Clip the 'lines' parameter to scroll() at the size of the scroll

window. scroll() iterates that many times, so this prevents a tedious
wait if you give a very large parameter to ESC[L or ESC[M, for
example.

A side effect is that very large requests for upward scrolling in a
context that affects the scrollback will not actually wipe out the
whole scrollback: instead they push just the current lines of the
screen into the scrollback, and don't continue on to fill it up with
endless boring blank lines. I think this is likely to be more useful
in general, since it avoids wiping out lots of useful scrollback data
by mistake. I can imagine that people might have been using it
precisely _to_ wipe the scrollback in some situations, but if so then
they should use CSI 3 J instead.

git-svn-id: svn://svn.tartarus.org/sgt/putty@9677 cda61777-01e9-0310-a592-d414129be87e

diff --git a/terminal.c b/terminal.c
index 72bfbc9..febd897 100644 (file)
--- a/terminal.c
+++ b/terminal.c
@@ -1978,7 +1978,7 @@ static void check_selection(Terminal *term, pos from, pos to)
 static void scroll(Terminal *term, int topline, int botline, int lines, int sb)
 {
     termline *line;
-    int i, seltop;
+    int i, seltop, scrollwinsize;
 #ifdef OPTIMISE_SCROLL
     int olddisptop, shift;
 #endif /* OPTIMISE_SCROLL */
@@ -1990,8 +1990,14 @@ static void scroll(Terminal *term, int topline, int botline, int lines, int sb)
     olddisptop = term->disptop;
     shift = lines;
 #endif /* OPTIMISE_SCROLL */
+
+    scrollwinsize = botline - topline + 1;
+
     if (lines < 0) {
-       while (lines < 0) {
+        lines = -lines;
+        if (lines > scrollwinsize)
+            lines = scrollwinsize;
+       while (lines-- > 0) {
            line = delpos234(term->screen, botline);
             resizeline(term, line, term->cols);
            for (i = 0; i < term->cols; i++)
@@ -2013,11 +2019,11 @@ static void scroll(Terminal *term, int topline, int botline, int lines, int sb)
                    term->selend.x = 0;
                }
            }
-
-           lines++;
        }
     } else {
-       while (lines > 0) {
+        if (lines > scrollwinsize)
+            lines = scrollwinsize;
+       while (lines-- > 0) {
            line = delpos234(term->screen, topline);
 #ifdef TERM_CC_DIAGS
            cc_check(line);
@@ -2103,8 +2109,6 @@ static void scroll(Terminal *term, int topline, int botline, int lines, int sb)
                    }
                }
            }
-
-           lines--;
        }
     }
 #ifdef OPTIMISE_SCROLL