Merge pull request #62513 from reduz/shader_preprocessor_remake

22 files changed, 1468 insertions, 31 deletions

diff --git a/servers/rendering/dummy/storage/material_storage.h b/servers/rendering/dummy/storage/material_storage.h
index d4809f81e3..5d1f64991b 100644
--- a/servers/rendering/dummy/storage/material_storage.h
+++ b/servers/rendering/dummy/storage/material_storage.h
@@ -63,6 +63,8 @@ public:
 	virtual void shader_free(RID p_rid) override{};
 
 	virtual void shader_set_code(RID p_shader, const String &p_code) override {}
+	virtual void shader_set_path_hint(RID p_shader, const String &p_code) override {}
+
 	virtual String shader_get_code(RID p_shader) const override { return ""; }
 	virtual void shader_get_param_list(RID p_shader, List<PropertyInfo> *p_param_list) const override {}
 
diff --git a/servers/rendering/renderer_rd/forward_clustered/scene_shader_forward_clustered.cpp b/servers/rendering/renderer_rd/forward_clustered/scene_shader_forward_clustered.cpp
index 1951bfe915..a559241846 100644
--- a/servers/rendering/renderer_rd/forward_clustered/scene_shader_forward_clustered.cpp
+++ b/servers/rendering/renderer_rd/forward_clustered/scene_shader_forward_clustered.cpp
@@ -37,6 +37,10 @@
 
 using namespace RendererSceneRenderImplementation;
 
+void SceneShaderForwardClustered::ShaderData::set_path_hint(const String &p_path) {
+	path = p_path;
+}
+
 void SceneShaderForwardClustered::ShaderData::set_code(const String &p_code) {
 	//compile
 
diff --git a/servers/rendering/renderer_rd/forward_clustered/scene_shader_forward_clustered.h b/servers/rendering/renderer_rd/forward_clustered/scene_shader_forward_clustered.h
index 1cfe723174..05dabc1c56 100644
--- a/servers/rendering/renderer_rd/forward_clustered/scene_shader_forward_clustered.h
+++ b/servers/rendering/renderer_rd/forward_clustered/scene_shader_forward_clustered.h
@@ -180,6 +180,7 @@ public:
 		uint32_t index = 0;
 
 		virtual void set_code(const String &p_Code);
+		virtual void set_path_hint(const String &p_path);
 		virtual void set_default_texture_param(const StringName &p_name, RID p_texture, int p_index);
 		virtual void get_param_list(List<PropertyInfo> *p_param_list) const;
 		void get_instance_param_list(List<RendererMaterialStorage::InstanceShaderParam> *p_param_list) const;
diff --git a/servers/rendering/renderer_rd/forward_mobile/scene_shader_forward_mobile.cpp b/servers/rendering/renderer_rd/forward_mobile/scene_shader_forward_mobile.cpp
index dd00dc2bf9..afe4eac0b3 100644
--- a/servers/rendering/renderer_rd/forward_mobile/scene_shader_forward_mobile.cpp
+++ b/servers/rendering/renderer_rd/forward_mobile/scene_shader_forward_mobile.cpp
@@ -39,6 +39,10 @@ using namespace RendererSceneRenderImplementation;
 
 /* ShaderData */
 
+void SceneShaderForwardMobile::ShaderData::set_path_hint(const String &p_path) {
+	path = p_path;
+}
+
 void SceneShaderForwardMobile::ShaderData::set_code(const String &p_code) {
 	//compile
 
diff --git a/servers/rendering/renderer_rd/forward_mobile/scene_shader_forward_mobile.h b/servers/rendering/renderer_rd/forward_mobile/scene_shader_forward_mobile.h
index 88c2143b09..651155932a 100644
--- a/servers/rendering/renderer_rd/forward_mobile/scene_shader_forward_mobile.h
+++ b/servers/rendering/renderer_rd/forward_mobile/scene_shader_forward_mobile.h
@@ -139,6 +139,8 @@ public:
 		uint32_t index = 0;
 
 		virtual void set_code(const String &p_Code);
+		virtual void set_path_hint(const String &p_path);
+
 		virtual void set_default_texture_param(const StringName &p_name, RID p_texture, int p_index);
 		virtual void get_param_list(List<PropertyInfo> *p_param_list) const;
 		void get_instance_param_list(List<RendererMaterialStorage::InstanceShaderParam> *p_param_list) const;
diff --git a/servers/rendering/renderer_rd/renderer_canvas_render_rd.cpp b/servers/rendering/renderer_rd/renderer_canvas_render_rd.cpp
index 7d55be1216..b8ad4e4511 100644
--- a/servers/rendering/renderer_rd/renderer_canvas_render_rd.cpp
+++ b/servers/rendering/renderer_rd/renderer_canvas_render_rd.cpp
@@ -1968,6 +1968,10 @@ void RendererCanvasRenderRD::occluder_polygon_set_cull_mode(RID p_occluder, RS::
 	oc->cull_mode = p_mode;
 }
 
+void RendererCanvasRenderRD::CanvasShaderData::set_path_hint(const String &p_path) {
+	path = p_path;
+}
+
 void RendererCanvasRenderRD::CanvasShaderData::set_code(const String &p_code) {
 	//compile
 
diff --git a/servers/rendering/renderer_rd/renderer_canvas_render_rd.h b/servers/rendering/renderer_rd/renderer_canvas_render_rd.h
index 2ab5a7c831..c0e6b27587 100644
--- a/servers/rendering/renderer_rd/renderer_canvas_render_rd.h
+++ b/servers/rendering/renderer_rd/renderer_canvas_render_rd.h
@@ -178,6 +178,7 @@ class RendererCanvasRenderRD : public RendererCanvasRender {
 		bool uses_time = false;
 
 		virtual void set_code(const String &p_Code);
+		virtual void set_path_hint(const String &p_path);
 		virtual void set_default_texture_param(const StringName &p_name, RID p_texture, int p_index);
 		virtual void get_param_list(List<PropertyInfo> *p_param_list) const;
 		virtual void get_instance_param_list(List<RendererMaterialStorage::InstanceShaderParam> *p_param_list) const;
diff --git a/servers/rendering/renderer_rd/renderer_scene_render_rd.cpp b/servers/rendering/renderer_rd/renderer_scene_render_rd.cpp
index 73028f38bf..3176af07b6 100644
--- a/servers/rendering/renderer_rd/renderer_scene_render_rd.cpp
+++ b/servers/rendering/renderer_rd/renderer_scene_render_rd.cpp
@@ -3689,6 +3689,10 @@ void RendererSceneRenderRD::_setup_decals(const PagedArray<RID> &p_decals, const
 ////////////////////////////////////////////////////////////////////////////////
 // FOG SHADER
 
+void RendererSceneRenderRD::FogShaderData::set_path_hint(const String &p_path) {
+	path = p_path;
+}
+
 void RendererSceneRenderRD::FogShaderData::set_code(const String &p_code) {
 	//compile
 
diff --git a/servers/rendering/renderer_rd/renderer_scene_render_rd.h b/servers/rendering/renderer_rd/renderer_scene_render_rd.h
index 16cf99314a..8ee2f87feb 100644
--- a/servers/rendering/renderer_rd/renderer_scene_render_rd.h
+++ b/servers/rendering/renderer_rd/renderer_scene_render_rd.h
@@ -915,6 +915,7 @@ private:
 		bool uses_time = false;
 
 		virtual void set_code(const String &p_Code);
+		virtual void set_path_hint(const String &p_hint);
 		virtual void set_default_texture_param(const StringName &p_name, RID p_texture, int p_index);
 		virtual void get_param_list(List<PropertyInfo> *p_param_list) const;
 		virtual void get_instance_param_list(List<RendererMaterialStorage::InstanceShaderParam> *p_param_list) const;
diff --git a/servers/rendering/renderer_rd/renderer_scene_sky_rd.cpp b/servers/rendering/renderer_rd/renderer_scene_sky_rd.cpp
index 73175d3cf3..689fbba885 100644
--- a/servers/rendering/renderer_rd/renderer_scene_sky_rd.cpp
+++ b/servers/rendering/renderer_rd/renderer_scene_sky_rd.cpp
@@ -42,6 +42,10 @@
 ////////////////////////////////////////////////////////////////////////////////
 // SKY SHADER
 
