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1 @c -*-texinfo-*-
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2 @c This is part of the XEmacs Lisp Reference Manual.
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3 @c Copyright (C) 1990, 1991, 1992, 1993, 1994 Free Software Foundation, Inc.
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4 @c See the file lispref.texi for copying conditions.
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5 @setfilename ../../info/positions.info
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6 @node Positions, Markers, Consoles and Devices, Top
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7 @chapter Positions
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8 @cindex position (in buffer)
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9
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10 A @dfn{position} is the index of a character in the text of a buffer.
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11 More precisely, a position identifies the place between two characters
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12 (or before the first character, or after the last character), so we can
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13 speak of the character before or after a given position. However, we
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14 often speak of the character ``at'' a position, meaning the character
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15 after that position.
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16
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17 Positions are usually represented as integers starting from 1, but can
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18 also be represented as @dfn{markers}---special objects that relocate
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19 automatically when text is inserted or deleted so they stay with the
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20 surrounding characters. @xref{Markers}.
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21
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22 @menu
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23 * Point:: The special position where editing takes place.
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24 * Motion:: Changing point.
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25 * Excursions:: Temporary motion and buffer changes.
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26 * Narrowing:: Restricting editing to a portion of the buffer.
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27 @end menu
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28
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29 @node Point
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30 @section Point
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31 @cindex point
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32
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33 @dfn{Point} is a special buffer position used by many editing
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34 commands, including the self-inserting typed characters and text
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35 insertion functions. Other commands move point through the text
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36 to allow editing and insertion at different places.
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37
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38 Like other positions, point designates a place between two characters
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39 (or before the first character, or after the last character), rather
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40 than a particular character. Usually terminals display the cursor over
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41 the character that immediately follows point; point is actually before
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42 the character on which the cursor sits.
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43
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44 @cindex point with narrowing
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45 The value of point is a number between 1 and the buffer size plus 1.
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46 If narrowing is in effect (@pxref{Narrowing}), then point is constrained
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47 to fall within the accessible portion of the buffer (possibly at one end
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48 of it).
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49
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50 Each buffer has its own value of point, which is independent of the
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51 value of point in other buffers. Each window also has a value of point,
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52 which is independent of the value of point in other windows on the same
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53 buffer. This is why point can have different values in various windows
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54 that display the same buffer. When a buffer appears in only one window,
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55 the buffer's point and the window's point normally have the same value,
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56 so the distinction is rarely important. @xref{Window Point}, for more
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57 details.
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58
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59 @defun point &optional buffer
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60 @cindex current buffer position
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61 This function returns the value of point in @var{buffer}, as an integer.
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62 @var{buffer} defaults to the current buffer if omitted.
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63
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64 @need 700
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65 @example
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66 @group
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67 (point)
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68 @result{} 175
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69 @end group
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70 @end example
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71 @end defun
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72
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73 @defun point-min &optional buffer
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74 This function returns the minimum accessible value of point in
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75 @var{buffer}. This is normally 1, but if narrowing is in effect, it is
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76 the position of the start of the region that you narrowed to.
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77 (@xref{Narrowing}.) @var{buffer} defaults to the current buffer if
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78 omitted.
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79 @end defun
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80
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81 @defun point-max &optional buffer
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82 This function returns the maximum accessible value of point in
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83 @var{buffer}. This is @code{(1+ (buffer-size buffer))}, unless
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84 narrowing is in effect, in which case it is the position of the end of
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85 the region that you narrowed to. (@xref{Narrowing}). @var{buffer}
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86 defaults to the current buffer if omitted.
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87 @end defun
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88
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89 @defun buffer-end flag &optional buffer
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90 This function returns @code{(point-min buffer)} if @var{flag} is less
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91 than 1, @code{(point-max buffer)} otherwise. The argument @var{flag}
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92 must be a number. @var{buffer} defaults to the current buffer if
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93 omitted.
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94 @end defun
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95
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96 @defun buffer-size &optional buffer
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97 This function returns the total number of characters in @var{buffer}.
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98 In the absence of any narrowing (@pxref{Narrowing}), @code{point-max}
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99 returns a value one larger than this. @var{buffer} defaults to the
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100 current buffer if omitted.
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101
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102 @example
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103 @group
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104 (buffer-size)
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105 @result{} 35
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106 @end group
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107 @group
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108 (point-max)
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109 @result{} 36
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110 @end group
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111 @end example
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112 @end defun
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113
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114 @defvar buffer-saved-size
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115 The value of this buffer-local variable is the former length of the
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116 current buffer, as of the last time it was read in, saved or auto-saved.
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117 @end defvar
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118
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119 @node Motion
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120 @section Motion
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121
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122 Motion functions change the value of point, either relative to the
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123 current value of point, relative to the beginning or end of the buffer,
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124 or relative to the edges of the selected window. @xref{Point}.
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125
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126 @menu
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127 * Character Motion:: Moving in terms of characters.
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128 * Word Motion:: Moving in terms of words.
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129 * Buffer End Motion:: Moving to the beginning or end of the buffer.
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130 * Text Lines:: Moving in terms of lines of text.
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131 * Screen Lines:: Moving in terms of lines as displayed.
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132 * List Motion:: Moving by parsing lists and sexps.
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133 * Skipping Characters:: Skipping characters belonging to a certain set.
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134 @end menu
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135
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136 @node Character Motion
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137 @subsection Motion by Characters
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138
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139 These functions move point based on a count of characters.
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140 @code{goto-char} is the fundamental primitive; the other functions use
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141 that.
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142
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143 @deffn Command goto-char position &optional buffer
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144 This function sets point in @code{buffer} to the value @var{position}.
