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| author | Henry Thompson <ht@markup.co.uk> |
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| date | Thu, 16 Dec 2021 18:48:58 +0000 |
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| rev | line source |
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| 428 | 1 |
| 2 @node Display, Search, Registers, Top | |
| 3 @chapter Controlling the Display | |
| 4 | |
| 5 Since only part of a large buffer fits in the window, XEmacs tries to show | |
| 6 the part that is likely to be interesting. The display control commands | |
| 7 allow you to specify which part of the text you want to see. | |
| 8 | |
| 9 @table @kbd | |
| 10 @item C-l | |
| 11 Clear frame and redisplay, scrolling the selected window to center | |
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12 point vertically within it (@code{recenter-top-bottom}). |
| 428 | 13 @item C-v |
| 14 @itemx pgdn | |
| 15 @itemx next | |
| 16 Scroll forward (a windowful or a specified number of lines) (@code{scroll-up}). | |
| 17 On most X keyboards, you can get this functionality using the key | |
| 18 labelled @samp{Page Down}, which generates either @kbd{next} or @kbd{pgdn}. | |
| 19 @item M-v | |
| 20 @itemx pgup | |
| 21 @itemx prior | |
| 22 Scroll backward (@code{scroll-down}). On most X keyboards, you can get | |
| 23 this functionality using the key labelled @samp{Page Up}, which | |
| 24 generates either @kbd{prior} or @kbd{pgup}. | |
| 25 @item @var{arg} C-l | |
| 26 Scroll so point is on line @var{arg} (@code{recenter}). | |
| 27 @item C-x < | |
| 28 @itemx C-pgdn | |
| 29 @itemx C-next | |
| 30 Scroll text in current window to the left (@code{scroll-left}). | |
| 31 @item C-x > | |
| 32 @itemx C-pgup | |
| 33 @itemx C-prior | |
| 34 Scroll to the right (@code{scroll-right}). | |
| 35 @item C-x $ | |
| 36 Make deeply indented lines invisible (@code{set-selective-display}). | |
| 37 @end table | |
| 38 | |
| 39 @menu | |
| 40 * Scrolling:: Moving text up and down in a window. | |
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41 * Recentering:: A scroll command that centers the current line. |
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42 * Automatic Scrolling:: Redisplay scrolls text automatically when needed. |
| 428 | 43 * Horizontal Scrolling:: Moving text left and right in a window. |
| 44 * Selective Display:: Hiding lines with lots of indentation. | |
| 45 * Display Vars:: Information on variables for customizing display. | |
| 46 @end menu | |
| 47 | |
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48 @node Scrolling, Recentering, Display, Display |
| 428 | 49 @section Scrolling |
| 50 | |
| 51 If a buffer contains text that is too large to fit entirely within the | |
| 52 window that is displaying the buffer, XEmacs shows a contiguous section of | |
| 53 the text. The section shown always contains point. | |
| 54 | |
| 55 @cindex scrolling | |
| 56 @dfn{Scrolling} means moving text up or down in the window so that | |
| 57 different parts of the text are visible. Scrolling forward means that text | |
| 58 moves up, and new text appears at the bottom. Scrolling backward moves | |
| 59 text down and new text appears at the top. | |
| 60 | |
| 61 Scrolling happens automatically if you move point past the bottom or top | |
| 62 of the window. You can also explicitly request scrolling with the commands | |
| 63 in this section. | |
| 64 | |
| 65 @ifinfo | |
| 66 @table @kbd | |
| 67 @item C-v | |
| 68 @itemx pgdn | |
| 69 @itemx next | |
| 70 Scroll forward (a windowful or a specified number of lines) (@code{scroll-up}). | |
| 71 @item M-v | |
| 72 @itemx pgup | |
| 73 @itemx prior | |
| 74 Scroll backward (@code{scroll-down}). | |
| 75 @end table | |
| 76 @end ifinfo | |
| 77 | |
| 78 @kindex C-v | |
| 79 @kindex M-v | |
| 80 @kindex pgup | |
| 81 @kindex pgdn | |
| 82 @kindex next | |
| 83 @kindex prior | |
| 84 @findex scroll-up | |
| 85 @findex scroll-down | |
| 86 The scrolling commands @kbd{C-v} and @kbd{M-v} let you move all the text | |
| 87 in the window up or down a few lines. @kbd{C-v} (@code{scroll-up}) with an | |
| 88 argument shows you that many more lines at the bottom of the window, moving | |
| 89 the text and point up together as @kbd{C-l} might. @kbd{C-v} with a | |
| 90 negative argument shows you more lines at the top of the window. | |
| 91 @kbd{Meta-v} (@code{scroll-down}) is like @kbd{C-v}, but moves in the | |
| 92 opposite direction.@refill | |
| 93 | |
| 94 @vindex next-screen-context-lines | |
| 95 To read the buffer a windowful at a time, use @kbd{C-v} with no | |
| 96 argument. @kbd{C-v} takes the last two lines at the bottom of the | |
| 97 window and puts them at the top, followed by nearly a whole windowful of | |
