1 files changed, 23 insertions, 11 deletions

diff --git a/src/nvim/ui_compositor.c b/src/nvim/ui_compositor.c
index 9d3ec21949..a2e9266fbb 100644
--- a/src/nvim/ui_compositor.c
+++ b/src/nvim/ui_compositor.c
@@ -127,6 +127,9 @@ bool ui_comp_put_grid(ScreenGrid *grid, int row, int col, int height, int width,
                       bool valid, bool on_top)
 {
   bool moved;
+
+  grid->comp_height = height;
+  grid->comp_width = width;
   if (grid->comp_index != 0) {
     moved = (row != grid->comp_row) || (col != grid->comp_col);
     if (ui_comp_should_draw()) {
@@ -157,7 +160,7 @@ bool ui_comp_put_grid(ScreenGrid *grid, int row, int col, int height, int width,
 #ifndef NDEBUG
     for (size_t i = 0; i < kv_size(layers); i++) {
       if (kv_A(layers, i) == grid) {
-        assert(false);
+        abort();
       }
     }
 #endif
@@ -181,14 +184,12 @@ bool ui_comp_put_grid(ScreenGrid *grid, int row, int col, int height, int width,
       insert_at--;
     }
     // not found: new grid
-    kv_push(layers, grid);
-    if (insert_at < kv_size(layers)-1) {
-      for (size_t i = kv_size(layers)-1; i > insert_at; i--) {
-        kv_A(layers, i) = kv_A(layers, i-1);
-        kv_A(layers, i)->comp_index = i;
-      }
-      kv_A(layers, insert_at) = grid;
+    kv_pushp(layers);
+    for (size_t i = kv_size(layers)-1; i > insert_at; i--) {
+      kv_A(layers, i) = kv_A(layers, i-1);
+      kv_A(layers, i)->comp_index = i;
     }
+    kv_A(layers, insert_at) = grid;
 
     grid->comp_row = row;
     grid->comp_col = col;
@@ -277,6 +278,9 @@ static void ui_comp_grid_cursor_goto(UI *ui, Integer grid_handle,
   // should configure all grids before entering win_update()
   if (curgrid != &default_grid) {
     size_t new_index = kv_size(layers)-1;
+    if (kv_A(layers, new_index) == &msg_grid) {
+      new_index--;
+    }
     if (kv_A(layers, new_index) == &pum_grid) {
       new_index--;
     }
@@ -334,17 +338,25 @@ static void compose_line(Integer row, Integer startcol, Integer endcol,
   sattr_T *bg_attrs = &default_grid.attrs[default_grid.line_offset[row]
                                           +(size_t)startcol];
 
+  int grid_width, grid_height;
   while (col < endcol) {
     int until = 0;
     for (size_t i = 0; i < kv_size(layers); i++) {
       ScreenGrid *g = kv_A(layers, i);
-      if (g->comp_row > row || row >= g->comp_row + g->Rows
+      // compose_line may have been called after a shrinking operation but
+      // before the resize has actually been applied. Therefore, we need to
+      // first check to see if any grids have pending updates to width/height,
+      // to ensure that we don't accidentally put any characters into `linebuf`
+      // that have been invalidated.
+      grid_width = MIN(g->Columns, g->comp_width);
+      grid_height = MIN(g->Rows, g->comp_height);
+      if (g->comp_row > row || row >= g->comp_row + grid_height
           || g->comp_disabled) {
         continue;
       }
-      if (g->comp_col <= col && col < g->comp_col+g->Columns) {
+      if (g->comp_col <= col && col < g->comp_col + grid_width) {
         grid = g;
-        until = g->comp_col+g->Columns;
+        until = g->comp_col + grid_width;
       } else if (g->comp_col > col) {
         until = MIN(until, g->comp_col);
       }