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145 If @var{position} is less than 1, it moves point to the beginning of the
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146 buffer. If @var{position} is greater than the length of the buffer, it
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147 moves point to the end. @var{buffer} defaults to the current buffer if
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148 omitted.
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149
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150 If narrowing is in effect, @var{position} still counts from the
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151 beginning of the buffer, but point cannot go outside the accessible
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152 portion. If @var{position} is out of range, @code{goto-char} moves
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153 point to the beginning or the end of the accessible portion.
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154
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155 When this function is called interactively, @var{position} is the
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156 numeric prefix argument, if provided; otherwise it is read from the
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157 minibuffer.
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158
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159 @code{goto-char} returns @var{position}.
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160 @end deffn
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161
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162 @deffn Command forward-char &optional count buffer
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163 @c @kindex beginning-of-buffer
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164 @c @kindex end-of-buffer
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165 This function moves point @var{count} characters forward, towards the
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166 end of the buffer (or backward, towards the beginning of the buffer, if
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167 @var{count} is negative). If the function attempts to move point past
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168 the beginning or end of the buffer (or the limits of the accessible
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169 portion, when narrowing is in effect), an error is signaled with error
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170 code @code{beginning-of-buffer} or @code{end-of-buffer}. @var{buffer}
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171 defaults to the current buffer if omitted.
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172
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173
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174 In an interactive call, @var{count} is the numeric prefix argument.
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175 @end deffn
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176
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177 @deffn Command backward-char &optional count buffer
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178 This function moves point @var{count} characters backward, towards the
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179 beginning of the buffer (or forward, towards the end of the buffer, if
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180 @var{count} is negative). If the function attempts to move point past
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181 the beginning or end of the buffer (or the limits of the accessible
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182 portion, when narrowing is in effect), an error is signaled with error
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183 code @code{beginning-of-buffer} or @code{end-of-buffer}. @var{buffer}
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184 defaults to the current buffer if omitted.
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185
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186
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187 In an interactive call, @var{count} is the numeric prefix argument.
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188 @end deffn
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189
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190 @node Word Motion
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191 @subsection Motion by Words
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192
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193 These functions for parsing words use the syntax table to decide
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194 whether a given character is part of a word. @xref{Syntax Tables}.
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195
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196 @deffn Command forward-word count &optional buffer
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197 This function moves point forward @var{count} words (or backward if
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198 @var{count} is negative). Normally it returns @code{t}. If this motion
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199 encounters the beginning or end of the buffer, or the limits of the
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200 accessible portion when narrowing is in effect, point stops there and
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201 the value is @code{nil}. @var{buffer} defaults to the current buffer if
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202 omitted.
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203
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204 In an interactive call, @var{count} is set to the numeric prefix
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205 argument.
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206 @end deffn
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207
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208 @deffn Command backward-word count &optional buffer
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209 This function is just like @code{forward-word}, except that it moves
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210 backward until encountering the front of a word, rather than forward.
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211 @var{buffer} defaults to the current buffer if omitted.
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212
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213 In an interactive call, @var{count} is set to the numeric prefix
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214 argument.
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215
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216 This function is rarely used in programs, as it is more efficient to
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217 call @code{forward-word} with a negative argument.
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218 @end deffn
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219
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220 @defvar words-include-escapes
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221 @c Emacs 19 feature
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222 This variable affects the behavior of @code{forward-word} and everything
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223 that uses it. If it is non-@code{nil}, then characters in the
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224 ``escape'' and ``character quote'' syntax classes count as part of
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225 words. Otherwise, they do not.
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226 @end defvar
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227
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228 @node Buffer End Motion
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229 @subsection Motion to an End of the Buffer
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230
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231 To move point to the beginning of the buffer, write:
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232
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233 @example
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234 @group
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235 (goto-char (point-min))
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236 @end group
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237 @end example
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238
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239 @noindent
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240 Likewise, to move to the end of the buffer, use:
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241
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242 @example
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243 @group
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244 (goto-char (point-max))
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245 @end group
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246 @end example
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247
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248 Here are two commands that users use to do these things. They are
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249 documented here to warn you not to use them in Lisp programs, because
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250 they set the mark and display messages in the echo area.
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251
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252 @deffn Command beginning-of-buffer &optional n
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253 This function moves point to the beginning of the buffer (or the limits
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254 of the accessible portion, when narrowing is in effect), setting the
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255 mark at the previous position. If @var{n} is non-@code{nil}, then it
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256 puts point @var{n} tenths of the way from the beginning of the buffer.
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257
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258 In an interactive call, @var{n} is the numeric prefix argument,
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259 if provided; otherwise @var{n} defaults to @code{nil}.
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260
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261 Don't use this function in Lisp programs!
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262 @end deffn
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263
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264 @deffn Command end-of-buffer &optional n
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265 This function moves point to the end of the buffer (or the limits of
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266 the accessible portion, when narrowing is in effect), setting the mark
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267 at the previous position. If @var{n} is non-@code{nil}, then it puts
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268 point @var{n} tenths of the way from the end of the buffer.
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269
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270 In an interactive call, @var{n} is the numeric prefix argument,
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271 if provided; otherwise @var{n} defaults to @code{nil}.
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272
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273 Don't use this function in Lisp programs!
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274 @end deffn
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275
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276 @node Text Lines
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277 @subsection Motion by Text Lines
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278 @cindex lines
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279
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280 Text lines are portions of the buffer delimited by newline characters,
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281 which are regarded as part of the previous line. The first text line
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282 begins at the beginning of the buffer, and the last text line ends at
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283 the end of the buffer whether or not the last character is a newline.
