#!/usr/bin/python
# -*- coding: utf-8 -*-
#
# Urwid graphics widgets
#    Copyright (C) 2004-2011  Ian Ward
#
#    This library is free software; you can redistribute it and/or
#    modify it under the terms of the GNU Lesser General Public
#    License as published by the Free Software Foundation; either
#    version 2.1 of the License, or (at your option) any later version.
#
#    This library is distributed in the hope that it will be useful,
#    but WITHOUT ANY WARRANTY; without even the implied warranty of
#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
#    Lesser General Public License for more details.
#
#    You should have received a copy of the GNU Lesser General Public
#    License along with this library; if not, write to the Free Software
#    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
#
# Urwid web site: http://excess.org/urwid/

from urwid.util import decompose_tagmarkup, get_encoding_mode
from urwid.canvas import CompositeCanvas, CanvasJoin, TextCanvas, \
    CanvasCombine, SolidCanvas
from urwid.widget import WidgetMeta, Widget, BOX, FIXED, FLOW, \
    nocache_widget_render, nocache_widget_render_instance, fixed_size, \
    WidgetWrap, Divider, SolidFill, Text, CENTER, CLIP
from urwid.container import Pile, Columns
from urwid.display_common import AttrSpec
from urwid.decoration import WidgetDecoration


class BigText(Widget):
    _sizing = frozenset([FIXED])

    def __init__(self, markup, font):
        """
        markup -- same as Text widget markup
        font -- instance of a Font class
        """
        self.set_font(font)
        self.set_text(markup)

    def set_text(self, markup):
        self.text, self.attrib = decompose_tagmarkup(markup)
        self._invalidate()

    def get_text(self):
        """
        Returns (text, attributes).
        """
        return self.text, self.attrib

    def set_font(self, font):
        self.font = font
        self._invalidate()

    def pack(self, size=None, focus=False):
        rows = self.font.height
        cols = 0
        for c in self.text:
            cols += self.font.char_width(c)
        return cols, rows

    def render(self, size, focus=False):
        fixed_size(size)  # complain if parameter is wrong
        a = None
        ai = ak = 0
        o = []
        rows = self.font.height
        attrib = self.attrib + [(None, len(self.text))]
        for ch in self.text:
            if not ak:
                a, ak = attrib[ai]
                ai += 1
            ak -= 1
            width = self.font.char_width(ch)
            if not width:
                # ignore invalid characters
                continue
            c = self.font.render(ch)
            if a is not None:
                c = CompositeCanvas(c)
                c.fill_attr(a)
            o.append((c, None, False, width))
        if o:
            canv = CanvasJoin(o)
        else:
            canv = TextCanvas([""] * rows, maxcol=0,
                              check_width=False)
            canv = CompositeCanvas(canv)
        canv.set_depends([])
        return canv


class LineBox(WidgetDecoration, WidgetWrap):

    def __init__(self, original_widget, title="",
                 tlcorner='┌', tline='─', lline='│',
                 trcorner='┐', blcorner='└', rline='│',
                 bline='─', brcorner='┘'):
        """
        Draw a line around original_widget.

        Use 'title' to set an initial title text with will be centered
        on top of the box.

        You can also override the widgets used for the lines/corners:
            tline: top line
            bline: bottom line
            lline: left line
            rline: right line
            tlcorner: top left corner
            trcorner: top right corner
            blcorner: bottom left corner
            brcorner: bottom right corner

        """

        tline, bline = Divider(tline), Divider(bline)
        lline, rline = SolidFill(lline), SolidFill(rline)
        tlcorner, trcorner = Text(tlcorner), Text(trcorner)
        blcorner, brcorner = Text(blcorner), Text(brcorner)

        self.title_widget = Text(self.format_title(title))
        self.tline_widget = Columns([
            tline,
            ('flow', self.title_widget),
            tline,
        ])

        top = Columns([
            ('fixed', 1, tlcorner),
            self.tline_widget,
            ('fixed', 1, trcorner)
        ])

        middle = Columns([
            ('fixed', 1, lline),
            original_widget,
            ('fixed', 1, rline),
        ], box_columns=[0, 2], focus_column=1)

        bottom = Columns([
            ('fixed', 1, blcorner), bline, ('fixed', 1, brcorner)
        ])

        pile = Pile([('flow', top), middle, ('flow', bottom)], focus_item=1)

        WidgetDecoration.__init__(self, original_widget)
        WidgetWrap.__init__(self, pile)

    def format_title(self, text):
        if len(text) > 0:
            return " %s " % text
        else:
            return ""

    def set_title(self, text):
        self.title_widget.set_text(self.format_title(text))
        self.tline_widget._invalidate()


class BarGraphMeta(WidgetMeta):
    """
    Detect subclass get_data() method and dynamic change to
    get_data() method and disable caching in these cases.

