Godot 4.0 Migration/Upgrade guide

gistfile2.txt

## For a beginner-friendly version of the following (more advanced users likely will get better use of the below, 
## if you're just starting out...), see this new gist: 
##   https://gist.github.com/WolfgangSenff/0a9c1d800db42a9a9441b2d0288ed0fd


This document represents the beginning of an upgrade or migration document for GDScript 2.0 and Godot 4.0. I'm focusing on 2D
at the moment as I'm upgrading a 2D game, but will hopefully have more to add for 3D afterward.

## If you want more content like this, please help fund my cat's medical bills at https://ko-fi.com/kyleszklenski - thank you very much! On to the migration guide.

# Godot 4.0 Upgrade/Migration Guide

# GDScript:
    Renames - the following classes have been renamed:
    Node.raise() -> CanvasItem.move_to_front()
    SceneTree.change_scene -> SceneTree.change_scene_to_file
    SceneTree.change_scene_to -> SceneTree.change_scene_to_packed
    ssl -> tls in properties and methods across the board
    in range properties: or_lesser -> or_less
    Curve/Curve2D/Curve3D/Gradient interpolate -> sample
    caret_blink_speed -> caret_blink_interval
    CanvasItem update -> queue_redraw
    AABB/Rect2/Rect2i has_no_* methods -> has_* methods
    TileMap/GridMap world_to_map -> local_to_map
    TileMap/GridMap map_to_world -> map_to_local
    uniform -> parameter in various places across the engine
    ProgressBar percent_visible -> show_percentage
    Object constant CONNECT_ONESHOT -> CONNECT_ONE_SHOT
    JavaScript singleton -> JavaScriptBridge
    range_lerp -> remap
    PopupMenu get_current_index -> get_focused_item
    StreamPeerSSL -> StreamPeerTLS
    EditorInterface get_editor_main_control -> get_editor_main_screen
    str2var -> str_to_var
    deg2rad -> deg_to_rad
    rad2deg -> rad_to_deg
    ParticlesMaterial -> ParticlesProcessMaterial
    Position2D -> Marker2D
    Position3D -> Marker3D
    Label & RichTextLabel percent_visible -> visible_ratio
    PathFollow's offsets -> progress & progress_ratio
    hint_tooltip -> tooltip_text
    Rename JavaScript platform to Web
    PoolByteArray -> PackedByteArray
    PoolColorArray -> PackedColorArray
    PoolFloat32Array -> PackedFloat32Array
    PoolFloat64Array -> PackedFloat64Array
    PoolInt32Array -> PackedInt32Array
    PoolInt64Array -> PackedInt64Array
    PoolStringArray -> PackedStringArray
    PoolVector2Array -> PackedVector2Array
    PoolVector3Array -> PackedVector3Array
    
    
# Multiplayer:
    The arguments that can be used with @rpc must be one of: 
      mode: call_local, call_remote
      sync: any_peer, authority
      transfer_mode: reliable, unreliable, or unreliable_ordered
      channel: this is just an integer, not a string, and represents what channel you may want to send data on, so you aren't cluttering up the main channel with text for chat (for instance)
      
      With the above values for mode, sync, and transfer_mode, you can just write the exact value as a string in your @rpc annotation; it does not have to be quoted like most strings in GDScript.
    
    
## Variables:
    
    `instance()` has been renamed to `instantiate()`.

## Exports:

        Switch to @export; if you have a type hint in parentheses and no default value, add the hint at the end after a colon, like so:
            @export var Speed: float

        You *must* provide a minimum amount of type information at the current time, by including a : hint value, or a default value representing the type.

