGLES);
        node->setGeometry(geometry);
    } else {
        geometry = node->geometry();
        geometry->allocate(vertexCount);
    }
    if (textChanged){
        //For every Glyph in Text:
        //Calc x + y position for glyph in texture (between 0-1)
        //Create vertexes with calculated texture coordinates and calculated x coordinate
        geometry->vertexDataAsTexturedPoint2D()[index].set(...);
        ...
        node->markDirty(QSGNode::DirtyGeometry);
    }
    //you could start timer here which call update() methode
    return node;
}