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284 The division of the buffer into text lines is not affected by the width
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285 of the window, by line continuation in display, or by how tabs and
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286 control characters are displayed.
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287
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288 @deffn Command goto-line line
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289 This function moves point to the front of the @var{line}th line,
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290 counting from line 1 at beginning of the buffer. If @var{line} is less
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291 than 1, it moves point to the beginning of the buffer. If @var{line} is
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292 greater than the number of lines in the buffer, it moves point to the
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293 end of the buffer---that is, the @emph{end of the last line} of the
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294 buffer. This is the only case in which @code{goto-line} does not
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295 necessarily move to the beginning of a line.
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296
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297 If narrowing is in effect, then @var{line} still counts from the
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298 beginning of the buffer, but point cannot go outside the accessible
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299 portion. So @code{goto-line} moves point to the beginning or end of the
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300 accessible portion, if the line number specifies an inaccessible
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301 position.
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302
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303 The return value of @code{goto-line} is the difference between
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304 @var{line} and the line number of the line to which point actually was
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305 able to move (in the full buffer, before taking account of narrowing).
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306 Thus, the value is positive if the scan encounters the real end of the
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307 buffer. The value is zero if scan encounters the end of the accessible
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308 portion but not the real end of the buffer.
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309
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310 In an interactive call, @var{line} is the numeric prefix argument if
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311 one has been provided. Otherwise @var{line} is read in the minibuffer.
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312 @end deffn
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313
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314 @deffn Command beginning-of-line &optional count buffer
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315 This function moves point to the beginning of the current line. With an
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316 argument @var{count} not @code{nil} or 1, it moves forward
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317 @var{count}@minus{}1 lines and then to the beginning of the line.
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318 @var{buffer} defaults to the current buffer if omitted.
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319
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320 If this function reaches the end of the buffer (or of the accessible
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321 portion, if narrowing is in effect), it positions point there. No error
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322 is signaled.
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323 @end deffn
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324
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325 @deffn Command end-of-line &optional count buffer
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326 This function moves point to the end of the current line. With an
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327 argument @var{count} not @code{nil} or 1, it moves forward
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328 @var{count}@minus{}1 lines and then to the end of the line.
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329 @var{buffer} defaults to the current buffer if omitted.
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330
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331 If this function reaches the end of the buffer (or of the accessible
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332 portion, if narrowing is in effect), it positions point there. No error
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333 is signaled.
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334 @end deffn
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335
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336 @deffn Command forward-line &optional count buffer
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337 @cindex beginning of line
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338 This function moves point forward @var{count} lines, to the beginning of
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339 the line. If @var{count} is negative, it moves point
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340 @minus{}@var{count} lines backward, to the beginning of a line. If
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341 @var{count} is zero, it moves point to the beginning of the current
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342 line. @var{buffer} defaults to the current buffer if omitted.
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343
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344 If @code{forward-line} encounters the beginning or end of the buffer (or
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345 of the accessible portion) before finding that many lines, it sets point
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346 there. No error is signaled.
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347
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348 @code{forward-line} returns the difference between @var{count} and the
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349 number of lines actually moved. If you attempt to move down five lines
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350 from the beginning of a buffer that has only three lines, point stops at
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351 the end of the last line, and the value will be 2.
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352
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353 In an interactive call, @var{count} is the numeric prefix argument.
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354 @end deffn
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355
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356 @defun count-lines start end
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357 @cindex lines in region
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358 This function returns the number of lines between the positions
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359 @var{start} and @var{end} in the current buffer. If @var{start} and
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360 @var{end} are equal, then it returns 0. Otherwise it returns at least
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361 1, even if @var{start} and @var{end} are on the same line. This is
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362 because the text between them, considered in isolation, must contain at
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363 least one line unless it is empty.
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364
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365 Here is an example of using @code{count-lines}:
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366
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367 @example
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368 @group
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369 (defun current-line ()
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370 "Return the vertical position of point@dots{}"
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371 (+ (count-lines (window-start) (point))
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372 (if (= (current-column) 0) 1 0)
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373 -1))
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374 @end group
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375 @end example
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376 @end defun
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377
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378 @ignore
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379 @c ================
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380 The @code{previous-line} and @code{next-line} commands are functions
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381 that should not be used in programs. They are for users and are
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382 mentioned here only for completeness.
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383
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384 @deffn Command previous-line count
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385 @cindex goal column
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386 This function moves point up @var{count} lines (down if @var{count}
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387 is negative). In moving, it attempts to keep point in the ``goal column''
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388 (normally the same column that it was at the beginning of the move).
|
|
|
389
|
|
|
390 If there is no character in the target line exactly under the current
|
|
|
391 column, point is positioned after the character in that line which
|
|
|
392 spans this column, or at the end of the line if it is not long enough.
|
|
|
393
|
|
|
394 If it attempts to move beyond the top or bottom of the buffer (or clipped
|
|
|
395 region), then point is positioned in the goal column in the top or
|
|
|
396 bottom line. No error is signaled.
|
|
|
397
|
|
|
398 In an interactive call, @var{count} will be the numeric
|
|
|
399 prefix argument.
|
|
|
400
|
|
|
401 The command @code{set-goal-column} can be used to create a semipermanent
|
|
|
402 goal column to which this command always moves. Then it does not try to
|
|
|
403 move vertically.
|
|
|
404
|
|
|
405 If you are thinking of using this in a Lisp program, consider using
|
|
|
406 @code{forward-line} with a negative argument instead. It is usually easier
|
|
|
407 to use and more reliable (no dependence on goal column, etc.).