+void RendererSceneSkyRD::SkyShaderData::set_path_hint(const String &p_path) {
+	path = p_path;
+}
+
 void RendererSceneSkyRD::SkyShaderData::set_code(const String &p_code) {
 	//compile
 
diff --git a/servers/rendering/renderer_rd/renderer_scene_sky_rd.h b/servers/rendering/renderer_rd/renderer_scene_sky_rd.h
index a8ee406abc..4376fe4c5b 100644
--- a/servers/rendering/renderer_rd/renderer_scene_sky_rd.h
+++ b/servers/rendering/renderer_rd/renderer_scene_sky_rd.h
@@ -128,6 +128,7 @@ private:
 		bool uses_light = false;
 
 		virtual void set_code(const String &p_Code);
+		virtual void set_path_hint(const String &p_hint);
 		virtual void set_default_texture_param(const StringName &p_name, RID p_texture, int p_index);
 		virtual void get_param_list(List<PropertyInfo> *p_param_list) const;
 		virtual void get_instance_param_list(List<RendererMaterialStorage::InstanceShaderParam> *p_param_list) const;
diff --git a/servers/rendering/renderer_rd/storage_rd/material_storage.cpp b/servers/rendering/renderer_rd/storage_rd/material_storage.cpp
index fcd25852eb..af2f5aafed 100644
--- a/servers/rendering/renderer_rd/storage_rd/material_storage.cpp
+++ b/servers/rendering/renderer_rd/storage_rd/material_storage.cpp
@@ -2341,6 +2341,7 @@ void MaterialStorage::shader_set_code(RID p_shader, const String &p_code) {
 	}
 
 	if (shader->data) {
+		shader->data->set_path_hint(shader->path_hint);
 		shader->data->set_code(p_code);
 	}
 
@@ -2351,6 +2352,16 @@ void MaterialStorage::shader_set_code(RID p_shader, const String &p_code) {
 	}
 }
 
+void MaterialStorage::shader_set_path_hint(RID p_shader, const String &p_path) {
+	Shader *shader = shader_owner.get_or_null(p_shader);
+	ERR_FAIL_COND(!shader);
+
+	shader->path_hint = p_path;
+	if (shader->data) {
+		shader->data->set_path_hint(p_path);
+	}
+}
+
 String MaterialStorage::shader_get_code(RID p_shader) const {
 	Shader *shader = shader_owner.get_or_null(p_shader);
 	ERR_FAIL_COND_V(!shader, String());
diff --git a/servers/rendering/renderer_rd/storage_rd/material_storage.h b/servers/rendering/renderer_rd/storage_rd/material_storage.h
index e35d5e7669..b083968e5f 100644
--- a/servers/rendering/renderer_rd/storage_rd/material_storage.h
+++ b/servers/rendering/renderer_rd/storage_rd/material_storage.h
@@ -57,6 +57,7 @@ enum ShaderType {
 
 struct ShaderData {
 	virtual void set_code(const String &p_Code) = 0;
+	virtual void set_path_hint(const String &p_hint) = 0;
 	virtual void set_default_texture_param(const StringName &p_name, RID p_texture, int p_index) = 0;
 	virtual void get_param_list(List<PropertyInfo> *p_param_list) const = 0;
 
@@ -77,6 +78,7 @@ struct Material;
 struct Shader {
 	ShaderData *data = nullptr;
 	String code;
+	String path_hint;
 	ShaderType type;
 	HashMap<StringName, HashMap<int, RID>> default_texture_parameter;
 	HashSet<Material *> owners;
@@ -364,6 +366,7 @@ public:
 	virtual void shader_free(RID p_rid) override;
 
 	virtual void shader_set_code(RID p_shader, const String &p_code) override;
+	virtual void shader_set_path_hint(RID p_shader, const String &p_path) override;
 	virtual String shader_get_code(RID p_shader) const override;
 	virtual void shader_get_param_list(RID p_shader, List<PropertyInfo> *p_param_list) const override;
 
diff --git a/servers/rendering/renderer_rd/storage_rd/particles_storage.cpp b/servers/rendering/renderer_rd/storage_rd/particles_storage.cpp
index 5200e0d318..ea4bd6ab0b 100644
--- a/servers/rendering/renderer_rd/storage_rd/particles_storage.cpp
+++ b/servers/rendering/renderer_rd/storage_rd/particles_storage.cpp
@@ -1512,6 +1512,9 @@ bool ParticlesStorage::particles_is_inactive(RID p_particles) const {
 
 /* Particles SHADER */
 
+void ParticlesStorage::ParticlesShaderData::set_path_hint(const String &p_path) {
+	path = p_path;
+}
 void ParticlesStorage::ParticlesShaderData::set_code(const String &p_code) {
 	ParticlesStorage *particles_storage = ParticlesStorage::get_singleton();
 	//compile
diff --git a/servers/rendering/renderer_rd/storage_rd/particles_storage.h b/servers/rendering/renderer_rd/storage_rd/particles_storage.h
index 70ac6f0349..f3a4e97fa7 100644
--- a/servers/rendering/renderer_rd/storage_rd/particles_storage.h
+++ b/servers/rendering/renderer_rd/storage_rd/particles_storage.h
@@ -363,6 +363,7 @@ private:
 		uint32_t userdata_count = 0;
 
 		virtual void set_code(const String &p_Code);
+		virtual void set_path_hint(const String &p_hint);
 		virtual void set_default_texture_param(const StringName &p_name, RID p_texture, int p_index);
 		virtual void get_param_list(List<PropertyInfo> *p_param_list) const;
 		virtual void get_instance_param_list(List<RendererMaterialStorage::InstanceShaderParam> *p_param_list) const;
diff --git a/servers/rendering/rendering_server_default.h b/servers/rendering/rendering_server_default.h
index 429b8a06e2..4e41a87a2c 100644
--- a/servers/rendering/rendering_server_default.h
+++ b/servers/rendering/rendering_server_default.h
@@ -224,6 +224,7 @@ public:
 	FUNCRIDSPLIT(shader)
 
 	FUNC2(shader_set_code, RID, const String &)
+	FUNC2(shader_set_path_hint, RID, const String &)
 	FUNC1RC(String, shader_get_code, RID)
 
 	FUNC2SC(shader_get_param_list, RID, List<PropertyInfo> *)
diff --git a/servers/rendering/shader_compiler.cpp b/servers/rendering/shader_compiler.cpp
index 463b67033d..e291246d01 100644
--- a/servers/rendering/shader_compiler.cpp
+++ b/servers/rendering/shader_compiler.cpp
@@ -1323,18 +1323,76 @@ Error ShaderCompiler::compile(RS::ShaderMode p_mode, const String &p_code, Ident
 	Error err = parser.compile(p_code, info);
 
 	if (err != OK) {
+		Vector<ShaderLanguage::FilePosition> include_positions = parser.get_include_positions();
+
+		String current;
+		HashMap<String, Vector<String>> includes;
+		includes[""] = Vector<String>();
+		Vector<String> include_stack;
 		Vector<String> shader = p_code.split("\n");
+
+		// Reconstruct the files.
 		for (int i = 0; i < shader.size(); i++) {
-			if (i + 1 == parser.get_error_line()) {
-				// Mark the error line to be visible without having to look at
-				// the trace at the end.
-				print_line(vformat("E%4d-> %s", i + 1, shader[i]));
+			String l = shader[i];
+			if (l.begins_with("@@>")) {
+				String inc_path = l.replace_first("@@>", "");
+
+				l = "#include \"" + inc_path + "\"";
+				includes[current].append("#include \"" + inc_path + "\""); // Restore the include directive
+				include_stack.push_back(current);
+				current = inc_path;
+				includes[inc_path] = Vector<String>();
+
+			} else if (l.begins_with("@@<")) {
+				if (include_stack.size()) {
+					current = include_stack[include_stack.size() - 1];
+					include_stack.resize(include_stack.size() - 1);
+				}
+			} else {
+				includes[current].push_back(l);
+			}
+		}
+
+		// Print the files.
+		for (const KeyValue<String, Vector<String>> &E : includes) {
+			if (E.key.is_empty()) {
+				if (p_path == "") {
+					print_line("--Main Shader--");
+				} else {
+					print_line("--" + p_path + "--");
+				}
 			} else {
-				print_line(vformat("%5d | %s", i + 1, shader[i]));
+				print_line("--" + E.key + "--");
 			}
+			int err_line = -1;
+			for (int i = 0; i < include_positions.size(); i++) {
+				if (include_positions[i].file == E.key) {
+					err_line = include_positions[i].line;
+				}
+			}
+			const Vector<String> &V = E.value;
+			for (int i = 0; i < V.size(); i++) {
+				if (i == err_line - 1) {
+					// Mark the error line to be visible without having to look at
+					// the trace at the end.
+					print_line(vformat("E%4d-> %s", i + 1, V[i]));
+				} else {
+					print_line(vformat("%5d | %s", i + 1, V[i]));
+				}
+			}
+		}
+
+		String file;
+		int line;
+		if (include_positions.size() > 1) {
+			file = include_positions[include_positions.size() - 1].file;
+			line = include_positions[include_positions.size() - 1].line;
+		} else {
+			file = p_path;
+			line = parser.get_error_line();
 		}
 
