1 | """Generic output formatting. |
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2 | |
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3 | Formatter objects transform an abstract flow of formatting events into |
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4 | specific output events on writer objects. Formatters manage several stack |
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5 | structures to allow various properties of a writer object to be changed and |
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6 | restored; writers need not be able to handle relative changes nor any sort |
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7 | of ``change back'' operation. Specific writer properties which may be |
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8 | controlled via formatter objects are horizontal alignment, font, and left |
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9 | margin indentations. A mechanism is provided which supports providing |
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10 | arbitrary, non-exclusive style settings to a writer as well. Additional |
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11 | interfaces facilitate formatting events which are not reversible, such as |
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12 | paragraph separation. |
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13 | |
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14 | Writer objects encapsulate device interfaces. Abstract devices, such as |
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15 | file formats, are supported as well as physical devices. The provided |
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16 | implementations all work with abstract devices. The interface makes |
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17 | available mechanisms for setting the properties which formatter objects |
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18 | manage and inserting data into the output. |
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19 | """ |
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20 | |
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21 | import sys |
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22 | |
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23 | |
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24 | AS_IS = None |
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25 | |
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26 | |
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27 | class NullFormatter: |
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28 | """A formatter which does nothing. |
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29 | |
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30 | If the writer parameter is omitted, a NullWriter instance is created. |
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31 | No methods of the writer are called by NullFormatter instances. |
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32 | |
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33 | Implementations should inherit from this class if implementing a writer |
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34 | interface but don't need to inherit any implementation. |
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35 | |
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36 | """ |
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37 | |
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38 | def __init__(self, writer=None): |
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39 | if writer is None: |
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40 | writer = NullWriter() |
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41 | self.writer = writer |
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42 | def end_paragraph(self, blankline): pass |
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43 | def add_line_break(self): pass |
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44 | def add_hor_rule(self, *args, **kw): pass |
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45 | def add_label_data(self, format, counter, blankline=None): pass |
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46 | def add_flowing_data(self, data): pass |
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47 | def add_literal_data(self, data): pass |
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48 | def flush_softspace(self): pass |
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49 | def push_alignment(self, align): pass |
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50 | def pop_alignment(self): pass |
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51 | def push_font(self, x): pass |
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52 | def pop_font(self): pass |
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53 | def push_margin(self, margin): pass |
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54 | def pop_margin(self): pass |
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55 | def set_spacing(self, spacing): pass |
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56 | def push_style(self, *styles): pass |
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57 | def pop_style(self, n=1): pass |
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58 | def assert_line_data(self, flag=1): pass |
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59 | |
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60 | |
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61 | class AbstractFormatter: |
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62 | """The standard formatter. |
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63 | |
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64 | This implementation has demonstrated wide applicability to many writers, |
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65 | and may be used directly in most circumstances. It has been used to |
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66 | implement a full-featured World Wide Web browser. |
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67 | |
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68 | """ |
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69 | |
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70 | # Space handling policy: blank spaces at the boundary between elements |
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71 | # are handled by the outermost context. "Literal" data is not checked |
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72 | # to determine context, so spaces in literal data are handled directly |
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73 | # in all circumstances. |
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74 | |
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75 | def __init__(self, writer): |
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76 | self.writer = writer # Output device |
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77 | self.align = None # Current alignment |
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78 | self.align_stack = [] # Alignment stack |
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79 | self.font_stack = [] # Font state |
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80 | self.margin_stack = [] # Margin state |
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81 | self.spacing = None # Vertical spacing state |
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82 | self.style_stack = [] # Other state, e.g. color |
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83 | self.nospace = 1 # Should leading space be suppressed |
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84 | self.softspace = 0 # Should a space be inserted |
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85 | self.para_end = 1 # Just ended a paragraph |
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86 | self.parskip = 0 # Skipped space between paragraphs? |
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87 | self.hard_break = 1 # Have a hard break |
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88 | self.have_label = 0 |
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89 | |
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90 | def end_paragraph(self, blankline): |
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91 | if not self.hard_break: |
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92 | self.writer.send_line_break() |
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93 | self.have_label = 0 |
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94 | if self.parskip < blankline and not self.have_label: |
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95 | self.writer.send_paragraph(blankline - self.parskip) |
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96 | self.parskip = blankline |
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97 | self.have_label = 0 |
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98 | self.hard_break = self.nospace = self.para_end = 1 |
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99 | self.softspace = 0 |
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100 | |
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101 | def add_line_break(self): |
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102 | if not (self.hard_break or self.para_end): |
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103 | self.writer.send_line_break() |
