[3.x] Make TextureButton and Button update on texture change

[AThousandShips]

• 3.x version of: Make TextureButton and Button update on texture change #77159

Currently unable to verify functionality on 3.x builds, code should work but would appreciate someone verifying

[YuriSizov]

Logic slightly changes, as in 3.x we didn't check if (destination == p_texture) for TextureButton textures before. So with this change there won't be updates triggered if someone sets the exactly the same value to a member.

I think it should be fine though. And the code adaptation to 3.x LGTM.

[AThousandShips]

Can remove the check for same value as well if wanted to keep parity with 3.x, though the changes to TextureRect added such a check in #81100

[timothyqiu]

DEV_ASSERT should only be used for bottleneck code. A regular check here won't matter.

But I think a better way is to pass by non-const reference, so we don't have to do any check.

[AThousandShips]

See: #77159 (comment)

Also DEV_ASSERT is for crashing, not performance critical AFAIK

Keeping the code as proven in 4.x for now

[timothyqiu]

That won't work, assigning to the reference won't update the texture itself

The referenced Ref object won't change. What will be updated is the content of that Ref, which is the texture.

Also DEV_ASSERT is for crashing, not performance critical AFAIK

A note was added recently:

godot/core/error/error_macros.h

Lines 797 to 801 in 8449592

	* DEV_ASSERT should generally only be used when both of the following conditions are met:
	* 1) Bottleneck code where a check in release would be too expensive.
	* 2) Situations where the check would fail obviously and straight away during the maintenance of the code
	* (i.e. strict conditions that should be true no matter what)
	* and that can't fail for other contributors once the code is finished and merged.

But anyway, I think it's fine if the Godot 4 version uses this. I should have read the original PR, sorry :(

[AThousandShips]

No problem, all the changes except to fit it to 3.x code are from the 4.x one, now minus the is_valid part

Checked in 4.x and passing by reference works there, but don't want any potential unseen side effects for a cheery pick, thank you for feedback

[akien-mga]

Thanks!

[AThousandShips]

Thank you!

[akien-mga]

Cherry-picked for 3.5.3.