-		_err_print_error(nullptr, p_path.utf8().get_data(), parser.get_error_line(), parser.get_error_text().utf8().get_data(), false, ERR_HANDLER_SHADER);
+		_err_print_error(nullptr, file.utf8().get_data(), line, parser.get_error_text().utf8().get_data(), false, ERR_HANDLER_SHADER);
 		return err;
 	}
 
diff --git a/servers/rendering/shader_language.cpp b/servers/rendering/shader_language.cpp
index ad9b51ac0c..d2b80fb277 100644
--- a/servers/rendering/shader_language.cpp
+++ b/servers/rendering/shader_language.cpp
@@ -32,6 +32,7 @@
 
 #include "core/os/os.h"
 #include "core/string/print_string.h"
+#include "core/templates/local_vector.h"
 #include "servers/rendering_server.h"
 
 #define HAS_WARNING(flag) (warning_flags & flag)
@@ -574,6 +575,37 @@ ShaderLanguage::Token ShaderLanguage::_get_token() {
 
 				return _make_token(TK_OP_MOD);
 			} break;
+			case '@': {
+				if (GETCHAR(0) == '@' && GETCHAR(1) == '>') {
+					char_idx += 2;
+
+					LocalVector<char32_t> incp;
+					while (GETCHAR(0) != '\n') {
+						incp.push_back(GETCHAR(0));
+						char_idx++;
+					}
+					incp.push_back(0); // Zero end it.
+					String include_path(incp.ptr());
+					include_positions.write[include_positions.size() - 1].line = tk_line;
+					FilePosition fp;
+					fp.file = include_path;
+					fp.line = 0;
+					tk_line = 0;
+					include_positions.push_back(fp);
+
+				} else if (GETCHAR(0) == '@' && GETCHAR(1) == '<') {
+					if (include_positions.size() == 1) {
+						return _make_token(TK_ERROR, "Invalid include exit hint @@< without matching enter hint.");
+					}
+					char_idx += 2;
+
+					include_positions.resize(include_positions.size() - 1); // Pop back.
+					tk_line = include_positions[include_positions.size() - 1].line; // Restore line.
+
+				} else {
+					return _make_token(TK_ERROR, "Invalid include enter/exit hint token (@@> and @@<)");
+				}
+			} break;
 			default: {
 				char_idx--; //go back one, since we have no idea what this is
 
@@ -1122,6 +1154,9 @@ void ShaderLanguage::clear() {
 	completion_base = TYPE_VOID;
 	completion_base_array = false;
 
+	include_positions.clear();
+	include_positions.push_back(FilePosition());
+
 #ifdef DEBUG_ENABLED
 	keyword_completion_context = CF_GLOBAL_SPACE;
 	used_constants.clear();
@@ -7677,35 +7712,39 @@ Error ShaderLanguage::_validate_precision(DataType p_type, DataPrecision p_preci
 	return OK;
 }
 
-Error ShaderLanguage::_parse_shader(const HashMap<StringName, FunctionInfo> &p_functions, const Vector<ModeInfo> &p_render_modes, const HashSet<String> &p_shader_types) {
-	Token tk = _get_token();
+Error ShaderLanguage::_parse_shader(const HashMap<StringName, FunctionInfo> &p_functions, const Vector<ModeInfo> &p_render_modes, const HashSet<String> &p_shader_types, bool p_is_include) {
+	Token tk;
 	TkPos prev_pos;
 	Token next;
 
-	if (tk.type != TK_SHADER_TYPE) {
-		_set_error(vformat(RTR("Expected '%s' at the beginning of shader. Valid types are: %s."), "shader_type", _get_shader_type_list(p_shader_types)));
-		return ERR_PARSE_ERROR;
-	}
+	if (!p_is_include) {
+		tk = _get_token();
+
+		if (tk.type != TK_SHADER_TYPE) {
+			_set_error(vformat(RTR("Expected '%s' at the beginning of shader. Valid types are: %s."), "shader_type", _get_shader_type_list(p_shader_types)));
+			return ERR_PARSE_ERROR;
+		}
 #ifdef DEBUG_ENABLED
-	keyword_completion_context = CF_UNSPECIFIED;
+		keyword_completion_context = CF_UNSPECIFIED;
 #endif // DEBUG_ENABLED
 
-	_get_completable_identifier(nullptr, COMPLETION_SHADER_TYPE, shader_type_identifier);
-	if (shader_type_identifier == StringName()) {
-		_set_error(vformat(RTR("Expected an identifier after '%s', indicating the type of shader. Valid types are: %s."), "shader_type", _get_shader_type_list(p_shader_types)));
-		return ERR_PARSE_ERROR;
-	}
-	if (!p_shader_types.has(shader_type_identifier)) {
-		_set_error(vformat(RTR("Invalid shader type. Valid types are: %s"), _get_shader_type_list(p_shader_types)));
-		return ERR_PARSE_ERROR;
-	}
-	prev_pos = _get_tkpos();
-	tk = _get_token();
+		_get_completable_identifier(nullptr, COMPLETION_SHADER_TYPE, shader_type_identifier);
+		if (shader_type_identifier == StringName()) {
+			_set_error(vformat(RTR("Expected an identifier after '%s', indicating the type of shader. Valid types are: %s."), "shader_type", _get_shader_type_list(p_shader_types)));
+			return ERR_PARSE_ERROR;
+		}
+		if (!p_shader_types.has(shader_type_identifier)) {
+			_set_error(vformat(RTR("Invalid shader type. Valid types are: %s"), _get_shader_type_list(p_shader_types)));
+			return ERR_PARSE_ERROR;
+		}
+		prev_pos = _get_tkpos();
+		tk = _get_token();
 
-	if (tk.type != TK_SEMICOLON) {
-		_set_tkpos(prev_pos);
-		_set_expected_after_error(";", "shader_type " + String(shader_type_identifier));
-		return ERR_PARSE_ERROR;
+		if (tk.type != TK_SEMICOLON) {
+			_set_tkpos(prev_pos);
+			_set_expected_after_error(";", "shader_type " + String(shader_type_identifier));
+			return ERR_PARSE_ERROR;
+		}
 	}
 
 #ifdef DEBUG_ENABLED
@@ -9511,12 +9550,13 @@ Error ShaderLanguage::compile(const String &p_code, const ShaderCompileInfo &p_i
 
 	code = p_code;
 	global_var_get_type_func = p_info.global_variable_type_func;
+
 	varying_function_names = p_info.varying_function_names;
 
 	nodes = nullptr;
 
 	shader = alloc_node<ShaderNode>();
-	Error err = _parse_shader(p_info.functions, p_info.render_modes, p_info.shader_types);
+	Error err = _parse_shader(p_info.functions, p_info.render_modes, p_info.shader_types, p_info.is_include);
 
 #ifdef DEBUG_ENABLED
 	if (check_warnings) {
@@ -9540,7 +9580,7 @@ Error ShaderLanguage::complete(const String &p_code, const ShaderCompileInfo &p_
 	global_var_get_type_func = p_info.global_variable_type_func;
 
 	shader = alloc_node<ShaderNode>();
-	_parse_shader(p_info.functions, p_info.render_modes, p_info.shader_types);
+	_parse_shader(p_info.functions, p_info.render_modes, p_info.shader_types, p_info.is_include);
 
 #ifdef DEBUG_ENABLED
 	// Adds context keywords.
@@ -10066,6 +10106,10 @@ String ShaderLanguage::get_error_text() {
 	return error_str;
 }
 
+Vector<ShaderLanguage::FilePosition> ShaderLanguage::get_include_positions() {
+	return include_positions;
+}
+
 int ShaderLanguage::get_error_line() {
 	return error_line;
 }
diff --git a/servers/rendering/shader_language.h b/servers/rendering/shader_language.h
index 2b147fbeb1..4e7283a714 100644
--- a/servers/rendering/shader_language.h
+++ b/servers/rendering/shader_language.h
@@ -38,6 +38,7 @@
 #include "core/templates/rb_map.h"
 #include "core/typedefs.h"
 #include "core/variant/variant.h"
+#include "scene/resources/shader_include.h"
 
 #ifdef DEBUG_ENABLED
 #include "shader_warnings.h"
@@ -867,6 +868,11 @@ public:
 
 	typedef DataType (*GlobalVariableGetTypeFunc)(const StringName &p_name);
 
+	struct FilePosition {
+		String file;
+		int line = 0;
+	};
+
 private:
 	struct KeyWord {
 		TokenType token;
@@ -884,6 +890,8 @@ private:
 	String error_str;
 	int error_line = 0;
 
+	Vector<FilePosition> include_positions;
+
 #ifdef DEBUG_ENABLED
 	struct Usage {
 		int decl_line;
@@ -951,6 +959,7 @@ private:
 		error_line = tk_line;
 		error_set = true;
 		error_str = p_str;
+		include_positions.write[include_positions.size() - 1].line = tk_line;
 	}
 
 	void _set_expected_error(const String &p_what) {
@@ -1070,7 +1079,7 @@ private:
 	String _get_shader_type_list(const HashSet<String> &p_shader_types) const;
 	String _get_qualifier_str(ArgumentQualifier p_qualifier) const;
 