    This is for backwards compatibility only, new programs
    should use set_data() instead of overriding get_data().
    """
    def __init__(cls, name, bases, d):
        super(BarGraphMeta, cls).__init__(name, bases, d)

        if "get_data" in d:
            cls.render = nocache_widget_render(cls)
            cls._get_data = cls.get_data
        cls.get_data = property(
            lambda self: self._get_data,
            nocache_bargraph_get_data)


def nocache_bargraph_get_data(self, get_data_fn):
    """
    Disable caching on this bargraph because get_data_fn needs
    to be polled to get the latest data.
    """
    self.render = nocache_widget_render_instance(self)
    self._get_data = get_data_fn

class BarGraphError(Exception):
    pass

class BarGraph(Widget, metaclass=BarGraphMeta):
    _sizing = frozenset([BOX])

    ignore_focus = True

    eighths = ' ▁▂▃▄▅▆▇'
    hlines = '_⎺⎻─⎼⎽'

    def __init__(self, attlist, hatt=None, satt=None):
        """
        Create a bar graph with the passed display characteristics.
        see set_segment_attributes for a description of the parameters.
        """

        self.set_segment_attributes(attlist, hatt, satt)
        self.set_data([], 1, None)
        self.set_bar_width(None)

    def set_segment_attributes(self, attlist, hatt=None, satt=None):
        """
        :param attlist: list containing display attribute or
                        (display attribute, character) tuple for background,
                        first segment, and optionally following segments.
                        ie. len(attlist) == num segments+1
                        character defaults to ' ' if not specified.
        :param hatt: list containing attributes for horizontal lines. First
                     element is for lines on background, second is for lines
                     on first segment, third is for lines on second segment
                     etc.
        :param satt: dictionary containing attributes for smoothed
                     transitions of bars in UTF-8 display mode. The values
                     are in the form:

                       (fg,bg) : attr

                     fg and bg are integers where 0 is the graph background,
                     1 is the first segment, 2 is the second, ...
                     fg > bg in all values.  attr is an attribute with a
                     foreground corresponding to fg and a background
                     corresponding to bg.

        If satt is not None and the bar graph is being displayed in
        a terminal using the UTF-8 encoding then the character cell
        that is shared between the segments specified will be smoothed
        with using the UTF-8 vertical eighth characters.

        eg: set_segment_attributes( ['no', ('unsure',"?"), 'yes'] )
        will use the attribute 'no' for the background (the area from
        the top of the graph to the top of the bar), question marks
        with the attribute 'unsure' will be used for the topmost
        segment of the bar, and the attribute 'yes' will be used for
        the bottom segment of the bar.
        """
        self.attr = []
        self.char = []
        if len(attlist) < 2:
            raise BarGraphError("attlist must include at least background and seg1: %r" % (attlist,))
        assert len(attlist) >= 2, 'must at least specify bg and fg!'
        for a in attlist:
            if type(a) != tuple:
                self.attr.append(a)
                self.char.append(' ')
            else:
                attr, ch = a
                self.attr.append(attr)
                self.char.append(ch)

        self.hatt = []
        if hatt is None:
            hatt = [self.attr[0]]
        elif type(hatt) != list:
            hatt = [hatt]
        self.hatt = hatt

        if satt is None:
            satt = {}
        for i in list(satt.items()):
            try:
                (fg, bg), attr = i
            except ValueError:
                raise BarGraphError("satt not in (fg,bg:attr) form: %r" % (i,))
            if type(fg) != int or fg >= len(attlist):
                raise BarGraphError("fg not valid integer: %r" % (fg,))
            if type(bg) != int or bg >= len(attlist):
                raise BarGraphError("bg not valid integer: %r" % (fg,))
            if fg <= bg:
                raise BarGraphError("fg (%s) not > bg (%s)" % (fg, bg))
        self.satt = satt

    def set_data(self, bardata, top, hlines=None):
        """
        Store bar data, bargraph top and horizontal line positions.

        bardata -- a list of bar values.
        top -- maximum value for segments within bardata
        hlines -- None or a bar value marking horizontal line positions

        bar values are [ segment1, segment2, ... ] lists where top is
        the maximal value corresponding to the top of the bar graph and
        segment1, segment2, ... are the values for the top of each
        segment of this bar.  Simple bar graphs will only have one
        segment in each bar value.

