High Performance Auto Layout

WWDC 2018

High Performance Auto Layout

WWDC 2018

updateConstraints()

DO NOT Removes & Adds constraint every time

Minimize update constraints

Render Loop

Render Loop

Activating a Constraint

Internal structure

Triggering the layout pass

layoutSubviews()

Copying data from engine to subView

Local vs Global Layout

Performance Scales

Model The Problem Naturally

Using constraints
Don’t wedge two layouts into one set of constraints

Don’t wedge

Error Minimization

Engine is not perfect. The engine try to minimize errors.

Minimize error

Performance Intuition

Don’t churn
Basic algebra
Engine is a layout cache and tracker
You pay for what you use

Building Efficient Layouts

Instruments for Layouts 👍

More Performance Layout

More Performance Layout

UIView.noIntrinsicMetric

To parent,
“hey I already have my size, don’t bother to do the text measurement”

noIntrinsicMetric

System Layout Size Fitting Size

systemLayoutSizeFitting(_ targetSize:)

Unsatisfiable Constraints

There is no solution for the specified constraints
Logging will help you to debug
Can mask other issues
See related session for debugging tips

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