        If you have a range to limit your floats, switch to use @export_range(float, float);

        If exporting a string or integer as an enum, switch to @export_enum(VALUE1, VALUE2, VALUE3) var Name

        If exporting a named enum, switch to @export with hint at the end, e.g.:
            enum weapon_type { Sword, Gun, SwordGun, Knife, KnifeGun}
            @export var WeaponType: weapon_type

        If exporting strings, you can force the editor to show a large textbox for your string with @export_multiline

        You may use @export and @onready at the same time, just like before:
            @export @onready var MaxHitPoints = 10 # See onready below for more

        Other useful hints:
            https://docs.godotengine.org/en/latest/tutorials/scripting/gdscript/gdscript_exports.html


## Onready:
        Switch to @onready


## Properties:
        Properties now follow the form:
            var hp_value: int:
                set(value):
                    hp_value = value
                    hpvalue_changed.emit(hp_value)
                get:
                    return hp_value
                    

## Tweens:
    Tweens are not nodes anymore! These are references, similar to timers you create with the scene tree.
        var sprite = $Sprite
        var tween := get_tree().create_tween() # can omit get_tree() if you wish; this will bind the tween to the node, see below for more
        tween.tween_property(sprite, "position", sprite.position + Vector2(16.0, 16.0), 1.0)
        # Object to tween, nodepath to property to tween, end goal for the value, amount of time to take in seconds

    There is also tween_interval, which waits for a given amount of time before tweening (similar to a timer), tween_callback, which does
    the same thing as interpolate_callback, and tween_method, which calls a method on an object with an argument that goes from the initial
    value to the final value, or in other words the same as interpolate_method.

    You can chain tweening methods together - call one after the other, like so:
        // above
        
        tween.tween_property(sprite, "position", sprite.position + Vector2(16.0, 16.0), 1.0)
        tween.tween_property(sprite, "rotation", sprite.rotation + deg2rad(180.0), 1.0)
 
### Tween binding:
        A tween can be bound to a node so that if the node is either not in the tree or paused, it will affect the tween as well.

### Tween looping:
        Tweens can have any number of loops by using the set_loops(loops) method; 0 will cause infinite loops.

    You can stop/reset, pause, resume, or destroy a tween

    Tweens can run in parallel with tween.parallel()

    Similarly, tweens can have all subsequent tween calls be parallel after calling Tween.set_parallel(true)

    You can use tween.set_ease() and tween.set_trans() to set the easing function and transition type respectively

    You can use as_relative() to make the final value be relative:
        // Equivalent to above
        
        tween.tween_property(sprite, "position", Vector2(16.0, 16.0), 1.0).as_relative()

    To consistently move the same amount from one spot to the next, such as grid-based movement, you can do the above and set the number of loops.


# Yield/await:

    No more yields, only awaits! Ultimately, this comes down to:
        yield(get_tree(), "idle_frame")

        becomes:

        await get_tree().process_frame
        
    Similarly, to await a common signal, you might do something like:
        await $AnimationPlayer.animation_finished


# Signals:
    For yielding/awaiting signals, see yield/await above.
    
    Note that signals are now first-class language features, meaning you no longer rely on strings for them. That means you can swap any connect calls like this:

        button.connect("pressed", self, "_on_button_pressed")

    to:

        button.pressed.connect(_on_button_pressed) # Feel the power!
        
    Further:
        button.connect("pressed", self, "_on_button_pressed", [button], CONNECT_DEFERRED) 
    
    becomes:
        button.pressed.connect(_on_button_pressed.bind(button)), CONNECT_DEFERRED)

    Additionally:
    
        `button.connect("pressed", other_object, "on_button_pressed", [button], CONNECT_DEFERRED)`

    becomes:

        `button.pressed.connect(other_object.on_button_pressed.bind(button)), CONNECT_DEFERRED)`


    This also changes how you have to call to emit signals. It is now:

        signal_name.emit(arg1, arg2, etc_arg)

## Functions:

    Functions are now also first-class language features. That means you can use lambda expressions, which are concise bits of code representing a function, like so:
        var _current_value = 0
        @onready var _button = $Button
        @onready var _text = $LineEdit

        func _ready():
            _button.pressed.connect(func(): _current_value += float(_text.text)) # Convert to a float and add to the current value to place a bet

    
    It's important to note that just because you *can* add a lambda expression, you probably shouldn't always do it. It is often much cleaner to make a separate method,
    like in 3.x, and attach it instead of a lambda.


## Resources:
    If you need to load a resource in a script, when you drag the resource into the script in order to get the exact path, you can hold down ctrl while doing so and have it automatically place the preload.
    
