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2 @node Picture, Sending Mail, Abbrevs, Top
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3 @chapter Editing Pictures
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4 @cindex pictures
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5 @findex edit-picture
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6
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7 If you want to create a picture made out of text characters (for example,
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8 a picture of the division of a register into fields, as a comment in a
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9 program), use the command @code{edit-picture} to enter Picture mode.
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10
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11 In Picture mode, editing is based on the @dfn{quarter-plane} model of
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12 text. In this model, the text characters lie studded on an area that
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13 stretches infinitely far to the right and downward. The concept of the end
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14 of a line does not exist in this model; the most you can say is where the
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15 last non-blank character on the line is found.
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16
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17 Of course, Emacs really always considers text as a sequence of
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18 characters, and lines really do have ends. But in Picture mode most
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19 frequently-used keys are rebound to commands that simulate the
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20 quarter-plane model of text. They do this by inserting spaces or by
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21 converting tabs to spaces.
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22
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23 Most of the basic editing commands of Emacs are redefined by Picture mode
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24 to do essentially the same thing but in a quarter-plane way. In addition,
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25 Picture mode defines various keys starting with the @kbd{C-c} prefix to
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26 run special picture editing commands.
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27
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28 One of these keys, @kbd{C-c C-c}, is pretty important. Often a picture
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29 is part of a larger file that is usually edited in some other major mode.
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30 @kbd{M-x edit-picture} records the name of the previous major mode.
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31 You can then use the @kbd{C-c C-c} command (@code{picture-mode-exit}) to
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32 restore that mode. @kbd{C-c C-c} also deletes spaces from the ends of
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33 lines, unless you give it a numeric argument.
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34
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35 The commands used in Picture mode all work in other modes (provided the
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36 @file{picture} library is loaded), but are only bound to keys in
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37 Picture mode. Note that the descriptions below talk of moving ``one
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38 column'' and so on, but all the picture mode commands handle numeric
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39 arguments as their normal equivalents do.
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40
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41 @vindex picture-mode-hook
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42 Turning on Picture mode calls the value of the variable
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43 @code{picture-mode-hook} as a function, with no arguments, if that value
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44 exists and is non-@code{nil}.
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45
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46 @menu
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47 * Basic Picture:: Basic concepts and simple commands of Picture Mode.
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48 * Insert in Picture:: Controlling direction of cursor motion
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49 after "self-inserting" characters.
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50 * Tabs in Picture:: Various features for tab stops and indentation.
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51 * Rectangles in Picture:: Clearing and superimposing rectangles.
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52 @end menu
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53
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54 @node Basic Picture, Insert in Picture, Picture, Picture
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55 @section Basic Editing in Picture Mode
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56
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57 @findex picture-forward-column
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58 @findex picture-backward-column
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59 @findex picture-move-down
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60 @findex picture-move-up
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61 Most keys do the same thing in Picture mode that they usually do, but do
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62 it in a quarter-plane style. For example, @kbd{C-f} is rebound to run
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63 @code{picture-forward-column}, which moves point one column to
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64 the right, by inserting a space if necessary, so that the actual end of the
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65 line makes no difference. @kbd{C-b} is rebound to run
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66 @code{picture-backward-column}, which always moves point left one column,
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67 converting a tab to multiple spaces if necessary. @kbd{C-n} and @kbd{C-p}
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68 are rebound to run @code{picture-move-down} and @code{picture-move-up},
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69 which can either insert spaces or convert tabs as necessary to make sure
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70 that point stays in exactly the same column. @kbd{C-e} runs
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71 @code{picture-end-of-line}, which moves to after the last non-blank
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72 character on the line. There was no need to change @kbd{C-a}, as the choice
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73 of screen model does not affect beginnings of lines.@refill
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74
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75 @findex picture-newline
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76 Insertion of text is adapted to the quarter-plane screen model through
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77 the use of Overwrite mode (@pxref{Minor Modes}). Self-inserting characters
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78 replace existing text, column by column, rather than pushing existing text
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79 to the right. @key{RET} runs @code{picture-newline}, which just moves to
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80 the beginning of the following line so that new text will replace that
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81 line.
