Obey line length while scrolling - scroll - scrollbackbuffer program for st

git clone git://git.suckless.org/scroll

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---

commit 247a9b042655291ab64aa9c43f9e89d820e932ee

parent 6d1a3bbbb870a303b47f790ba76146e61a4c7b6a

Author: Jochen Sprickerhof 

Date:   Wed, 29 Apr 2020 23:46:11 +0200

Obey line length while scrolling

Diffstat:
  M scroll.c                            |      23 +++++++++++++++--------

1 file changed, 15 insertions(+), 8 deletions(-)
---

diff --git a/scroll.c b/scroll.c

@@ -295,7 +295,7 @@ redraw()
 void
 scrollup(int n)
 {
-        int rows = 2, x, y;
+        int rows = 2, x, y, extra = 0;
         struct line *scrollend = bottom;
 
         if (bottom == NULL)
@@ -306,18 +306,24 @@ scrollup(int n)
         if (n < 0) /* scroll by fraction of ws.ws_row, but at least one line */
                 n = ws.ws_row > (-n) ? ws.ws_row / (-n) : 1;
 
-        /* wind back scrollend pointer by one page plus n */
-        for (; TAILQ_NEXT(scrollend, entries) != NULL &&
-            rows < y + n; rows++)
+        /* wind back scrollend pointer by the current screen */
+        while (rows < y && TAILQ_NEXT(scrollend, entries) != NULL) {
                 scrollend = TAILQ_NEXT(scrollend, entries);
-
-        rows -= y;
+                rows += (scrollend->len - 1) / ws.ws_col + 1;
+        }
 
         if (rows <= 0)
                 return;
 
+        /* wind back scrollend pointer n lines */
+        for (rows = 0; rows + extra < n &&
+            TAILQ_NEXT(scrollend, entries) != NULL; rows++) {
+                scrollend = TAILQ_NEXT(scrollend, entries);
+                extra += (scrollend->len - 1) / ws.ws_col;
+        }
+
         /* move the text in terminal rows lines down */
-        dprintf(STDOUT_FILENO, "\033[%dT", rows);
+        dprintf(STDOUT_FILENO, "\033[%dT", n);
         /* set cursor position to upper left corner */
         write(STDOUT_FILENO, "\033[0;0H", 6);
         /* hide cursor */
@@ -357,9 +363,10 @@ scrolldown(char *buf, size_t size, int n)
 
         bottom = TAILQ_PREV(bottom, tailhead, entries);
         /* print n lines */
-        for (; n > 0 && bottom != NULL && bottom != TAILQ_FIRST(&head); n--) {
+        while (n > 0 && bottom != NULL && bottom != TAILQ_FIRST(&head)) {
                 bottom = TAILQ_PREV(bottom, tailhead, entries);
                 write(STDOUT_FILENO, bottom->buf, bottom->size);
+                n -= (bottom->len - 1) / ws.ws_col + 1;
         }
         if (n > 0 && bottom == TAILQ_FIRST(&head)) {
                 write(STDOUT_FILENO, "\033[?25h", 6);        /* show cursor */