    
# Nodes:

YSort node removed, functionality moved to Node2D

### Renamed nodes:
Spatial → Node3D
GIProbe → VoxelGI
BakedLightmap → LightmapGI
Light2D -> PointLight2D
VisibilityNotifier2D -> VisibleOnScreenNotifier2D (this removes Viewport-related signals)
VisibilityNotifier3D -> VisibleOnScreenNotifier3D (this removes Viewport-related signals)
VisibilityEnabler2D -> VisibleOnScreenEnabler2D
VisibilityEnabler3D -> VisibleOnScreenEnabler3D


The Pool*Array nodes have been renamed to Packed*Array, and instead of being passed by value, they are now passed by reference.

## Physics changes:

Physics2DDirectSpaceState
is renamed to:
PhysicsDirectSpaceState2D

The physics queries now have to have parameters created and passed to the various ray functions, like so:

var params = PhysicsRayQueryParameters3D.new()
params.from = first_pos
params.to = second_pos
params.exclude = obstacles

var result = space_state.intersect_ray(params)

RayCast2D.cast_to -> target_position

File dropping functionality is now moved from SceneTree (3.x) to Viewport (4.x).
Also it doesn't emit the screen argument anymore.

# 3.x

func _ready() -> void:
  get_tree().connect("files_dropped", self, "_on_files_dropped")

func _on_files_dropped(files: PoolStringArray, screen: int) -> void:
  ...
# 4.x

func _ready() -> void:
    get_viewport().files_dropped.connect(on_files_dropped)

func on_files_dropped(files: PackedStringArray) -> void:
   ...
   
File is now FileAccess and open() is now a static method that returns such object. To then check for errors, call file_access.get_error()

## KinematicBody2D:
    KinematicBody2D has been renamed to CharacterBody2D, and a bunch of features have been added to it, such as:
    - A new template script, that already implements basic movement and jumping for a 2d-platform style game
    - Moving is now built-in to the class, which contains lots of properties to define how the movement works
    - move_and_slide now no longer takes any parameters, and uses built-in velocity to control where it is going.
        Before:
            var velocity = Vector2.ZERO
            func _process(delta):
                velocity = velocity.move_towards(direction*200)
                velocity = move_and_slide(velocity)
        Now:
            func _process(delta)
                velocity = velocity.move_towards(direction*200)
    - It has built-in collision including slopes and moving platforms

CollisionObject2D: The type of the first parameter of the method _input_event() was changed from Object to Viewport. (This may only matter if static typing is being used.)

CollisionObject3D (renamed from CollisionObject): The type of the first parameter of the method _input_event() was changed from Object to Camera3D. (This may only matter if static typing is being used.)

String constructor String(int) removed. Suggested replacement: global method str().

""" triple quote multi line string can no longer be used as comment

In Godot 3, the modulate would be independent of the shader material and it would affect whatever the shader material produced in COLOR. However, in Godot 4, modulate is the "input" of the shader material and whatever is written to COLOR in the shader will be the final result, see: godotengine/godot#49781

Godot 3's FuncRef

was replaced & extended with

Godot 4's Callable

Texture get_data renamed to Texture2D get_image

3.x Image get_rect renamed in 4 to get_region

3.x Image create

var img = Image.new()
img.create(width, height, false, Image.FORMAT_RGBA8)

4.x Image create

var img = Image.create(width, height, false, Image.FORMAT_RGBA8)

Engine.editor_hint is now Engine.is_editor_hint()

EditorImportPlugin, and probably most other plugin methods, have renamed all the require function overloads. In most cases, though, it should just be adding and underscore _ to the function names. For instance, import(parameters) becomes _import(parameters).