| 98 lines not previously visible. Point moves to the new top of the window | |
| 99 if it was in the text scrolled off the top. @kbd{M-v} with no argument | |
| 100 moves backward with similar overlap. The number of lines of overlap | |
| 101 across a @kbd{C-v} or @kbd{M-v} is controlled by the variable | |
| 102 @code{next-screen-context-lines}; by default, it is two. | |
| 103 | |
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104 @node Recentering, Automatic Scrolling, Scrolling, Display |
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105 @section Recentering |
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106 |
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107 @table @kbd |
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108 @item C-l |
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109 Scroll the selected window so the current line is the center-most text |
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110 line; on subsequent consecutive invocations, make the current line the |
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111 top line, the bottom line, and so on in cyclic order. Possibly |
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112 redisplay the screen too (@code{recenter-top-bottom}). |
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113 |
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114 @item M-x recenter |
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115 Scroll the selected window so the current line is the center-most text |
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116 line. Possibly redisplay the screen too. |
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117 |
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118 @item C-M-l |
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119 Scroll heuristically to bring useful information onto the screen |
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120 (@code{reposition-window}). |
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121 @end table |
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122 |
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123 @kindex C-l |
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124 @findex recenter-top-bottom |
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125 The @kbd{C-l} (@code{recenter-top-bottom}) command @dfn{recenters} |
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126 the selected window, scrolling it so that the current screen line is |
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127 exactly in the center of the window, or as close to the center as |
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128 possible. |
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129 |
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130 Typing @kbd{C-l} twice in a row (@kbd{C-l C-l}) scrolls the window |
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131 so that point is on the topmost screen line. Typing a third @kbd{C-l} |
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132 scrolls the window so that point is on the bottom-most screen line. |
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133 Each successive @kbd{C-l} cycles through these three positions. |
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134 |
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135 @vindex recenter-positions |
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136 You can change the cycling order by customizing the list variable |
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137 @code{recenter-positions}. Each list element should be the symbol |
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138 @code{top}, @code{middle}, or @code{bottom}, or a number; an integer |
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139 means to move the line to the specified screen line, while a |
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140 floating-point number between 0.0 and 1.0 specifies a percentage of |
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141 the screen space from the top of the window. The default, |
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142 @code{(middle top bottom)}, is the cycling order described above. |
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143 Furthermore, if you change the variable @code{scroll-margin} to a |
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144 non-zero value @var{n}, @kbd{C-l} always leaves at least @var{n} |
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145 screen lines between point and the top or bottom of the window |
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146 (@pxref{Automatic Scrolling}). |
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147 |
