ui: fix glitches where scrolling region affects clearing of screen

the first implemented UI protocol clients (python-gui and builitin TUI)
allowed the cleared region to be restricted by setting the scroll region.
This was never used by nvim though, and not documented and implemented by
newer clients, to check we remain compatible with both kind of clients,
ensure the scroll region is in a reset state.

3 files changed, 11 insertions, 2 deletions

diff --git a/src/nvim/api/ui.c b/src/nvim/api/ui.c
index 63c2c4a1b9..d0db43c588 100644
--- a/src/nvim/api/ui.c
+++ b/src/nvim/api/ui.c
@@ -302,6 +302,15 @@ static void remote_ui_grid_scroll(UI *ui, Integer grid, Integer top,
     args = (Array)ARRAY_DICT_INIT;
     ADD(args, INTEGER_OBJ(rows));
     push_call(ui, "scroll", args);
+
+    // some clients have "clear" being affected by scroll region,
+    // so reset it.
+    args = (Array)ARRAY_DICT_INIT;
+    ADD(args, INTEGER_OBJ(0));
+    ADD(args, INTEGER_OBJ(ui->height-1));
+    ADD(args, INTEGER_OBJ(0));
+    ADD(args, INTEGER_OBJ(ui->width-1));
+    push_call(ui, "set_scroll_region", args);
   }
 }
 
diff --git a/src/nvim/tui/tui.c b/src/nvim/tui/tui.c
index 56c47ed6cc..cfcfaa83a0 100644
--- a/src/nvim/tui/tui.c
+++ b/src/nvim/tui/tui.c
@@ -823,7 +823,7 @@ static void tui_grid_clear(UI *ui, Integer g)
   UGrid *grid = &data->grid;
   ugrid_clear(grid);
   kv_size(data->invalid_regions) = 0;
-  clear_region(ui, grid->top, grid->bot, grid->left, grid->right,
+  clear_region(ui, 0, grid->height-1, 0, grid->width-1,
                data->clear_attrs);
 }
 
diff --git a/src/nvim/ugrid.c b/src/nvim/ugrid.c
index 48f3cff2d7..36936970f8 100644
--- a/src/nvim/ugrid.c
+++ b/src/nvim/ugrid.c
@@ -44,7 +44,7 @@ void ugrid_resize(UGrid *grid, int width, int height)
 
 void ugrid_clear(UGrid *grid)
 {
-  clear_region(grid, grid->top, grid->bot, grid->left, grid->right,
+  clear_region(grid, 0, grid->height-1, 0, grid->width-1,
                HLATTRS_INIT);
 }