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1
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2 @node Display, Search, Registers, Top
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3 @chapter Controlling the Display
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4
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5 Since only part of a large buffer fits in the window, XEmacs tries to show
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6 the part that is likely to be interesting. The display control commands
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7 allow you to specify which part of the text you want to see.
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8
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9 @table @kbd
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10 @item C-l
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11 Clear frame and redisplay, scrolling the selected window to center
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12 point vertically within it (@code{recenter}).
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13 @item C-v
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14 @itemx pgdn
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15 @itemx next
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16 Scroll forward (a windowful or a specified number of lines) (@code{scroll-up}).
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17 On most X keyboards, you can get this functionality using the key
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18 labelled @samp{Page Down}, which generates either @kbd{next} or @kbd{pgdn}.
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19 @item M-v
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20 @itemx pgup
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21 @itemx prior
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22 Scroll backward (@code{scroll-down}). On most X keyboards, you can get
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23 this functionality using the key labelled @samp{Page Up}, which
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24 generates either @kbd{prior} or @kbd{pgup}.
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25 @item @var{arg} C-l
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26 Scroll so point is on line @var{arg} (@code{recenter}).
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27 @item C-x <
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28 @itemx C-pgdn
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29 @itemx C-next
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30 Scroll text in current window to the left (@code{scroll-left}).
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31 @item C-x >
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32 @itemx C-pgup
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33 @itemx C-prior
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34 Scroll to the right (@code{scroll-right}).
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35 @item C-x $
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36 Make deeply indented lines invisible (@code{set-selective-display}).
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37 @end table
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38
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39 @menu
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40 * Scrolling:: Moving text up and down in a window.
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41 * Horizontal Scrolling:: Moving text left and right in a window.
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42 * Selective Display:: Hiding lines with lots of indentation.
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43 * Display Vars:: Information on variables for customizing display.
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44 @end menu
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45
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46 @node Scrolling, Horizontal Scrolling, Display, Display
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47 @section Scrolling
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48
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49 If a buffer contains text that is too large to fit entirely within the
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50 window that is displaying the buffer, XEmacs shows a contiguous section of
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51 the text. The section shown always contains point.
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52
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53 @cindex scrolling
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54 @dfn{Scrolling} means moving text up or down in the window so that
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55 different parts of the text are visible. Scrolling forward means that text
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56 moves up, and new text appears at the bottom. Scrolling backward moves
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57 text down and new text appears at the top.
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58
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59 Scrolling happens automatically if you move point past the bottom or top
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60 of the window. You can also explicitly request scrolling with the commands
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61 in this section.
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62
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63 @ifinfo
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64 @table @kbd
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65 @item C-l
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66 Clear frame and redisplay, scrolling the selected window to center
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67 point vertically within it (@code{recenter}).
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68 @item C-v
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69 @itemx pgdn
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70 @itemx next
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71 Scroll forward (a windowful or a specified number of lines) (@code{scroll-up}).
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72 @item M-v
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73 @itemx pgup
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74 @itemx prior
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75 Scroll backward (@code{scroll-down}).
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76 @item @var{arg} C-l
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77 Scroll so point is on line @var{arg} (@code{recenter}).
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78 @end table
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79 @end ifinfo
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80
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81 @kindex C-l
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82 @findex recenter
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83 The most basic scrolling command is @kbd{C-l} (@code{recenter}) with no
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84 argument. It clears the entire frame and redisplays all windows. In
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85 addition, it scrolls the selected window so that point is halfway down
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86 from the top of the window.
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87
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88 @kindex C-v
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89 @kindex M-v
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90 @kindex pgup
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91 @kindex pgdn
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92 @kindex next
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93 @kindex prior
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94 @findex scroll-up
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95 @findex scroll-down
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96 The scrolling commands @kbd{C-v} and @kbd{M-v} let you move all the text
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97 in the window up or down a few lines. @kbd{C-v} (@code{scroll-up}) with an
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98 argument shows you that many more lines at the bottom of the window, moving
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99 the text and point up together as @kbd{C-l} might. @kbd{C-v} with a
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100 negative argument shows you more lines at the top of the window.
