Revert "Remove NOTIFICATION_ENTER_TREE when paired with NOTIFICATION_THEME_CHANGED"

This reverts commit 4b817a565cab8af648c88cfc7ab6481e86ee3625.

Fixes #64988.
Fixes #64997.

This caused several regressions (#64988, #64997,
https://github.com/godotengine/godot/issues/64997#issuecomment-1229970605)
which point at a flaw in the current logic:

- `Control::NOTIFICATION_ENTER_TREE` triggers a *deferred* notification with
  `NOTIFCATION_THEME_CHANGED` as introduced in #62845.
- Some classes use their `THEME_CHANGED` to cache theme items in
  member variables (e.g. `style_normal`, etc.), and use those member
  variables in `ENTER_TREE`, `READY`, `DRAW`, etc. Since the `THEME_CHANGE`
  notification is now deferred, they end up accessing invalid state and this
  can lead to not applying theme properly (e.g. for EditorHelp) or crashing
  (e.g. for EditorLog or CodeEdit).

So we need to go back to the drawing board and see if `THEME_CHANGED` can be
called earlier so that the previous logic still works?

Or can we refactor all engine code to make sure that:
- `ENTER_TREE` and similar do not depend on theme properties cached in member
  variables.
- Or `THEME_CHANGE` does trigger a general UI update to make sure that any
  bad theme handling in `ENTER_TREE` and co. gets fixed when `THEME_CHANGE`
  does arrive for the first time. But that means having a temporary invalid
  (and possibly still crashing) state, and doing some computations twice
  which might be heavy (e.g. `EditorHelp::_update_doc()`).

2 files changed, 10 insertions, 4 deletions

diff --git a/modules/gridmap/editor/grid_map_editor_plugin.cpp b/modules/gridmap/editor/grid_map_editor_plugin.cpp
index b0f73a98c9..17f9832096 100644
--- a/modules/gridmap/editor/grid_map_editor_plugin.cpp
+++ b/modules/gridmap/editor/grid_map_editor_plugin.cpp
@@ -1011,6 +1011,13 @@ void GridMapEditor::_draw_grids(const Vector3 &cell_size) {
 	}
 }
 
+void GridMapEditor::_update_theme() {
+	options->set_icon(get_theme_icon(SNAME("GridMap"), SNAME("EditorIcons")));
+	search_box->set_right_icon(get_theme_icon(SNAME("Search"), SNAME("EditorIcons")));
+	mode_thumbnail->set_icon(get_theme_icon(SNAME("FileThumbnail"), SNAME("EditorIcons")));
+	mode_list->set_icon(get_theme_icon(SNAME("FileList"), SNAME("EditorIcons")));
+}
+
 void GridMapEditor::_notification(int p_what) {
 	switch (p_what) {
 		case NOTIFICATION_ENTER_TREE: {
@@ -1031,6 +1038,7 @@ void GridMapEditor::_notification(int p_what) {
 
 			_update_selection_transform();
 			_update_paste_indicator();
+			_update_theme();
 		} break;
 
 		case NOTIFICATION_EXIT_TREE: {
@@ -1071,10 +1079,7 @@ void GridMapEditor::_notification(int p_what) {
 		} break;
 
 		case NOTIFICATION_THEME_CHANGED: {
-			options->set_icon(get_theme_icon(SNAME("GridMap"), SNAME("EditorIcons")));
-			search_box->set_right_icon(get_theme_icon(SNAME("Search"), SNAME("EditorIcons")));
-			mode_thumbnail->set_icon(get_theme_icon(SNAME("FileThumbnail"), SNAME("EditorIcons")));
-			mode_list->set_icon(get_theme_icon(SNAME("FileList"), SNAME("EditorIcons")));
+			_update_theme();
 		} break;
 
 		case NOTIFICATION_APPLICATION_FOCUS_OUT: {
diff --git a/modules/gridmap/editor/grid_map_editor_plugin.h b/modules/gridmap/editor/grid_map_editor_plugin.h
index 773bf4b6a4..a64dc4a80b 100644
--- a/modules/gridmap/editor/grid_map_editor_plugin.h
+++ b/modules/gridmap/editor/grid_map_editor_plugin.h
@@ -193,6 +193,7 @@ class GridMapEditor : public VBoxContainer {
 	void _item_selected_cbk(int idx);
 	void _update_cursor_transform();
 	void _update_cursor_instance();
+	void _update_theme();
 
 	void _text_changed(const String &p_text);
 	void _sbox_input(const Ref<InputEvent> &p_ie);