OS.get_window_safe_area() -> DisplayServer.get_display_safe_area()

Godot 4 beta 13 removed the global class list cache altogether from project.godot into a separate file in the .godot folder. Also removed retrieving the global class list from ProjectSettings. The new way to retrieve that is:

```
var config = ConfigFile.new()
config.load("res://.godot/global_script_class_cache.cfg")
var classes = config.get_value('', 'list', [])
```

# Shaders:

SCREEN_TEXTURE is no longer available in shaders; instead, you do this at the top of your shader where you define your uniforms:
`uniform sampler2D SCREEN_TEXTURE: hint_screen_texture, filter_linear_mipmap;`

When using a ShaderMaterial, shader_param has been renamed to shader_parameter, e.g.:

`create_tween().tween_property(target.material, "shader_param/transparency", 1.0, 2.0)`

changes to

`create_tween().tween_property(target.material, "shader_parameter/transparency", 1.0, 2.0)`

Some further changes to shader naming:
ALPHA_SCISSOR -> ALPHA_SCISSOR_THRESHOLD
CAMERA_MATRIX -> INV_VIEW_MATRIX
INV_CAMERA_MATRIX -> VIEW_MATRIX
NORMALMAP -> NORMAL_MAP
NORMALMAP_DEPTH -> NORMAL_MAP_DEPTH
TRANSMISSION -> BACKLIGHT
WORLD_MATRIX -> MODEL_MATRIX
depth_draw_alpha_prepass -> depth_draw_opaque
hint_aniso -> hint_anisotropy
hint_black -> hint_default_black
hint_black_albedo -> hint_default_black
hint_albedo -> source_color
hint_color -> source_color
hint_white -> hint_default_white

OS.has_touchscreen_ui_hint()
has become:
DisplayServer.is_touchscreen_available()

## Logical tests:
You can no longer test an object's nullness simply by saying "if object:", nor with `not` like so: "if not object:". There's no longer any implicit conversion between these.

The end of array.slice() is no longer inclusive of the final element, as it has been changed to exclusive ending.

Change log:
1/27 - initial add
1/27 - Bitron adds yield/await, signals
1/27 - Kyle adds functions
1/29 - Kyle adds instanciate(), preload trick
1/29 - Kobewi adds new example for connecting in a deferred fashion to signals
1/30 - Kyle adds YSort and other node info, add property syntax
2/1 - Dardan adds Pool* vs Packed* array info
2/20 - Deanut adds Physics-related changes
3/27 - Deanut adds further examples for await changes
9/13 - Kyle adds renames
9/28 - Bitbrain adds File changes, and Fenix adds file dropping changes.
9/29 - Kyle adds some multiplayer love with the @rpc annotation information
9/29 - Zemeio adds KinematicBody2D to CharacterBody2D updates
11/27 - hsandt updates signal connect examples
1/2/23 - DaveTheOldCoder adds CollisionObjectXD updates! As well as String constructor.
       - filipworksdev adds triple quote comment note
       - bitbrain adds modulate-related changes
       - Structed adds note about FuncRef
       - afk-mario adds notes about Texture's get_data change and get_rect on 3.x Image, and finally creating an image by code.
1/9/23 - sztrovacsek92 adds shader editor info for hint_color vs source_color.
2/8/23 - dploeger adds editor_hint changes
       - chucklepie adds some other VisibleOnScreenNotifier2D changes and EditorImportPlugin changes
       - kristijandraca adds change to OS for window safe area to DisplayServer
       - Structed adds global class list cache changes
       - Bitbrain adds u-seful shader updates
       - nonunknown adds multiple shader-related renames
       - Added link to new beginner-friendly guide that I've created to help beginners understand the differences
3/9/23 - naturally-intelligent added change for OS.has_touchscreen_ui_hint(), and changes in logical tests
       - Kyle adds some formatting to make the beginnger conversion guide more obvious
       - afk-mario adds RayCast2D changes
       - ChronoDK adds array slice changes

I know this is a more obscure upgrade, but if anyone has a better solution please share it!

https://docs.godotengine.org/en/latest/classes/class_fileaccess.html#class-fileaccess-method-file-exists

do somebody know what name replaced the GDScriptFunctionState class name ?

