multigrid: reset win scrolling after swap message

4 files changed, 22 insertions, 12 deletions

diff --git a/src/nvim/globals.h b/src/nvim/globals.h
index ccdf8f87ab..f47697b190 100644
--- a/src/nvim/globals.h
+++ b/src/nvim/globals.h
@@ -194,12 +194,15 @@ EXTERN int compl_cont_status INIT(= 0);
 EXTERN int cmdmsg_rl INIT(= false);  // cmdline is drawn right to left
 EXTERN int msg_col;
 EXTERN int msg_row;
-EXTERN int msg_scrolled;        /* Number of screen lines that windows have
-                                * scrolled because of printing messages. */
-EXTERN int msg_scrolled_ign INIT(= FALSE);
-/* when TRUE don't set need_wait_return in
-   msg_puts_attr() when msg_scrolled is
-   non-zero */
+EXTERN int msg_scrolled;        // Number of screen lines that windows have
+                                // scrolled because of printing messages.
+// when true don't set need_wait_return in msg_puts_attr()
+// when msg_scrolled is non-zero
+EXTERN bool msg_scrolled_ign INIT(= false);
+// Whether the screen is damaged due to scrolling. Sometimes msg_scrolled
+// is reset before the screen is redrawn, so we need to keep track of this.
+EXTERN bool msg_did_scroll INIT(= false);
+
 
 EXTERN char_u   *keep_msg INIT(= NULL);     /* msg to be shown after redraw */
 EXTERN int keep_msg_attr INIT(= 0);         /* highlight attr for keep_msg */
diff --git a/src/nvim/memline.c b/src/nvim/memline.c
index 4c4f7d65bd..662eda3c7c 100644
--- a/src/nvim/memline.c
+++ b/src/nvim/memline.c
@@ -3412,7 +3412,9 @@ static char *findswapname(buf_T *buf, char **dirp, char *old_fname,
 # endif
             xfree(name);
 
-            /* pretend screen didn't scroll, need redraw anyway */
+            // pretend screen didn't scroll, need redraw anyway
+            // TODO(bfredl): when doing the message grid refactor,
+            // simplify this special case.
             msg_scrolled = 0;
             redraw_all_later(NOT_VALID);
           }
diff --git a/src/nvim/message.c b/src/nvim/message.c
index 1330460867..4552999256 100644
--- a/src/nvim/message.c
+++ b/src/nvim/message.c
@@ -1960,8 +1960,9 @@ int msg_scrollsize(void)
  */
 static void msg_scroll_up(void)
 {
-  if (msg_scrolled == 0) {
+  if (!msg_did_scroll) {
     ui_call_win_scroll_over_start();
+    msg_did_scroll = true;
   }
   if (dy_flags & DY_MSGSEP) {
     if (msg_scrolled == 0) {
diff --git a/src/nvim/screen.c b/src/nvim/screen.c
index 7252289e0e..759eefaecc 100644
--- a/src/nvim/screen.c
+++ b/src/nvim/screen.c
@@ -307,11 +307,15 @@ void update_screen(int type)
   ++display_tick;           /* let syntax code know we're in a next round of
                              * display updating */
 
-  /*
-   * if the screen was scrolled up when displaying a message, scroll it down
-   */
-  if (msg_scrolled) {
+  // Tricky: vim code can reset msg_scrolled behind our back, so need
+  // separate bookkeeping for now.
+  if (msg_did_scroll) {
     ui_call_win_scroll_over_reset();
+    msg_did_scroll = false;
+  }
+
+  // if the screen was scrolled up when displaying a message, scroll it down
+  if (msg_scrolled) {
     clear_cmdline = true;
     if (dy_flags & DY_MSGSEP) {
       int valid = MAX(Rows - msg_scrollsize(), 0);