MiniTeX is a typesetting system implemented as a library in a programming language.

The document produced by MiniTeX is a box, which can be rendered on screen. The user may pick individual boxes inside the rendered document.

Documents are composed from combinators. They're functions that take in environment and produce a list of boxes. Here's an implementation of par -combinator:

def par(env):
    return [vglue(env.font_size)]

Combinators are passed to functions that produce larger combinators, for exapmle vbox or table:

vbox(["first paragraph", par, "second paragraph"])

    ["a", "b", "c"],
    ["d", "f", "g"],

The user can produce his own combinators to supplement additional needs. Here's an implementation of scope -combinator:

def scope(contents, values={}):
    def _scope(env):
        env = Environ.let(env, values)
        for item in contents:
            for box in fold(item, env):
                yield box
    return _scope

The fold function invokes a combinator. It allows strings literals to be to be treated as combinators, eg.

fold("string", env) -> [s t r i n g]
fold(par, env) -> [vglue(env.font_size)]

The user may adjust rendering by giving parameters to the environment. For example scale and font size may be changed.

Finally the combinators can be gathered into a list to produce the document and display it:

env = Environ.root(width=screen.width)
box = toplevel([
    "Hello World"
], env)
print box.width, box.height, box.depth
display(box, x, y)

I've got one of these in textended-editor, but it's not suitable for a library release. I don't have good enough rendering infrastructure in place.