Fixes TreeItem minimum width calculations

1. Adds missing margins to `TreeItem::get_minimum_size`.
2. Sets minimum size dirty flags when an item is (un)collapsed.
3. Fixes depth calculation in `Tree::get_column_minimum_width` that was using
the next visible item's depth when calculating the current item's minimum width.

Fixes #84015.

scene/gui/tree.cpp

@@ -615,6 +615,15 @@ void TreeItem::set_collapsed(bool p_collapsed) {
  return;
  }
  collapsed = p_collapsed;
+
+ for (int i = 0; i < cells.size(); i++) {
+ cells.write[i].cached_minimum_size_dirty = true;
+ }
+
+ for (int i = 0; i < tree->columns.size(); i++) {
+ tree->columns.write[i].cached_minimum_width_dirty = true;
+ }
+
  TreeItem *ci = tree->selected_item;
  if (ci) {
  while (ci && ci != this) {
@@ -1483,6 +1492,14 @@ Size2 TreeItem::get_minimum_size(int p_column) {
  if (cell.cached_minimum_size_dirty) {
  Size2 size;
 
+ size.width += parent_tree->theme_cache.inner_item_margin_left + parent_tree->theme_cache.inner_item_margin_right;
+
+ if (p_column == 0 && !(disable_folding || parent_tree->hide_folding)) {
+ size.width += parent_tree->theme_cache.item_margin;
+ } else {
+ size.width += parent_tree->theme_cache.h_separation;
+ }
+
  // Text.
  if (!cell.text.is_empty()) {
  if (cell.dirty) {
@@ -4683,8 +4700,19 @@ int Tree::get_column_minimum_width(int p_column) const {
  int depth = 0;
  TreeItem *next;
  for (TreeItem *item = get_root(); item; item = next) {
+ // Get the item minimum size.
+ Size2 item_size = item->get_minimum_size(p_column);
+ if (p_column == 0) {
+ item_size.width += theme_cache.item_margin * depth;
+ } else {
+ item_size.width += theme_cache.h_separation;
+ }
+
+ // Check if the item is wider.
+ min_width = MAX(min_width, item_size.width);
+
+ // Compute the depth of the next item.
  next = item->get_next_visible();
- // Compute the depth in tree.
  if (next && p_column == 0) {
  if (next->get_parent() == item) {
  depth += 1;
@@ -4696,17 +4724,6 @@ int Tree::get_column_minimum_width(int p_column) const {
  }
  }
  }
-
- // Get the item minimum size.
- Size2 item_size = item->get_minimum_size(p_column);
- if (p_column == 0) {
- item_size.width += theme_cache.item_margin * depth;
- } else {
- item_size.width += theme_cache.h_separation;
- }
-
- // Check if the item is wider.
- min_width = MAX(min_width, item_size.width);
  }
  }