opengl 2d shapes and textures

OpenGL OpenGL: Basic Coding
1

hello.
I’m creating a 2d interface in opengl with lines , rectangle and some other 2d shapes in qt.
I must have a background texture and the shapes on it.
I use vbo , shader ecc…
How i can positioning the lines and the shapes for appear on the background texture?
and what i can use for display the background texture?
i can create a textured plane for example with z = 0 and the shapes with z = 0.01 ecc…?
Is a correct approach?

thanks.

2

To draw the GUI a better approach is to disable the z test and Z write and write the various layer in order.
So first draw a quad with background then shapes and line over the background.