From 9e9bac1549cb293850feac145622267153f9c7aa Mon Sep 17 00:00:00 2001
From: Tom Coxon <tom.c.coxon@googlemail.com>
Date: Mon, 6 Sep 2021 13:32:59 +0100
Subject: [PATCH] Prevent shaders from generating code before the constructor
 finishes.

Fixes #43733: "creating SpatialMaterial in a separate thread creates invalid
shaders (temporarily)."

The bug occurred because various setters called in materials' constructors add
materials to queues that are processed on the main thread. This means that
when the materials are created in another thread, they can be processed on the
main thread before the constructor has finished.

The fix adds a flag to affected materials that prevents them from being added
to the queue until their constructors have finished initialising all the
members.
---
 scene/2d/canvas_item.cpp               | 3 ++-
 scene/2d/canvas_item.h                 | 1 +
 scene/resources/material.cpp           | 3 ++-
 scene/resources/material.h             | 1 +
 scene/resources/particles_material.cpp | 3 ++-
 scene/resources/particles_material.h   | 1 +
 6 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/scene/2d/canvas_item.cpp b/scene/2d/canvas_item.cpp
index 7e97872469af..f65bd8ddc90c 100644
--- a/scene/2d/canvas_item.cpp
+++ b/scene/2d/canvas_item.cpp
@@ -176,7 +176,7 @@ void CanvasItemMaterial::flush_changes() {
 void CanvasItemMaterial::_queue_shader_change() {
 	material_mutex.lock();
 
-	if (!element.in_list()) {
+	if (is_initialized && !element.in_list()) {
 		dirty_materials->add(&element);
 	}
 
@@ -313,6 +313,7 @@ CanvasItemMaterial::CanvasItemMaterial() :
 
 	current_key.key = 0;
 	current_key.invalid_key = 1;
+	is_initialized = true;
 	_queue_shader_change();
 }
 
diff --git a/scene/2d/canvas_item.h b/scene/2d/canvas_item.h
index ae0e638fdfd8..9ea94154459c 100644
--- a/scene/2d/canvas_item.h
+++ b/scene/2d/canvas_item.h
@@ -113,6 +113,7 @@ class CanvasItemMaterial : public Material {
 	_FORCE_INLINE_ void _queue_shader_change();
 	_FORCE_INLINE_ bool _is_shader_dirty() const;
 
+	bool is_initialized = false;
 	BlendMode blend_mode;
 	LightMode light_mode;
 	bool particles_animation;
diff --git a/scene/resources/material.cpp b/scene/resources/material.cpp
index 36c56847e220..4cf8a83e9572 100644
--- a/scene/resources/material.cpp
+++ b/scene/resources/material.cpp
@@ -1073,7 +1073,7 @@ void SpatialMaterial::flush_changes() {
 void SpatialMaterial::_queue_shader_change() {
 	material_mutex.lock();
 
-	if (!element.in_list()) {
+	if (is_initialized && !element.in_list()) {
 		dirty_materials->add(&element);
 	}
 
@@ -2317,6 +2317,7 @@ SpatialMaterial::SpatialMaterial() :
 
 	current_key.key = 0;
 	current_key.invalid_key = 1;
+	is_initialized = true;
 	_queue_shader_change();
 }
 
diff --git a/scene/resources/material.h b/scene/resources/material.h
index e8e772386c6a..94ab38304e5f 100644
--- a/scene/resources/material.h
+++ b/scene/resources/material.h
@@ -366,6 +366,7 @@ class SpatialMaterial : public Material {
 	_FORCE_INLINE_ void _queue_shader_change();
 	_FORCE_INLINE_ bool _is_shader_dirty() const;
 
+	bool is_initialized = false;
 	Color albedo;
 	float specular;
 	float metallic;
diff --git a/scene/resources/particles_material.cpp b/scene/resources/particles_material.cpp
index 74034c560042..ae7008f5b8e5 100644
--- a/scene/resources/particles_material.cpp
+++ b/scene/resources/particles_material.cpp
@@ -690,7 +690,7 @@ void ParticlesMaterial::flush_changes() {
 void ParticlesMaterial::_queue_shader_change() {
 	material_mutex.lock();
 
-	if (!element.in_list()) {
+	if (is_initialized && !element.in_list()) {
 		dirty_materials->add(&element);
 	}
 
@@ -1367,6 +1367,7 @@ ParticlesMaterial::ParticlesMaterial() :
 	current_key.key = 0;
 	current_key.invalid_key = 1;
 
+	is_initialized = true;
 	_queue_shader_change();
 }
 
diff --git a/scene/resources/particles_material.h b/scene/resources/particles_material.h
index f82274bde2f0..3d564c7880aa 100644
--- a/scene/resources/particles_material.h
+++ b/scene/resources/particles_material.h
@@ -203,6 +203,7 @@ class ParticlesMaterial : public Material {
 	_FORCE_INLINE_ void _queue_shader_change();
 	_FORCE_INLINE_ bool _is_shader_dirty() const;
 
+	bool is_initialized = false;
 	Vector3 direction;
 	float spread;
 	float flatness;