        Eg: if top is 100 and there is a bar value of [ 80, 30 ] then
        the top of this bar will be at 80% of full height of the graph
        and it will have a second segment that starts at 30%.
        """
        if hlines is not None:
            hlines = hlines[:]  # shallow copy
            hlines.sort()
            hlines.reverse()
        self.data = bardata, top, hlines
        self._invalidate()

    def _get_data(self, size):
        """
        Return (bardata, top, hlines)

        This function is called by render to retrieve the data for
        the graph. It may be overloaded to create a dynamic bar graph.

        This implementation will truncate the bardata list returned
        if not all bars will fit within maxcol.
        """
        (maxcol, maxrow) = size
        bardata, top, hlines = self.data
        widths = self.calculate_bar_widths((maxcol, maxrow), bardata)

        if len(bardata) > len(widths):
            return bardata[:len(widths)], top, hlines

        return bardata, top, hlines

    def set_bar_width(self, width):
        """
        Set a preferred bar width for calculate_bar_widths to use.

        width -- width of bar or None for automatic width adjustment
        """
        assert width is None or width > 0
        self.bar_width = width
        self._invalidate()

    def calculate_bar_widths(self, size, bardata):
        """
        Return a list of bar widths, one for each bar in data.

        If self.bar_width is None this implementation will stretch
        the bars across the available space specified by maxcol.
        """
        (maxcol, maxrow) = size

        if self.bar_width is not None:
            return [self.bar_width] * min(
                len(bardata), maxcol / self.bar_width)

        if len(bardata) >= maxcol:
            return [1] * maxcol

        widths = []
        grow = maxcol
        remain = len(bardata)
        for row in bardata:
            w = int(float(grow) / remain + 0.5)
            widths.append(w)
            grow -= w
            remain -= 1
        return widths

    def selectable(self):
        """
        Return False.
        """
        return False

    def use_smoothed(self):
        return self.satt and get_encoding_mode() == "utf8"

    def calculate_display(self, size):
        """
        Calculate display data.
        """
        (maxcol, maxrow) = size
        bardata, top, hlines = self.get_data((maxcol, maxrow))
        widths = self.calculate_bar_widths((maxcol, maxrow), bardata)

        if self.use_smoothed():
            disp = calculate_bargraph_display(bardata, top, widths,
                                              maxrow * 8)
            disp = self.smooth_display(disp)

        else:
            disp = calculate_bargraph_display(bardata, top, widths,
                                              maxrow)

        if hlines:
            disp = self.hlines_display(disp, top, hlines, maxrow)

        return disp

    def hlines_display(self, disp, top, hlines, maxrow):
        """
        Add hlines to display structure represented as bar_type tuple
        values:
        (bg, 0-5)
        bg is the segment that has the hline on it
        0-5 is the hline graphic to use where 0 is a regular underscore
        and 1-5 are the UTF-8 horizontal scan line characters.
        """
        if self.use_smoothed():
            shiftr = 0
            r = [(0.2, 1),
                 (0.4, 2),
                 (0.6, 3),
                 (0.8, 4),
                 (1.0, 5), ]
        else:
            shiftr = 0.5
            r = [(1.0, 0), ]

        # reverse the hlines to match screen ordering
        rhl = []
        for h in hlines:
            rh = float(top - h) * maxrow / top - shiftr
            if rh < 0:
                continue
            rhl.append(rh)

        # build a list of rows that will have hlines
        hrows = []
        last_i = -1
        for rh in rhl:
            i = int(rh)
            if i == last_i:
                continue
            f = rh - i
            for spl, chnum in r:
                if f < spl:
                    hrows.append((i, chnum))
                    break
            last_i = i

