I have implemented a little engine for drawing in opengl(2d) inside a qt interface .
Now i must implement something like at the acrobat reader's interface :
A document area with zoom and scroll.
I don't need perspective, but whats I use for the scrolling and the zoom?
I must do all with glortho?
I use shaders and the vbos , how i can get a matrix from glortho for send it to the shader param where is multiplied for each point?
Is like the projection transformation and the 4x4 matrix MVP(model view projection)?

and how i can translate the coordinates of qt opengl widget to the opengl viewport?