Prevent errors when using ViewportTexture

doc/classes/Node.xml

@@ -500,6 +500,13 @@
 				Returns [code]true[/code] if the local system is the multiplayer authority of this node.
 			</description>
 		</method>
+		<method name="is_node_ready" qualifiers="const">
+			<return type="bool" />
+			<description>
+				Returns [code]true[/code] if the node is ready, i.e. it's inside scene tree and all its children are initialized.
+				[method request_ready] resets it back to [code]false[/code].
+			</description>
+		</method>
 		<method name="is_physics_processing" qualifiers="const">
 			<return type="bool" />
 			<description>

doc/classes/ViewportTexture.xml

@@ -6,7 +6,7 @@
 	<description>
 		Displays the content of a [Viewport] node as a dynamic [Texture2D]. This can be used to mix controls, 2D, and 3D elements in the same scene.
 		To create a ViewportTexture in code, use the [method Viewport.get_texture] method on the target viewport.
-		[b]Note:[/b] When local to scene, this texture uses [method Resource.setup_local_to_scene] to set the proxy texture and flags in the local viewport.
+		[b]Note:[/b] When local to scene, this texture uses [method Resource.setup_local_to_scene] to set the proxy texture and flags in the local viewport. Local to scene viewport textures will return incorrect data until the scene root is ready (see [signal Node.ready]).
 	</description>
 	<tutorials>
 		<link title="GUI in 3D Demo">https://godotengine.org/asset-library/asset/127</link>

scene/main/node.cpp

@@ -2786,6 +2786,10 @@ bool Node::is_displayed_folded() const {
 	return data.display_folded;
 }
 
+bool Node::is_ready() const {
+	return !data.ready_first;
+}
+
 void Node::request_ready() {
 	data.ready_first = true;
 }
@@ -2932,6 +2936,7 @@ void Node::_bind_methods() {
 	ClassDB::bind_method(D_METHOD("queue_free"), &Node::queue_free);
 
 	ClassDB::bind_method(D_METHOD("request_ready"), &Node::request_ready);
+	ClassDB::bind_method(D_METHOD("is_node_ready"), &Node::is_ready);
 
 	ClassDB::bind_method(D_METHOD("set_multiplayer_authority", "id", "recursive"), &Node::set_multiplayer_authority, DEFVAL(true));
 	ClassDB::bind_method(D_METHOD("get_multiplayer_authority"), &Node::get_multiplayer_authority);

scene/main/node.h

@@ -500,6 +500,7 @@ class Node : public Object {
 	bool can_process_notification(int p_what) const;
 	bool is_enabled() const;
 
+	bool is_ready() const;
 	void request_ready();
 
 	static void print_orphan_nodes();

scene/main/viewport.cpp

@@ -61,6 +61,10 @@
 #include "servers/rendering/rendering_server_globals.h"
 
 void ViewportTexture::setup_local_to_scene() {
+	if (vp_pending) {
+		return;
+	}
+
 	Node *loc_scene = get_local_scene();
 	if (!loc_scene) {
 		return;
@@ -72,22 +76,11 @@ void ViewportTexture::setup_local_to_scene() {
 
 	vp = nullptr;
 
-	Node *vpn = loc_scene->get_node(path);
-	ERR_FAIL_COND_MSG(!vpn, "ViewportTexture: Path to node is invalid.");
-
-	vp = Object::cast_to<Viewport>(vpn);
-
-	ERR_FAIL_COND_MSG(!vp, "ViewportTexture: Path to node does not point to a viewport.");
-
-	vp->viewport_textures.insert(this);
-
-	ERR_FAIL_NULL(RenderingServer::get_singleton());
-	if (proxy_ph.is_valid()) {
-		RS::get_singleton()->texture_proxy_update(proxy, vp->texture_rid);
-		RS::get_singleton()->free(proxy_ph);
+	if (loc_scene->is_ready()) {
+		_setup_local_to_scene(loc_scene);
 	} else {
-		ERR_FAIL_COND(proxy.is_valid()); // Should be invalid.
-		proxy = RS::get_singleton()->texture_proxy_create(vp->texture_rid);
+		loc_scene->connect(SNAME("ready"), callable_mp(this, &ViewportTexture::_setup_local_to_scene).bind(loc_scene), CONNECT_ONE_SHOT);
+		vp_pending = true;
 	}
 }
 
