Alternate scrolling rules.

diff --git a/src/nnn.c b/src/nnn.c
index 75df0e7f8a3de9b062ea49cb6876cc4ecc5131d2..f2741b6069c75cfe6b0882dc5aade8a982576e31 100644 (file)
--- a/src/nnn.c
+++ b/src/nnn.c
@@ -473,6 +473,7 @@ static void redraw(char *path);
 static int spawn(char *file, char *arg1, char *arg2, const char *dir, uchar flag);
 static int (*nftw_fn)(const char *fpath, const struct stat *sb, int typeflag, struct FTW *ftwbuf);
 static int dentfind(const char *fname, int n);
+static void move_cursor(int target, int ignore_scrolloff);
 
 /* Functions */
 
@@ -1656,7 +1657,7 @@ end:
        if (*ch != '\t')
                g_ctx[cfg.curctx].c_fltr[0] = g_ctx[cfg.curctx].c_fltr[1] = '\0';
 
-       curscroll = MAX(0, cur - SCROLLOFF);
+       move_cursor(cur, 0);
 
        curs_set(FALSE);
        settimeout();
@@ -2881,11 +2882,33 @@ static void populate(char *path, char *lastname)
        /* Find cur from history */
        /* No NULL check for lastname, always points to an array */
        if (!*lastname)
-               cur = 0;
+               move_cursor(0, 0);
        else
-               cur = dentfind(lastname, ndents);
+               move_cursor(dentfind(lastname, ndents), 0);
+}
 
-       curscroll = MAX(0, cur - SCROLLOFF);
+static void move_cursor(int target, int ignore_scrolloff)
+{
+       int delta, scrolloff, onscreen = xlines - 4;
+       target = MAX(0, MIN(ndents - 1, target));
+       delta = target - cur;
+       cur = target;
+       if (!ignore_scrolloff) {
+               scrolloff = MIN(SCROLLOFF, onscreen >> 1);
+               /* 
+                * When ignore_scrolloff is 1, the cursor can jump into the scrolloff
+                * margin area, but when ignore_scrolloff is 0, act like a boa
+                * constrictor and squeeze the cursor towards the middle region of the
+                * screen by allowing it to move inward and disallowing it to move
+                * outward (deeper into the scrolloff margin area).
+                */
+               if (cur < curscroll + scrolloff && delta < 0)
+                       curscroll += delta;
+               else if (cur > curscroll + onscreen - scrolloff - 1 && delta > 0)
+                       curscroll += delta;
+       }
+       curscroll = MIN(curscroll, MIN(cur, ndents - onscreen));
+       curscroll = MAX(curscroll, MAX(cur - (onscreen - 1), 0));
 }
 
 static void redraw(char *path)
@@ -2895,7 +2918,6 @@ static void redraw(char *path)
 
        int ncols = (xcols <= PATH_MAX) ? xcols : PATH_MAX;
        int lastln = xlines, onscreen = xlines - 4;
-       int scrolloff = MIN(SCROLLOFF, onscreen >> 1);
        int i, attrs;
        char buf[12];
        char c;
@@ -2905,12 +2927,8 @@ static void redraw(char *path)
        /* Clear screen */
        erase();
 
-       if (ndents <= onscreen)
-               curscroll = 0;
-       else if (cur < curscroll + scrolloff)
-               curscroll = MAX(0, cur - scrolloff);
-       else if (cur > curscroll + onscreen - scrolloff - 1)
-               curscroll = MIN(ndents - onscreen, cur - onscreen + scrolloff + 1);
+       /* Enforce scroll/cursor invariants */
+       move_cursor(cur, 1);
 
 #ifdef DIR_LIMITED_COPY
        if (cfg.copymode)
@@ -3168,7 +3186,7 @@ nochange:
                                if (r >= ndents)
                                        goto nochange;
 
-                               cur = r;
+                               move_cursor(r, 1);
 
                                // Single click just selects, double click also opens
                                if (event.bstate != BUTTON1_DOUBLE_CLICKED)
@@ -3264,42 +3282,38 @@ nochange:
                                goto nochange;
                        }
                case SEL_NEXT:
-                       if (cur < ndents - 1)
-                               ++cur;
-                       else if (ndents)
-                               /* Roll over, set cursor to first entry */
-                               cur = 0;
+                       if (ndents)
+                               move_cursor((cur + 1) % ndents, 0);
                        break;
                case SEL_PREV:
-                       if (cur > 0)
-                               --cur;
-                       else if (ndents)
-                               /* Roll over, set cursor to last entry */
-                               cur = ndents - 1;
+                       if (ndents)
+                               move_cursor((cur + ndents - 1) % ndents, 0);
                        break;
                case SEL_PGDN: // fallthrough
+                       onscreen = xlines - 4;
+                       move_cursor(curscroll + (onscreen - 1), 1);
+                       curscroll += onscreen - 1;
+                       break;
                case SEL_CTRL_D:
                        onscreen = xlines - 4;
-                       r = sel == SEL_PGDN ? onscreen - 1 : onscreen >> 1;
-                       curscroll = MIN(ndents - onscreen, curscroll + r);
-                       cur = (curscroll == ndents - onscreen) ? cur + r :
-                               curscroll + MIN(SCROLLOFF, onscreen >> 1);
-                       cur = MIN(ndents - 1, cur);
+                       move_cursor(curscroll + (onscreen - 1), 1);
+                       curscroll += onscreen >> 1;
                        break;
                case SEL_PGUP: // fallthrough
+                       onscreen = xlines - 4;
+                       move_cursor(curscroll, 1);
+                       curscroll -= onscreen - 1;
+                       break;
                case SEL_CTRL_U:
                        onscreen = xlines - 4;
-                       r = sel == SEL_PGUP ? onscreen - 1 : onscreen >> 1;
-                       curscroll = MAX(0, curscroll - r);
-                       cur = (curscroll == 0) ? cur - r :
-                               curscroll + onscreen - MIN(SCROLLOFF, onscreen >> 1) - 1;
-                       cur = MAX(0, cur);
+                       move_cursor(curscroll, 1);
+                       curscroll -= onscreen >> 1;
                        break;
                case SEL_HOME:
-                       cur = 0;
+                       move_cursor(0, 1);
                        break;
                case SEL_END:
-                       cur = ndents - 1;
+                       move_cursor(ndents - 1, 1);
                        break;
                case SEL_CDHOME: // fallthrough
                case SEL_CDBEGIN: // fallthrough
@@ -3797,7 +3811,7 @@ nochange:
 
                        /* Don't optimize cur if filtering is on */
                        if (!cfg.filtermode && cur && access(newpath, F_OK) == -1)
-                               --cur;
+                               move_cursor(cur - 1, 0);
 
                        /* We reduce cur only if it is > 0, so it's at least 0 */
                        copycurname();