|
|
|
408 @end deffn
|
|
|
409
|
|
|
410 @deffn Command next-line count
|
|
|
411 This function moves point down @var{count} lines (up if @var{count}
|
|
|
412 is negative). In moving, it attempts to keep point in the ``goal column''
|
|
|
413 (normally the same column that it was at the beginning of the move).
|
|
|
414
|
|
|
415 If there is no character in the target line exactly under the current
|
|
|
416 column, point is positioned after the character in that line which
|
|
|
417 spans this column, or at the end of the line if it is not long enough.
|
|
|
418
|
|
|
419 If it attempts to move beyond the top or bottom of the buffer (or clipped
|
|
|
420 region), then point is positioned in the goal column in the top or
|
|
|
421 bottom line. No error is signaled.
|
|
|
422
|
|
|
423 In the case where the @var{count} is 1, and point is on the last
|
|
|
424 line of the buffer (or clipped region), a new empty line is inserted at the
|
|
|
425 end of the buffer (or clipped region) and point moved there.
|
|
|
426
|
|
|
427 In an interactive call, @var{count} will be the numeric
|
|
|
428 prefix argument.
|
|
|
429
|
|
|
430 The command @code{set-goal-column} can be used to create a semipermanent
|
|
|
431 goal column to which this command always moves. Then it does not try to
|
|
|
432 move vertically.
|
|
|
433
|
|
|
434 If you are thinking of using this in a Lisp program, consider using
|
|
|
435 @code{forward-line} instead. It is usually easier
|
|
|
436 to use and more reliable (no dependence on goal column, etc.).
|
|
|
437 @end deffn
|
|
|
438
|
|
|
439 @c ================
|
|
|
440 @end ignore
|
|
|
441
|
|
|
442 Also see the functions @code{bolp} and @code{eolp} in @ref{Near Point}.
|
|
|
443 These functions do not move point, but test whether it is already at the
|
|
|
444 beginning or end of a line.
|
|
|
445
|
|
|
446 @node Screen Lines
|
|
|
447 @subsection Motion by Screen Lines
|
|
|
448
|
|
|
449 The line functions in the previous section count text lines, delimited
|
|
|
450 only by newline characters. By contrast, these functions count screen
|
|
|
451 lines, which are defined by the way the text appears on the screen. A
|
|
|
452 text line is a single screen line if it is short enough to fit the width
|
|
|
453 of the selected window, but otherwise it may occupy several screen
|
|
|
454 lines.
|
|
|
455
|
|
|
456 In some cases, text lines are truncated on the screen rather than
|
|
|
457 continued onto additional screen lines. In these cases,
|
|
|
458 @code{vertical-motion} moves point much like @code{forward-line}.
|
|
|
459 @xref{Truncation}.
|
|
|
460
|
|
|
461 Because the width of a given string depends on the flags that control
|
|
|
462 the appearance of certain characters, @code{vertical-motion} behaves
|
|
|
463 differently, for a given piece of text, depending on the buffer it is
|
|
|
464 in, and even on the selected window (because the width, the truncation
|
|
|
465 flag, and display table may vary between windows). @xref{Usual
|
|
|
466 Display}.
|
|
|
467
|
|
|
468 These functions scan text to determine where screen lines break, and
|
|
|
469 thus take time proportional to the distance scanned. If you intend to
|
|
|
470 use them heavily, Emacs provides caches which may improve the
|
|
|
471 performance of your code. @xref{Text Lines, cache-long-line-scans}.
|
|
|
472
|
|
|
473
|
|
292
|
474 @defun vertical-motion count &optional window pixels
|
|
290
|
475 This function moves point to the start of the frame line @var{count}
|
|
|
476 frame lines down from the frame line containing point. If @var{count}
|
|
292
|
477 is negative, it moves up instead. The optional second argument
|
|
|
478 @var{window} may be used to specify a window other than the
|
|
|
479 selected window in which to perform the motion.
|
|
0
|
480
|
|
292
|
481 Normally, @code{vertical-motion} returns the number of lines moved. The
|
|
|
482 value may be less in absolute value than @var{count} if the beginning or
|
|
|
483 end of the buffer was reached. If the optional third argument,
|
|
|
484 @var{pixels} is non-@code{nil}, the vertical pixel height of the motion
|
|
|
485 which took place is returned instead of the actual number of lines
|
|
|
486 moved. A motion of zero lines returns the height of the current line.
|
|
0
|
487
|
|
290
|
488 Note that @code{vertical-motion} sets @var{window}'s buffer's point, not
|
|
|
489 @var{window}'s point. (This differs from FSF Emacs, which buggily always
|
|
|
490 sets current buffer's point, regardless of @var{window}.)
|
|
|
491 @end defun
|
|
|
492
|
|
292
|
493 @defun vertical-motion-pixels count &optional window how
|
|
|
494 This function moves point to the start of the frame line @var{pixels}
|
|
|
495 vertical pixels down from the frame line containing point, or up if
|
|
|
496 @var{pixels} is negative. The optional second argument @var{window} is
|
|
|
497 the window to move in, and defaults to the selected window. The
|
|
|
498 optional third argument @var{how} specifies the stopping condition. A
|
|
|
499 negative integer indicates that the motion should be no more
|
|
|
500 than @var{pixels}. A positive value indicates that the
|
|
|
501 motion should be at least @var{pixels}. Any other value indicates
|
|
|
502 that the motion should be as close as possible to @var{pixels}.
