Rotation Pivots for Guis on Roblox

Pivot.lua

-- Pivot.lua by jaipack17
-- Last updated: 02/04/2022
-- License: MIT

-- Easily create rotation pivots for GuiObjects on Roblox.
-- The API is similar to the Pivot API available for BaseParts.

-- Pivot.SetAngleMode(angleMode: string) -> Set angle mode for the pivot. Either DEGREES or RADIANS. By default set to DEGREES.
-- Pivot.ApplyIgnoreGuiInsetOffset(apply: boolean) -> Apply Offset of Vector2.new(0, 36) to the center position of the GuiObject. 
-- Set this to true if your ScreenGui is ignoring GuiInset.

-- Pivot.new(object: GuiObject, pivotOffset: Vector2, keepPositionUnchanged: boolean, keepRotationUnchanged: boolean) -> Creates a pivot for the GuiObject given a pivot offset relative to the GuiObject's center
-- Pivot:Rotate(angle: number) -> Rotate the GuiObject around its pivot given an angle.
-- Pivot:GetPivotOffset() Vector2 -> Returns the pivot offset for the GuiObject
-- Pivot:GetPivot() Vector2 -> Returns the position of the pivot point on screen
-- Pivot:SetPivotOffset(pivotOffset: Vector2) -> Set a new pivot offset for the GuiObject.
-- Pivot:PivotTo(pivotPosition: Vector2) -> Move the pivot to somewhere else. This moves the GuiObject along with the pivot.
-- Pivot:CenterTo(centerPoisition: Vector2) -> Move the GuiObject to somewhere else. This moves the pivot along with the GuiObject.

local Pivot = {}
Pivot.__index = Pivot

local Settings = {
	_angleMode = "DEGREES",
	_applyIgnoreGuiInsetOffset = false
}

local function Offset(self)
	return (if Settings._applyIgnoreGuiInsetOffset then Vector2.new(0, 36) else Vector2.new())
end

local function GetCenter(self)
	return self.Object.AbsolutePosition + self.Object.AbsoluteSize/2 + Offset(self)
end

function Pivot.new(object: GuiObject, pivotOffset: Vector2, keepPositionUnchanged: boolean?, keepRotationUnchanged: boolean?)
	local self = setmetatable({
		Object = object,
		PivotOffset = pivotOffset,
		_applyIgnoreGuiInsetOffset = false,
		_angleMode = "DEGREES",
		_objectCenter = nil,
		_pivotPosition = nil,
		_overwritePosition = not keepPositionUnchanged,
		_overwriteRotation = not keepRotationUnchanged
	}, Pivot)	

	self._objectCenter = GetCenter(self)
	self._pivotPosition = self._objectCenter + self.PivotOffset	

	return self
end

function Pivot.SetAngleMode(mode: string)
	mode = mode:upper()

	if mode == "DEGREES" or mode == "RADIANS" then 
		Settings._angleMode = mode
	end
end

function Pivot.ApplyIgnoreGuiInsetOffset(apply: boolean)
	Settings._applyIgnoreGuiInsetOffset = apply
end

function Pivot:Rotate(angle: number)
	if Settings._angleMode == "DEGREES" then 
		angle = math.rad(angle)
	end

	local difference = self._objectCenter - self._pivotPosition
	local theta = angle + math.atan2(difference.Y, difference.X)	
	local pos = self._pivotPosition + Vector2.new(math.cos(theta), math.sin(theta)) * difference.Magnitude

	local offset = Vector2.new(.5, .5) - self.Object.AnchorPoint
	offset *= self.Object.AbsoluteSize
	pos -= offset
	
	if self._overwritePosition then
		self.Object.Position = UDim2.fromOffset(pos.X, pos.Y)
	end
	if self._overwriteRotation then
		self.Object.Rotation = math.deg(angle)
	end
end

function Pivot:GetPivot()
	return self._pivotPosition
end

function Pivot:GetPivotOffset()
	return self.PivotOffset
end

function Pivot:SetPivotOffset(pivotOffset: Vector2)
	self.PivotOffset = pivotOffset
	self._objectCenter = GetCenter(self)
	self._pivotPosition = self._objectCenter + self.PivotOffset	
end

function Pivot:CenterTo(centerPosition: Vector2)
	self._objectCenter = centerPosition
	self._pivotPosition = self._objectCenter + self.PivotOffset	
end

function Pivot:PivotTo(pivotPosition: Vector2)
	self._pivotPosition = pivotPosition
	self._objectCenter = self._pivotPosition - self.PivotOffset	
end

return Pivot