[hackers] [scroll] don't scroll if alternative screen is active || Jan Klemkow

[git]

commit db13d11496626604931053ac2d5a12f022efca43
Author:     Jan Klemkow <j.klem...@wemelug.de>
AuthorDate: Thu Apr 2 23:02:38 2020 +0200
Commit:     Jan Klemkow <j.klem...@wemelug.de>
CommitDate: Thu Apr 2 23:02:38 2020 +0200

    don't scroll if alternative screen is active

diff --git a/scroll.c b/scroll.c
index 69189ae..ceed4ef 100644
--- a/scroll.c
+++ b/scroll.c
@@ -58,6 +58,7 @@ pid_t child;
 int mfd;
 struct termios dfl;
 struct winsize ws;
+static bool altscreen = false; /* is alternative screen active */
 
 void
 die(const char *fmt, ...)
@@ -188,7 +189,6 @@ strelen(const char *buf, size_t size)
 bool
 isaltscreen(char c)
 {
-       static bool alt = false;
        static enum {CHAR, BREK, ESC} state = CHAR;
        static char buf[BUFSIZ];
        static size_t i = 0;
@@ -219,18 +219,18 @@ isaltscreen(char c)
                        if (strcmp(buf, "?1049h") == 0 ||
                            strcmp(buf, "?1047h") == 0 ||
                            strcmp(buf, "?47h"  ) == 0)
-                               alt = true;
+                               altscreen = true;
 
                        /* esc seq. disable alternative screen */
                        if (strcmp(buf, "?1049l") == 0 ||
                            strcmp(buf, "?1047l") == 0 ||
                            strcmp(buf, "?47l"  ) == 0)
-                               alt = false;
+                               altscreen = false;
                }
                break;
        }
 
-       return alt;
+       return altscreen;
 }
 
 void
@@ -389,11 +389,13 @@ main(int argc, char *argv[])
                        if (n <= 0 && errno != EINTR)
                                die("read:");
 
-                       if (strncmp(KB_SCROLL_UP, input, n) == 0 ||
-                           strncmp(MS_SCROLL_UP, input, n) == 0)
+                       if (!altscreen &&
+                           (strncmp(KB_SCROLL_UP, input, n) == 0 ||
+                           strncmp(MS_SCROLL_UP, input, n) == 0))
                                scrollup();
-                       else if (strncmp(KB_SCROLL_DOWN, input, n) == 0 ||
-                           strncmp(MS_SCROLL_DOWN, input, n) == 0)
+                       else if (!altscreen &&
+                           (strncmp(KB_SCROLL_DOWN, input, n) == 0 ||
+                           strncmp(MS_SCROLL_DOWN, input, n) == 0))
                                scrolldown(buf, pos);
                        else if (write(mfd, input, n) == -1)
                                die("write:");