|
|
0
|
503 @end defun
|
|
|
504
|
|
|
505 @deffn Command move-to-window-line count &optional window
|
|
|
506 This function moves point with respect to the text currently displayed
|
|
|
507 in @var{window}, which defaults to the selected window. It moves point
|
|
|
508 to the beginning of the screen line @var{count} screen lines from the
|
|
|
509 top of the window. If @var{count} is negative, that specifies a
|
|
|
510 position @w{@minus{}@var{count}} lines from the bottom (or the last line
|
|
|
511 of the buffer, if the buffer ends above the specified screen position).
|
|
|
512
|
|
|
513 If @var{count} is @code{nil}, then point moves to the beginning of the
|
|
|
514 line in the middle of the window. If the absolute value of @var{count}
|
|
|
515 is greater than the size of the window, then point moves to the place
|
|
|
516 that would appear on that screen line if the window were tall enough.
|
|
|
517 This will probably cause the next redisplay to scroll to bring that
|
|
|
518 location onto the screen.
|
|
|
519
|
|
|
520 In an interactive call, @var{count} is the numeric prefix argument.
|
|
|
521
|
|
|
522 The value returned is the window line number point has moved to, with
|
|
|
523 the top line in the window numbered 0.
|
|
|
524 @end deffn
|
|
|
525
|
|
|
526 @ignore Not in XEmacs
|
|
|
527 @defun compute-motion from frompos to topos width offsets window
|
|
|
528 This function scans the current buffer, calculating screen positions.
|
|
|
529 It scans the buffer forward from position @var{from}, assuming that is
|
|
|
530 at screen coordinates @var{frompos}, to position @var{to} or coordinates
|
|
|
531 @var{topos}, whichever comes first. It returns the ending buffer
|
|
|
532 position and screen coordinates.
|
|
|
533
|
|
|
534 The coordinate arguments @var{frompos} and @var{topos} are cons cells of
|
|
|
535 the form @code{(@var{hpos} . @var{vpos})}.
|
|
|
536
|
|
|
537 The argument @var{width} is the number of columns available to display
|
|
|
538 text; this affects handling of continuation lines. Use the value
|
|
|
539 returned by @code{window-width} for the window of your choice;
|
|
|
540 normally, use @code{(window-width @var{window})}.
|
|
|
541
|
|
|
542 The argument @var{offsets} is either @code{nil} or a cons cell of the
|
|
|
543 form @code{(@var{hscroll} . @var{tab-offset})}. Here @var{hscroll} is
|
|
|
544 the number of columns not being displayed at the left margin; most
|
|
|
545 callers get this from @code{window-hscroll}. Meanwhile,
|
|
|
546 @var{tab-offset} is the offset between column numbers on the screen and
|
|
|
547 column numbers in the buffer. This can be nonzero in a continuation
|
|
|
548 line, when the previous screen lines' widths do not add up to a multiple
|
|
|
549 of @code{tab-width}. It is always zero in a non-continuation line.
|
|
|
550
|
|
|
551 The window @var{window} serves only to specify which display table to
|
|
|
552 use. @code{compute-motion} always operates on the current buffer,
|
|
|
553 regardless of what buffer is displayed in @var{window}.
|
|
|
554
|
|
|
555 The return value is a list of five elements:
|
|
|
556
|
|
|
557 @example
|
|
|
558 (@var{pos} @var{vpos} @var{hpos} @var{prevhpos} @var{contin})
|
|
|
559 @end example
|
|
|
560
|
|
|
561 @noindent
|
|
|
562 Here @var{pos} is the buffer position where the scan stopped, @var{vpos}
|
|
|
563 is the vertical screen position, and @var{hpos} is the horizontal screen
|
|
|
564 position.
|
|
|
565
|
|
|
566 The result @var{prevhpos} is the horizontal position one character back
|
|
|
567 from @var{pos}. The result @var{contin} is @code{t} if the last line
|
|
|
568 was continued after (or within) the previous character.
|
|
|
569
|
|
|
570 For example, to find the buffer position of column @var{col} of line
|
|
|
571 @var{line} of a certain window, pass the window's display start location
|
|
|
572 as @var{from} and the window's upper-left coordinates as @var{frompos}.
|
|
|
573 Pass the buffer's @code{(point-max)} as @var{to}, to limit the scan to
|
|
|
574 the end of the accessible portion of the buffer, and pass @var{line} and
|
|
|
575 @var{col} as @var{topos}. Here's a function that does this:
|
|
|
576
|
|
|
577 @example
|
|
|
578 (defun coordinates-of-position (col line)
|
|
|
579 (car (compute-motion (window-start)
|
|
|
580 '(0 . 0)
|
|
|
581 (point-max)
|
|
|
582 (cons col line)
|
|
|
583 (window-width)
|
|
|
584 (cons (window-hscroll) 0)
|
|
|
585 (selected-window))))
|
|
|
586 @end example
|
|
|
587
|
|
|
588 When you use @code{compute-motion} for the minibuffer, you need to use
|
|
|
589 @code{minibuffer-prompt-width} to get the horizontal position of the
|
|
|
590 beginning of the first screen line. @xref{Minibuffer Misc}.
