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