def __init__(self, text=None, attr=None, cs=None,
        cursor=None, maxcol=None, check_width=True):
        """
        text -- list of strings, one for each line
        attr -- list of run length encoded attributes for text
        cs -- list of run length encoded character set for text
        cursor -- (x,y) of cursor or None
        maxcol -- screen columns taken by this canvas
        check_width -- check and fix width of all lines in text
        """
        Canvas.__init__(self)
        if text == None:
            text = []

        if check_width:
            widths = []
            for t in text:
                if type(t) != bytes:
                    raise CanvasError("Canvas text must be plain strings encoded in the screen's encoding", repr(text))
                widths.append( calc_width( t, 0, len(t)) )
        else:
            assert type(maxcol) == int
            widths = [maxcol] * len(text)

        if maxcol is None:
            if widths:
                # find maxcol ourselves
                maxcol = max(widths)
            else:
                maxcol = 0

        if attr == None:
            attr = [[] for x in range(len(text))]
        if cs == None:
            cs = [[] for x in range(len(text))]

        # pad text and attr to maxcol
        for i in range(len(text)):
            w = widths[i]
            if w > maxcol:
                raise CanvasError("Canvas text is wider than the maxcol specified \n%r\n%r\n%r"%(maxcol,widths,text))
            if w < maxcol:
                text[i] = text[i] + bytes().rjust(maxcol-w)
            a_gap = len(text[i]) - rle_len( attr[i] )
            if a_gap < 0:
                raise CanvasError("Attribute extends beyond text \n%r\n%r" % (text[i],attr[i]) )
            if a_gap:
                rle_append_modify( attr[i], (None, a_gap))

            cs_gap = len(text[i]) - rle_len( cs[i] )
            if cs_gap < 0:
                raise CanvasError("Character Set extends beyond text \n%r\n%r" % (text[i],cs[i]) )
            if cs_gap:
                rle_append_modify( cs[i], (None, cs_gap))

        self._attr = attr
        self._cs = cs
        self.cursor = cursor
        self._text = text
        self._maxcol = maxcol

def calc_coords( text, layout, pos, clamp=1 ):
    """
    Calculate the coordinates closest to position pos in text with layout.

    text -- raw string or unicode string
    layout -- layout structure applied to text
    pos -- integer position into text
    clamp -- ignored right now
    """
    closest = None
    y = 0
    for line_layout in layout:
        x = 0
        for seg in line_layout:
            s = LayoutSegment(seg)
            if s.offs is None:
                x += s.sc
                continue
            if s.offs == pos:
                return x,y
            if s.end is not None and s.offs<=pos and s.end>pos:
                x += calc_width( text, s.offs, pos )
                return x,y
            distance = abs(s.offs - pos)
            if s.end is not None and s.end<pos:
                distance = pos - (s.end-1)
            if closest is None or distance < closest[0]:
                closest = distance, (x,y)
            x += s.sc
        y += 1

    if closest:
        return closest[1]
    return 0,0

def text_width(txt):
    """
    Return the width of the text in the terminal

    Use this instead of len() whenever txt could contain double- or zero-width
    Unicode characters.

    """
    return calc_width(txt, 0, len(txt))

    def _last_row(self, row):
        """On the last row we need to slide the bottom right character
        into place. Calculate the new line, attr and an insert sequence
        to do that.

        eg. last row:
        XXXXXXXXXXXXXXXXXXXXYZ

        Y will be drawn after Z, shifting Z into position.
        """

        new_row = row[:-1]
        z_attr, z_cs, last_text = row[-1]
        last_cols = util.calc_width(last_text, 0, len(last_text))
        last_offs, z_col = util.calc_text_pos(last_text, 0, 
            len(last_text), last_cols-1)
        if last_offs == 0:
            z_text = last_text
            del new_row[-1]
            # we need another segment
            y_attr, y_cs, nlast_text = row[-2]
            nlast_cols = util.calc_width(nlast_text, 0, 
                len(nlast_text))
            z_col += nlast_cols
            nlast_offs, y_col = util.calc_text_pos(nlast_text, 0,
                len(nlast_text), nlast_cols-1)
            y_text = nlast_text[nlast_offs:]
            if nlast_offs:
                new_row.append((y_attr, y_cs, 
                    nlast_text[:nlast_offs]))
        else:
            z_text = last_text[last_offs:]
            y_attr, y_cs = z_attr, z_cs
            nlast_cols = util.calc_width(last_text, 0,
                last_offs)
            nlast_offs, y_col = util.calc_text_pos(last_text, 0,
                last_offs, nlast_cols-1)
            y_text = last_text[nlast_offs:last_offs]
            if nlast_offs:
                new_row.append((y_attr, y_cs,
                    last_text[:nlast_offs]))
        