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148 You can also give @kbd{C-l} a prefix argument. A plain prefix |
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149 argument, @kbd{C-u C-l}, simply recenters point. A positive argument |
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150 @var{n} puts point @var{n} lines down from the top of the window. An |
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151 argument of zero puts point on the topmost line. A negative argument |
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152 @var{-n} puts point @var{n} lines from the bottom of the window. When |
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153 given an argument, @kbd{C-l} does not clear the screen or cycle |
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154 through different screen positions. |
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155 |
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156 @findex recenter |
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157 The more primitive command @kbd{M-x recenter} behaves like |
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158 @code{recenter-top-bottom}, but does not cycle among screen positions. |
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159 |
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160 @node Automatic Scrolling, Horizontal Scrolling, Recentering, Display |
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161 @section Automatic Scrolling |
| 428 | 162 |
| 163 @vindex scroll-step | |
| 164 Scrolling happens automatically if point has moved out of the visible | |
| 165 portion of the text when it is time to display. Usually scrolling is | |
| 166 done to put point vertically centered within the window. However, if | |
| 167 the variable @code{scroll-step} has a non-zero value, an attempt is made to | |
| 168 scroll the buffer by that many lines; if that is enough to bring point back | |
| 169 into visibility, that is what happens. | |
| 170 | |
| 171 Scrolling happens automatically if point has moved out of the visible | |
| 172 portion of the text when it is time to display. Usually scrolling is | |
| 173 done to put point vertically centered within the window. However, if | |
| 174 the variable @code{scroll-step} has a non-zero value, an attempt is made to | |
| 175 scroll the buffer by that many lines; if that is enough to bring point back | |
| 176 into visibility, that is what happens. | |
| 177 | |
| 178 @vindex scroll-conservatively | |
| 179 If you set @code{scroll-step} to a small value because you want to use | |
| 180 arrow keys to scroll the screen without recentering, the redisplay | |
| 181 preemption will likely make XEmacs keep recentering the screen when | |
| 182 scrolling fast, regardless of @code{scroll-step}. To prevent this, set | |
| 183 @code{scroll-conservatively} to a small value, which will have the | |
| 184 result of overriding the redisplay preemption. | |
| 185 | |
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186 @node Horizontal Scrolling, Selective Display, Automatic Scrolling, Display |
| 428 | 187 @section Horizontal Scrolling |
| 188 | |
| 189 @ifinfo | |
| 190 @table @kbd | |
| 191 @item C-x < | |
| 192 Scroll text in current window to the left (@code{scroll-left}). | |
| 193 @item C-x > | |
| 194 Scroll to the right (@code{scroll-right}). | |
| 195 @end table | |
| 196 @end ifinfo | |
| 197 | |
| 198 @kindex C-x < | |
| 199 @kindex C-x > | |
| 200 @findex scroll-left | |
| 201 @findex scroll-right | |
| 202 @cindex horizontal scrolling | |
| 203 The text in a window can also be scrolled horizontally. This means that | |
| 204 each line of text is shifted sideways in the window, and one or more | |
| 205 characters at the beginning of each line are not displayed at all. When a | |
| 206 window has been scrolled horizontally in this way, text lines are truncated | |
| 207 rather than continued (@pxref{Continuation Lines}), with a @samp{$} appearing | |
| 208 in the first column when there is text truncated to the left, and in the | |
| 209 last column when there is text truncated to the right. | |
| 210 | |
| 211 The command @kbd{C-x <} (@code{scroll-left}) scrolls the selected | |
| 212 window to the left by @var{n} columns with argument @var{n}. With no | |
| 213 argument, it scrolls by almost the full width of the window (two columns | |
| 214 less, to be precise). @kbd{C-x >} (@code{scroll-right}) scrolls | |
| 215 similarly to the right. The window cannot be scrolled any farther to | |
| 216 the right once it is displaying normally (with each line starting at the | |
| 217 window's left margin); attempting to do so has no effect. | |
| 218 | |
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219 @node Selective Display, Display Vars, Horizontal Scrolling, Display |