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82
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83 @findex picture-backward-clear-column
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84 @findex picture-clear-column
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85 @findex picture-clear-line
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86 Text is erased instead of deleted and killed. @key{DEL}
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87 (@code{picture-backward-clear-column}) replaces the preceding character
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88 with a space rather than removing it. @kbd{C-d}
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89 (@code{picture-clear-column}) does the same in a forward direction.
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90 @kbd{C-k} (@code{picture-clear-line}) really kills the contents of lines,
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91 but never removes the newlines from a buffer.@refill
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92
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93 @findex picture-open-line
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94 To do actual insertion, you must use special commands. @kbd{C-o}
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95 (@code{picture-open-line}) creates a blank line, but does so after
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96 the current line; it never splits a line. @kbd{C-M-o}, @code{split-line},
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97 makes sense in Picture mode, so it remains unchanged. @key{LFD}
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98 (@code{picture-duplicate-line}) inserts another line
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99 with the same contents below the current line.@refill
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100
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101 @kindex C-c C-d (Picture mode)
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102 @findex delete-char
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103
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104 To actually delete parts of the picture, use @kbd{C-w}, or with
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105 @kbd{C-c C-d} (which is defined as @code{delete-char}, as @kbd{C-d} is
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106 in other modes), or with one of the picture rectangle commands
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107 (@pxref{Rectangles in Picture}).
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108
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109 @node Insert in Picture, Tabs in Picture, Basic Picture, Picture
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110 @section Controlling Motion After Insert
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111
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112 @findex picture-movement-up
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113 @findex picture-movement-down
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114 @findex picture-movement-left
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115 @findex picture-movement-right
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116 @findex picture-movement-nw
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117 @findex picture-movement-ne
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118 @findex picture-movement-sw
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119 @findex picture-movement-se
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120 @kindex C-c < (Picture mode)
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121 @kindex C-c > (Picture mode)
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122 @kindex C-c ^ (Picture mode)
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123 @kindex C-c . (Picture mode)
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124 @kindex C-c ` (Picture mode)
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125 @kindex C-c ' (Picture mode)
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126 @kindex C-c / (Picture mode)
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127 @kindex C-c \ (Picture mode)
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128 Since ``self-inserting'' characters just overwrite and move point in
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129 Picture mode, there is no essential restriction on how point should be
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130 moved. Normally point moves right, but you can specify any of the eight
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131 orthogonal or diagonal directions for motion after a ``self-inserting''
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132 character. This is useful for drawing lines in the buffer.
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133
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134 @table @kbd
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135 @item C-c <
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136 Move left after insertion (@code{picture-movement-left}).
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137 @item C-c >
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138 Move right after insertion (@code{picture-movement-right}).
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139 @item C-c ^
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140 Move up after insertion (@code{picture-movement-up}).
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141 @item C-c .
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142 Move down after insertion (@code{picture-movement-down}).
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143 @item C-c `
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144 Move up and left (``northwest'') after insertion @*(@code{picture-movement-nw}).
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145 @item C-c '
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146 Move up and right (``northeast'') after insertion @*
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147 (@code{picture-movement-ne}).
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148 @item C-c /
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149 Move down and left (``southwest'') after insertion
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150 @*(@code{picture-movement-sw}).
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151 @item C-c \
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152 Move down and right (``southeast'') after insertion
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153 @*(@code{picture-movement-se}).
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154 @end table
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155
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156 @kindex C-c C-f (Picture mode)
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157 @kindex C-c C-b (Picture mode)
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158 @findex picture-motion
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159 @findex picture-motion-reverse
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160 Two motion commands move based on the current Picture insertion
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161 direction. The command @kbd{C-c C-f} (@code{picture-motion}) moves in the
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162 same direction as motion after ``insertion'' currently does, while @kbd{C-c
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163 C-b} (@code{picture-motion-reverse}) moves in the opposite direction.
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164
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165 @node Tabs in Picture, Rectangles in Picture, Insert in Picture, Picture
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166 @section Picture Mode Tabs
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167
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168 @kindex M-TAB
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169 @findex picture-tab-search
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170 @vindex picture-tab-chars
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171 Two kinds of tab-like action are provided in Picture mode.
