2 * Copyright (C) 1984-2011 Mark Nudelman
4 * You may distribute under the terms of either the GNU General Public
5 * License or the Less License, as specified in the README file.
7 * For more information about less, or for information on how to
8 * contact the author, see the README file.
13 * Routines dealing with the "position" table.
14 * This is a table which tells the position (in the input file) of the
15 * first char on each currently displayed line.
17 * {{ The position table is scrolled by moving all the entries.
18 * Would be better to have a circular table
19 * and just change a couple of pointers. }}
25 static POSITION *table = NULL; /* The position table */
26 static int table_size;
28 extern int sc_width, sc_height;
31 * Return the starting file position of a line displayed on the screen.
32 * The line may be specified as a line number relative to the top
33 * of the screen, but is usually one of these special cases:
34 * the top (first) line on the screen
35 * the second line on the screen
36 * the bottom line on the screen
37 * the line after the bottom line on the screen
46 where = sc_height - 2;
49 where = sc_height - 1;
52 where = (sc_height - 1) / 2;
54 return (table[where]);
58 * Add a new file position to the bottom of the position table.
67 * Scroll the position table up.
69 for (i = 1; i < sc_height; i++)
70 table[i-1] = table[i];
71 table[sc_height - 1] = pos;
75 * Add a new file position to the top of the position table.
84 * Scroll the position table down.
86 for (i = sc_height - 1; i > 0; i--)
87 table[i] = table[i-1];
92 * Initialize the position table, done whenever we clear the screen.
99 for (i = 0; i < sc_height; i++)
100 table[i] = NULL_POSITION;
104 * Allocate or reallocate the position table.
109 struct scrpos scrpos;
111 if (sc_height <= table_size)
114 * If we already have a table, remember the first line in it
115 * before we free it, so we can copy that line to the new table.
122 scrpos.pos = NULL_POSITION;
123 table = (POSITION *) ecalloc(sc_height, sizeof(POSITION));
124 table_size = sc_height;
126 if (scrpos.pos != NULL_POSITION)
127 table[scrpos.ln-1] = scrpos.pos;
131 * See if the byte at a specified position is currently on the screen.
132 * Check the position table to see if the position falls within its range.
133 * Return the position table entry if found, -1 if not.
143 for (i = 1; i < sc_height; i++)
150 * See if the entire screen is empty.
155 return (empty_lines(0, sc_height-1));
165 for (i = s; i <= e; i++)
166 if (table[i] != NULL_POSITION)
172 * Get the current screen position.
173 * The screen position consists of both a file position and
174 * a screen line number where the file position is placed on the screen.
175 * Normally the screen line number is 0, but if we are positioned
176 * such that the top few lines are empty, we may have to set
177 * the screen line to a number > 0.
181 struct scrpos *scrpos;
186 * Find the first line on the screen which has something on it,
187 * and return the screen line number and the file position.
189 for (i = 0; i < sc_height; i++)
190 if (table[i] != NULL_POSITION)
193 scrpos->pos = table[i];
197 * The screen is empty.
199 scrpos->pos = NULL_POSITION;
203 * Adjust a screen line number to be a simple positive integer
204 * in the range { 0 .. sc_height-2 }.
205 * (The bottom line, sc_height-1, is reserved for prompts, etc.)
206 * The given "sline" may be in the range { 1 .. sc_height-1 }
207 * to refer to lines relative to the top of the screen (starting from 1),
208 * or it may be in { -1 .. -(sc_height-1) } to refer to lines
209 * relative to the bottom of the screen.
216 * Negative screen line number means
217 * relative to the bottom of the screen.
222 * Can't be less than 1 or greater than sc_height-1.
226 if (sline >= sc_height)
227 sline = sc_height - 1;
229 * Return zero-based line number, not one-based.