"""Generic output formatting.
Formatter objects transform an abstract flow of formatting events into
specific output events on writer objects. Formatters manage several stack
structures to allow various properties of a writer object to be changed and
restored; writers need not be able to handle relative changes nor any sort
of ``change back'' operation. Specific writer properties which may be
controlled via formatter objects are horizontal alignment, font, and left
margin indentations. A mechanism is provided which supports providing
arbitrary, non-exclusive style settings to a writer as well. Additional
interfaces facilitate formatting events which are not reversible, such as
paragraph separation.
Writer objects encapsulate device interfaces. Abstract devices, such as
file formats, are supported as well as physical devices. The provided
implementations all work with abstract devices. The interface makes
available mechanisms for setting the properties which formatter objects
manage and inserting data into the output.
"""
import sys
AS_IS = None
class NullFormatter:
"""A formatter which does nothing.
If the writer parameter is omitted, a NullWriter instance is created.
No methods of the writer are called by NullFormatter instances.
Implementations should inherit from this class if implementing a writer
interface but don't need to inherit any implementation.
"""
def __init__(self, writer=None):
if writer is None:
writer = NullWriter()
self.writer = writer
def end_paragraph(self, blankline): pass
def add_line_break(self): pass
def add_hor_rule(self, *args, **kw): pass
def add_label_data(self, format, counter, blankline=None): pass
def add_flowing_data(self, data): pass
def add_literal_data(self, data): pass
def flush_softspace(self): pass
def push_alignment(self, align): pass
def pop_alignment(self): pass
def push_font(self, x): pass
def pop_font(self): pass
def push_margin(self, margin): pass
def pop_margin(self): pass
def set_spacing(self, spacing): pass
def push_style(self, *styles): pass
def pop_style(self, n=1): pass
def assert_line_data(self, flag=1): pass
class AbstractFormatter:
"""The standard formatter.
This implementation has demonstrated wide applicability to many writers,
and may be used directly in most circumstances. It has been used to
implement a full-featured World Wide Web browser.
"""
# Space handling policy: blank spaces at the boundary between elements
# are handled by the outermost context. "Literal" data is not checked
# to determine context, so spaces in literal data are handled directly
# in all circumstances.
def __init__(self, writer):
self.writer = writer # Output device
self.align = None # Current alignment
self.align_stack = [] # Alignment stack
self.font_stack = [] # Font state
self.margin_stack = [] # Margin state
self.spacing = None # Vertical spacing state
self.style_stack = [] # Other state, e.g. color
self.nospace = 1 # Should leading space be suppressed
self.softspace = 0 # Should a space be inserted
self.para_end = 1 # Just ended a paragraph
self.parskip = 0 # Skipped space between paragraphs?
self.hard_break = 1 # Have a hard break
self.have_label = 0
def end_paragraph(self, blankline):
if not self.hard_break:
self.writer.send_line_break()
self.have_label = 0
if self.parskip < blankline and not self.have_label:
self.writer.send_paragraph(blankline - self.parskip)
self.parskip = blankline
self.have_label = 0
self.hard_break = self.nospace = self.para_end = 1
self.softspace = 0
def add_line_break(self):
if not (self.hard_break or self.para_end):
self.writer.send_line_break()
self.have_label = self.parskip = 0
self.hard_break = self.nospace = 1
self.softspace = 0
def add_hor_rule(self, *args, **kw):
if not self.hard_break:
self.writer.send_line_break()
self.writer.send_hor_rule(*args, **kw)
self.hard_break = self.nospace = 1
self.have_label = self.para_end = self.softspace = self.parskip = 0
def add_label_data(self, format, counter, blankline = None):
if self.have_label or not self.hard_break:
self.writer.send_line_break()
if not self.para_end:
self.writer.send_paragraph((blankline and 1) or 0)
if isinstance(format, str):
self.writer.send_label_data(self.format_counter(format, counter))
else:
self.writer.send_label_data(format)
self.nospace = self.have_label = self.hard_break = self.para_end = 1
self.softspace = self.parskip = 0
def format_counter(self, format, counter):
label = ''
for c in format:
if c == '1':
label = label + ('%d' % counter)
elif c in 'aA':
if counter > 0:
label = label + self.format_letter(c, counter)
elif c in 'iI':
if counter > 0:
label = label + self.format_roman(c, counter)
else:
label = label + c
return label
def format_letter(self, case, counter):
label = ''
while counter > 0:
counter, x = divmod(counter-1, 26)
