FitContent

Auto-sizes a container to fit its children with optional padding.

Basic Usage

local ui = require("tecs2d.ui")
local FitContent = ui.FitContent
local LayoutBox = ui.LayoutBox

-- Container that auto-sizes to fit children with 10px padding
local container = world:spawn(
    Transform(100, 100),
    Rectangle(0, 0),  -- size set by FitContent
    LayoutBox(Rectangle, nil, 0, 0),
    FitContent(10, Rectangle)
)

-- Add a child
world:spawn(
    ChildOf(container),
    RelativeTransform.new({x = 0, y = 0}),
    Text(font, "Hello!"),
    LayoutBox(Text, nil, 0, 0)
)

Fields

Field	Type	Description
padding	number	Uniform padding on all sides
paddingTop	number	Top padding (overrides uniform)
paddingRight	number	Right padding (overrides uniform)
paddingBottom	number	Bottom padding (overrides uniform)
paddingLeft	number	Left padding (overrides uniform)
adjustComponentId	integer	Component to update with new dimensions

Constructor

-- Uniform padding, no render adjustment
FitContent(10)

-- Uniform padding, adjust Rectangle component
FitContent(10, Rectangle)

-- Config table for per-side padding
FitContent({
    padding = 10,
    paddingTop = 20,
    adjust = Rectangle
})

How It Works

Each frame, FitContent:

1. Measures the bounding box of all children with LayoutBox
2. Adds padding to calculate final dimensions
3. Updates the entity's LayoutBox width/height
4. Optionally updates a render component's width/height

Requirements

FitContent requires a LayoutBox component on the same entity. Children must also have LayoutBox for measurement.

-- This works
world:spawn(
    Transform(0, 0),
    Rectangle(0, 0),
    LayoutBox(Rectangle, nil, 0, 0),
    FitContent(10, Rectangle)
)

-- Children need LayoutBox too
world:spawn(
    ChildOf(container),
    RelativeTransform.new({x = 0, y = 0}),
    Text(font, "Content"),
    LayoutBox(Text, nil, 0, 0)  -- Required for measurement
)

Dynamic Resizing

FitContent recalculates every frame, so containers automatically resize when children change:

-- Text changes → container resizes automatically
local text = world:get(textEntity, Text)
text:setText("Longer text content!")
-- Container will grow on next frame