GDScriptFunctionState is not exposed to gdscript anymore, but it is still possible to obtain one by using Object.call(methodNameAsString)

extends Node
func asdf():
	print('= asdf before')
	await get_tree().process_frame
	print('= asdf middle')
	await get_tree().process_frame
	print('= asdf after')
func _ready():
	print('===== BEGIN')
	var a
#	a = asdf() # parser error: function asdf() is a coroutine etc
#	a = asdf.call() # does not give a parser error, but yields a runtime error: trying to call an async function without await
	a = call('asdf') # does not yield any error
	print('_ ready before')
	a.resume()
	print('_ ready middle')
	await a
	print('_ ready after')
	print(a.get_class()) # GDScriptFunctionState
	print(ClassDB.get_parent_class(a.get_class())) # RefCounted
	var r = RefCounted.new()
	print(a.get_method_list().map(func(i):return i.name).filter(func(i):return not r.has_method(i))) # ["resume", "is_valid", "_signal_callback", "_notification", "_set", "_get", "_get_property_list", "_property_can_revert", "_property_get_revert", "_init", "_to_string"]
	print(a.get_property_list().map(func(i):return i.name).filter(func(i):return not i in r and not i in ['RefCounted', 'GDScriptFunctionState'])) # []
	print('===== END')

I recently found this page in the official documentation:
https://docs.godotengine.org/en/4.0/tutorials/migrating/upgrading_to_godot_4.html

Does that supercede this Godot 4.0 Migration/Upgrade guide? I.e., is it better to submit new information at https://github.com/godotengine/godot-docs/issues, rather than here?

@daveTheOldCoder ideally, anything that is on here but not on https://docs.godotengine.org/en/latest/tutorials/migrating/upgrading_to_godot_4.html yet should be "ported over" - however, this document is still a great place to collect information.

Raycast2D cast_to renamed to target_position

Array slice method "end" is exclusive. It was inclusive before.

Maybe we should start the gist by mentioning https://docs.godotengine.org/en/4.0/tutorials/migrating/upgrading_to_godot_4.html and, to follow a similar structure, that you should --convert-3to4 to auto-convert most of the code (under VCS to ensure control of changes), then finish the job manually for the least obvious changes?

Otherwise there will be a lot of renames to fill according to https://github.com/godotengine/godot/blob/master/editor/renames_map_3_to_4.cpp

So I think we should focus on the big changes may be automated but still important for the user to know about (conceptual change, very common symbols, etc.), the changes that need manual work (when the new code we need depends on user intention/design, when function signature changes, etc.) and in particular things not already mentioned in the official upgrade guide (so Godot devs can easily find just the extra tips and merge them fast later).

I see a lot of info not in the official guide so I'll point the devs at this page so they can gradually add such info.

@hsandt - that's probably why I included this line near the very beginning: https://gist.github.com/WolfgangSenff/0a9c1d800db42a9a9441b2d0288ed0fd

Which includes the step-by-step conversion tutorial that I've put together, including the very link you mentioned.

I saw the new gist, it looks good!

I saw the new gist, it looks good!

It's not new, been there a while. 😉

Then: I saw the new link to the old gist, it looks good!

Btw I mentioned this page on godotengine/godot-docs#5121, will see from times to times if we got nice tips to include the official doc.

The quit confirmation editor setting apparently doesn't exist anymore. In was previously in "Editor >> Editor Settings >> Interface >> Editor >> Quit Confirmation" but it's no longer there nor there seems to be any equivalent.

This doesn't impact migrating projects from 3 to 4 but is something worth knowing.

The quit confirmation feature was intentionally removed. There was an explanation somewhere. If I find it, I'll post it or a link.

Looks like ShortCut has been renamed Shortcut - the letter 'c' became lowercase, causing compiler errors.

A few things I've noticed so far:

• Node.filename is now Node.scene_file_path
• AnimatedSprite2D.frames is now AnimatedSprite2D.sprite_frames.
• My input map in project settings was completely reset and I had to set it all again, for some reason.
• Stretch modes changed (and the docs still use the 3.0 terminology it seems). What used to be 2d is now called canvas_items, I had to change it manually.
• Textures are now told to repeat via the CanvasItem section of the node they belong to. I'm updating them all manually, not sure if there's a better way.
• RectangleShape2D no longer has a property called extents, but rather size. Instead of the half-width/height, it stores the full width and height. The built-in 3-to-4 converter correctly renames extents to size in scene files, but it keeps the numbers the same, which results in every single RectangeShape2D being half the intended size. Circles seem unaffected, but I haven't checked any other shapes. I think you can at least speed up the process by searching for type="RectangleShape2D" across all tscn files. Not sure if there's a better way, but it's better than opening scene files one-by-one.