|
|
|
591 @end defun
|
|
|
592 @end ignore
|
|
|
593
|
|
|
594 @node List Motion
|
|
|
595 @subsection Moving over Balanced Expressions
|
|
|
596 @cindex sexp motion
|
|
|
597 @cindex Lisp expression motion
|
|
|
598 @cindex list motion
|
|
|
599
|
|
|
600 Here are several functions concerned with balanced-parenthesis
|
|
|
601 expressions (also called @dfn{sexps} in connection with moving across
|
|
|
602 them in XEmacs). The syntax table controls how these functions interpret
|
|
|
603 various characters; see @ref{Syntax Tables}. @xref{Parsing
|
|
|
604 Expressions}, for lower-level primitives for scanning sexps or parts of
|
|
|
605 sexps. For user-level commands, see @ref{Lists and Sexps,,, emacs, XEmacs
|
|
|
606 Reference Manual}.
|
|
|
607
|
|
|
608 @deffn Command forward-list &optional arg
|
|
|
609 This function moves forward across @var{arg} balanced groups of
|
|
|
610 parentheses. (Other syntactic entities such as words or paired string
|
|
|
611 quotes are ignored.) @var{arg} defaults to 1 if omitted. If @var{arg}
|
|
|
612 is negative, move backward across that many groups of parentheses.
|
|
|
613 @end deffn
|
|
|
614
|
|
|
615 @deffn Command backward-list &optional arg
|
|
|
616 This function moves backward across @var{arg} balanced groups of
|
|
|
617 parentheses. (Other syntactic entities such as words or paired string
|
|
|
618 quotes are ignored.) @var{arg} defaults to 1 if omitted. If @var{arg}
|
|
|
619 is negative, move forward across that many groups of parentheses.
|
|
|
620 @end deffn
|
|
|
621
|
|
|
622 @deffn Command up-list arg
|
|
|
623 This function moves forward out of @var{arg} levels of parentheses.
|
|
|
624 A negative argument means move backward but still to a less deep spot.
|
|
|
625 @end deffn
|
|
|
626
|
|
|
627 @deffn Command down-list arg
|
|
|
628 This function moves forward into @var{arg} levels of parentheses. A
|
|
|
629 negative argument means move backward but still go
|
|
|
630 deeper in parentheses (@minus{}@var{arg} levels).
|
|
|
631 @end deffn
|
|
|
632
|
|
|
633 @deffn Command forward-sexp &optional arg
|
|
|
634 This function moves forward across @var{arg} balanced expressions.
|
|
|
635 Balanced expressions include both those delimited by parentheses and
|
|
|
636 other kinds, such as words and string constants. @var{arg} defaults to
|
|
|
637 1 if omitted. If @var{arg} is negative, move backward across that many
|
|
|
638 balanced expressions. For example,
|
|
|
639
|
|
|
640 @example
|
|
|
641 @group
|
|
|
642 ---------- Buffer: foo ----------
|
|
|
643 (concat@point{} "foo " (car x) y z)
|
|
|
644 ---------- Buffer: foo ----------
|
|
|
645 @end group
|
|
|
646
|
|
|
647 @group
|
|
|
648 (forward-sexp 3)
|
|
|
649 @result{} nil
|
|
|
650
|
|
|
651 ---------- Buffer: foo ----------
|
|
|
652 (concat "foo " (car x) y@point{} z)
|
|
|
653 ---------- Buffer: foo ----------
|
|
|
654 @end group
|
|
|
655 @end example
|
|
|
656 @end deffn
|
|
|
657
|
|
|
658 @deffn Command backward-sexp &optional arg
|
|
|
659 This function moves backward across @var{arg} balanced expressions.
|
|
|
660 @var{arg} defaults to 1 if omitted. If @var{arg} is negative, move
|
|
|
661 forward across that many balanced expressions.
|
|
|
662 @end deffn
|
|
|
663
|
|
|
664 @deffn Command beginning-of-defun &optional arg
|
|
|
665 This function moves back to the @var{arg}th beginning of a defun. If
|
|
|
666 @var{arg} is negative, this actually moves forward, but it still moves
|
|
|
667 to the beginning of a defun, not to the end of one. @var{arg} defaults
|
|
|
668 to 1 if omitted.
|
|
|
669 @end deffn
|
|
|
670
|
|
|
671 @deffn Command end-of-defun &optional arg
|
|
|
672 This function moves forward to the @var{arg}th end of a defun. If
|
|
|
673 @var{arg} is negative, this actually moves backward, but it still moves
|
|
|
674 to the end of a defun, not to the beginning of one. @var{arg} defaults
|
|
|
675 to 1 if omitted.
|
|
|
676 @end deffn
|
|
|
677
|
|
|
678 @defopt defun-prompt-regexp
|
|
|
679 If non-@code{nil}, this variable holds a regular expression that
|
|
|
680 specifies what text can appear before the open-parenthesis that starts a
|
|
|
681 defun. That is to say, a defun begins on a line that starts with a
|
|
|
682 match for this regular expression, followed by a character with
|
|
|
683 open-parenthesis syntax.
|
|
|
684 @end defopt
|
|
|
685
|
|
|
686 @node Skipping Characters
|
|
|
687 @subsection Skipping Characters
|
|
|
688 @cindex skipping characters
|
|
|
689
|
|
|
690 The following two functions move point over a specified set of
|
|
|
691 characters. For example, they are often used to skip whitespace. For
|
|
|
692 related functions, see @ref{Motion and Syntax}.
|
|
|
693
|
|
|
694 @defun skip-chars-forward character-set &optional limit buffer
|
|
|
695 This function moves point in @var{buffer} forward, skipping over a
|
|
|
696 given set of characters. It examines the character following point,
|
|
|
697 then advances point if the character matches @var{character-set}. This
|
|
|
698 continues until it reaches a character that does not match. The
|
|
|
699 function returns @code{nil}. @var{buffer} defaults to the current
|
|
|
700 buffer if omitted.
