From b574d44dd711ddb550d91a68c9e628f0bddc2b1e Mon Sep 17 00:00:00 2001
From: Relintai <relintai@protonmail.com>
Date: Mon, 14 Nov 2022 23:08:37 +0100
Subject: [PATCH] Also register PaintCanvasBackground to the ClassDB, and fix
 crash on exit with it.

---
 modules/paint/register_types.cpp             |  2 +-
 modules/paint/ui/paint_canvas_background.cpp | 41 +++++++++++++-------
 modules/paint/ui/paint_canvas_background.h   |  2 +
 3 files changed, 29 insertions(+), 16 deletions(-)

diff --git a/modules/paint/register_types.cpp b/modules/paint/register_types.cpp
index 90b2c0791..57296e100 100644
--- a/modules/paint/register_types.cpp
+++ b/modules/paint/register_types.cpp
@@ -65,7 +65,7 @@ void register_paint_types() {
 	ClassDB::register_class<RainbowAction>();
 	ClassDB::register_class<RectAction>();
 
-	//ClassDB::register_class<PaintCanvasBackground>();
+	ClassDB::register_class<PaintCanvasBackground>();
 	ClassDB::register_class<PaintCanvasOutline>();
 	ClassDB::register_class<PaintColorGrid>();
 	ClassDB::register_class<PaintSelectionBox>();
diff --git a/modules/paint/ui/paint_canvas_background.cpp b/modules/paint/ui/paint_canvas_background.cpp
index 753c75086..aab9aee0e 100644
--- a/modules/paint/ui/paint_canvas_background.cpp
+++ b/modules/paint/ui/paint_canvas_background.cpp
@@ -24,9 +24,9 @@ SOFTWARE.
 
 #include "paint_canvas_background.h"
 
+#include "core/io/image.h"
 #include "scene/resources/material.h"
 #include "scene/resources/shader.h"
-#include "core/io/image.h"
 #include "scene/resources/texture.h"
 
 #include "../shaders/shaders.h"
@@ -39,7 +39,9 @@ float PaintCanvasBackground::get_pixel_size() const {
 void PaintCanvasBackground::set_pixel_size(const float val) {
 	_pixel_size = val;
 
-	_material->set_shader_param("pixel_size", _pixel_size);
+	if (_material.is_valid()) {
+		_material->set_shader_param("pixel_size", _pixel_size);
+	}
 }
 
 PaintCanvasBackground::PaintCanvasBackground() {
@@ -47,22 +49,31 @@ PaintCanvasBackground::PaintCanvasBackground() {
 
 	set_expand(true);
 	set_stretch_mode(TextureRect::STRETCH_TILE);
-
-	set_texture(PaintIcons::make_icon_grid_png());
-
-	_shader.instance();
-	_shader->set_code(background_shader_shader_code);
-
-	_material.instance();
-	_material->set_shader(_shader);
-	_material->set_shader_param("pixel_size", _pixel_size);
-
-	set_material(_material);
 }
 
 PaintCanvasBackground::~PaintCanvasBackground() {
-	_material.unref();
-	_shader.unref();
+}
+
+void PaintCanvasBackground::_notification(int p_what) {
+	switch (p_what) {
+		case NOTIFICATION_ENTER_TREE:
+			_shader.instance();
+			_shader->set_code(background_shader_shader_code);
+
+			_material.instance();
+			_material->set_shader(_shader);
+			_material->set_shader_param("pixel_size", _pixel_size);
+
+			set_material(_material);
+
+			set_texture(PaintIcons::make_icon_grid_png());
+			break;
+		case NOTIFICATION_EXIT_TREE:
+			set_material(Ref<Material>());
+			_shader.unref();
+			_material.unref();
+			break;
+	}
 }
 
 void PaintCanvasBackground::_bind_methods() {
diff --git a/modules/paint/ui/paint_canvas_background.h b/modules/paint/ui/paint_canvas_background.h
index 7627eff9b..d908b7612 100644
--- a/modules/paint/ui/paint_canvas_background.h
+++ b/modules/paint/ui/paint_canvas_background.h
@@ -44,6 +44,8 @@ public:
 	~PaintCanvasBackground();
 
 protected:
+	void _notification(int p_what);
+
 	static void _bind_methods();
 
 	float _pixel_size;