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104 | self.have_label = self.parskip = 0 |
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105 | self.hard_break = self.nospace = 1 |
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106 | self.softspace = 0 |
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107 | |
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108 | def add_hor_rule(self, *args, **kw): |
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109 | if not self.hard_break: |
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110 | self.writer.send_line_break() |
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111 | self.writer.send_hor_rule(*args, **kw) |
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112 | self.hard_break = self.nospace = 1 |
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113 | self.have_label = self.para_end = self.softspace = self.parskip = 0 |
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114 | |
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115 | def add_label_data(self, format, counter, blankline = None): |
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116 | if self.have_label or not self.hard_break: |
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117 | self.writer.send_line_break() |
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118 | if not self.para_end: |
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119 | self.writer.send_paragraph((blankline and 1) or 0) |
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120 | if isinstance(format, str): |
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121 | self.writer.send_label_data(self.format_counter(format, counter)) |
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122 | else: |
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123 | self.writer.send_label_data(format) |
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124 | self.nospace = self.have_label = self.hard_break = self.para_end = 1 |
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125 | self.softspace = self.parskip = 0 |
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126 | |
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127 | def format_counter(self, format, counter): |
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128 | label = '' |
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129 | for c in format: |
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130 | if c == '1': |
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131 | label = label + ('%d' % counter) |
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132 | elif c in 'aA': |
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133 | if counter > 0: |
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134 | label = label + self.format_letter(c, counter) |
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135 | elif c in 'iI': |
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136 | if counter > 0: |
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137 | label = label + self.format_roman(c, counter) |
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138 | else: |
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139 | label = label + c |
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140 | return label |
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141 | |
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142 | def format_letter(self, case, counter): |
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143 | label = '' |
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144 | while counter > 0: |
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145 | counter, x = divmod(counter-1, 26) |
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146 | # This makes a strong assumption that lowercase letters |
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147 | # and uppercase letters form two contiguous blocks, with |
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148 | # letters in order! |
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149 | s = chr(ord(case) + x) |
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150 | label = s + label |
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151 | return label |
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152 | |
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153 | def format_roman(self, case, counter): |
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154 | ones = ['i', 'x', 'c', 'm'] |
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155 | fives = ['v', 'l', 'd'] |
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156 | label, index = '', 0 |
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157 | # This will die of IndexError when counter is too big |
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158 | while counter > 0: |
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159 | counter, x = divmod(counter, 10) |
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160 | if x == 9: |
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161 | label = ones[index] + ones[index+1] + label |
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162 | elif x == 4: |
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163 | label = ones[index] + fives[index] + label |
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164 | else: |
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165 | if x >= 5: |
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166 | s = fives[index] |
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167 | x = x-5 |
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168 | else: |
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169 | s = '' |
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170 | s = s + ones[index]*x |
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171 | label = s + label |
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172 | index = index + 1 |
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173 | if case == 'I': |
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174 | return label.upper() |
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175 | return label |
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176 | |
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177 | def add_flowing_data(self, data): |
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178 | if not data: return |
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179 | prespace = data[:1].isspace() |
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180 | postspace = data[-1:].isspace() |
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181 | data = " ".join(data.split()) |
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182 | if self.nospace and not data: |
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183 | return |
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184 | elif prespace or self.softspace: |
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185 | if not data: |
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186 | if not self.nospace: |
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187 | self.softspace = 1 |
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188 | self.parskip = 0 |
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189 | return |
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190 | if not self.nospace: |
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191 | data = ' ' + data |
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192 | self.hard_break = self.nospace = self.para_end = \ |
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193 | self.parskip = self.have_label = 0 |
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194 | self.softspace = postspace |
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195 | self.writer.send_flowing_data(data) |
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196 | |
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197 | def add_literal_data(self, data): |
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198 | if not data: return |
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199 | if self.softspace: |
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200 | self.writer.send_flowing_data(" ") |
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201 | self.hard_break = data[-1:] == '\n' |
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202 | self.nospace = self.para_end = self.softspace = \ |
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203 | self.parskip = self.have_label = 0 |
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204 | self.writer.send_literal_data(data) |
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205 | |
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206 | def flush_softspace(self): |
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207 | if self.softspace: |
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208 | self.hard_break = self.para_end = self.parskip = \ |
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209 | self.have_label = self.softspace = 0 |
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210 | self.nospace = 1 |
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211 | self.writer.send_flowing_data(' ') |
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212 | |
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213 | def push_alignment(self, align): |
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214 | if align and align != self.align: |
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215 | self.writer.new_alignment(align) |