        # fill hlines into disp data
        def fill_row(row, chnum):
            rout = []
            for bar_type, width in row:
                if (type(bar_type) == int and
                        len(self.hatt) > bar_type):
                    rout.append(((bar_type, chnum), width))
                    continue
                rout.append((bar_type, width))
            return rout

        o = []
        k = 0
        rnum = 0
        for y_count, row in disp:
            if k >= len(hrows):
                o.append((y_count, row))
                continue
            end_block = rnum + y_count
            while k < len(hrows) and hrows[k][0] < end_block:
                i, chnum = hrows[k]
                if i - rnum > 0:
                    o.append((i - rnum, row))
                o.append((1, fill_row(row, chnum)))
                rnum = i + 1
                k += 1
            if rnum < end_block:
                o.append((end_block - rnum, row))
                rnum = end_block

        #assert 0, o
        return o

    def smooth_display(self, disp):
        """
        smooth (col, row*8) display into (col, row) display using
        UTF vertical eighth characters represented as bar_type
        tuple values:
        ( fg, bg, 1-7 )
        where fg is the lower segment, bg is the upper segment and
        1-7 is the vertical eighth character to use.
        """
        o = []
        r = 0  # row remainder

        def seg_combine(xxx_todo_changeme, xxx_todo_changeme1):
            (bt1, w1) = xxx_todo_changeme
            (bt2, w2) = xxx_todo_changeme1
            if (bt1, w1) == (bt2, w2):
                return (bt1, w1), None, None
            wmin = min(w1, w2)
            l1 = l2 = None
            if w1 > w2:
                l1 = (bt1, w1 - w2)
            elif w2 > w1:
                l2 = (bt2, w2 - w1)
            if type(bt1) == tuple:
                return (bt1, wmin), l1, l2
            if (bt2, bt1) not in self.satt:
                if r < 4:
                    return (bt2, wmin), l1, l2
                return (bt1, wmin), l1, l2
            return ((bt2, bt1, 8 - r), wmin), l1, l2

        def row_combine_last(count, row):
            o_count, o_row = o[-1]
            row = row[:]  # shallow copy, so we don't destroy orig.
            o_row = o_row[:]
            l = []
            while row:
                (bt, w), l1, l2 = seg_combine(
                    o_row.pop(0), row.pop(0))
                if l and l[-1][0] == bt:
                    l[-1] = (bt, l[-1][1] + w)
                else:
                    l.append((bt, w))
                if l1:
                    o_row = [l1] + o_row
                if l2:
                    row = [l2] + row

            assert not o_row
            o[-1] = (o_count + count, l)

        # regroup into actual rows (8 disp rows == 1 actual row)
        for y_count, row in disp:
            if r:
                count = min(8 - r, y_count)
                row_combine_last(count, row)
                y_count -= count
                r += count
                r = r % 8
                if not y_count:
                    continue
            assert r == 0
            # copy whole blocks
            if y_count > 7:
                o.append((y_count // 8 * 8, row))
                y_count = y_count % 8
                if not y_count:
                    continue
            o.append((y_count, row))
            r = y_count
        return [(y // 8, row) for (y, row) in o]

    def render(self, size, focus=False):
        """
        Render BarGraph.
        """
        (maxcol, maxrow) = size
        disp = self.calculate_display((maxcol, maxrow))

        combinelist = []
        for y_count, row in disp:
            l = []
            for bar_type, width in row:
                if type(bar_type) == tuple:
                    if len(bar_type) == 3:
                        # vertical eighths
                        fg, bg, k = bar_type
                        a = self.satt[(fg, bg)]
                        t = self.eighths[k] * width
                    else:
                        # horizontal lines
                        bg, k = bar_type
                        a = self.hatt[bg]
                        t = self.hlines[k] * width
                else:
                    a = self.attr[bar_type]
                    t = self.char[bar_type] * width
                l.append((a, t))
            c = Text(l).render((maxcol,))
            assert c.rows() == 1, "Invalid characters in BarGraph!"
            combinelist += [(c, None, False)] * y_count

        canv = CanvasCombine(combinelist)
        return canv


def calculate_bargraph_display(bardata, top, bar_widths, maxrow):
    """
    Calculate a rendering of the bar graph described by data, bar_widths
    and height.

    bardata -- bar information with same structure as BarGraph.data
    top -- maximal value for bardata segments
    bar_widths -- list of integer column widths for each bar
    maxrow -- rows for display of bargraph

    Returns a structure as follows:
      [ ( y_count, [ ( bar_type, width), ... ] ), ... ]

    The outer tuples represent a set of identical rows. y_count is
    the number of rows in this set, the list contains the data to be
    displayed in the row repeated through the set.

