Window.size_changed and NOTIFICATION_WM_SIZE_CHANGED are not triggered when "window.content_scale_mode == Window.ContentScaleMode.CONTENT_SCALE_MODE_VIEWPORT"

[Gnumaru]

Godot version

v4.1.stable.official [9704596]

System information

Godot v4.1.stable - Windows 10.0.19044 - Vulkan (Compatibility) - NVIDIA GeForce GTX 1050 Ti (NVIDIA; 31.0.15.2647) - Intel(R) Core(TM) i7-7700 CPU @ 3.60GHz (8 Threads)

Issue description

When using a ContentScaleMode equal to CONTENT_SCALE_MODE_VIEWPORT, the size_changed signal of the root window is not emited regardless of changing the size via code or resizing the window manually. not only the signal is not emited, but the notification is also not triggered. Look at output log:

Steps to reproduce

On a new project, on a new scene, create a script in the scene root, paste this script and run it

extends Node2D
var mold_size:Vector2i
func _ready()->void:
	print('==================== BEGIN')
	var vwindow:Window = get_window()
	print('_ready(): connecting size_changed to on_size_changed')
	vwindow.size_changed.connect(on_size_changed)
	print('\n_ready(): changing scale to CONTENT_SCALE_MODE_DISABLED')
	vwindow.content_scale_mode = Window.ContentScaleMode.CONTENT_SCALE_MODE_DISABLED
	print('_ready(): changing to 1')
	vwindow.size = Vector2i.ONE
	print('_ready(): changing to 128')
	vwindow.size = Vector2i.ONE * 128
	print('\n_ready(): changing scale to CONTENT_SCALE_MODE_CANVAS_ITEMS')
	vwindow.content_scale_mode = Window.ContentScaleMode.CONTENT_SCALE_MODE_CANVAS_ITEMS
	print('_ready(): changing to 1')
	vwindow.size = Vector2i.ONE
	print('_ready(): changing to 128')
	vwindow.size = Vector2i.ONE * 128
	print('\n_ready(): changing scale to CONTENT_SCALE_MODE_VIEWPORT')
	vwindow.content_scale_mode = Window.ContentScaleMode.CONTENT_SCALE_MODE_VIEWPORT
	print('_ready(): changing to 1')
	vwindow.size = Vector2i.ONE
	print('_ready(): changing to 128')
	vwindow.size = Vector2i.ONE * 128
	print('==================== END')
func _notification(pwhat:int)->void:
	if pwhat == Node.NOTIFICATION_WM_SIZE_CHANGED: print('_notification(NOTIFICATION_WM_SIZE_CHANGED)')
func on_size_changed()->void:
	var vnewsize:Vector2i = get_window().size
	print('    on_size_changed(): changed from %s to %s'%[mold_size, vnewsize])
	mold_size = vnewsize
func _physics_process(delta:float)->void:
	if Engine.get_physics_frames() % 60 != 0: return
	print('_physics_process(): window size: %s'%get_window().size)

Minimal reproduction project

N/A

[Sauermann]

Technically this works as expected, because the signal is only sent, when the size of the viewport changes

godot/scene/main/viewport.cpp

Line 968 in 23318e8

emit_signal(SNAME("size_changed"));

CONTENT_SCALE_MODE_VIEWPORT has in this case the effect, that the size of the viewport stays the same, so the signal is not emitted, even though the size of the Window has changed.

Please try instead to watch for the notification NOTIFICATION_WM_SIZE_CHANGED, if you want to get notified, when the size of the window changes.

[Gnumaru]

The notification is also not triggered, but the window size property does change.

That is, the viewport size property is reflecting not the "render size", but the actual window usable area without decorations.

[Sauermann]

After digging into this deeper, `NOTIFICATION_WM_SIZE_CHANGED´ is only sent to the Window, but not to the nodes inside the window. In your script, you listen for that notification in a node, that is inside the window.

So in order to achieve your goal, you need to listen on the root node for that notification. Here is a demo project, how this can be done: RootSizeChange.zip

Does this solve your problem?

[WarrenMarshall]

That's clever but what on earth ... is there really no way to simply be told, "Hey, the window was resized"? That seems like baseline functionality.

[Zireael07]

Yes there is a way, @Sauermann demoed it for you

[WarrenMarshall]

Your definition of "simply" differs from mine. But sure, yeah ...

[Zireael07]

It's very common in Godot to have to go up/down the node tree for certain things specific to certain node types.

[WarrenMarshall]

I'm sure you're right, I'll get used to doing things this way.

[Sauermann]

The current behavior should be documented better.

[ForestGameDev]

This is very confusing, please correct me if I didn't get this:
When using Display > Window > Stretch > Mode > viewport, you cannot use signals:

• get_window().size_changed
• get_viewport().size_changed

The only alternative is to follow the example above which consists of loading another script to the root node by running in some different script the following:

$"/root".set_script(load("res://rw.gd"))

Where rw.gd contains the following:

extends Window

func _notification(what):
	if what == NOTIFICATION_WM_SIZE_CHANGED:
		print("New Root Size detected: ", size)

If I got this right, this should not be considered a documentation issue only. If making the signals respond as most people would expect is for some reason not desired, maybe we should have some other signal to use instead.

[wgetJane]

why not add a signal to Window (not Viewport) called something like window_resized that it emits when it receives the NOTIFICATION_WM_SIZE_CHANGED notification?

i don't think one can argue that the current solution is elegant or intuitive at all

[Sauermann]

While this is solved for now by adjusting the documentation, we should continue the discussion about improving the situation in the form of a proposal: godotengine/godot-proposals#8788