An incomplete toy RTL text layout class for Urwid

gistfile1.py

import urwid
from urwid.util import calc_width

class RTLTextLayout(urwid.TextLayout):
    """
    A toy text layout that arranges all characters from
    right to left.

    Only works with unicode strings and narrow characters
    Currently fails if text is too long for the line
    (clipping not yet implemented)
    """
    def layout(self, text, width, align, wrap):
        assert isinstance(text, unicode), 'bytes not handled yet'
        p = 0
        b = []
        while p <= len(text):
            n_cr = text.find(u'\n', p)
            if n_cr == -1:
                n_cr = len(text)
            sc = calc_width(text, p, n_cr)
            #FIXME this doesn't actually check what it's claiming:
            assert sc == n_cr - p, 'wide/combining characters not handled yet'
            assert sc <= width, 'sorry, clipping not yet implementd'
            l = [(width - sc, None)]
            l += [(1, x, x+1) for x in reversed(range(p, n_cr))]
            b.append(l)
            p = n_cr+1
        return b

    def supports_align_mode(self, align):
        return align == 'right'
    def supports_wrap_mode(self, wrap):
        return wrap == 'clip'

rtl_layout = RTLTextLayout()
text = urwid.Text(u"hello\nworld\n", align='right', wrap='clip', layout=rtl_layout)
edit = urwid.Edit(u"caption: ", u"value", align='right', wrap='clip', layout=rtl_layout)

urwid.MainLoop(urwid.Filler(urwid.Pile([text, edit]))).run()