        new_row.append((z_attr, z_cs, z_text))
        return new_row, z_col-y_col, (y_attr, y_cs, y_text)

    def draw_screen(self, xxx_todo_changeme, r ):
        """Create an html fragment from the render object. 
        Append it to HtmlGenerator.fragments list.
        """
        (cols, rows) = xxx_todo_changeme
        l = []
        
        assert r.rows() == rows
    
        if r.cursor is not None:
            cx, cy = r.cursor
        else:
            cx = cy = None
        
        y = -1
        for row in r.content():
            y += 1
            col = 0
            
            for a, cs, run in row:
                run = run.translate(_trans_table)
                if isinstance(a, AttrSpec):
                    aspec = a
                else:
                    aspec = self._palette[a][
                        {1: 1, 16: 0, 88:2, 256:3}[self.colors]]

                if y == cy and col <= cx:
                    run_width = util.calc_width(run, 0,
                        len(run))
                    if col+run_width > cx:
                        l.append(html_span(run,
                            aspec, cx-col))
                    else:
                        l.append(html_span(run, aspec))
                    col += run_width
                else:
                    l.append(html_span(run, aspec))

            l.append("\n")
                        
        # add the fragment to the list
        self.fragments.append( "<pre>%s</pre>" % "".join(l) )

    def pack(self, size=None, focus=False):
        """
        Return the number of screen columns and rows required for
        this Text widget to be displayed without wrapping or 
        clipping, as a single element tuple.

        size -- None for unlimited screen columns or (maxcol,) to
                specify a maximum column size

        >>> Text(u"important things").pack()
        (16, 1)
        >>> Text(u"important things").pack((15,))
        (9, 2)
        >>> Text(u"important things").pack((8,))
        (8, 2)
        """
        text, attr = self.get_text()

        if size is not None:
            (maxcol,) = size
            if not hasattr(self.layout, "pack"):
                return size
            trans = self.get_line_translation( maxcol, (text,attr))
            cols = self.layout.pack( maxcol, trans )
            return (cols, len(trans))

        i = 0
        cols = 0
        while i < len(text):
            j = text.find('\n', i)
            if j == -1:
                j = len(text)
            c = calc_width(text, i, j)
            if c>cols:
                cols = c
            i = j+1
        return (cols, text.count('\n') + 1)

    def calculate_text_segments(self, text, width, wrap):
        """
        Calculate the segments of text to display given width screen
        columns to display them.

        text - unicode text or byte string to display
        width - number of available screen columns
        wrap - wrapping mode used

        Returns a layout structure without alignment applied.
        """
        nl, nl_o, sp_o = "\n", "\n", " "
        if PYTHON3 and isinstance(text, bytes):
            nl = B(nl) # can only find bytes in python3 bytestrings
            nl_o = ord(nl_o) # + an item of a bytestring is the ordinal value
            sp_o = ord(sp_o)
        b = []
        p = 0
        if wrap == 'clip':
            # no wrapping to calculate, so it's easy.
            while p<=len(text):
                n_cr = text.find(nl, p)
                if n_cr == -1:
                    n_cr = len(text)
                sc = calc_width(text, p, n_cr)
                l = [(0,n_cr)]
                if p!=n_cr:
                    l = [(sc, p, n_cr)] + l
                b.append(l)
                p = n_cr+1
            return b


        while p<=len(text):
            # look for next eligible line break
            n_cr = text.find(nl, p)
            if n_cr == -1:
                n_cr = len(text)
            sc = calc_width(text, p, n_cr)
            if sc == 0:
                # removed character hint
                b.append([(0,n_cr)])
                p = n_cr+1
                continue
            if sc <= width:
                # this segment fits
                b.append([(sc,p,n_cr),
                    # removed character hint
                    (0,n_cr)])

