Input accumulation is off by default but the documentation states it is on by default

[m4nu3lf]

Godot version

da5c843

System information

OS: Arch Linux, CPU: Ryzen 5, GUP: RX 480

Issue description

The documentation states that input accumulation is enabled by default, but I'm pretty sure it isn't. I get many InputMouseMotion events every frame unless I explicitly call Input.set_use_accumualted_input(true).

Should we change the docs or the implementation?

Steps to reproduce

Create a scene with a node and attach a script. Add something like this:

func _input(event: InputEvent) -> void:
  if event is InputEventMouseMotion:
     print(Engine.get_drawn_frames())

You should see the same frame number show up multiple times.

[Calinou]

I'm pretty sure input accumulation is supposed to be enabled by default. I wonder if #42220 changed anything in this regard. Can you reproduce this in 3.3.4?

[m4nu3lf]

I can reproduce it with the latest commit 4508878
This is the code:

extends Spatial

func _ready() -> void:
	Input.set_use_accumulated_input(true)

func _input(event) -> void:
	if event is InputEventMouseMotion:
		print(Engine.get_frames_drawn())

Try to comment/uncomment the _ready() method to see the issue.

[Calinou]

See also #54066.

[akien-mga]

main/input_default.cpp has use_input_accumulation set to false, so it's indeed disabled by default. It used to be true but this was changed in #42220. It is however enabled by default in the editor (editor/editor_node.cpp sets it on).

I don't know if making it off-by-default was intentional. If so, maybe the documentation simply needs to be updated. What part of the documentation says that it's enabled by default?

[RandomShaper]

I think that disabling it was not intentional. I've checked the code and can't find a reason why I changed that to false. However, at this point I'm not sure what the best action would be. Maybe consider it was just changed for 3.5 and just document it indeed?

[akien-mga]

Yeah given that this was changed in 3.4, users are now used to the new default value, even if it wasn't intended. So I would keep it as is in 3.5, it's too late now to revert back (there might be bugs with input accumulation that we haven't caught during beta phase due to it being off by default).

So documenting it should be enough indeed. We could consider turning it back on for 3.6 with some extensive testing.

[akien-mga]

Given the amount of regression reports we got which ended up due to input accumulation being mistakenly turned off in 3.4, I've been thinking about turning it back on for 3.5, even if it's quite late to do so now as discussed above.

Notably:

• Performance drops on camera rotation #54531
• HSlider value_changed signal now emitted multiple times per frame when moving slider. (changed 3.3-3.4) #54909
• Large idle times (>95% of frame time) when using Godot's drag-and-drop built-in functions #57039
• Behavior of Input event changed since Godot 3.3.2 #57386
• FPS drops when moving mouse with high polling rate #57599
• Apparently related but in a confusing way: Thrustmaster T.Flight HOTAS X controller not working as expected #53334 Change scene on InputEventJoypadMotion in _input(event) disconnects joy controller #55098

We'll have 3.5 RC 6 to try it out, which should have at least 10 days of testing as I'll be away on holiday :)
So we can assess whether testers seem to be fine with the change or not. And then eventually either flip it back to false if we find new issues with input accumulation and prefer to go back to the 3.4 behavior, or keep it true to get back the 3.1 - 3.3 behavior and (when relevant) improved input handling performance.

[akien-mga]

Fixed by #62826.