    The inner tuple describes a run of width characters of bar_type.
    bar_type is an integer starting from 0 for the background, 1 for
    the 1st segment, 2 for the 2nd segment etc..

    This function should complete in approximately O(n+m) time, where
    n is the number of bars displayed and m is the number of rows.
    """

    assert len(bardata) == len(bar_widths)

    maxcol = sum(bar_widths)

    # build intermediate data structure
    rows = [None] * maxrow

    def add_segment(seg_num, col, row, width, rows=rows):
        if rows[row]:
            last_seg, last_col, last_end = rows[row][-1]
            if last_end > col:
                if last_col >= col:
                    del rows[row][-1]
                else:
                    rows[row][-1] = (last_seg,
                                     last_col, col)
            elif last_seg == seg_num and last_end == col:
                rows[row][-1] = (last_seg, last_col,
                                 last_end + width)
                return
        elif rows[row] is None:
            rows[row] = []
        rows[row].append((seg_num, col, col + width))

    col = 0
    barnum = 0
    for bar in bardata:
        width = bar_widths[barnum]
        if width < 1:
            continue
        # loop through in reverse order
        tallest = maxrow
        segments = scale_bar_values(bar, top, maxrow)
        for k in range(len(bar) - 1, -1, -1):
            s = segments[k]

            if s >= maxrow:
                continue
            if s < 0:
                s = 0
            if s < tallest:
                # add only properly-overlapped bars
                tallest = s
                add_segment(k + 1, col, s, width)
        col += width
        barnum += 1

    #print repr(rows)
    # build rowsets data structure
    rowsets = []
    y_count = 0
    last = [(0, maxcol)]

    for r in rows:
        if r is None:
            y_count = y_count + 1
            continue
        if y_count:
            rowsets.append((y_count, last))
            y_count = 0

        i = 0  # index into "last"
        la, ln = last[i]  # last attribute, last run length
        c = 0  # current column
        o = []  # output list to be added to rowsets
        for seg_num, start, end in r:
            while start > c + ln:
                o.append((la, ln))
                i += 1
                c += ln
                la, ln = last[i]

            if la == seg_num:
                # same attribute, can combine
                o.append((la, end - c))
            else:
                if start - c > 0:
                    o.append((la, start - c))
                o.append((seg_num, end - start))

            if end == maxcol:
                i = len(last)
                break

            # skip past old segments covered by new one
            while end >= c + ln:
                i += 1
                c += ln
                la, ln = last[i]

            if la != seg_num:
                ln = c + ln - end
                c = end
                continue

            # same attribute, can extend
            oa, on = o[-1]
            on += c + ln - end
            o[-1] = oa, on

            i += 1
            c += ln
            if c == maxcol:
                break
            assert i < len(last), repr((on, maxcol))
            la, ln = last[i]

        if i < len(last):
            o += [(la, ln)] + last[i + 1:]
        last = o
        y_count += 1

    if y_count:
        rowsets.append((y_count, last))

    return rowsets


class GraphVScale(Widget):
    _sizing = frozenset([BOX])

    def __init__(self, labels, top):
        """
        GraphVScale( [(label1 position, label1 markup),...], top )
        label position -- 0 < position < top for the y position
        label markup -- text markup for this label
        top -- top y position

        This widget is a vertical scale for the BarGraph widget that
        can correspond to the BarGraph's horizontal lines
        """
        self.set_scale(labels, top)

    def set_scale(self, labels, top):
        """
        set_scale( [(label1 position, label1 markup),...], top )
        label position -- 0 < position < top for the y position
        label markup -- text markup for this label
        top -- top y position
        """

        labels = labels[:]  # shallow copy
        labels.sort()
        labels.reverse()
        self.pos = []
        self.txt = []
        for y, markup in labels:
            self.pos.append(y)
            self.txt.append(Text(markup))
        self.top = top

    def selectable(self):
        """
        Return False.
        """
        return False

    def render(self, size, focus=False):
        """
        Render GraphVScale.
        """
        (maxcol, maxrow) = size
        pl = scale_bar_values(self.pos, self.top, maxrow)

