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Loading Spinner

This example implements a procedural spinning animation using Fusion's Roblox APIs.

Overview

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local RunService = game:GetService("RunService")

local Fusion = -- initialise Fusion here however you please!
local scoped = Fusion.scoped
local Children = Fusion.Children
type UsedAs<T> = Fusion.UsedAs<T>

local SPIN_DEGREES_PER_SECOND = 180
local SPIN_SIZE = 50

local function Spinner(
    scope: Fusion.Scope,
    props: {
        Layout: {
            LayoutOrder: UsedAs<number>?,
            Position: UsedAs<UDim2>?,
            AnchorPoint: UsedAs<Vector2>?,
            ZIndex: UsedAs<number>?
        },
        CurrentTime: UsedAs<number>,
    }
): Fusion.Child
    return scope:New "ImageLabel" {
        Name = "Spinner",

        LayoutOrder = props.Layout.LayoutOrder,
        Position = props.Layout.Position,
        AnchorPoint = props.Layout.AnchorPoint,
        ZIndex = props.Layout.ZIndex,

        Size = UDim2.fromOffset(SPIN_SIZE, SPIN_SIZE),

        BackgroundTransparency = 1,
        Image = "rbxassetid://your-loading-spinner-image", -- replace this!

        Rotation = scope:Computed(function(use)
            return (use(props.CurrentTime) * SPIN_DEGREES_PER_SECOND) % 360
        end)
    }
end

-- Don't forget to pass this to `doCleanup` if you disable the script.
local scope = scoped(Fusion, {
    Spinner = Spinner
})

local currentTime = scope:Value(os.clock())
table.insert(scope,
    RunService.RenderStepped:Connect(function()
        currentTime:set(os.clock())
    end)
)

local spinner = scope:Spinner {
    Layout = {
        Position = UDim2.fromScale(0.5, 0.5),
        AnchorPoint = Vector2.new(0.5, 0.5),
        Size = UDim2.fromOffset(50, 50)
    },
    CurrentTime = currentTime
}

Explanation

The Spinner components implements the animation for the loading spinner. It's largely a standard Fusion component definition.

The main thing to note is that it asks for a CurrentTime property.

local function Spinner(
    scope: Fusion.Scope,
    props: {
        Layout: {
            LayoutOrder: UsedAs<number>?,
            Position: UsedAs<UDim2>?,
            AnchorPoint: UsedAs<Vector2>?,
            ZIndex: UsedAs<number>?
        },
        CurrentTime: UsedAs<number>,
    }
): Fusion.Child

The CurrentTime is used to drive the rotation of the loading spinner.

        Rotation = scope:Computed(function(use)
            return (use(props.CurrentTime) * SPIN_DEGREES_PER_SECOND) % 360
        end)

That's all that's required for the Spinner component.

Later on, the example creates a Value object that will store the current time, and starts a process to keep it up to date.

local currentTime = scope:Value(os.clock())
table.insert(scope,
    RunService.RenderStepped:Connect(function()
        currentTime:set(os.clock())
    end)
)

This can then be passed in as CurrentTime when the Spinner is created.

local spinner = scope:Spinner {
    Layout = {
        Position = UDim2.fromScale(0.5, 0.5),
        AnchorPoint = Vector2.new(0.5, 0.5),
        Size = UDim2.fromOffset(50, 50)
    },
    CurrentTime = currentTime
}
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