Add AbsoluteContentSize to UIGridStyleLayout and UIListLayout

lib/instances/UIGridStyleLayout.lua

@@ -3,11 +3,40 @@ local FillDirection = import("../Enum/FillDirection")
 local HorizontalAlignment = import("../Enum/HorizontalAlignment")
 local InstanceProperty = import("../InstanceProperty")
 local SortOrder = import("../Enum/SortOrder")
-local VerticalAlignment = import("../Enum/VerticalAlignment")
 local Vector2 = import("../types/Vector2")
+local VerticalAlignment = import("../Enum/VerticalAlignment")
 
 local UIGridStyleLayout = BaseInstance:extend("UIGridStyleLayout")
 
+UIGridStyleLayout.properties.AbsoluteContentSize = InstanceProperty.readOnly({
+	get = function(self)
+		local x = 0
+		local y = 0
+		if self:FindFirstAncestorWhichIsA("ScreenGui") then
+			-- Sum the size of the children in the fill direction and get
+			-- the maximum size of the children in the other direction.
+			for _, child in pairs(self.Parent:GetChildren()) do
+				if child:IsA("GuiObject") then
+					if self.FillDirection == FillDirection.Horizontal then
+						x = x + child.AbsoluteSize.X
+						local childHeight = child.AbsoluteSize.Y
+						if childHeight > y then
+							y = childHeight
+						end
+					else
+						y = y + child.AbsoluteSize.Y
+						local childWidth = child.AbsoluteSize.X
+						if childWidth > x then
+							x = childWidth
+						end
+					end
+				end
+			end
+		end
+		return Vector2.new(x, y)
+	end,
+})
+
 UIGridStyleLayout.properties.FillDirection = InstanceProperty.enum(FillDirection, {
 	getDefault = function()
 		return FillDirection.Horizontal
@@ -32,10 +61,4 @@ UIGridStyleLayout.properties.VerticalAlignment = InstanceProperty.enum(VerticalA
 	end,
 })
 
-UIGridStyleLayout.properties.AbsoluteContentSize = InstanceProperty.readOnly({
-	get = function(self)
-		return Vector2.new(0, 0)
-	end,
-})
-
 return UIGridStyleLayout

lib/instances/UIGridStyleLayout_spec.lua

@@ -1,11 +1,17 @@
 local FillDirection = import("../Enum/FillDirection")
 local HorizontalAlignment = import("../Enum/HorizontalAlignment")
+local Instance = import("../Instance")
 local SortOrder = import("../Enum/SortOrder")
 local typeof = import("../functions/typeof")
+local UDim2 = import("../types/UDim2")
 local VerticalAlignment = import("../Enum/VerticalAlignment")
 
 local UIGridStyleLayout = import("./UIGridStyleLayout")
 
+local function extractVector2(vector2)
+	return { vector2.X, vector2.Y }
+end
+
 describe("instances.UIGridStyleLayout", function()
 	it("should instantiate", function()
 		local instance = UIGridStyleLayout:new()
@@ -16,6 +22,7 @@ describe("instances.UIGridStyleLayout", function()
 	it("should have properties defined", function()
 		local instance = UIGridStyleLayout:new()
 
+		assert.equals(typeof(instance.AbsoluteContentSize), "Vector2")
 		assert.equals(typeof(instance.FillDirection), "EnumItem")
 		assert.equals(instance.FillDirection.EnumType, FillDirection)
 		assert.equals(typeof(instance.HorizontalAlignment), "EnumItem")
@@ -26,4 +33,27 @@ describe("instances.UIGridStyleLayout", function()
 		assert.equal(instance.VerticalAlignment.EnumType, VerticalAlignment)
 		assert.equals(typeof(instance.AbsoluteContentSize), "Vector2")
 	end)
+
+	describe("AbsoluteContentSize", function()
+		it("should change based on the sizes of the layout's siblings", function()
+			local screenGui = Instance.new("ScreenGui")
+
+			local instance = UIGridStyleLayout:new()
+			instance.Parent = screenGui
+
+			local frame1 = Instance.new("Frame")
+			frame1.Size = UDim2.new(0, 300, 0, 400)
+			frame1.Parent = screenGui
+
+			local frame2 = Instance.new("Frame")
+			frame2.Size = UDim2.new(0, 200, 0, 500)
+			frame2.Parent = screenGui
+
+			local frame3 = Instance.new("Frame")
+			frame3.Size = UDim2.new(0, 100, 0, 100)
+			frame3.Parent = screenGui
+
+			assert.same({ 600, 500 }, extractVector2(instance.AbsoluteContentSize))
+		end)
+	end)
 end)