-	Error _parse_shader(const HashMap<StringName, FunctionInfo> &p_functions, const Vector<ModeInfo> &p_render_modes, const HashSet<String> &p_shader_types);
+	Error _parse_shader(const HashMap<StringName, FunctionInfo> &p_functions, const Vector<ModeInfo> &p_render_modes, const HashSet<String> &p_shader_types, bool p_is_include);
 
 	Error _find_last_flow_op_in_block(BlockNode *p_block, FlowOperation p_op);
 	Error _find_last_flow_op_in_op(ControlFlowNode *p_flow, FlowOperation p_op);
@@ -1098,12 +1107,14 @@ public:
 		VaryingFunctionNames varying_function_names = VaryingFunctionNames();
 		HashSet<String> shader_types;
 		GlobalVariableGetTypeFunc global_variable_type_func = nullptr;
+		bool is_include = false;
 	};
 
 	Error compile(const String &p_code, const ShaderCompileInfo &p_info);
 	Error complete(const String &p_code, const ShaderCompileInfo &p_info, List<ScriptLanguage::CodeCompletionOption> *r_options, String &r_call_hint);
 
 	String get_error_text();
+	Vector<FilePosition> get_include_positions();
 	int get_error_line();
 
 	ShaderNode *get_shader();
diff --git a/servers/rendering/shader_preprocessor.cpp b/servers/rendering/shader_preprocessor.cpp
new file mode 100644
index 0000000000..9623d11010
--- /dev/null
+++ b/servers/rendering/shader_preprocessor.cpp
@@ -0,0 +1,1074 @@
+/*************************************************************************/
+/*  shader_preprocessor.cpp                                              */
+/*************************************************************************/
+/*                       This file is part of:                           */
+/*                           GODOT ENGINE                                */
+/*                      https://godotengine.org                          */
+/*************************************************************************/
+/* Copyright (c) 2007-2022 Juan Linietsky, Ariel Manzur.                 */
+/* Copyright (c) 2014-2022 Godot Engine contributors (cf. AUTHORS.md).   */
+/*                                                                       */
+/* Permission is hereby granted, free of charge, to any person obtaining */
+/* a copy of this software and associated documentation files (the       */
+/* "Software"), to deal in the Software without restriction, including   */
+/* without limitation the rights to use, copy, modify, merge, publish,   */
+/* distribute, sublicense, and/or sell copies of the Software, and to    */
+/* permit persons to whom the Software is furnished to do so, subject to */
+/* the following conditions:                                             */
+/*                                                                       */
+/* The above copyright notice and this permission notice shall be        */
+/* included in all copies or substantial portions of the Software.       */
+/*                                                                       */
+/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,       */
+/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF    */
+/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.*/
+/* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY  */
+/* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,  */
+/* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE     */
+/* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                */
+/*************************************************************************/
+
+#include "shader_preprocessor.h"
+#include "core/math/expression.h"
+
+const char32_t CURSOR = 0xFFFF;
+
+// Tokenizer
+
+void ShaderPreprocessor::Tokenizer::add_generated(const ShaderPreprocessor::Token &p_t) {
+	generated.push_back(p_t);
+}
+
+char32_t ShaderPreprocessor::Tokenizer::next() {
+	if (index < size) {
+		return code[index++];
+	}
+	return 0;
+}
+
+int ShaderPreprocessor::Tokenizer::get_line() const {
+	return line;
+}
+
+int ShaderPreprocessor::Tokenizer::get_index() const {
+	return index;
+}
+
+void ShaderPreprocessor::Tokenizer::get_and_clear_generated(Vector<ShaderPreprocessor::Token> *r_out) {
+	for (int i = 0; i < generated.size(); i++) {
+		r_out->push_back(generated[i]);
+	}
+	generated.clear();
+}
+
+void ShaderPreprocessor::Tokenizer::backtrack(char32_t p_what) {
+	while (index >= 0) {
+		char32_t c = code[index];
+		if (c == p_what) {
+			break;
+		}
+		index--;
+	}
+}
+
+char32_t ShaderPreprocessor::Tokenizer::peek() {
+	if (index < size) {
+		return code[index];
+	}
+	return 0;
+}
+
+LocalVector<ShaderPreprocessor::Token> ShaderPreprocessor::Tokenizer::advance(char32_t p_what) {
+	LocalVector<ShaderPreprocessor::Token> tokens;
+
+	while (index < size) {
+		char32_t c = code[index++];
+
+		tokens.push_back(ShaderPreprocessor::Token(c, line));
+
+		if (c == '\n') {
+			add_generated(ShaderPreprocessor::Token('\n', line));
+			line++;
+		}
+
+		if (c == p_what || c == 0) {
+			return tokens;
+		}
+	}
+	return LocalVector<ShaderPreprocessor::Token>();
+}
+
+void ShaderPreprocessor::Tokenizer::skip_whitespace() {
+	while (is_char_space(peek())) {
+		next();
+	}
+}
+
+String ShaderPreprocessor::Tokenizer::get_identifier(bool *r_is_cursor, bool p_started) {
+	if (r_is_cursor != nullptr) {
+		*r_is_cursor = false;
+	}
+
+	LocalVector<char32_t> text;
+
+	while (true) {
+		char32_t c = peek();
+		if (is_char_end(c) || c == '(' || c == ')' || c == ',' || c == ';') {
+			break;
+		}
+
+		if (is_whitespace(c) && p_started) {
+			break;
+		}
+		if (!is_whitespace(c)) {
+			p_started = true;
+		}
+
+		char32_t n = next();
+		if (n == CURSOR) {
+			if (r_is_cursor != nullptr) {
+				*r_is_cursor = true;
+			}
+		} else {
+			if (p_started) {
+				text.push_back(n);
+			}
+		}
+	}
+
+	String id = vector_to_string(text);
+	if (!id.is_valid_identifier()) {
+		return "";
+	}
+
+	return id;
+}
+
+String ShaderPreprocessor::Tokenizer::peek_identifier() {
+	const int original = index;
+	String id = get_identifier();
+	index = original;
+	return id;
+}
+
+ShaderPreprocessor::Token ShaderPreprocessor::Tokenizer::get_token() {
+	while (index < size) {
+		const char32_t c = code[index++];
+		const Token t = ShaderPreprocessor::Token(c, line);
+
+		switch (c) {
+			case ' ':
+			case '\t':
+				skip_whitespace();
+				return ShaderPreprocessor::Token(' ', line);
+			case '\n':
+				line++;
+				return t;
+			default:
+				return t;
+		}
+	}
+	return ShaderPreprocessor::Token(char32_t(0), line);
+}
+
+ShaderPreprocessor::Tokenizer::Tokenizer(const String &p_code) {
+	code = p_code;
+	line = 0;
+	index = 0;
+	size = code.size();
+}
+
+// ShaderPreprocessor::CommentRemover
+
+String ShaderPreprocessor::CommentRemover::get_error() const {
+	if (comments_open != 0) {
+		return "Block comment mismatch";
+	}
+	return "";
+}
+
+int ShaderPreprocessor::CommentRemover::get_error_line() const {
+	if (comments_open != 0) {
+		return comment_line_open;
+	}
+	return -1;
+}
+
+char32_t ShaderPreprocessor::CommentRemover::peek() const {
+	if (index < code.size()) {
+		return code[index];
+	}
+	return 0;
+}
+
+bool ShaderPreprocessor::CommentRemover::advance(char32_t p_what) {
+	while (index < code.size()) {
+		char32_t c = code[index++];
+
+		if (c == '\n') {
+			line++;
+			stripped.push_back('\n');
+		}
+
+		if (c == p_what) {
+			return true;
+		}
+	}
+	return false;
+}
+
+String ShaderPreprocessor::CommentRemover::strip() {
+	stripped.clear();
+	index = 0;
+	line = 0;
+	comment_line_open = 0;
+	comments_open = 0;
+	strings_open = 0;
+
+	while (index < code.size()) {
+		char32_t c = code[index++];
+
+		if (c == CURSOR) {
+			// Cursor. Maintain.
+			stripped.push_back(c);
+		} else if (c == '"') {
+			if (strings_open <= 0) {
+				strings_open++;
+			} else {
+				strings_open--;
+			}
+			stripped.push_back(c);
+		} else if (c == '/' && strings_open == 0) {
+			char32_t p = peek();
+			if (p == '/') { // Single line comment.
+				advance('\n');
+			} else if (p == '*') { // Start of a block comment.
+				index++;
