fix(api): fix inconsistent behavior of topline touched in recent refactor

The change in #24824 0081549 was not a regression, however it was an
incomplete change. Unfortunately some common plugins come to depend on
this exising self-inconsistent behavior. These plugins are going to need
to update for 0.10

nvim_buf_set_lines used to NOT adjust the topline correctly if a buffer
was displayed in just one window. However, if displayed in multiple
windows, it was correctly adjusted for any window not deemed the
current window for the buffer (which could be an arbitrary choice if the
buffer was not already current, as noted in the last rafactor)

This fixes so that all windows have their topline adjusted. The added
tests show this behavior, which should be the reasonable one.

1 files changed, 6 insertions, 4 deletions

diff --git a/src/nvim/api/buffer.c b/src/nvim/api/buffer.c
index 775b6e8ea7..d36f0dd050 100644
--- a/src/nvim/api/buffer.c
+++ b/src/nvim/api/buffer.c
@@ -472,9 +472,11 @@ void nvim_buf_set_lines(uint64_t channel_id, Buffer buffer, Integer start, Integ
                  kExtmarkUndo);
 
   changed_lines(buf, (linenr_T)start, 0, (linenr_T)end, (linenr_T)extra, true);
-  if (curwin->w_buffer == buf) {
-    // mark_adjust_buf handles non-current windows
-    fix_cursor(curwin, (linenr_T)start, (linenr_T)end, (linenr_T)extra);
+
+  FOR_ALL_TAB_WINDOWS(tp, win) {
+    if (win->w_buffer == buf) {
+      fix_cursor(win, (linenr_T)start, (linenr_T)end, (linenr_T)extra);
+    }
   }
 
 end:
@@ -710,7 +712,7 @@ void nvim_buf_set_text(uint64_t channel_id, Buffer buffer, Integer start_row, In
   // changed range, and move any in the remainder of the buffer.
   // Do not adjust any cursors. need to use column-aware logic (below)
   mark_adjust_buf(buf, (linenr_T)start_row, (linenr_T)end_row, MAXLNUM, (linenr_T)extra,
-                  true, false, kExtmarkNOOP);
+                  true, true, kExtmarkNOOP);
 
   extmark_splice(buf, (int)start_row - 1, (colnr_T)start_col,
                  (int)(end_row - start_row), col_extent, old_byte,