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101 @kbd{Meta-v} (@code{scroll-down}) is like @kbd{C-v}, but moves in the
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102 opposite direction.@refill
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103
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104 @vindex next-screen-context-lines
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105 To read the buffer a windowful at a time, use @kbd{C-v} with no
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106 argument. @kbd{C-v} takes the last two lines at the bottom of the
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107 window and puts them at the top, followed by nearly a whole windowful of
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108 lines not previously visible. Point moves to the new top of the window
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109 if it was in the text scrolled off the top. @kbd{M-v} with no argument
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110 moves backward with similar overlap. The number of lines of overlap
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111 across a @kbd{C-v} or @kbd{M-v} is controlled by the variable
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112 @code{next-screen-context-lines}; by default, it is two.
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113
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114 Another way to scroll is using @kbd{C-l} with a numeric argument.
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115 @kbd{C-l} does not clear the frame when given an argument; it only
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116 scrolls the selected window. With a positive argument @var{n}, @kbd{C-l}
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117 repositions text to put point @var{n} lines down from the top. An
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118 argument of zero puts point on the very top line. Point does not move
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119 with respect to the text; rather, the text and point move rigidly on the
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120 frame. @kbd{C-l} with a negative argument puts point that many lines
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121 from the bottom of the window. For example, @kbd{C-u - 1 C-l} puts
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122 point on the bottom line, and @kbd{C-u - 5 C-l} puts it five lines from
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123 the bottom. Just @kbd{C-u} as argument, as in @kbd{C-u C-l}, scrolls
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124 point to the center of the frame.
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125
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126 @vindex scroll-step
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127 Scrolling happens automatically if point has moved out of the visible
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128 portion of the text when it is time to display. Usually scrolling is
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129 done to put point vertically centered within the window. However, if
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130 the variable @code{scroll-step} has a non-zero value, an attempt is made to
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131 scroll the buffer by that many lines; if that is enough to bring point back
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132 into visibility, that is what happens.
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133
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134 Scrolling happens automatically if point has moved out of the visible
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135 portion of the text when it is time to display. Usually scrolling is
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136 done to put point vertically centered within the window. However, if
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137 the variable @code{scroll-step} has a non-zero value, an attempt is made to
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138 scroll the buffer by that many lines; if that is enough to bring point back
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139 into visibility, that is what happens.
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140
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141 @vindex scroll-conservatively
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142 If you set @code{scroll-step} to a small value because you want to use
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143 arrow keys to scroll the screen without recentering, the redisplay
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144 preemption will likely make XEmacs keep recentering the screen when
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145 scrolling fast, regardless of @code{scroll-step}. To prevent this, set
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146 @code{scroll-conservatively} to a small value, which will have the
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147 result of overriding the redisplay preemption.
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148
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149 @node Horizontal Scrolling,, Scrolling, Display
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150 @section Horizontal Scrolling
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151
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152 @ifinfo
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153 @table @kbd
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154 @item C-x <
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155 Scroll text in current window to the left (@code{scroll-left}).
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156 @item C-x >
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157 Scroll to the right (@code{scroll-right}).
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158 @end table
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159 @end ifinfo
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160
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161 @kindex C-x <
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162 @kindex C-x >
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163 @findex scroll-left
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164 @findex scroll-right
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165 @cindex horizontal scrolling
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166 The text in a window can also be scrolled horizontally. This means that
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167 each line of text is shifted sideways in the window, and one or more
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168 characters at the beginning of each line are not displayed at all. When a
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169 window has been scrolled horizontally in this way, text lines are truncated
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170 rather than continued (@pxref{Continuation Lines}), with a @samp{$} appearing
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171 in the first column when there is text truncated to the left, and in the
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172 last column when there is text truncated to the right.
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173
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174 The command @kbd{C-x <} (@code{scroll-left}) scrolls the selected
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175 window to the left by @var{n} columns with argument @var{n}. With no
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176 argument, it scrolls by almost the full width of the window (two columns
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177 less, to be precise). @kbd{C-x >} (@code{scroll-right}) scrolls
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178 similarly to the right. The window cannot be scrolled any farther to
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179 the right once it is displaying normally (with each line starting at the
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180 window's left margin); attempting to do so has no effect.
