feat(ui): indicate margins for the area used by win_viewport

Problem: using win_viewport for implementing smooth scrolling in an external
UI might run into problems when winbar or borders is used, as there is
no indication that the entire grid is not used for scrolled buffer text.

Solution: add `win_viewport_margins` event.

1 files changed, 4 insertions, 0 deletions

diff --git a/src/nvim/api/ui_events.in.h b/src/nvim/api/ui_events.in.h
index c2f02c34f8..2bd8792d71 100644
--- a/src/nvim/api/ui_events.in.h
+++ b/src/nvim/api/ui_events.in.h
@@ -118,6 +118,10 @@ void win_viewport(Integer grid, Window win, Integer topline, Integer botline, In
                   Integer curcol, Integer line_count, Integer scroll_delta)
   FUNC_API_SINCE(7) FUNC_API_CLIENT_IGNORE;
 
+void win_viewport_margins(Integer grid, Window win, Integer top, Integer bottom, Integer left,
+                          Integer right)
+  FUNC_API_SINCE(12) FUNC_API_CLIENT_IGNORE;
+
 void win_extmark(Integer grid, Window win, Integer ns_id, Integer mark_id, Integer row, Integer col)
   FUNC_API_SINCE(10) FUNC_API_REMOTE_ONLY;