import ctypes
import cairo


_initialized = False


def create_cairo_font_face_for_file(filename, faceindex=0, loadoptions=0):
    class PycairoContext(ctypes.Structure):
        _fields_ = [
            ("PyObject_HEAD", ctypes.c_byte * object.__basicsize__),
            ("ctx", ctypes.c_void_p),
            ("base", ctypes.c_void_p),
        ]

    global _initialized
    global _freetype_so
    global _cairo_so
    global _ft_lib
    global _surface

    CAIRO_STATUS_SUCCESS = 0
    FT_Err_Ok = 0

    if not _initialized:

        # find shared objects
        _freetype_so = ctypes.CDLL("libfreetype.so.6")
        _cairo_so = ctypes.CDLL("libcairo.so.2")

        _cairo_so.cairo_ft_font_face_create_for_ft_face.restype = ctypes.c_void_p
        _cairo_so.cairo_ft_font_face_create_for_ft_face.argtypes = [
            ctypes.c_void_p,
            ctypes.c_int,
        ]
        _cairo_so.cairo_set_font_face.argtypes = [ctypes.c_void_p, ctypes.c_void_p]
        _cairo_so.cairo_font_face_status.argtypes = [ctypes.c_void_p]
        _cairo_so.cairo_status.argtypes = [ctypes.c_void_p]

        # initialize freetype
        _ft_lib = ctypes.c_void_p()
        if FT_Err_Ok != _freetype_so.FT_Init_FreeType(ctypes.byref(_ft_lib)):
            raise Exception("Error initialising FreeType library.")

        _surface = cairo.ImageSurface(cairo.FORMAT_A8, 0, 0)

        _initialized = True

    # create freetype face
    ft_face = ctypes.c_void_p()
    cairo_ctx = cairo.Context(_surface)
    cairo_t = PycairoContext.from_address(id(cairo_ctx)).ctx

    if FT_Err_Ok != _freetype_so.FT_New_Face(
        _ft_lib, filename, faceindex, ctypes.byref(ft_face)
    ):
        raise Exception("Error creating FreeType font face for " + filename)

    # create cairo font face for freetype face
    cr_face = _cairo_so.cairo_ft_font_face_create_for_ft_face(ft_face, loadoptions)
    if CAIRO_STATUS_SUCCESS != _cairo_so.cairo_font_face_status(cr_face):
        raise Exception("Error creating cairo font face for " + filename)

    _cairo_so.cairo_set_font_face(cairo_t, cr_face)
    if CAIRO_STATUS_SUCCESS != _cairo_so.cairo_status(cairo_t):
        raise Exception("Error creating cairo font face for " + filename)

    face = cairo_ctx.get_font_face()

    return face


if __name__ == "__main__":

    face = create_cairo_font_face_for_file(
        "/usr/share/fonts/dejavu-lgc/DejaVuLGCSerif.ttf", 0
    )

    surface = cairo.ImageSurface(cairo.FORMAT_ARGB32, 128, 128)

    ctx = cairo.Context(surface)

    ctx.set_font_face(face)
    ctx.set_font_size(30)
    ctx.move_to(0, 44)
    ctx.show_text("Hello,")

    ctx.move_to(30, 74)
    ctx.show_text("world!")

    del ctx

    surface.write_to_png("hello.png")
