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
44 where = sc_height - 2;
47 where = sc_height - 1;
50 where = (sc_height - 1) / 2;
52 return (table[where]);
56 * Add a new file position to the bottom of the position table.
59 add_forw_pos(POSITION pos)
64 * Scroll the position table up.
66 for (i = 1; i < sc_height; i++)
67 table[i-1] = table[i];
68 table[sc_height - 1] = pos;
72 * Add a new file position to the top of the position table.
75 add_back_pos(POSITION pos)
80 * Scroll the position table down.
82 for (i = sc_height - 1; i > 0; i--)
83 table[i] = table[i-1];
88 * Initialize the position table, done whenever we clear the screen.
95 for (i = 0; i < sc_height; i++)
96 table[i] = NULL_POSITION;
100 * Allocate or reallocate the position table.
105 struct scrpos scrpos;
107 if (sc_height <= table_size)
110 * If we already have a table, remember the first line in it
111 * before we free it, so we can copy that line to the new table.
118 scrpos.pos = NULL_POSITION;
119 table = (POSITION *) ecalloc(sc_height, sizeof(POSITION));
120 table_size = sc_height;
122 if (scrpos.pos != NULL_POSITION)
123 table[scrpos.ln-1] = scrpos.pos;
127 * See if the byte at a specified position is currently on the screen.
128 * Check the position table to see if the position falls within its range.
129 * Return the position table entry if found, -1 if not.
132 onscreen(POSITION pos)
138 for (i = 1; i < sc_height; i++)
145 * See if the entire screen is empty.
150 return (empty_lines(0, sc_height-1));
154 empty_lines(int s, int e)
158 for (i = s; i <= e; i++)
159 if (table[i] != NULL_POSITION && table[i] != 0)
165 * Get the current screen position.
166 * The screen position consists of both a file position and
167 * a screen line number where the file position is placed on the screen.
168 * Normally the screen line number is 0, but if we are positioned
169 * such that the top few lines are empty, we may have to set
170 * the screen line to a number > 0.
173 get_scrpos(struct scrpos *scrpos)
178 * Find the first line on the screen which has something on it,
179 * and return the screen line number and the file position.
181 for (i = 0; i < sc_height; i++)
182 if (table[i] != NULL_POSITION)
185 scrpos->pos = table[i];
189 * The screen is empty.
191 scrpos->pos = NULL_POSITION;
195 * Adjust a screen line number to be a simple positive integer
196 * in the range { 0 .. sc_height-2 }.
197 * (The bottom line, sc_height-1, is reserved for prompts, etc.)
198 * The given "sline" may be in the range { 1 .. sc_height-1 }
199 * to refer to lines relative to the top of the screen (starting from 1),
200 * or it may be in { -1 .. -(sc_height-1) } to refer to lines
201 * relative to the bottom of the screen.
207 * Negative screen line number means
208 * relative to the bottom of the screen.
213 * Can't be less than 1 or greater than sc_height-1.
217 if (sline >= sc_height)
218 sline = sc_height - 1;
220 * Return zero-based line number, not one-based.