The class Reference has been renamed to RefCounted

A few things I've noticed so far:

• Node.filename is now Node.scene_file_path
• AnimatedSprite2D.frames is now AnimatedSprite2D.sprite_frames.
• My input map in project settings was completely reset and I had to set it all again, for some reason.
• Stretch modes changed (and the docs still use the 3.0 terminology it seems). What used to be 2d is now called canvas_items, I had to change it manually.
• Textures are now told to repeat via the CanvasItem section of the node they belong to. I'm updating them all manually, not sure if there's a better way.

For this, you can change that under I believe it's Textures in Project Settings. Leave the value on the node set to inherit, and change it in the Textures.

• RectangleShape2D no longer has a property called extents, but rather size. Instead of the half-width/height, it stores the full width and height. The built-in 3-to-4 converter correctly renames extents to size in scene files, but it keeps the numbers the same, which results in every single RectangeShape2D being half the intended size. Circles seem unaffected, but I haven't checked any other shapes. I think you can at least speed up the process by searching for type="RectangleShape2D" across all tscn files. Not sure if there's a better way, but it's better than opening scene files one-by-one.

Great callouts, will try to add them when I have time, thanks!

set_as_toplevel

set_as_toplevel -> set_as_top_level
#or just set the value:
top_level = true | false

I have also noticed tool has become @tool and export has become @export

https://docs.godotengine.org/en/stable/tutorials/scripting/gdscript/gdscript_exports.html

From @hsandt :

Otherwise there will be a lot of renames to fill according to https://github.com/godotengine/godot/blob/master/editor/renames_map_3_to_4.cpp

How did I miss this? Yes this is exactly what is needed.

They renamed speed to velocity

for example like this one for InputEventMouseMotion : godotengine/godot#56322

stepify > snapped

The cartesian2polar and polar2cartesian built-in functions are gone. I haven't found an alternative built-in function or a static method on Vector2 to do that. I'm pretty sure there must be something somewhere, but I couldn't find it. yet

Also, the ord(String)->int: built-in function which gives you an unicode codepoint of a given one character string is gone (as a built-in function). Now we should use the String instance function unicode_at(int)->int: which gives you the unicode code point at the given character index.

I used the VisibilityNotifier2D to make the owner invisible or visible.
But the new VisibleOnScreenNotifier2D only works if it is visible itself, so it's a nasty trap if it makes its owner invisible and thus itself too.

I used the VisibilityNotifier2D to make the owner invisible or visible.
But the new VisibleOnScreenNotifier2D only works if it is visible itself, so it's a nasty trap if it makes its owner invisible and thus itself too.

I suppose that by "owner" you actually meant "parent". If this is happening I think this should actually be a bug, not the intended behavior. Meanwhile, instead of hiding the parent, you could set "modulate.a8 = 1", which will basically make it humanly impossible to see BUT will count as visible and allow VisibleOnScreenNotifier2D to work as expected

Making many objects that are not currently on the screen invisible saves a lot of computing time, at least in Godot 3. So the invisibility is just a side effect. :)
But I suspect the culling under Godot 4 will make this technique obsolete anyway.

The behavior of the VisibleOnScreenNotifier2D is actually not a bug. It is mentioned in the documentation:
Note: VisibleOnScreenNotifier2D uses the render culling code to determine whether it's visible on screen, which also means that its CanvasItem.visible must be true to work correctly.

I knew about the impact of hiding offscreen nodes on godot 3 but I haven't noticed until now that the expected behavior of VisibleOnScreenNotifier2D is different from the old VisibilityNotifier2D. I've just made some tests and indeed there is no longer need to hide offscreen nodes, when the canvas item is offscreen it does not affect rendering

2023-08-22_17-11-52.mp4

Don't mind the weird bug where the icon is not rendered. If I add at least one icon directly in the scene and save it it gets rendered (but the performance is even worse when the icons are on screen)

2023-08-22_17-21-27.mp4

Cool, that's good news! :)