@@ -108,17 +101,32 @@ NodePath ViewportTexture::get_viewport_path_in_scene() const {
 }
 
 int ViewportTexture::get_width() const {
-	ERR_FAIL_COND_V_MSG(!vp, 0, "Viewport Texture must be set to use it.");
+	if (!vp) {
+		if (!vp_pending) {
+			ERR_PRINT("Viewport Texture must be set to use it.");
+		}
+		return 0;
+	}
 	return vp->size.width;
 }
 
 int ViewportTexture::get_height() const {
-	ERR_FAIL_COND_V_MSG(!vp, 0, "Viewport Texture must be set to use it.");
+	if (!vp) {
+		if (!vp_pending) {
+			ERR_PRINT("Viewport Texture must be set to use it.");
+		}
+		return 0;
+	}
 	return vp->size.height;
 }
 
 Size2 ViewportTexture::get_size() const {
-	ERR_FAIL_COND_V_MSG(!vp, Size2(), "Viewport Texture must be set to use it.");
+	if (!vp) {
+		if (!vp_pending) {
+			ERR_PRINT("Viewport Texture must be set to use it.");
+		}
+		return Size2();
+	}
 	return vp->size;
 }
 
@@ -135,10 +143,36 @@ bool ViewportTexture::has_alpha() const {
 }
 
 Ref<Image> ViewportTexture::get_image() const {
-	ERR_FAIL_COND_V_MSG(!vp, Ref<Image>(), "Viewport Texture must be set to use it.");
+	if (!vp) {
+		if (!vp_pending) {
+			ERR_PRINT("Viewport Texture must be set to use it.");
+		}
+		return Ref<Image>();
+	}
 	return RS::get_singleton()->texture_2d_get(vp->texture_rid);
 }
 
+void ViewportTexture::_setup_local_to_scene(const Node *p_loc_scene) {
+	Node *vpn = p_loc_scene->get_node(path);
+	ERR_FAIL_COND_MSG(!vpn, "ViewportTexture: Path to node is invalid.");
+
+	vp = Object::cast_to<Viewport>(vpn);
+
+	ERR_FAIL_COND_MSG(!vp, "ViewportTexture: Path to node does not point to a viewport.");
+
+	vp->viewport_textures.insert(this);
+
+	ERR_FAIL_NULL(RenderingServer::get_singleton());
+	if (proxy_ph.is_valid()) {
+		RS::get_singleton()->texture_proxy_update(proxy, vp->texture_rid);
+		RS::get_singleton()->free(proxy_ph);
+	} else {
+		ERR_FAIL_COND(proxy.is_valid()); // Should be invalid.
+		proxy = RS::get_singleton()->texture_proxy_create(vp->texture_rid);
+	}
+	vp_pending = false;
+}
+
 void ViewportTexture::_bind_methods() {
 	ClassDB::bind_method(D_METHOD("set_viewport_path_in_scene", "path"), &ViewportTexture::set_viewport_path_in_scene);
 	ClassDB::bind_method(D_METHOD("get_viewport_path_in_scene"), &ViewportTexture::get_viewport_path_in_scene);

scene/main/viewport.h

@@ -59,6 +59,9 @@ class ViewportTexture : public Texture2D {
 
 	friend class Viewport;
 	Viewport *vp = nullptr;
+	bool vp_pending = false;
+
+	void _setup_local_to_scene(const Node *p_loc_scene);
 
 	mutable RID proxy_ph;
 	mutable RID proxy;