2 * Copyright (C) 1984-2015 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, see the README file.
12 * Routines dealing with the "position" table.
13 * This is a table which tells the position (in the input file) of the
14 * first char on each currently displayed line.
16 * {{ The position table is scrolled by moving all the entries.
17 * Would be better to have a circular table
18 * and just change a couple of pointers. }}
24 static POSITION *table = NULL; /* The position table */
25 static int table_size;
27 extern int sc_width, sc_height;
30 * Return the starting file position of a line displayed on the screen.
31 * The line may be specified as a line number relative to the top
32 * of the screen, but is usually one of these special cases:
33 * the top (first) line on the screen
34 * the second line on the screen
35 * the bottom line on the screen
36 * the line after the bottom line on the screen
45 where = sc_height - 2;
48 where = sc_height - 1;
51 where = (sc_height - 1) / 2;
53 return (table[where]);
57 * Add a new file position to the bottom of the position table.
66 * Scroll the position table up.
68 for (i = 1; i < sc_height; i++)
69 table[i-1] = table[i];
70 table[sc_height - 1] = pos;
74 * Add a new file position to the top of the position table.
83 * Scroll the position table down.
85 for (i = sc_height - 1; i > 0; i--)
86 table[i] = table[i-1];
91 * Initialize the position table, done whenever we clear the screen.
98 for (i = 0; i < sc_height; i++)
99 table[i] = NULL_POSITION;
103 * Allocate or reallocate the position table.
108 struct scrpos scrpos;
110 if (sc_height <= table_size)
113 * If we already have a table, remember the first line in it
114 * before we free it, so we can copy that line to the new table.
121 scrpos.pos = NULL_POSITION;
122 table = (POSITION *) ecalloc(sc_height, sizeof(POSITION));
123 table_size = sc_height;
125 if (scrpos.pos != NULL_POSITION)
126 table[scrpos.ln-1] = scrpos.pos;
130 * See if the byte at a specified position is currently on the screen.
131 * Check the position table to see if the position falls within its range.
132 * Return the position table entry if found, -1 if not.
142 for (i = 1; i < sc_height; i++)
149 * See if the entire screen is empty.
154 return (empty_lines(0, sc_height-1));
164 for (i = s; i <= e; i++)
165 if (table[i] != NULL_POSITION && table[i] != 0)
171 * Get the current screen position.
172 * The screen position consists of both a file position and
173 * a screen line number where the file position is placed on the screen.
174 * Normally the screen line number is 0, but if we are positioned
175 * such that the top few lines are empty, we may have to set
176 * the screen line to a number > 0.
180 struct scrpos *scrpos;
185 * Find the first line on the screen which has something on it,
186 * and return the screen line number and the file position.
188 for (i = 0; i < sc_height; i++)
189 if (table[i] != NULL_POSITION)
192 scrpos->pos = table[i];
196 * The screen is empty.
198 scrpos->pos = NULL_POSITION;
202 * Adjust a screen line number to be a simple positive integer
203 * in the range { 0 .. sc_height-2 }.
204 * (The bottom line, sc_height-1, is reserved for prompts, etc.)
205 * The given "sline" may be in the range { 1 .. sc_height-1 }
206 * to refer to lines relative to the top of the screen (starting from 1),
207 * or it may be in { -1 .. -(sc_height-1) } to refer to lines
208 * relative to the bottom of the screen.
215 * Negative screen line number means
216 * relative to the bottom of the screen.
221 * Can't be less than 1 or greater than sc_height-1.
225 if (sline >= sc_height)
226 sline = sc_height - 1;
228 * Return zero-based line number, not one-based.