# This makes a strong assumption that lowercase letters
# and uppercase letters form two contiguous blocks, with
# letters in order!
s = chr(ord(case) + x)
label = s + label
return label
def format_roman(self, case, counter):
ones = ['i', 'x', 'c', 'm']
fives = ['v', 'l', 'd']
label, index = '', 0
# This will die of IndexError when counter is too big
while counter > 0:
counter, x = divmod(counter, 10)
if x == 9:
label = ones[index] + ones[index+1] + label
elif x == 4:
label = ones[index] + fives[index] + label
else:
if x >= 5:
s = fives[index]
x = x-5
else:
s = ''
s = s + ones[index]*x
label = s + label
index = index + 1
if case == 'I':
return label.upper()
return label
def add_flowing_data(self, data):
if not data: return
prespace = data[:1].isspace()
postspace = data[-1:].isspace()
data = " ".join(data.split())
if self.nospace and not data:
return
elif prespace or self.softspace:
if not data:
if not self.nospace:
self.softspace = 1
self.parskip = 0
return
if not self.nospace:
data = ' ' + data
self.hard_break = self.nospace = self.para_end = \
self.parskip = self.have_label = 0
self.softspace = postspace
self.writer.send_flowing_data(data)
def add_literal_data(self, data):
if not data: return
if self.softspace:
self.writer.send_flowing_data(" ")
self.hard_break = data[-1:] == '\n'
self.nospace = self.para_end = self.softspace = \
self.parskip = self.have_label = 0
self.writer.send_literal_data(data)
def flush_softspace(self):
if self.softspace:
self.hard_break = self.para_end = self.parskip = \
self.have_label = self.softspace = 0
self.nospace = 1
self.writer.send_flowing_data(' ')
def push_alignment(self, align):
if align and align != self.align:
self.writer.new_alignment(align)
self.align = align
self.align_stack.append(align)
else:
self.align_stack.append(self.align)
def pop_alignment(self):
if self.align_stack:
del self.align_stack[-1]
if self.align_stack:
self.align = align = self.align_stack[-1]
self.writer.new_alignment(align)
else:
self.align = None
self.writer.new_alignment(None)
def push_font(self, font):
size, i, b, tt = font
if self.softspace:
self.hard_break = self.para_end = self.softspace = 0
self.nospace = 1
self.writer.send_flowing_data(' ')
if self.font_stack:
csize, ci, cb, ctt = self.font_stack[-1]
if size is AS_IS: size = csize
if i is AS_IS: i = ci
if b is AS_IS: b = cb
if tt is AS_IS: tt = ctt
font = (size, i, b, tt)
self.font_stack.append(font)
self.writer.new_font(font)
def pop_font(self):
if self.font_stack:
del self.font_stack[-1]
if self.font_stack:
font = self.font_stack[-1]
else:
font = None
self.writer.new_font(font)
def push_margin(self, margin):
self.margin_stack.append(margin)
fstack = [m for m in self.margin_stack if m]
if not margin and fstack:
margin = fstack[-1]
self.writer.new_margin(margin, len(fstack))
def pop_margin(self):
if self.margin_stack:
del self.margin_stack[-1]
fstack = [m for m in self.margin_stack if m]
if fstack:
margin = fstack[-1]
else:
margin = None
self.writer.new_margin(margin, len(fstack))
def set_spacing(self, spacing):
self.spacing = spacing
self.writer.new_spacing(spacing)
def push_style(self, *styles):
if self.softspace:
self.hard_break = self.para_end = self.softspace = 0
self.nospace = 1
self.writer.send_flowing_data(' ')
for style in styles:
self.style_stack.append(style)
self.writer.new_styles(tuple(self.style_stack))
def pop_style(self, n=1):
del self.style_stack[-n:]
self.writer.new_styles(tuple(self.style_stack))
def assert_line_data(self, flag=1):
self.nospace = self.hard_break = not flag
self.para_end = self.parskip = self.have_label = 0
class NullWriter:
"""Minimal writer interface to use in testing & inheritance.