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216 | self.align = align |
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217 | self.align_stack.append(align) |
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218 | else: |
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219 | self.align_stack.append(self.align) |
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220 | |
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221 | def pop_alignment(self): |
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222 | if self.align_stack: |
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223 | del self.align_stack[-1] |
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224 | if self.align_stack: |
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225 | self.align = align = self.align_stack[-1] |
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226 | self.writer.new_alignment(align) |
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227 | else: |
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228 | self.align = None |
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229 | self.writer.new_alignment(None) |
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230 | |
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231 | def push_font(self, font): |
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232 | size, i, b, tt = font |
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233 | if self.softspace: |
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234 | self.hard_break = self.para_end = self.softspace = 0 |
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235 | self.nospace = 1 |
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236 | self.writer.send_flowing_data(' ') |
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237 | if self.font_stack: |
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238 | csize, ci, cb, ctt = self.font_stack[-1] |
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239 | if size is AS_IS: size = csize |
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240 | if i is AS_IS: i = ci |
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241 | if b is AS_IS: b = cb |
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242 | if tt is AS_IS: tt = ctt |
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243 | font = (size, i, b, tt) |
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244 | self.font_stack.append(font) |
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245 | self.writer.new_font(font) |
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246 | |
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247 | def pop_font(self): |
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248 | if self.font_stack: |
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249 | del self.font_stack[-1] |
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250 | if self.font_stack: |
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251 | font = self.font_stack[-1] |
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252 | else: |
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253 | font = None |
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254 | self.writer.new_font(font) |
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255 | |
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256 | def push_margin(self, margin): |
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257 | self.margin_stack.append(margin) |
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258 | fstack = filter(None, self.margin_stack) |
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259 | if not margin and fstack: |
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260 | margin = fstack[-1] |
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261 | self.writer.new_margin(margin, len(fstack)) |
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262 | |
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263 | def pop_margin(self): |
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264 | if self.margin_stack: |
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265 | del self.margin_stack[-1] |
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266 | fstack = filter(None, self.margin_stack) |
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267 | if fstack: |
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268 | margin = fstack[-1] |
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269 | else: |
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270 | margin = None |
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271 | self.writer.new_margin(margin, len(fstack)) |
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272 | |
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273 | def set_spacing(self, spacing): |
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274 | self.spacing = spacing |
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275 | self.writer.new_spacing(spacing) |
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276 | |
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277 | def push_style(self, *styles): |
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278 | if self.softspace: |
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279 | self.hard_break = self.para_end = self.softspace = 0 |
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280 | self.nospace = 1 |
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281 | self.writer.send_flowing_data(' ') |
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282 | for style in styles: |
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283 | self.style_stack.append(style) |
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284 | self.writer.new_styles(tuple(self.style_stack)) |
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285 | |
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286 | def pop_style(self, n=1): |
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287 | del self.style_stack[-n:] |
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288 | self.writer.new_styles(tuple(self.style_stack)) |
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289 | |
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290 | def assert_line_data(self, flag=1): |
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291 | self.nospace = self.hard_break = not flag |
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292 | self.para_end = self.parskip = self.have_label = 0 |
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293 | |
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294 | |
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295 | class NullWriter: |
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296 | """Minimal writer interface to use in testing & inheritance. |
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297 | |
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298 | A writer which only provides the interface definition; no actions are |
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299 | taken on any methods. This should be the base class for all writers |
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300 | which do not need to inherit any implementation methods. |
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301 | |
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302 | """ |
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303 | def __init__(self): pass |
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304 | def flush(self): pass |
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305 | def new_alignment(self, align): pass |
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306 | def new_font(self, font): pass |
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307 | def new_margin(self, margin, level): pass |
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308 | def new_spacing(self, spacing): pass |
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309 | def new_styles(self, styles): pass |
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310 | def send_paragraph(self, blankline): pass |
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311 | def send_line_break(self): pass |
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312 | def send_hor_rule(self, *args, **kw): pass |
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313 | def send_label_data(self, data): pass |
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314 | def send_flowing_data(self, data): pass |
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315 | def send_literal_data(self, data): pass |
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316 | |
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317 | |
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318 | class AbstractWriter(NullWriter): |
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319 | """A writer which can be used in debugging formatters, but not much else. |
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320 | |
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321 | Each method simply announces itself by printing its name and |
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322 | arguments on standard output. |
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323 | |
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324 | """ |
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325 | |
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326 | def new_alignment(self, align): |
