Qt Quick SceneGraph: Indices alignment problem

According to the official documentation, the QSGGeometry also allows to use not float types for GL-attributes: GL_BYTE, GL_UNSIGNED_BYTE, GL_SHORT and etc. But in some cases, the usage of these types leads to rendering errors: node not completely drawn. Show on a real example.

In the above example, it is necessary to draw 3 triangles. Each vertex contains two coordinates (2 × GL_FLOAT) and a RGB-color (3 × GL_UNSIGNED_BYTE) that in total equals 11 bytes (structure must be packed). In most cases the default/batch [render|https://code.qt.io/cgit/qt/qtdeclarative.git/tree/src/quick/scenegraph/coreapi/qsgbatchrenderer.cpp] (OpenGL-implementation) uses one buffer for vertices and indices (as shown in the picture) that causes the item to not be drawn. Sometimes we also use the same buffer for vertices/indices. We came to the conclusion that in similar situations it is necessary to align the index part of buffer object (index-type alignment) for excluding described effect.