| 428 | 220 @section Selective Display |
| 221 @findex set-selective-display | |
| 222 @kindex C-x $ | |
| 223 | |
| 224 XEmacs can hide lines indented more than a certain number | |
| 225 of columns (you specify how many columns). This allows you to get an | |
| 226 overview of a part of a program. | |
| 227 | |
| 228 To hide lines, type @kbd{C-x $} (@code{set-selective-display}) with a | |
| 229 numeric argument @var{n}. (@xref{Arguments}, for information on giving | |
| 230 the argument.) Lines with at least @var{n} columns of indentation | |
| 231 disappear from the screen. The only indication of their presence are | |
| 232 three dots (@samp{@dots{}}), which appear at the end of each visible | |
| 233 line that is followed by one or more invisible ones.@refill | |
| 234 | |
| 235 The invisible lines are still present in the buffer, and most editing | |
| 236 commands see them as usual, so it is very easy to put point in the middle | |
| 237 of invisible text. When this happens, the cursor appears at the end of the | |
| 238 previous line, after the three dots. If point is at the end of the visible | |
| 239 line, before the newline that ends it, the cursor appears before the three | |
| 240 dots. | |
| 241 | |
| 242 The commands @kbd{C-n} and @kbd{C-p} move across the invisible lines | |
| 243 as if they were not there. | |
| 244 | |
| 245 To make everything visible again, type @kbd{C-x $} with no argument. | |
| 246 | |
| 247 @node Display Vars,, Selective Display, Display | |
| 248 @section Variables Controlling Display | |
| 249 | |
| 250 This section contains information for customization only. Beginning | |
| 251 users should skip it. | |
| 252 | |
| 253 @vindex no-redraw-on-reenter | |
| 254 When you reenter XEmacs after suspending, XEmacs normally clears the | |
| 255 screen and redraws the entire display. On some terminals with more than | |
| 256 one page of memory, it is possible to arrange the termcap entry so that | |
| 257 the @samp{ti} and @samp{te} strings (output to the terminal when XEmacs | |
| 258 is entered and exited, respectively) switch between pages of memory so | |
| 259 as to use one page for XEmacs and another page for other output. In that | |
| 260 case, you might want to set the variable @code{no-redraw-on-reenter} to | |
| 261 non-@code{nil} so that XEmacs will assume, when resumed, that the screen | |
| 262 page it is using still contains what XEmacs last wrote there. | |
| 263 | |
| 264 @vindex echo-keystrokes | |
| 265 The variable @code{echo-keystrokes} controls the echoing of multi-character | |
| 266 keys; its value is the number of seconds of pause required to cause echoing | |
| 267 to start, or zero, meaning don't echo at all. @xref{Echo Area}. | |
| 268 | |
| 269 @vindex ctl-arrow | |
| 270 If the variable @code{ctl-arrow} is @code{nil}, control characters in the | |
| 271 buffer are displayed with octal escape sequences, all except newline and | |
| 272 tab. If its value is @code{t}, then control characters will be printed | |
| 273 with an up-arrow, for example @kbd{^A}. | |
| 274 | |
| 275 If its value is not @code{t} and not @code{nil}, then characters whose | |
| 276 code is greater than 160 (that is, the space character (32) with its | |
| 277 high bit set) will be assumed to be printable, and will be displayed | |
| 278 without alteration. This is the default when running under X Windows, | |
| 279 since XEmacs assumes an ISO/8859-1 character set (also known as | |
| 280 ``Latin1''). The @code{ctl-arrow} variable may also be set to an | |
| 281 integer, in which case all characters whose codes are greater than or | |
| 282 equal to that value will be assumed to be printable. | |
| 283 | |
| 284 Altering the value of @code{ctl-arrow} makes it local to the current | |
| 285 buffer; until that time, the default value is in effect. @xref{Locals}. | |
| 286 | |
| 287 @vindex tab-width | |
| 288 Normally, a tab character in the buffer is displayed as whitespace which | |
| 289 extends to the next display tab stop position, and display tab stops come | |
| 290 at intervals equal to eight spaces. The number of spaces per tab is | |
| 291 controlled by the variable @code{tab-width}, which is made local by | |
| 292 changing it, just like @code{ctl-arrow}. Note that how the tab character | |
| 293 in the buffer is displayed has nothing to do with the definition of | |
| 294 @key{TAB} as a command. | |
| 295 | |
| 296 @vindex selective-display-ellipses | |
| 297 If you set the variable @code{selective-display-ellipses} to @code{nil}, | |
| 298 the three dots at the end of a line that precedes invisible | |
| 299 lines do not appear. There is no visible indication of the invisible lines. | |
| 300 This variable becomes local automatically when set. |