+				comment_line_open = line;
+				comments_open++;
+				while (advance('*')) {
+					if (peek() == '/') { // End of a block comment.
+						comments_open--;
+						index++;
+						break;
+					}
+				}
+			} else {
+				stripped.push_back(c);
+			}
+		} else if (c == '*' && strings_open == 0) {
+			if (peek() == '/') { // Unmatched end of a block comment.
+				comment_line_open = line;
+				comments_open--;
+			} else {
+				stripped.push_back(c);
+			}
+		} else if (c == '\n') {
+			line++;
+			stripped.push_back(c);
+		} else {
+			stripped.push_back(c);
+		}
+	}
+	return vector_to_string(stripped);
+}
+
+ShaderPreprocessor::CommentRemover::CommentRemover(const String &p_code) {
+	code = p_code;
+	index = 0;
+	line = 0;
+	comment_line_open = 0;
+	comments_open = 0;
+	strings_open = 0;
+}
+
+// ShaderPreprocessor::Token
+
+ShaderPreprocessor::Token::Token() {
+	text = 0;
+	line = -1;
+}
+
+ShaderPreprocessor::Token::Token(char32_t p_text, int p_line) {
+	text = p_text;
+	line = p_line;
+}
+
+// ShaderPreprocessor
+
+bool ShaderPreprocessor::is_char_word(char32_t p_char) {
+	if ((p_char >= '0' && p_char <= '9') ||
+			(p_char >= 'a' && p_char <= 'z') ||
+			(p_char >= 'A' && p_char <= 'Z') ||
+			p_char == '_') {
+		return true;
+	}
+
+	return false;
+}
+
+bool ShaderPreprocessor::is_char_space(char32_t p_char) {
+	return p_char == ' ' || p_char == '\t';
+}
+
+bool ShaderPreprocessor::is_char_end(char32_t p_char) {
+	return p_char == '\n' || p_char == 0;
+}
+
+String ShaderPreprocessor::vector_to_string(const LocalVector<char32_t> &p_v, int p_start, int p_end) {
+	const int stop = (p_end == -1) ? p_v.size() : p_end;
+	const int count = stop - p_start;
+
+	String result;
+	result.resize(count + 1);
+	for (int i = 0; i < count; i++) {
+		result[i] = p_v[p_start + i];
+	}
+	result[count] = 0; // Ensure string is null terminated for length() to work.
+	return result;
+}
+
+String ShaderPreprocessor::tokens_to_string(const LocalVector<Token> &p_tokens) {
+	LocalVector<char32_t> result;
+	for (uint32_t i = 0; i < p_tokens.size(); i++) {
+		result.push_back(p_tokens[i].text);
+	}
+	return vector_to_string(result);
+}
+
+void ShaderPreprocessor::process_directive(Tokenizer *p_tokenizer) {
+	bool is_cursor;
+	String directive = p_tokenizer->get_identifier(&is_cursor, true);
+	if (is_cursor) {
+		state->completion_type = COMPLETION_TYPE_DIRECTIVE;
+	}
+
+	if (directive == "if") {
+		if (check_directive_before_type(p_tokenizer, directive)) {
+			process_if(p_tokenizer);
+		}
+	} else if (directive == "ifdef") {
+		if (check_directive_before_type(p_tokenizer, directive)) {
+			process_ifdef(p_tokenizer);
+		}
+	} else if (directive == "ifndef") {
+		if (check_directive_before_type(p_tokenizer, directive)) {
+			process_ifndef(p_tokenizer);
+		}
+	} else if (directive == "else") {
+		if (check_directive_before_type(p_tokenizer, directive)) {
+			process_else(p_tokenizer);
+		}
+	} else if (directive == "endif") {
+		if (check_directive_before_type(p_tokenizer, directive)) {
+			process_endif(p_tokenizer);
+		}
+	} else if (directive == "define") {
+		if (check_directive_before_type(p_tokenizer, directive)) {
+			process_define(p_tokenizer);
+		}
+	} else if (directive == "undef") {
+		if (check_directive_before_type(p_tokenizer, directive)) {
+			process_undef(p_tokenizer);
+		}
+	} else if (directive == "include") {
+		if (check_directive_before_type(p_tokenizer, directive)) {
+			process_include(p_tokenizer);
+		}
+	} else if (directive == "pragma") {
+		if (check_directive_before_type(p_tokenizer, directive)) {
+			process_pragma(p_tokenizer);
+		}
+	} else {
+		set_error(RTR("Unknown directive."), p_tokenizer->get_line());
+	}
+}
+
+void ShaderPreprocessor::process_define(Tokenizer *p_tokenizer) {
+	const int line = p_tokenizer->get_line();
+
+	String label = p_tokenizer->get_identifier();
+	if (label.is_empty()) {
+		set_error(RTR("Invalid macro name."), line);
+		return;
+	}
+
+	if (state->defines.has(label)) {
+		set_error(RTR("Macro redefinition."), line);
+		return;
+	}
+
+	if (p_tokenizer->peek() == '(') {
+		// Macro has arguments.
+		p_tokenizer->get_token();
+
+		Vector<String> args;
+		while (true) {
+			String name = p_tokenizer->get_identifier();
+			if (name.is_empty()) {
+				set_error(RTR("Invalid argument name."), line);
+				return;
+			}
+			args.push_back(name);
+
+			p_tokenizer->skip_whitespace();
+			char32_t next = p_tokenizer->get_token().text;
+			if (next == ')') {
+				break;
+			} else if (next != ',') {
+				set_error(RTR("Expected a comma in the macro argument list."), line);
+				return;
+			}
+		}
+
+		Define *define = memnew(Define);
+		define->arguments = args;
+		define->body = tokens_to_string(p_tokenizer->advance('\n')).strip_edges();
+		state->defines[label] = define;
+	} else {
+		// Simple substitution macro.
+		Define *define = memnew(Define);
+		define->body = tokens_to_string(p_tokenizer->advance('\n')).strip_edges();
+		state->defines[label] = define;
+	}
+}
+
+void ShaderPreprocessor::process_else(Tokenizer *p_tokenizer) {
+	if (state->skip_stack_else.is_empty()) {
+		set_error(RTR("Unmatched else."), p_tokenizer->get_line());
+		return;
+	}
+	p_tokenizer->advance('\n');
+
+	bool skip = state->skip_stack_else[state->skip_stack_else.size() - 1];
+	state->skip_stack_else.remove_at(state->skip_stack_else.size() - 1);
+
+	Vector<SkippedCondition *> vec = state->skipped_conditions[state->current_include];
+	int index = vec.size() - 1;
+	if (index >= 0) {
+		SkippedCondition *cond = vec[index];
+		if (cond->end_line == -1) {
+			cond->end_line = p_tokenizer->get_line();
+		}
+	}
+
+	if (skip) {
+		Vector<String> ends;
+		ends.push_back("endif");
+		next_directive(p_tokenizer, ends);
+	}
+}
+
+void ShaderPreprocessor::process_endif(Tokenizer *p_tokenizer) {
+	state->condition_depth--;
+	if (state->condition_depth < 0) {
+		set_error(RTR("Unmatched endif."), p_tokenizer->get_line());
+		return;
+	}
+
+	Vector<SkippedCondition *> vec = state->skipped_conditions[state->current_include];
+	int index = vec.size() - 1;
+	if (index >= 0) {
+		SkippedCondition *cond = vec[index];
+		if (cond->end_line == -1) {
+			cond->end_line = p_tokenizer->get_line();
+		}
+	}
+
+	p_tokenizer->advance('\n');
+}
+
+void ShaderPreprocessor::process_if(Tokenizer *p_tokenizer) {
+	int line = p_tokenizer->get_line();
+
+	String body = tokens_to_string(p_tokenizer->advance('\n')).strip_edges();
+	if (body.is_empty()) {
+		set_error(RTR("Missing condition."), line);
+		return;
+	}
+
+	Error error = expand_macros(body, line, body);
+	if (error != OK) {
+		return;
+	}
+
+	Expression expression;
+	Vector<String> names;
+	error = expression.parse(body, names);
+	if (error != OK) {
+		set_error(expression.get_error_text(), line);
+		return;
+	}
+
+	Variant v = expression.execute(Array(), nullptr, false);
+	if (v.get_type() == Variant::NIL) {
+		set_error(RTR("Condition evaluation error."), line);
+		return;
+	}
+
+	bool success = v.booleanize();
+	start_branch_condition(p_tokenizer, success);
+}
+
+void ShaderPreprocessor::process_ifdef(Tokenizer *p_tokenizer) {
+	const int line = p_tokenizer->get_line();
+
+	String label = p_tokenizer->get_identifier();
+	if (label.is_empty()) {
+		set_error(RTR("Invalid macro name."), line);
+		return;
+	}
+
+	p_tokenizer->skip_whitespace();
+	if (!is_char_end(p_tokenizer->peek())) {
+		set_error(RTR("Invalid ifdef."), line);
+		return;
+	}
+	p_tokenizer->advance('\n');
+
+	bool success = state->defines.has(label);
+	start_branch_condition(p_tokenizer, success);
+}
+
+void ShaderPreprocessor::process_ifndef(Tokenizer *p_tokenizer) {
+	const int line = p_tokenizer->get_line();
+
+	String label = p_tokenizer->get_identifier();
+	if (label.is_empty()) {
+		set_error(RTR("Invalid macro name."), line);
+		return;
+	}
+
+	p_tokenizer->skip_whitespace();
+	if (!is_char_end(p_tokenizer->peek())) {
+		set_error(RTR("Invalid ifndef."), line);
+		return;
+	}