                p = n_cr+1
                continue
            pos, sc = calc_text_pos( text, p, n_cr, width )
            if pos == p: # pathological width=1 double-byte case
                raise CanNotDisplayText(
                    "Wide character will not fit in 1-column width")
            if wrap == 'any':
                b.append([(sc,p,pos)])
                p = pos
                continue
            assert wrap == 'space'
            if text[pos] == sp_o:
                # perfect space wrap
                b.append([(sc,p,pos),
                    # removed character hint
                    (0,pos)])
                p = pos+1
                continue
            if is_wide_char(text, pos):
                # perfect next wide
                b.append([(sc,p,pos)])
                p = pos
                continue
            prev = pos
            while prev > p:
                prev = move_prev_char(text, p, prev)
                if text[prev] == sp_o:
                    sc = calc_width(text,p,prev)
                    l = [(0,prev)]
                    if p!=prev:
                        l = [(sc,p,prev)] + l
                    b.append(l)
                    p = prev+1
                    break
                if is_wide_char(text,prev):
                    # wrap after wide char
                    next = move_next_char(text, prev, pos)
                    sc = calc_width(text,p,next)
                    b.append([(sc,p,next)])
                    p = next
                    break
            else:
                # unwrap previous line space if possible to
                # fit more text (we're breaking a word anyway)
                if b and (len(b[-1]) == 2 or ( len(b[-1])==1
                        and len(b[-1][0])==2 )):
                    # look for removed space above
                    if len(b[-1]) == 1:
                        [(h_sc, h_off)] = b[-1]
                        p_sc = 0
#.........这里部分代码省略.........

    def calculate_text_segments( self, text, width, wrap ):
        """
        Calculate the segments of text to display given width screen 
        columns to display them.  
        
        text - text to display
        width - number of available screen columns
        wrap - wrapping mode used
        
        Returns a layout structure without aligmnent applied.
        """
        b = []
        p = 0
        if wrap == 'clip':
            # no wrapping to calculate, so it's easy.
            while p<=len(text):
                n_cr = text.find("\n", p)
                if n_cr == -1: 
                    n_cr = len(text)
                sc = calc_width(text, p, n_cr)
                l = [(0,n_cr)]
                if p!=n_cr:
                    l = [(sc, p, n_cr)] + l
                b.append(l)
                p = n_cr+1
            return b

        
        while p<=len(text):
            # look for next eligible line break
            n_cr = text.find("\n", p)
            if n_cr == -1: 
                n_cr = len(text)
            sc = calc_width(text, p, n_cr)
            if sc == 0:
                # removed character hint
                b.append([(0,n_cr)])
                p = n_cr+1
                continue
            if sc <= width:
                # this segment fits
                b.append([(sc,p,n_cr),
                    # removed character hint
                    (0,n_cr)])
                
                p = n_cr+1
                continue
            pos, sc = calc_text_pos( text, p, n_cr, width )
            # FIXME: handle pathological width=1 double-byte case
            if wrap == 'any':
                b.append([(sc,p,pos)])
                p = pos
                continue
            assert wrap == 'space'
            if text[pos] == " ":
                # perfect space wrap
                b.append([(sc,p,pos),
                    # removed character hint
                    (0,pos)])
                p = pos+1
                continue
            if is_wide_char(text, pos):
                # perfect next wide
                b.append([(sc,p,pos)])
                p = pos
                continue
            prev = pos    
            while prev > p:
                prev = move_prev_char(text, p, prev)
                if text[prev] == " ":
                    sc = calc_width(text,p,prev)
                    l = [(0,prev)]
                    if p!=prev:
                        l = [(sc,p,prev)] + l
                    b.append(l)
                    p = prev+1 
                    break
                if is_wide_char(text,prev):
                    # wrap after wide char
                    next = move_next_char(text, prev, pos)
                    sc = calc_width(text,p,next)
                    b.append([(sc,p,next)])
                    p = next
                    break
            else:
                # unwrap previous line space if possible to
                # fit more text (we're breaking a word anyway)
                if b and (len(b[-1]) == 2 or ( len(b[-1])==1 
                        and len(b[-1][0])==2 )):
                    # look for removed space above
                    if len(b[-1]) == 1:
                        [(h_sc, h_off)] = b[-1]
                        p_sc = 0
                        p_off = p_end = h_off
                    else:
                        [(p_sc, p_off, p_end),
                               (h_sc, h_off)] = b[-1]
                    if (p_sc < width and h_sc==0 and
                        text[h_off] == " "):
                        # combine with previous line
#.........这里部分代码省略.........

    def calculate_text_segments(self, text, width, wrap):
        """
        Calculate the segments of text to display given width screen
        columns to display them.

        text - unicode text or byte string to display
        width - number of available screen columns
        wrap - wrapping mode used

        Returns a layout structure without alignment applied.
        """

        # TODO: This function is a horror and a mess, and really hard to
        # understand. It's based on urwids StandardLayout, which by itself
        # is overly complex, and I added tab handling, which made it worse.
        # It's a prime candidate for refacturing, making easier to understand
        # and as it is heavily used, profiling would be nice too.