|
|
|
701
|
|
|
702 The argument @var{character-set} is like the inside of a
|
|
|
703 @samp{[@dots{}]} in a regular expression except that @samp{]} is never
|
|
|
704 special and @samp{\} quotes @samp{^}, @samp{-} or @samp{\}. Thus,
|
|
|
705 @code{"a-zA-Z"} skips over all letters, stopping before the first
|
|
108
|
706 non-letter, and @code{"^a-zA-Z}" skips non-letters stopping before the
|
|
0
|
707 first letter. @xref{Regular Expressions}.
|
|
|
708
|
|
|
709 If @var{limit} is supplied (it must be a number or a marker), it
|
|
|
710 specifies the maximum position in the buffer that point can be skipped
|
|
|
711 to. Point will stop at or before @var{limit}.
|
|
|
712
|
|
|
713 In the following example, point is initially located directly before the
|
|
|
714 @samp{T}. After the form is evaluated, point is located at the end of
|
|
|
715 that line (between the @samp{t} of @samp{hat} and the newline). The
|
|
|
716 function skips all letters and spaces, but not newlines.
|
|
|
717
|
|
|
718 @example
|
|
|
719 @group
|
|
|
720 ---------- Buffer: foo ----------
|
|
|
721 I read "@point{}The cat in the hat
|
|
|
722 comes back" twice.
|
|
|
723 ---------- Buffer: foo ----------
|
|
|
724 @end group
|
|
|
725
|
|
|
726 @group
|
|
|
727 (skip-chars-forward "a-zA-Z ")
|
|
|
728 @result{} nil
|
|
|
729
|
|
|
730 ---------- Buffer: foo ----------
|
|
|
731 I read "The cat in the hat@point{}
|
|
|
732 comes back" twice.
|
|
|
733 ---------- Buffer: foo ----------
|
|
|
734 @end group
|
|
|
735 @end example
|
|
|
736 @end defun
|
|
|
737
|
|
|
738 @defun skip-chars-backward character-set &optional limit buffer
|
|
|
739 This function moves point backward, skipping characters that match
|
|
|
740 @var{character-set}, until @var{limit}. It just like
|
|
|
741 @code{skip-chars-forward} except for the direction of motion.
|
|
|
742 @end defun
|
|
|
743
|
|
|
744 @node Excursions
|
|
|
745 @section Excursions
|
|
|
746 @cindex excursion
|
|
|
747
|
|
|
748 It is often useful to move point ``temporarily'' within a localized
|
|
|
749 portion of the program, or to switch buffers temporarily. This is
|
|
|
750 called an @dfn{excursion}, and it is done with the @code{save-excursion}
|
|
|
751 special form. This construct saves the current buffer and its values of
|
|
|
752 point and the mark so they can be restored after the completion of the
|
|
|
753 excursion.
|
|
|
754
|
|
|
755 The forms for saving and restoring the configuration of windows are
|
|
|
756 described elsewhere (see @ref{Window Configurations} and @pxref{Frame
|
|
|
757 Configurations}).
|
|
|
758
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759 @defspec save-excursion forms@dots{}
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760 @cindex mark excursion
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761 @cindex point excursion
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762 @cindex current buffer excursion
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763 The @code{save-excursion} special form saves the identity of the current
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764 buffer and the values of point and the mark in it, evaluates
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765 @var{forms}, and finally restores the buffer and its saved values of
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766 point and the mark. All three saved values are restored even in case of
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767 an abnormal exit via @code{throw} or error (@pxref{Nonlocal Exits}).
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768
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769 The @code{save-excursion} special form is the standard way to switch
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770 buffers or move point within one part of a program and avoid affecting
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771 the rest of the program. It is used more than 500 times in the Lisp
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772 sources of XEmacs.
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773
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774 @code{save-excursion} does not save the values of point and the mark for
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775 other buffers, so changes in other buffers remain in effect after
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776 @code{save-excursion} exits.
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777
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778 @cindex window excursions
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779 Likewise, @code{save-excursion} does not restore window-buffer
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780 correspondences altered by functions such as @code{switch-to-buffer}.
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781 One way to restore these correspondences, and the selected window, is to
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782 use @code{save-window-excursion} inside @code{save-excursion}
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783 (@pxref{Window Configurations}).
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784
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785 The value returned by @code{save-excursion} is the result of the last of
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786 @var{forms}, or @code{nil} if no @var{forms} are given.
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787
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788 @example
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789 @group
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790 (save-excursion
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791 @var{forms})
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792 @equiv{}
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793 (let ((old-buf (current-buffer))
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794 (old-pnt (point-marker))
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795 (old-mark (copy-marker (mark-marker))))
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796 (unwind-protect
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797 (progn @var{forms})
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798 (set-buffer old-buf)
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799 (goto-char old-pnt)
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800 (set-marker (mark-marker) old-mark)))
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801 @end group
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802 @end example
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803 @end defspec
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804
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805 @defspec save-current-buffer forms@dots{}
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806 This special form is similar to @code{save-excursion} but it only
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280
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807 saves and restores the current buffer. Beginning with XEmacs 20.3,
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808 @code{save-current-buffer} is a primitive.
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809 @end defspec
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810
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811 @defspec with-current-buffer buffer forms@dots{}
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812 This special form evaluates @var{forms} with @var{buffer} as the current
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813 buffer. It returns the value of the last form.
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814 @end defspec
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815
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816 @defspec with-temp-file file forms@dots{}
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817 This special form creates a new buffer, evaluates @var{forms} there, and
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818 writes the buffer to @var{file}. It returns the value of the last form
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819 evaluated.
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0
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820 @end defspec
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821
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822 @defspec save-selected-window forms@dots{}
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823 This special form is similar to @code{save-excursion} but it saves and
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824 restores the selected window and nothing else.