+	p_tokenizer->advance('\n');
+
+	bool success = !state->defines.has(label);
+	start_branch_condition(p_tokenizer, success);
+}
+
+void ShaderPreprocessor::process_include(Tokenizer *p_tokenizer) {
+	const int line = p_tokenizer->get_line();
+
+	p_tokenizer->advance('"');
+	String path = tokens_to_string(p_tokenizer->advance('"'));
+	for (int i = 0; i < path.length(); i++) {
+		if (path[i] == '\n') {
+			break; //stop parsing
+		}
+		if (path[i] == CURSOR) {
+			state->completion_type = COMPLETION_TYPE_INCLUDE_PATH;
+			break;
+		}
+	}
+	path = path.substr(0, path.length() - 1);
+	p_tokenizer->skip_whitespace();
+
+	if (path.is_empty() || !is_char_end(p_tokenizer->peek())) {
+		set_error(RTR("Invalid path."), line);
+		return;
+	}
+
+	Ref<Resource> res = ResourceLoader::load(path);
+	if (res.is_null()) {
+		set_error(RTR("Shader include load failed. Does the shader include exist? Is there a cyclic dependency?"), line);
+		return;
+	}
+
+	Ref<ShaderInclude> shader_inc = res;
+	if (shader_inc.is_null()) {
+		set_error(RTR("Shader include resource type is wrong."), line);
+		return;
+	}
+
+	String included = shader_inc->get_code();
+	if (!included.is_empty()) {
+		uint64_t code_hash = included.hash64();
+		if (state->cyclic_include_hashes.find(code_hash)) {
+			set_error(RTR("Cyclic include found."), line);
+			return;
+		}
+	}
+
+	state->shader_includes.insert(shader_inc);
+
+	const String real_path = shader_inc->get_path();
+	if (state->includes.has(real_path)) {
+		// Already included, skip.
+		// This is a valid check because 2 separate include paths could use some
+		// of the same shared functions from a common shader include.
+		return;
+	}
+
+	// Mark as included.
+	state->includes.insert(real_path);
+
+	state->include_depth++;
+	if (state->include_depth > 25) {
+		set_error(RTR("Shader max include depth exceeded."), line);
+		return;
+	}
+
+	String old_include = state->current_include;
+	state->current_include = real_path;
+	ShaderPreprocessor processor;
+
+	int prev_condition_depth = state->condition_depth;
+	state->condition_depth = 0;
+
+	FilePosition fp;
+	fp.file = state->current_include;
+	fp.line = line;
+	state->include_positions.push_back(fp);
+
+	String result;
+	processor.preprocess(state, included, result);
+	add_to_output("@@>" + real_path + "\n"); // Add token for enter include path
+	add_to_output(result);
+	add_to_output("\n@@<\n"); // Add token for exit include path
+
+	// Reset to last include if there are no errors. We want to use this as context.
+	if (state->error.is_empty()) {
+		state->current_include = old_include;
+		state->include_positions.pop_back();
+	} else {
+		return;
+	}
+
+	state->include_depth--;
+	state->condition_depth = prev_condition_depth;
+}
+
+void ShaderPreprocessor::process_pragma(Tokenizer *p_tokenizer) {
+	const int line = p_tokenizer->get_line();
+
+	bool is_cursor;
+	const String label = p_tokenizer->get_identifier(&is_cursor);
+	if (is_cursor) {
+		state->completion_type = COMPLETION_TYPE_PRAGMA;
+	}
+
+	if (label.is_empty()) {
+		set_error(RTR("Invalid pragma directive."), line);
+		return;
+	}
+
+	// Rxplicitly handle pragma values here.
+	// If more pragma options are created, then refactor into a more defined structure.
+	if (label == "disable_preprocessor") {
+		state->disabled = true;
+	} else {
+		set_error(RTR("Invalid pragma directive."), line);
+		return;
+	}
+
+	p_tokenizer->advance('\n');
+}
+
+void ShaderPreprocessor::process_undef(Tokenizer *p_tokenizer) {
+	const int line = p_tokenizer->get_line();
+	const String label = p_tokenizer->get_identifier();
+	if (label.is_empty() || !state->defines.has(label)) {
+		set_error(RTR("Invalid name."), line);
+		return;
+	}
+
+	p_tokenizer->skip_whitespace();
+	if (!is_char_end(p_tokenizer->peek())) {
+		set_error(RTR("Invalid undef."), line);
+		return;
+	}
+
+	memdelete(state->defines[label]);
+	state->defines.erase(label);
+}
+
+void ShaderPreprocessor::start_branch_condition(Tokenizer *p_tokenizer, bool p_success) {
+	state->condition_depth++;
+
+	if (p_success) {
+		state->skip_stack_else.push_back(true);
+	} else {
+		SkippedCondition *cond = memnew(SkippedCondition());
+		cond->start_line = p_tokenizer->get_line();
+		state->skipped_conditions[state->current_include].push_back(cond);
+
+		Vector<String> ends;
+		ends.push_back("else");
+		ends.push_back("endif");
+		if (next_directive(p_tokenizer, ends) == "else") {
+			state->skip_stack_else.push_back(false);
+		} else {
+			state->skip_stack_else.push_back(true);
+		}
+	}
+}
+
+void ShaderPreprocessor::expand_output_macros(int p_start, int p_line_number) {
+	String line = vector_to_string(output, p_start, output.size());
+
+	Error error = expand_macros(line, p_line_number - 1, line); // We are already on next line, so -1.
+	if (error != OK) {
+		return;
+	}
+
+	output.resize(p_start);
+
+	add_to_output(line);
+}
+
+Error ShaderPreprocessor::expand_macros(const String &p_string, int p_line, String &r_expanded) {
+	Vector<Pair<String, Define *>> active_defines;
+	active_defines.resize(state->defines.size());
+	int index = 0;
+	for (const RBMap<String, Define *>::Element *E = state->defines.front(); E; E = E->next()) {
+		active_defines.set(index++, Pair<String, Define *>(E->key(), E->get()));
+	}
+
+	return expand_macros(p_string, p_line, active_defines, r_expanded);
+}
+
+Error ShaderPreprocessor::expand_macros(const String &p_string, int p_line, Vector<Pair<String, Define *>> p_defines, String &r_expanded) {
+	r_expanded = p_string;
+	// When expanding macros we must only evaluate them once.
+	// Later we continue expanding but with the already
+	// evaluated macros removed.
+	for (int i = 0; i < p_defines.size(); i++) {
+		Pair<String, Define *> define_pair = p_defines[i];
+
+		Error error = expand_macros_once(r_expanded, p_line, define_pair, r_expanded);
+		if (error != OK) {
+			return error;
+		}
+
+		// Remove expanded macro and recursively replace remaining.
+		p_defines.remove_at(i);
+		return expand_macros(r_expanded, p_line, p_defines, r_expanded);
+	}
+
+	return OK;
+}
+
+Error ShaderPreprocessor::expand_macros_once(const String &p_line, int p_line_number, Pair<String, Define *> p_define_pair, String &r_expanded) {
+	String result = p_line;
+
+	const String &key = p_define_pair.first;
+	const Define *define = p_define_pair.second;
+
+	int index_start = 0;
+	int index = 0;
+	while (find_match(result, key, index, index_start)) {
+		String body = define->body;
+		if (define->arguments.size() > 0) {
+			// Complex macro with arguments.
+			int args_start = index + key.length();
+			int args_end = p_line.find(")", args_start);
+			if (args_start == -1 || args_end == -1) {
+				set_error(RTR("Missing macro argument parenthesis."), p_line_number);
+				return FAILED;
+			}
+
+			String values = result.substr(args_start + 1, args_end - (args_start + 1));
+			Vector<String> args = values.split(",");
+			if (args.size() != define->arguments.size()) {
+				set_error(RTR("Invalid macro argument count."), p_line_number);
+				return FAILED;
+			}
+
+			// Insert macro arguments into the body.
+			for (int i = 0; i < args.size(); i++) {
+				String arg_name = define->arguments[i];
+				int arg_index_start = 0;
+				int arg_index = 0;
+				while (find_match(body, arg_name, arg_index, arg_index_start)) {
+					body = body.substr(0, arg_index) + args[i] + body.substr(arg_index + arg_name.length(), body.length() - (arg_index + arg_name.length()));
+					// Manually reset arg_index_start to where the arg value of the define finishes.
+					// This ensures we don't skip the other args of this macro in the string.
+					arg_index_start = arg_index + args[i].length() + 1;
+				}
+			}
+
+			result = result.substr(0, index) + " " + body + " " + result.substr(args_end + 1, result.length());
+		} else {
+			result = result.substr(0, index) + body + result.substr(index + key.length(), result.length() - (index + key.length()));