lib/instances/UIListLayout.lua

@@ -1,6 +1,8 @@
 local UIGridStyleLayout = import("./UIGridStyleLayout")
+local FillDirection = import("../Enum/FillDirection")
 local InstanceProperty = import("../InstanceProperty")
 local UDim = import("../types/UDim")
+local Vector2 = import("../types/Vector2")
 
 local UIListLayout = UIGridStyleLayout:extend("UIListLayout", {
 	creatable = true,
@@ -12,4 +14,33 @@ UIListLayout.properties.Padding = InstanceProperty.typed("UDim", {
 	end,
 })
 
+UIListLayout.properties.AbsoluteContentSize = InstanceProperty.readOnly({
+	get = function(self)
+		local size = UIGridStyleLayout.properties.AbsoluteContentSize.get(self)
+		if self.Padding ~= UDim.new(0, 0) and self:FindFirstAncestorWhichIsA("ScreenGui") then
+			local siblingCount = 0
+			for _, child in pairs(self.Parent:GetChildren()) do
+				if child:IsA("GuiObject") then
+					siblingCount = siblingCount + 1
+				end
+			end
+			if siblingCount > 0 then
+				local function getPadding(parentSizeInFillDirection)
+					return (siblingCount - 1) * (parentSizeInFillDirection * self.Padding.Scale + self.Padding.Offset)
+				end
+				local parentSize = self.Parent.AbsoluteSize
+				local x = size.X
+				local y = size.Y
+				if self.FillDirection == FillDirection.Horizontal then
+					x = x + getPadding(parentSize.X)
+				else
+					y = y + getPadding(parentSize.Y)
+				end
+				size = Vector2.new(x, y)
+			end
+		end
+		return size
+	end,
+})
+
 return UIListLayout

lib/instances/UIListLayout_spec.lua

@@ -1,5 +1,12 @@
+local FillDirection = import("../Enum/FillDirection")
 local Instance = import("../Instance")
 local typeof = import("../functions/typeof")
+local UDim = import("../types/UDim")
+local UDim2 = import("../types/UDim2")
+
+local function extractVector2(vector2)
+	return { vector2.X, vector2.Y }
+end
 
 describe("instances.UIListLayout", function()
 	it("should instantiate", function()
@@ -19,4 +26,52 @@ describe("instances.UIListLayout", function()
 
 		assert.equals(typeof(instance.Padding), "UDim")
 	end)
+
+	describe("AbsoluteContentSize", function()
+		it("should include padding vertically", function()
+			local screenGui = Instance.new("ScreenGui")
+
+			local instance = Instance.new("UIListLayout")
+			instance.Padding = UDim.new(0, 10)
+			instance.FillDirection = FillDirection.Vertical
+			instance.Parent = screenGui
+
+			local frame1 = Instance.new("Frame")
+			frame1.Size = UDim2.new(0, 300, 0, 400)
+			frame1.Parent = screenGui
+
+			local frame2 = Instance.new("Frame")
+			frame2.Size = UDim2.new(0, 200, 0, 500)
+			frame2.Parent = screenGui
+
+			local frame3 = Instance.new("Frame")
+			frame3.Size = UDim2.new(0, 100, 0, 100)
+			frame3.Parent = screenGui
+
+			assert.same({ 300, 1020 }, extractVector2(instance.AbsoluteContentSize))
+		end)
+
+		it("should include padding horizonally", function()
+			local screenGui = Instance.new("ScreenGui")
+
+			local instance = Instance.new("UIListLayout")
+			instance.Padding = UDim.new(0, 10)
+			instance.FillDirection = FillDirection.Horizontal
+			instance.Parent = screenGui
+
+			local frame1 = Instance.new("Frame")
+			frame1.Size = UDim2.new(0, 300, 0, 400)
+			frame1.Parent = screenGui
+
+			local frame2 = Instance.new("Frame")
+			frame2.Size = UDim2.new(0, 200, 0, 500)
+			frame2.Parent = screenGui
+
+			local frame3 = Instance.new("Frame")
+			frame3.Size = UDim2.new(0, 100, 0, 100)
+			frame3.Parent = screenGui
+
+			assert.same({ 620, 500 }, extractVector2(instance.AbsoluteContentSize))
+		end)
+	end)
 end)