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327 | print "new_alignment(%r)" % (align,) |
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328 | |
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329 | def new_font(self, font): |
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330 | print "new_font(%r)" % (font,) |
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331 | |
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332 | def new_margin(self, margin, level): |
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333 | print "new_margin(%r, %d)" % (margin, level) |
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334 | |
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335 | def new_spacing(self, spacing): |
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336 | print "new_spacing(%r)" % (spacing,) |
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337 | |
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338 | def new_styles(self, styles): |
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339 | print "new_styles(%r)" % (styles,) |
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340 | |
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341 | def send_paragraph(self, blankline): |
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342 | print "send_paragraph(%r)" % (blankline,) |
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343 | |
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344 | def send_line_break(self): |
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345 | print "send_line_break()" |
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346 | |
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347 | def send_hor_rule(self, *args, **kw): |
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348 | print "send_hor_rule()" |
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349 | |
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350 | def send_label_data(self, data): |
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351 | print "send_label_data(%r)" % (data,) |
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352 | |
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353 | def send_flowing_data(self, data): |
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354 | print "send_flowing_data(%r)" % (data,) |
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355 | |
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356 | def send_literal_data(self, data): |
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357 | print "send_literal_data(%r)" % (data,) |
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358 | |
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359 | |
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360 | class DumbWriter(NullWriter): |
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361 | """Simple writer class which writes output on the file object passed in |
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362 | as the file parameter or, if file is omitted, on standard output. The |
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363 | output is simply word-wrapped to the number of columns specified by |
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364 | the maxcol parameter. This class is suitable for reflowing a sequence |
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365 | of paragraphs. |
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366 | |
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367 | """ |
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368 | |
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369 | def __init__(self, file=None, maxcol=72): |
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370 | self.file = file or sys.stdout |
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371 | self.maxcol = maxcol |
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372 | NullWriter.__init__(self) |
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373 | self.reset() |
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374 | |
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375 | def reset(self): |
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376 | self.col = 0 |
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377 | self.atbreak = 0 |
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378 | |
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379 | def send_paragraph(self, blankline): |
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380 | self.file.write('\n'*blankline) |
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381 | self.col = 0 |
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382 | self.atbreak = 0 |
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383 | |
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384 | def send_line_break(self): |
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385 | self.file.write('\n') |
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386 | self.col = 0 |
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387 | self.atbreak = 0 |
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388 | |
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389 | def send_hor_rule(self, *args, **kw): |
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390 | self.file.write('\n') |
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391 | self.file.write('-'*self.maxcol) |
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392 | self.file.write('\n') |
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393 | self.col = 0 |
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394 | self.atbreak = 0 |
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395 | |
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396 | def send_literal_data(self, data): |
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397 | self.file.write(data) |
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398 | i = data.rfind('\n') |
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399 | if i >= 0: |
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400 | self.col = 0 |
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401 | data = data[i+1:] |
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402 | data = data.expandtabs() |
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403 | self.col = self.col + len(data) |
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404 | self.atbreak = 0 |
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405 | |
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406 | def send_flowing_data(self, data): |
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407 | if not data: return |
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408 | atbreak = self.atbreak or data[0].isspace() |
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409 | col = self.col |
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410 | maxcol = self.maxcol |
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411 | write = self.file.write |
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412 | for word in data.split(): |
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413 | if atbreak: |
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414 | if col + len(word) >= maxcol: |
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415 | write('\n') |
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416 | col = 0 |
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417 | else: |
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418 | write(' ') |
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419 | col = col + 1 |
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420 | write(word) |
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421 | col = col + len(word) |
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422 | atbreak = 1 |
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423 | self.col = col |
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424 | self.atbreak = data[-1].isspace() |
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425 | |
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426 | |
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427 | def test(file = None): |
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428 | w = DumbWriter() |
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429 | f = AbstractFormatter(w) |
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430 | if file is not None: |
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431 | fp = open(file) |
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432 | elif sys.argv[1:]: |
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433 | fp = open(sys.argv[1]) |
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434 | else: |
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435 | fp = sys.stdin |
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436 | for line in fp: |
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437 | if line == '\n': |
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438 | f.end_paragraph(1) |
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439 | else: |
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440 | f.add_flowing_data(line) |
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441 | f.end_paragraph(0) |
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442 | |
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443 | |
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444 | if __name__ == '__main__': |
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445 | test() |
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