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Optimize SwiftUIWrapperView #320

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merged 1 commit into from
Nov 10, 2024
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bryankeller
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This PR significantly reduces CPU use for people using SwiftUI views for their calendar items by making 2 optimizations:

  1. Don't add the UIHostingController as a child view controller, and just work with its hosting view directly
  2. Don't give every view a unique ID just to get onAppear and onDisappear callbacks - instead, set a hidden view's to just display an EmptyView

Together, these changes reduce CPU use by 35-40% when scrolling fast.

Related Issue

#299

Motivation and Context

Performance improvements.

How Has This Been Tested

Example app

Types of changes

  • Docs change / refactoring / dependency upgrade
  • Bug fix (non-breaking change which fixes an issue)
  • New feature (non-breaking change which adds functionality)
  • Breaking change (fix or feature that would cause existing functionality to change)

Checklist

  • My code follows the code style of this project.
  • My change requires a change to the documentation.
  • I have updated the documentation accordingly.
  • I have read the CONTRIBUTING document.
  • I have added tests to cover my changes.

@bryankeller bryankeller added the enhancement New feature or request label Nov 9, 2024
public override var isHidden: Bool {
didSet {
if isHidden {
hostingController.rootView = AnyView(EmptyView())
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not ideal, but way faster than the previous strategy of giving every view an ID

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We could also add an API in the future to opt-out of this behavior if someone doesn't need onAppear or onDisappear callbacks in their views, which would get them back ~20% CPU usage when scrolling fast 🤯

}

// MARK: Fileprivate

fileprivate var contentAndID: ContentAndID {
didSet {
hostingController.rootView = .init(content: contentAndID.content, id: contentAndID.id)
hostingController.rootView = AnyView(contentAndID.content)
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I profiled and there was no perf hit from switching to AnyView

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Nice findings!

@bryankeller bryankeller merged commit b7ebeee into master Nov 10, 2024
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2 participants