ncurses/tty/hardscroll.c

48 old screen (curscr) into a new screen (newscr) via vertical line moves.
50 Because the screen has a `grain' (there are insert/delete/scroll line
52 break the update algorithm into two pieces: a first stage that does only line
55 ncurses) that does only line transformations.
57 The common case we want hardware scrolling for is to handle line insertions
63 Now, to a discussion of the line-move computation.
67 Let a new line introduced by insertion, scrolling, or at the bottom of
68 the screen following a line delete be given the index -1.
71 the following possible line-oriented operations on the screen:
73 Insertion: inserts a line at a given screen row, forcing all lines below
74 to scroll forward.  The last screen line is lost.  For example, an insertion
75 at line 5 would produce: 0..4 -1 5..23.
77 Deletion: deletes a line at a given screen row, forcing all lines below
78 to scroll forward.  The last screen line is made new.  For example, a deletion
79 at line 7 would produce: 0..6 8..23 -1.
81 Scroll up: move a range of lines up 1.  The bottom line of the range
85 Scroll down: move a range of lines down 1.  The top line of the range
92 The key trick of this algorithm is that the original line indices described
94 structure, and stick to each line through scroll and insert/delete operations.
99 we can hand off to the second stage of the update algorithm, which does line
132 # An insertion (after line 12)
135 # A simple deletion (line 10)
167 /* OLDNUM(n) indicates which line will be shifted to the position n.
168    if OLDNUM(n) == _NEWINDEX, then the line n in new, not shifted from
291     char line[BUFSIZ], *st;
303 	if (fgets(line, sizeof(line), stdin) == (char *) NULL)
308 	if (line[0] == '#') {
309 	    (void) fputs(line, stderr);
312 	st = strtok(line, " ");