        nl, nl_o, sp_o, tab_o = "\n", "\n", " ", "\t"
        if PYTHON3 and isinstance(text, bytes):
            nl = B(nl)  # can only find bytes in python3 bytestrings
            nl_o = ord(nl_o)  # + an item of a bytestring is the ordinal value
            sp_o = ord(sp_o)
            tab_o = ord(tab_o)
        b = []
        p = 0
        if wrap == 'clip':
            # no wrapping to calculate, so it's easy.
            l = []
            while p <= len(text):
                n_cr = find_newline(text, p)
                if p != n_cr:
                    line = text[p:n_cr]
                    pt = 0
                    while pt < len(line):
                        n_tab = line.find(tab_o, pt)
                        if n_tab == -1:
                            end = len(line)
                        else:
                            end = n_tab

                        sc = calc_width(line, pt, end)
                        if sc != 0:
                            l.append((sc, p + pt, p + end))

                        if end == n_tab:  # A tab was found
                            extra_space = (self.tab_width - (
                                sc % self.tab_width))
                            l.append((extra_space, p + n_tab))

                        pt = end + 1

                l.append((0, n_cr))
                b.append(l)
                l = []
                if text[n_cr:n_cr+2] in TWOCHAR_NEWLINES:
                    # Two char newline:
                    p = n_cr + 2
                else:
                    p = n_cr + 1
            return b

        while p <= len(text):
            # look for next eligible line break
            n_cr = find_newline(text, p)

            line = text[p:n_cr]
            l = []
            pt = 0
            lc = 0
            while pt < len(line):
                n_tab = line.find(tab_o, pt)
                if n_tab == -1:
                    end = len(line)
                else:
                    end = n_tab

                sc = calc_width(line, pt, end)

                if lc + sc <= width:
                    # this segment fits
                    if sc:
                        l.append((sc, p + pt, p + end))
                    if end == n_tab:  # A tab was found
                        extra_space = self.tab_width - (sc % self.tab_width)
                        l.append((extra_space, p + n_tab))
                        lc += extra_space
                    else:
                        # removed character hint
                        l.append((0, p + end))

                    pt = end + 1
                    lc += sc

                    if lc >= width:
                        # The tab can sometimes push line length to width, and
                        # then we adjust the line length and make a new line.
                        overshoot = lc - width
                        spaces, pos = l[-1]
                        l[-1] = (spaces - overshoot, pos)
#.........这里部分代码省略.........

 def wtest(self, desc, s, exp):
     s = B(s)
     result = util.calc_width( s, 0, len(s))
     assert result==exp, "%s got:%r expected:%r" % (desc, result, exp)

    def draw_screen(self, xxx_todo_changeme, r ):
        """Send a screen update to the client."""
        (cols, rows) = xxx_todo_changeme
        if cols != self.last_screen_width:
            self.last_screen = {}

        sendq = [self.content_head]

        if self.update_method == "polling":
            send = sendq.append
        elif self.update_method == "polling child":
            signal.alarm( 0 )
            try:
                s, addr = self.server_socket.accept()
            except socket.timeout:
                sys.exit(0)
            send = s.sendall
        else:
            signal.alarm( 0 )
            send = sendq.append
            send("\r\n")
            self.content_head = ""

        assert r.rows() == rows

        if r.cursor is not None:
            cx, cy = r.cursor
        else:
            cx = cy = None

        new_screen = {}

        y = -1
        for row in r.content():
            y += 1
            row = list(row)

            l = []

            sig = tuple(row)
            if y == cy: sig = sig + (cx,)
            new_screen[sig] = new_screen.get(sig,[]) + [y]
            old_line_numbers = self.last_screen.get(sig, None)
            if old_line_numbers is not None:
                if y in old_line_numbers:
                    old_line = y
                else:
                    old_line = old_line_numbers[0]
                send( "<%d\n"%old_line )
                continue

            col = 0
            for (a, cs, run) in row:
                run = run.translate(_trans_table)
                if a is None:
                    fg,bg,mono = "black", "light gray", None
                else:
                    fg,bg,mono = self.palette[a]
                if y == cy and col <= cx:
                    run_width = util.calc_width(run, 0,
                        len(run))
                    if col+run_width > cx:
                        l.append(code_span(run, fg, bg,
                            cx-col))
                    else:
                        l.append(code_span(run, fg, bg))
                    col += run_width
                else:
                    l.append(code_span(run, fg, bg))

            send("".join(l)+"\n")
        self.last_screen = new_screen
        self.last_screen_width = cols

        if self.update_method == "polling":
            sys.stdout.write("".join(sendq))
            sys.stdout.flush()
            sys.stdout.close()
            self._fork_child()
        elif self.update_method == "polling child":
            s.close()
        else: # update_method == "multipart"
            send("\r\n--ZZ\r\n")
            sys.stdout.write("".join(sendq))
            sys.stdout.flush()

        signal.alarm( ALARM_DELAY )