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825 @end defspec
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826
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827 @node Narrowing
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828 @section Narrowing
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829 @cindex narrowing
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830 @cindex restriction (in a buffer)
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831 @cindex accessible portion (of a buffer)
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832
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833 @dfn{Narrowing} means limiting the text addressable by XEmacs editing
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834 commands to a limited range of characters in a buffer. The text that
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835 remains addressable is called the @dfn{accessible portion} of the
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836 buffer.
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837
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838 Narrowing is specified with two buffer positions which become the
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839 beginning and end of the accessible portion. For most editing commands
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840 and most Emacs primitives, these positions replace the values of the
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841 beginning and end of the buffer. While narrowing is in effect, no text
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842 outside the accessible portion is displayed, and point cannot move
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843 outside the accessible portion.
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844
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845 Values such as positions or line numbers, which usually count from the
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846 beginning of the buffer, do so despite narrowing, but the functions
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847 which use them refuse to operate on text that is inaccessible.
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848
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849 The commands for saving buffers are unaffected by narrowing; they save
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850 the entire buffer regardless of any narrowing.
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851
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852 @deffn Command narrow-to-region start end &optional buffer
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853 This function sets the accessible portion of @var{buffer} to start at
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854 @var{start} and end at @var{end}. Both arguments should be character
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855 positions. @var{buffer} defaults to the current buffer if omitted.
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856
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857 In an interactive call, @var{start} and @var{end} are set to the bounds
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858 of the current region (point and the mark, with the smallest first).
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859 @end deffn
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860
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861 @deffn Command narrow-to-page &optional move-count
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862 This function sets the accessible portion of the current buffer to
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863 include just the current page. An optional first argument
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864 @var{move-count} non-@code{nil} means to move forward or backward by
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865 @var{move-count} pages and then narrow. The variable
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866 @code{page-delimiter} specifies where pages start and end
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867 (@pxref{Standard Regexps}).
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868
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869 In an interactive call, @var{move-count} is set to the numeric prefix
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870 argument.
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871 @end deffn
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872
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873 @deffn Command widen &optional buffer
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874 @cindex widening
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875 This function cancels any narrowing in @var{buffer}, so that the
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876 entire contents are accessible. This is called @dfn{widening}.
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877 It is equivalent to the following expression:
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878
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879 @example
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880 (narrow-to-region 1 (1+ (buffer-size)))
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881 @end example
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882
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883 @var{buffer} defaults to the current buffer if omitted.
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884 @end deffn
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885
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886 @defspec save-restriction body@dots{}
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887 This special form saves the current bounds of the accessible portion,
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888 evaluates the @var{body} forms, and finally restores the saved bounds,
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889 thus restoring the same state of narrowing (or absence thereof) formerly
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890 in effect. The state of narrowing is restored even in the event of an
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891 abnormal exit via @code{throw} or error (@pxref{Nonlocal Exits}).
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892 Therefore, this construct is a clean way to narrow a buffer temporarily.
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893
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894 The value returned by @code{save-restriction} is that returned by the
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895 last form in @var{body}, or @code{nil} if no body forms were given.
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896
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897 @c Wordy to avoid overfull hbox. --rjc 16mar92
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898 @strong{Caution:} it is easy to make a mistake when using the
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899 @code{save-restriction} construct. Read the entire description here
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900 before you try it.
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901
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902 If @var{body} changes the current buffer, @code{save-restriction} still
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903 restores the restrictions on the original buffer (the buffer whose
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904 restructions it saved from), but it does not restore the identity of the
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905 current buffer.
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906
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907 @code{save-restriction} does @emph{not} restore point and the mark; use
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908 @code{save-excursion} for that. If you use both @code{save-restriction}
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909 and @code{save-excursion} together, @code{save-excursion} should come
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910 first (on the outside). Otherwise, the old point value would be
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911 restored with temporary narrowing still in effect. If the old point
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912 value were outside the limits of the temporary narrowing, this would
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913 fail to restore it accurately.
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914
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915 The @code{save-restriction} special form records the values of the
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916 beginning and end of the accessible portion as distances from the
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917 beginning and end of the buffer. In other words, it records the amount
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918 of inaccessible text before and after the accessible portion.
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919
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920 This method yields correct results if @var{body} does further narrowing.
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921 However, @code{save-restriction} can become confused if the body widens
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922 and then make changes outside the range of the saved narrowing. When
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923 this is what you want to do, @code{save-restriction} is not the right
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924 tool for the job. Here is what you must use instead:
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925
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926 @example
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927 @group
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928 (let ((beg (point-min-marker))
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929 (end (point-max-marker)))
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930 (unwind-protect
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931 (progn @var{body})
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932 (save-excursion
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933 (set-buffer (marker-buffer beg))
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934 (narrow-to-region beg end))))
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935 @end group
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936 @end example
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937
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938 Here is a simple example of correct use of @code{save-restriction}:
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939
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940 @example
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941 @group
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942 ---------- Buffer: foo ----------
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|
943 This is the contents of foo
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944 This is the contents of foo
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945 This is the contents of foo@point{}
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946 ---------- Buffer: foo ----------
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947 @end group
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948
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949 @group
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950 (save-excursion
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951 (save-restriction
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952 (goto-char 1)
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953 (forward-line 2)
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954 (narrow-to-region 1 (point))
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955 (goto-char (point-min))
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956 (replace-string "foo" "bar")))
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957
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958 ---------- Buffer: foo ----------
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|
959 This is the contents of bar
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|
960 This is the contents of bar
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|
961 This is the contents of foo@point{}
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962 ---------- Buffer: foo ----------
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963 @end group
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964 @end example
|
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965 @end defspec
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