A writer which only provides the interface definition; no actions are
taken on any methods. This should be the base class for all writers
which do not need to inherit any implementation methods.
"""
def __init__(self): pass
def flush(self): pass
def new_alignment(self, align): pass
def new_font(self, font): pass
def new_margin(self, margin, level): pass
def new_spacing(self, spacing): pass
def new_styles(self, styles): pass
def send_paragraph(self, blankline): pass
def send_line_break(self): pass
def send_hor_rule(self, *args, **kw): pass
def send_label_data(self, data): pass
def send_flowing_data(self, data): pass
def send_literal_data(self, data): pass
class AbstractWriter(NullWriter):
"""A writer which can be used in debugging formatters, but not much else.
Each method simply announces itself by printing its name and
arguments on standard output.
"""
def new_alignment(self, align):
print("new_alignment(%r)" % (align,))
def new_font(self, font):
print("new_font(%r)" % (font,))
def new_margin(self, margin, level):
print("new_margin(%r, %d)" % (margin, level))
def new_spacing(self, spacing):
print("new_spacing(%r)" % (spacing,))
def new_styles(self, styles):
print("new_styles(%r)" % (styles,))
def send_paragraph(self, blankline):
print("send_paragraph(%r)" % (blankline,))
def send_line_break(self):
print("send_line_break()")
def send_hor_rule(self, *args, **kw):
print("send_hor_rule()")
def send_label_data(self, data):
print("send_label_data(%r)" % (data,))
def send_flowing_data(self, data):
print("send_flowing_data(%r)" % (data,))
def send_literal_data(self, data):
print("send_literal_data(%r)" % (data,))
class DumbWriter(NullWriter):
"""Simple writer class which writes output on the file object passed in
as the file parameter or, if file is omitted, on standard output. The
output is simply word-wrapped to the number of columns specified by
the maxcol parameter. This class is suitable for reflowing a sequence
of paragraphs.
"""
def __init__(self, file=None, maxcol=72):
self.file = file or sys.stdout
self.maxcol = maxcol
NullWriter.__init__(self)
self.reset()
def reset(self):
self.col = 0
self.atbreak = 0
def send_paragraph(self, blankline):
self.file.write('\n'*blankline)
self.col = 0
self.atbreak = 0
def send_line_break(self):
self.file.write('\n')
self.col = 0
self.atbreak = 0
def send_hor_rule(self, *args, **kw):
self.file.write('\n')
self.file.write('-'*self.maxcol)
self.file.write('\n')
self.col = 0
self.atbreak = 0
def send_literal_data(self, data):
self.file.write(data)
i = data.rfind('\n')
if i >= 0:
self.col = 0
data = data[i+1:]
data = data.expandtabs()
self.col = self.col + len(data)
self.atbreak = 0
def send_flowing_data(self, data):
if not data: return
atbreak = self.atbreak or data[0].isspace()
col = self.col
maxcol = self.maxcol
write = self.file.write
for word in data.split():
if atbreak:
if col + len(word) >= maxcol:
write('\n')
col = 0
else:
write(' ')
col = col + 1
write(word)
col = col + len(word)
atbreak = 1
self.col = col
self.atbreak = data[-1].isspace()
def test(file = None):
w = DumbWriter()
f = AbstractFormatter(w)
if file is not None:
fp = open(file)
elif sys.argv[1:]:
fp = open(sys.argv[1])
else:
fp = sys.stdin
for line in fp:
if line == '\n':
f.end_paragraph(1)
else:
f.add_flowing_data(line)
f.end_paragraph(0)
if __name__ == '__main__':
test()