+			// Manually reset index_start to where the body value of the define finishes.
+			// This ensures we don't skip another instance of this macro in the string.
+			index_start = index + body.length() + 1;
+			break;
+		}
+	}
+	r_expanded = result;
+	return OK;
+}
+
+bool ShaderPreprocessor::find_match(const String &p_string, const String &p_value, int &r_index, int &r_index_start) {
+	// Looks for value in string and then determines if the boundaries
+	// are non-word characters. This method semi-emulates \b in regex.
+	r_index = p_string.find(p_value, r_index_start);
+	while (r_index > -1) {
+		if (r_index > 0) {
+			if (is_char_word(p_string[r_index - 1])) {
+				r_index_start = r_index + 1;
+				r_index = p_string.find(p_value, r_index_start);
+				continue;
+			}
+		}
+
+		if (r_index + p_value.length() < p_string.length()) {
+			if (is_char_word(p_string[r_index + p_value.length()])) {
+				r_index_start = r_index + p_value.length() + 1;
+				r_index = p_string.find(p_value, r_index_start);
+				continue;
+			}
+		}
+
+		// Return and shift index start automatically for next call.
+		r_index_start = r_index + p_value.length() + 1;
+		return true;
+	}
+
+	return false;
+}
+
+String ShaderPreprocessor::next_directive(Tokenizer *p_tokenizer, const Vector<String> &p_directives) {
+	const int line = p_tokenizer->get_line();
+	int nesting = 0;
+
+	while (true) {
+		p_tokenizer->advance('#');
+
+		String id = p_tokenizer->peek_identifier();
+		if (id.is_empty()) {
+			break;
+		}
+
+		if (nesting == 0) {
+			for (int i = 0; i < p_directives.size(); i++) {
+				if (p_directives[i] == id) {
+					p_tokenizer->backtrack('#');
+					return id;
+				}
+			}
+		}
+
+		if (id == "ifdef" || id == "ifndef" || id == "if") {
+			nesting++;
+		} else if (id == "endif") {
+			nesting--;
+		}
+	}
+
+	set_error(RTR("Can't find matching branch directive."), line);
+	return "";
+}
+
+void ShaderPreprocessor::add_to_output(const String &p_str) {
+	for (int i = 0; i < p_str.length(); i++) {
+		output.push_back(p_str[i]);
+	}
+}
+
+void ShaderPreprocessor::set_error(const String &p_error, int p_line) {
+	if (state->error.is_empty()) {
+		state->error = p_error;
+		FilePosition fp;
+		fp.line = p_line + 1;
+		state->include_positions.push_back(fp);
+	}
+}
+
+bool ShaderPreprocessor::check_directive_before_type(Tokenizer *p_tokenizer, const String &p_directive) {
+	if (p_tokenizer->get_index() < state->shader_type_pos) {
+		set_error(vformat(RTR("`#%s` may not be defined before `shader_type`."), p_directive), p_tokenizer->get_line());
+		return false;
+	}
+	return true;
+}
+
+ShaderPreprocessor::Define *ShaderPreprocessor::create_define(const String &p_body) {
+	ShaderPreprocessor::Define *define = memnew(Define);
+	define->body = p_body;
+	return define;
+}
+
+void ShaderPreprocessor::clear() {
+	if (state_owner && state != nullptr) {
+		for (const RBMap<String, Define *>::Element *E = state->defines.front(); E; E = E->next()) {
+			memdelete(E->get());
+		}
+
+		for (const RBMap<String, Vector<SkippedCondition *>>::Element *E = state->skipped_conditions.front(); E; E = E->next()) {
+			for (SkippedCondition *condition : E->get()) {
+				memdelete(condition);
+			}
+		}
+
+		memdelete(state);
+	}
+	state_owner = false;
+	state = nullptr;
+}
+
+Error ShaderPreprocessor::preprocess(State *p_state, const String &p_code, String &r_result) {
+	clear();
+
+	output.clear();
+
+	state = p_state;
+
+	CommentRemover remover(p_code);
+	String stripped = remover.strip();
+	String error = remover.get_error();
+	if (!error.is_empty()) {
+		set_error(error, remover.get_error_line());
+		return FAILED;
+	}
+
+	// Track code hashes to prevent cyclic include.
+	uint64_t code_hash = p_code.hash64();
+	state->cyclic_include_hashes.push_back(code_hash);
+
+	Tokenizer p_tokenizer(stripped);
+	int last_size = 0;
+	bool has_symbols_before_directive = false;
+
+	while (true) {
+		const Token &t = p_tokenizer.get_token();
+
+		if (t.text == 0) {
+			break;
+		}
+
+		if (state->disabled) {
+			// Preprocessor was disabled.
+			// Read the rest of the file into the output.
+			output.push_back(t.text);
+			continue;
+		} else {
+			// Add autogenerated tokens.
+			Vector<Token> generated;
+			p_tokenizer.get_and_clear_generated(&generated);
+			for (int i = 0; i < generated.size(); i++) {
+				output.push_back(generated[i].text);
+			}
+		}
+
+		if (t.text == '#') {
+			if (has_symbols_before_directive) {
+				set_error(RTR("Invalid symbols placed before directive."), p_tokenizer.get_line());
+				state->cyclic_include_hashes.erase(code_hash); // Remove this hash.
+				return FAILED;
+			}
+			process_directive(&p_tokenizer);
+		} else {
+			if (is_char_end(t.text)) {
+				expand_output_macros(last_size, p_tokenizer.get_line());
+				last_size = output.size();
+				has_symbols_before_directive = false;
+			} else if (!is_char_space(t.text)) {
+				has_symbols_before_directive = true;
+			}
+			output.push_back(t.text);
+		}
+
+		if (!state->error.is_empty()) {
+			state->cyclic_include_hashes.erase(code_hash); // Remove this hash.
+			return FAILED;
+		}
+	}
+	state->cyclic_include_hashes.erase(code_hash); // Remove this hash.
+
+	if (!state->disabled) {
+		if (state->condition_depth != 0) {
+			set_error(RTR("Unmatched conditional statement."), p_tokenizer.line);
+			return FAILED;
+		}
+
+		expand_output_macros(last_size, p_tokenizer.get_line());
+	}
+
+	r_result = vector_to_string(output);
+
+	return OK;
+}
+
+Error ShaderPreprocessor::preprocess(const String &p_code, String &r_result, String *r_error_text, List<FilePosition> *r_error_position, HashSet<Ref<ShaderInclude>> *r_includes, List<ScriptLanguage::CodeCompletionOption> *r_completion_options, IncludeCompletionFunction p_include_completion_func) {
+	State pp_state;
+	Error err = preprocess(&pp_state, p_code, r_result);
+	if (err != OK) {
+		if (r_error_text) {
+			*r_error_text = pp_state.error;
+		}
+		if (r_error_position) {
+			*r_error_position = pp_state.include_positions;
+		}
+	}
+	if (r_includes) {
+		*r_includes = pp_state.shader_includes;
+	}
+
+	if (r_completion_options) {
+		switch (pp_state.completion_type) {
+			case COMPLETION_TYPE_DIRECTIVE: {
+				List<String> options;
+				get_keyword_list(&options, true);
+
+				for (const String &E : options) {
+					ScriptLanguage::CodeCompletionOption option(E, ScriptLanguage::CODE_COMPLETION_KIND_PLAIN_TEXT);
+					r_completion_options->push_back(option);
+				}
+
+			} break;
+			case COMPLETION_TYPE_PRAGMA: {
+				List<String> options;
+
+				ShaderPreprocessor::get_pragma_list(&options);
+
+				for (const String &E : options) {
+					ScriptLanguage::CodeCompletionOption option(E, ScriptLanguage::CODE_COMPLETION_KIND_PLAIN_TEXT);
+					r_completion_options->push_back(option);
+				}
+
+			} break;
+			case COMPLETION_TYPE_INCLUDE_PATH: {
+				if (p_include_completion_func && r_completion_options) {
+					p_include_completion_func(r_completion_options);
+				}
+
+			} break;
+			default: {
+			}
+		}
+	}
+	return err;
+}
+
+void ShaderPreprocessor::get_keyword_list(List<String> *r_keywords, bool p_include_shader_keywords) {
+	r_keywords->push_back("define");
+	if (p_include_shader_keywords) {
+		r_keywords->push_back("else");
+	}
+	r_keywords->push_back("endif");
+	if (p_include_shader_keywords) {
+		r_keywords->push_back("if");
+	}
+	r_keywords->push_back("ifdef");
+	r_keywords->push_back("ifndef");
+	r_keywords->push_back("include");
+	r_keywords->push_back("pragma");
+	r_keywords->push_back("undef");
+}
+
+void ShaderPreprocessor::get_pragma_list(List<String> *r_pragmas) {
+	r_pragmas->push_back("disable_preprocessor");
+}
+
+ShaderPreprocessor::ShaderPreprocessor() {
+}
+
+ShaderPreprocessor::~ShaderPreprocessor() {
+	clear();
+}
diff --git a/servers/rendering/shader_preprocessor.h b/servers/rendering/shader_preprocessor.h
new file mode 100644
index 0000000000..9bac706049
--- /dev/null
+++ b/servers/rendering/shader_preprocessor.h
@@ -0,0 +1,202 @@