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181
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182 @node Selective Display, Display Vars, Display, Display
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183 @section Selective Display
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184 @findex set-selective-display
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185 @kindex C-x $
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186
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187 XEmacs can hide lines indented more than a certain number
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188 of columns (you specify how many columns). This allows you to get an
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189 overview of a part of a program.
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190
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191 To hide lines, type @kbd{C-x $} (@code{set-selective-display}) with a
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192 numeric argument @var{n}. (@xref{Arguments}, for information on giving
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193 the argument.) Lines with at least @var{n} columns of indentation
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194 disappear from the screen. The only indication of their presence are
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195 three dots (@samp{@dots{}}), which appear at the end of each visible
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196 line that is followed by one or more invisible ones.@refill
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197
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198 The invisible lines are still present in the buffer, and most editing
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199 commands see them as usual, so it is very easy to put point in the middle
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200 of invisible text. When this happens, the cursor appears at the end of the
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201 previous line, after the three dots. If point is at the end of the visible
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202 line, before the newline that ends it, the cursor appears before the three
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203 dots.
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204
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205 The commands @kbd{C-n} and @kbd{C-p} move across the invisible lines
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206 as if they were not there.
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207
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208 To make everything visible again, type @kbd{C-x $} with no argument.
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209
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210 @node Display Vars,, Selective Display, Display
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211 @section Variables Controlling Display
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212
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213 This section contains information for customization only. Beginning
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214 users should skip it.
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215
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216 @vindex no-redraw-on-reenter
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217 When you reenter XEmacs after suspending, XEmacs normally clears the
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218 screen and redraws the entire display. On some terminals with more than
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219 one page of memory, it is possible to arrange the termcap entry so that
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220 the @samp{ti} and @samp{te} strings (output to the terminal when XEmacs
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221 is entered and exited, respectively) switch between pages of memory so
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222 as to use one page for XEmacs and another page for other output. In that
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223 case, you might want to set the variable @code{no-redraw-on-reenter} to
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224 non-@code{nil} so that XEmacs will assume, when resumed, that the screen
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225 page it is using still contains what XEmacs last wrote there.
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226
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227 @vindex echo-keystrokes
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228 The variable @code{echo-keystrokes} controls the echoing of multi-character
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229 keys; its value is the number of seconds of pause required to cause echoing
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230 to start, or zero, meaning don't echo at all. @xref{Echo Area}.
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231
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232 @vindex ctl-arrow
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233 If the variable @code{ctl-arrow} is @code{nil}, control characters in the
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234 buffer are displayed with octal escape sequences, all except newline and
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235 tab. If its value is @code{t}, then control characters will be printed
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236 with an up-arrow, for example @kbd{^A}.
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237
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238 If its value is not @code{t} and not @code{nil}, then characters whose
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239 code is greater than 160 (that is, the space character (32) with its
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240 high bit set) will be assumed to be printable, and will be displayed
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241 without alteration. This is the default when running under X Windows,
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242 since XEmacs assumes an ISO/8859-1 character set (also known as
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243 ``Latin1''). The @code{ctl-arrow} variable may also be set to an
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244 integer, in which case all characters whose codes are greater than or
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245 equal to that value will be assumed to be printable.
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246
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247 Altering the value of @code{ctl-arrow} makes it local to the current
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248 buffer; until that time, the default value is in effect. @xref{Locals}.
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249
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250 @vindex tab-width
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251 Normally, a tab character in the buffer is displayed as whitespace which
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252 extends to the next display tab stop position, and display tab stops come
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253 at intervals equal to eight spaces. The number of spaces per tab is
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254 controlled by the variable @code{tab-width}, which is made local by
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255 changing it, just like @code{ctl-arrow}. Note that how the tab character
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256 in the buffer is displayed has nothing to do with the definition of
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257 @key{TAB} as a command.
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258
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259 @vindex selective-display-ellipses
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260 If you set the variable @code{selective-display-ellipses} to @code{nil},
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261 the three dots at the end of a line that precedes invisible
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262 lines do not appear. There is no visible indication of the invisible lines.
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263 This variable becomes local automatically when set.
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