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172 Context-based tabbing is done with @kbd{M-@key{TAB}}
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173 (@code{picture-tab-search}). With no argument, it moves to a point
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174 underneath the next ``interesting'' character that follows whitespace in
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175 the previous non-blank line. ``Next'' here means ``appearing at a
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176 horizontal position greater than the one point starts out at''. With an
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177 argument, as in @kbd{C-u M-@key{TAB}}, the command moves to the next such
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178 interesting character in the current line. @kbd{M-@key{TAB}} does not
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179 change the text; it only moves point. ``Interesting'' characters are
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180 defined by the variable @code{picture-tab-chars}, which contains a string
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181 of characters considered interesting. Its default value is
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182 @code{"!-~"}.@refill
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183
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184 @findex picture-tab
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185 @key{TAB} itself runs @code{picture-tab}, which operates based on the
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186 current tab stop settings; it is the Picture mode equivalent of
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187 @code{tab-to-tab-stop}. Without arguments it just moves point, but with
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188 a numeric argument it clears the text that it moves over.
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189
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190 @kindex C-c TAB (Picture mode)
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191 @findex picture-set-tab-stops
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192 The context-based and tab-stop-based forms of tabbing are brought
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193 together by the command @kbd{C-c @key{TAB}} (@code{picture-set-tab-stops}.)
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194 This command sets the tab stops to the positions which @kbd{M-@key{TAB}}
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195 would consider significant in the current line. If you use this command
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196 with @key{TAB}, you can get the effect of context-based tabbing. But
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197 @kbd{M-@key{TAB}} is more convenient in the cases where it is sufficient.
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198
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199 @node Rectangles in Picture,, Tabs in Picture, Picture
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200 @section Picture Mode Rectangle Commands
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201 @cindex rectangle
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202
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203 Picture mode defines commands for working on rectangular pieces of the
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204 text in ways that fit with the quarter-plane model. The standard rectangle
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205 commands may also be useful (@pxref{Rectangles}).
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206
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207 @table @kbd
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208 @item C-c C-k
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209 Clear out the region-rectangle (@code{picture-clear-rectangle}). With
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210 argument, kill it.
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211 @item C-c C-w @var{r}
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212 Similar but save rectangle contents in register @var{r} first
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213 (@code{picture-clear-rectangle-to-register}).
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214 @item C-c C-y
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215 Copy last killed rectangle into the buffer by overwriting, with upper
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216 left corner at point (@code{picture-yank-rectangle}). With argument,
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217 insert instead.
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218 @item C-c C-x @var{r}
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219 Similar, but use the rectangle in register @var{r}@*
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220 (@code{picture-yank-rectangle-from-register}).
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221 @end table
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222
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223 @kindex C-c C-k (Picture mode)
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224 @kindex C-c C-w (Picture mode)
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225 @findex picture-clear-rectangle
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226 @findex picture-clear-rectangle-to-register
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227 The picture rectangle commands @kbd{C-c C-k}
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228 (@code{picture-clear-rectangle}) and @kbd{C-c C-w}
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229 (@code{picture-clear-rectangle-to-register}) differ from the standard
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230 rectangle commands in that they normally clear the rectangle instead of
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231 deleting it; this is analogous with the way @kbd{C-d} is changed in Picture
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232 mode.@refill
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233
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234 However, deletion of rectangles can be useful in Picture mode, so these
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235 commands delete the rectangle if given a numeric argument.
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236
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237 @kindex C-c C-y (Picture mode)
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238 @kindex C-c C-x (Picture mode)
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239 @findex picture-yank-rectangle
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240 @findex picture-yank-rectangle-from-register
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241 The Picture mode commands for yanking rectangles differ from the standard
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242 ones in overwriting instead of inserting. This is the same way that
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243 Picture mode insertion of other text is different from other modes.
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244 @kbd{C-c C-y} (@code{picture-yank-rectangle}) inserts (by overwriting) the
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245 rectangle that was most recently killed, while @kbd{C-c C-x}
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246 (@code{picture-yank-rectangle-from-register}) does for the
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247 rectangle found in a specified register.
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248
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249 Since most region commands in Picture mode operate on rectangles, when you
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250 select a region of text with the mouse in Picture mode, it is highlighted
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251 as a rectangle.
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