+/*************************************************************************/
+/*  shader_preprocessor.h                                                */
+/*************************************************************************/
+/*                       This file is part of:                           */
+/*                           GODOT ENGINE                                */
+/*                      https://godotengine.org                          */
+/*************************************************************************/
+/* Copyright (c) 2007-2022 Juan Linietsky, Ariel Manzur.                 */
+/* Copyright (c) 2014-2022 Godot Engine contributors (cf. AUTHORS.md).   */
+/*                                                                       */
+/* Permission is hereby granted, free of charge, to any person obtaining */
+/* a copy of this software and associated documentation files (the       */
+/* "Software"), to deal in the Software without restriction, including   */
+/* without limitation the rights to use, copy, modify, merge, publish,   */
+/* distribute, sublicense, and/or sell copies of the Software, and to    */
+/* permit persons to whom the Software is furnished to do so, subject to */
+/* the following conditions:                                             */
+/*                                                                       */
+/* The above copyright notice and this permission notice shall be        */
+/* included in all copies or substantial portions of the Software.       */
+/*                                                                       */
+/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,       */
+/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF    */
+/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.*/
+/* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY  */
+/* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,  */
+/* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE     */
+/* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                */
+/*************************************************************************/
+
+#ifndef SHADER_PREPROCESSOR_H
+#define SHADER_PREPROCESSOR_H
+
+#include "core/string/ustring.h"
+#include "core/templates/list.h"
+#include "core/templates/local_vector.h"
+#include "core/templates/rb_map.h"
+#include "core/templates/rb_set.h"
+#include "core/typedefs.h"
+
+#include "core/io/resource_loader.h"
+#include "core/os/os.h"
+#include "scene/resources/shader.h"
+#include "scene/resources/shader_include.h"
+
+class ShaderPreprocessor {
+public:
+	enum CompletionType {
+		COMPLETION_TYPE_NONE,
+		COMPLETION_TYPE_DIRECTIVE,
+		COMPLETION_TYPE_PRAGMA_DIRECTIVE,
+		COMPLETION_TYPE_PRAGMA,
+		COMPLETION_TYPE_INCLUDE_PATH,
+	};
+
+	struct FilePosition {
+		String file;
+		int line = 0;
+	};
+
+private:
+	struct Token {
+		char32_t text;
+		int line;
+
+		Token();
+		Token(char32_t p_text, int p_line);
+	};
+
+	// The real preprocessor that understands basic shader and preprocessor language syntax.
+	class Tokenizer {
+	public:
+		String code;
+		int line;
+		int index;
+		int size;
+		Vector<Token> generated;
+
+	private:
+		void add_generated(const Token &p_t);
+		char32_t next();
+
+	public:
+		int get_line() const;
+		int get_index() const;
+		char32_t peek();
+
+		void get_and_clear_generated(Vector<Token> *r_out);
+		void backtrack(char32_t p_what);
+		LocalVector<Token> advance(char32_t p_what);
+		void skip_whitespace();
+		String get_identifier(bool *r_is_cursor = nullptr, bool p_started = false);
+		String peek_identifier();
+		Token get_token();
+
+		Tokenizer(const String &p_code);
+	};
+
+	class CommentRemover {
+	private:
+		LocalVector<char32_t> stripped;
+		String code;
+		int index;
+		int line;
+		int comment_line_open;
+		int comments_open;
+		int strings_open;
+
+	public:
+		String get_error() const;
+		int get_error_line() const;
+		char32_t peek() const;
+
+		bool advance(char32_t p_what);
+		String strip();
+
+		CommentRemover(const String &p_code);
+	};
+
+	struct Define {
+		Vector<String> arguments;
+		String body;
+	};
+
+	struct SkippedCondition {
+		int start_line = -1;
+		int end_line = -1;
+	};
+
+	struct State {
+		RBMap<String, Define *> defines;
+		Vector<bool> skip_stack_else;
+		int condition_depth = 0;
+		RBSet<String> includes;
+		List<uint64_t> cyclic_include_hashes; // Holds code hash of includes.
+		int include_depth = 0;
+		String current_include;
+		String current_shader_type;
+		int shader_type_pos = -1;
+		String error;
+		List<FilePosition> include_positions;
+		RBMap<String, Vector<SkippedCondition *>> skipped_conditions;
+		bool disabled = false;
+		CompletionType completion_type = COMPLETION_TYPE_NONE;
+		HashSet<Ref<ShaderInclude>> shader_includes;
+	};
+
+private:
+	LocalVector<char32_t> output;
+	State *state = nullptr;
+	bool state_owner = false;
+
+private:
+	static bool is_char_word(char32_t p_char);
+	static bool is_char_space(char32_t p_char);
+	static bool is_char_end(char32_t p_char);
+	static String vector_to_string(const LocalVector<char32_t> &p_v, int p_start = 0, int p_end = -1);
+	static String tokens_to_string(const LocalVector<Token> &p_tokens);
+
+	void process_directive(Tokenizer *p_tokenizer);
+	void process_define(Tokenizer *p_tokenizer);
+	void process_else(Tokenizer *p_tokenizer);
+	void process_endif(Tokenizer *p_tokenizer);
+	void process_if(Tokenizer *p_tokenizer);
+	void process_ifdef(Tokenizer *p_tokenizer);
+	void process_ifndef(Tokenizer *p_tokenizer);
+	void process_include(Tokenizer *p_tokenizer);
+	void process_pragma(Tokenizer *p_tokenizer);
+	void process_undef(Tokenizer *p_tokenizer);
+
+	void start_branch_condition(Tokenizer *p_tokenizer, bool p_success);
+
+	void expand_output_macros(int p_start, int p_line);
+	Error expand_macros(const String &p_string, int p_line, String &r_result);
+	Error expand_macros(const String &p_string, int p_line, Vector<Pair<String, Define *>> p_defines, String &r_result);
+	Error expand_macros_once(const String &p_line, int p_line_number, Pair<String, Define *> p_define_pair, String &r_expanded);
+	bool find_match(const String &p_string, const String &p_value, int &r_index, int &r_index_start);
+
+	String next_directive(Tokenizer *p_tokenizer, const Vector<String> &p_directives);
+	void add_to_output(const String &p_str);
+	void set_error(const String &p_error, int p_line);
+	bool check_directive_before_type(Tokenizer *p_tokenizer, const String &p_directive);
+
+	static Define *create_define(const String &p_body);
+
+	void clear();
+
+	Error preprocess(State *p_state, const String &p_code, String &r_result);
+
+public:
+	typedef void (*IncludeCompletionFunction)(List<ScriptLanguage::CodeCompletionOption> *);
+
+	Error preprocess(const String &p_code, String &r_result, String *r_error_text = nullptr, List<FilePosition> *r_error_position = nullptr, HashSet<Ref<ShaderInclude>> *r_includes = nullptr, List<ScriptLanguage::CodeCompletionOption> *r_completion_options = nullptr, IncludeCompletionFunction p_include_completion_func = nullptr);
+
+	static void get_keyword_list(List<String> *r_keywords, bool p_include_shader_keywords);
+	static void get_pragma_list(List<String> *r_pragmas);
+
+	ShaderPreprocessor();
+	~ShaderPreprocessor();
+};
+
+#endif // SHADER_PREPROCESSOR_H
diff --git a/servers/rendering/storage/material_storage.h b/servers/rendering/storage/material_storage.h
index 00790106af..4189e792db 100644
--- a/servers/rendering/storage/material_storage.h
+++ b/servers/rendering/storage/material_storage.h
@@ -61,6 +61,7 @@ public:
 	virtual void shader_free(RID p_rid) = 0;
 
 	virtual void shader_set_code(RID p_shader, const String &p_code) = 0;
+	virtual void shader_set_path_hint(RID p_shader, const String &p_path) = 0;
 	virtual String shader_get_code(RID p_shader) const = 0;
 	virtual void shader_get_param_list(RID p_shader, List<PropertyInfo> *p_param_list) const = 0;