        combinelist = []
        rows = 0
        for p, t in zip(pl, self.txt):
            p -= 1
            if p >= maxrow:
                break
            if p < rows:
                continue
            c = t.render((maxcol,))
            if p > rows:
                run = p - rows
                c = CompositeCanvas(c)
                c.pad_trim_top_bottom(run, 0)
            rows += c.rows()
            combinelist.append((c, None, False))
        if not combinelist:
            return SolidCanvas(" ", size[0], size[1])

        c = CanvasCombine(combinelist)
        if maxrow - rows:
            c.pad_trim_top_bottom(0, maxrow - rows)
        return c



def scale_bar_values( bar, top, maxrow ):
    """
    Return a list of bar values aliased to integer values of maxrow.
    """
    return [maxrow - int(float(v) * maxrow / top + 0.5) for v in bar]


class ProgressBar(Widget):
    _sizing = frozenset([FLOW])

    eighths = ' ▏▎▍▌▋▊▉'

    text_align = CENTER

    def __init__(self, normal, complete, current=0, done=100, satt=None):
        """
        :param normal: display attribute for incomplete part of progress bar
        :param complete: display attribute for complete part of progress bar
        :param current: current progress
        :param done: progress amount at 100%
        :param satt: display attribute for smoothed part of bar where the
                     foreground of satt corresponds to the normal part and the
                     background corresponds to the complete part.  If satt
                     is ``None`` then no smoothing will be done.
        """
        self.normal = normal
        self.complete = complete
        self._current = current
        self._done = done
        self.satt = satt

    def set_completion(self, current):
        """
        current -- current progress
        """
        self._current = current
        self._invalidate()
    current = property(lambda self: self._current, set_completion)

    def _set_done(self, done):
        """
        done -- progress amount at 100%
        """
        self._done = done
        self._invalidate()
    done = property(lambda self: self._done, _set_done)

    def rows(self, size, focus=False):
        return 1

    def get_text(self):
        """
        Return the progress bar percentage text.
        """
        percent = min(100, max(0, int(self.current * 100 / self.done)))
        return str(percent) + " %"

    def render(self, size, focus=False):
        """
        Render the progress bar.
        """
        (maxcol,) = size
        txt = Text(self.get_text(), self.text_align, CLIP)
        c = txt.render((maxcol,))

        cf = float(self.current) * maxcol / self.done
        ccol = int(cf)
        cs = 0
        if self.satt is not None:
            cs = int((cf - ccol) * 8)
        if ccol < 0 or (ccol == 0 and cs == 0):
            c._attr = [[(self.normal, maxcol)]]
        elif ccol >= maxcol:
            c._attr = [[(self.complete, maxcol)]]
        elif cs and c._text[0][ccol] == " ":
            t = c._text[0]
            cenc = self.eighths[cs].encode("utf-8")
            c._text[0] = t[:ccol] + cenc + t[ccol + 1:]
            a = []
            if ccol > 0:
                a.append((self.complete, ccol))
            a.append((self.satt, len(cenc)))
            if maxcol - ccol - 1 > 0:
                a.append((self.normal, maxcol - ccol - 1))
            c._attr = [a]
            c._cs = [[(None, len(c._text[0]))]]
        else:
            c._attr = [[(self.complete, ccol),
                        (self.normal, maxcol - ccol)]]
        return c


class PythonLogo(Widget):
    _sizing = frozenset([FIXED])

    def __init__(self):
        """
        Create canvas containing an ASCII version of the Python
        Logo and store it.
        """
        blu = AttrSpec('light blue', 'default')
        yel = AttrSpec('yellow', 'default')
        width = 17
        self._canvas = Text([
            (blu, "     ______\n"),
            (blu, "   _|_o__  |"), (yel, "__\n"),
            (blu, "  |   _____|"), (yel, "  |\n"),
            (blu, "  |__|  "), (yel, "______|\n"),
            (yel, "     |____o_|")]).render((width,))

    def pack(self, size=None, focus=False):
        """
        Return the size from our pre-rendered canvas.
        """
        return self._canvas.cols(), self._canvas.rows()

    def render(self, size, focus=False):
        """
        Return the pre-rendered canvas.
        """
        fixed_size(size)
        return self._canvas
