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//
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// ChatLayout
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// StateController.swift
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// https://github.com/ekazaev/ChatLayout
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//
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// Created by Eugene Kazaev in 2020-2022.
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// Distributed under the MIT license.
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//
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import Foundation
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import UIKit
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/// This protocol exists only to serve an ability to unit test `StateController`.
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protocol ChatLayoutRepresentation: AnyObject {
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var settings: ChatLayoutSettings { get }
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var viewSize: CGSize { get }
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var visibleBounds: CGRect { get }
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var layoutFrame: CGRect { get }
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var adjustedContentInset: UIEdgeInsets { get }
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var keepContentOffsetAtBottomOnBatchUpdates: Bool { get }
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func numberOfItems(in section: Int) -> Int
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func configuration(for element: ItemKind, at itemPath: ItemPath) -> ItemModel.Configuration
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func shouldPresentHeader(at sectionIndex: Int) -> Bool
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func shouldPresentFooter(at sectionIndex: Int) -> Bool
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}
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final class StateController {
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private enum CompensatingAction {
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case insert
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case delete
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case frameUpdate(previousFrame: CGRect, newFrame: CGRect)
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}
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// This thing exists here as `UICollectionView` calls `targetContentOffset(forProposedContentOffset proposedContentOffset: CGPoint)` only once at the
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// beginning of the animated updates. But we must compensate the other changes that happened during the update.
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var batchUpdateCompensatingOffset: CGFloat = 0
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var proposedCompensatingOffset: CGFloat = 0
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var totalProposedCompensatingOffset: CGFloat = 0
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var isAnimatedBoundsChange = false
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private(set) var storage: [ModelState: LayoutModel]
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private(set) var reloadedIndexes: Set<IndexPath> = []
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private(set) var insertedIndexes: Set<IndexPath> = []
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private(set) var movedIndexes: Set<IndexPath> = []
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private(set) var deletedIndexes: Set<IndexPath> = []
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private(set) var reloadedSectionsIndexes: Set<Int> = []
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private(set) var insertedSectionsIndexes: Set<Int> = []
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private(set) var deletedSectionsIndexes: Set<Int> = []
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private(set) var movedSectionsIndexes: Set<Int> = []
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private var cachedAttributesState: (rect: CGRect, attributes: [ChatLayoutAttributes])?
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private var cachedAttributeObjects = [ModelState: [ItemKind: [ItemPath: ChatLayoutAttributes]]]()
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private unowned var layoutRepresentation: ChatLayoutRepresentation
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init(layoutRepresentation: ChatLayoutRepresentation) {
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self.layoutRepresentation = layoutRepresentation
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self.storage = [.beforeUpdate: LayoutModel(sections: [], collectionLayout: self.layoutRepresentation)]
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resetCachedAttributeObjects()
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}
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func set(_ sections: [SectionModel], at state: ModelState) {
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var layoutModel = LayoutModel(sections: sections, collectionLayout: layoutRepresentation)
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layoutModel.assembleLayout()
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storage[state] = layoutModel
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}
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func contentHeight(at state: ModelState) -> CGFloat {
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guard let locationHeight = storage[state]?.sections.last?.locationHeight else {
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return 0
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}
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return locationHeight + layoutRepresentation.settings.additionalInsets.bottom
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}
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func layoutAttributesForElements(in rect: CGRect,
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state: ModelState,
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ignoreCache: Bool = false) -> [ChatLayoutAttributes] {
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let predicate: (ChatLayoutAttributes) -> ComparisonResult = { attributes in
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if attributes.frame.intersects(rect) {
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return .orderedSame
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}
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if attributes.frame.minY > rect.maxY {
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return .orderedDescending
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}
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return .orderedAscending
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}
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if !ignoreCache,
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let cachedAttributesState = cachedAttributesState,
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cachedAttributesState.rect.contains(rect) {
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return cachedAttributesState.attributes.binarySearchRange(predicate: predicate)
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} else {
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let totalRect: CGRect
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switch state {
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case .beforeUpdate:
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totalRect = rect.inset(by: UIEdgeInsets(top: -rect.height / 2, left: -rect.width / 2, bottom: -rect.height / 2, right: -rect.width / 2))
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case .afterUpdate:
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totalRect = rect
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}
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let attributes = allAttributes(at: state, visibleRect: totalRect)
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if !ignoreCache {
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cachedAttributesState = (rect: totalRect, attributes: attributes)
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}
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let visibleAttributes = rect != totalRect ? attributes.binarySearchRange(predicate: predicate) : attributes
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return visibleAttributes
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}
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}
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func resetCachedAttributes() {
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cachedAttributesState = nil
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}
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func resetCachedAttributeObjects() {
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ModelState.allCases.forEach { state in
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resetCachedAttributeObjects(at: state)
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}
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}
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private func resetCachedAttributeObjects(at state: ModelState) {
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cachedAttributeObjects[state] = [:]
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ItemKind.allCases.forEach { kind in
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cachedAttributeObjects[state]?[kind] = [:]
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}
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}
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func itemAttributes(for itemPath: ItemPath,
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kind: ItemKind,
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predefinedFrame: CGRect? = nil,
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at state: ModelState) -> ChatLayoutAttributes? {
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let attributes: ChatLayoutAttributes
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let itemIndexPath = itemPath.indexPath
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switch kind {
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case .header:
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guard itemPath.section < layout(at: state).sections.count,
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itemPath.item == 0 else {
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// This occurs when getting layout attributes for initial / final animations
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return nil
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}
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guard let headerFrame = predefinedFrame ?? itemFrame(for: itemPath, kind: kind, at: state, isFinal: true),
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let item = item(for: itemPath, kind: kind, at: state) else {
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return nil
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}
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if let cachedAttributes = cachedAttributeObjects[state]?[.header]?[itemPath] {
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attributes = cachedAttributes
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} else {
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attributes = ChatLayoutAttributes(forSupplementaryViewOfKind: UICollectionView.elementKindSectionHeader, with: itemIndexPath)
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cachedAttributeObjects[state]?[.header]?[itemPath] = attributes
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}
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#if DEBUG
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attributes.id = item.id
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#endif
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attributes.frame = headerFrame
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attributes.indexPath = itemIndexPath
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attributes.zIndex = 10
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attributes.alignment = item.alignment
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case .footer:
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guard itemPath.section < layout(at: state).sections.count,
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itemPath.item == 0 else {
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// This occurs when getting layout attributes for initial / final animations
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return nil
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}
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guard let footerFrame = predefinedFrame ?? itemFrame(for: itemPath, kind: kind, at: state, isFinal: true),
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let item = item(for: itemPath, kind: kind, at: state) else {
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return nil
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}
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if let cachedAttributes = cachedAttributeObjects[state]?[.footer]?[itemPath] {
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attributes = cachedAttributes
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} else {
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attributes = ChatLayoutAttributes(forSupplementaryViewOfKind: UICollectionView.elementKindSectionFooter, with: itemIndexPath)
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cachedAttributeObjects[state]?[.footer]?[itemPath] = attributes
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}
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#if DEBUG
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attributes.id = item.id
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#endif
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attributes.frame = footerFrame
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attributes.indexPath = itemIndexPath
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attributes.zIndex = 10
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attributes.alignment = item.alignment
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case .cell:
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guard itemPath.section < layout(at: state).sections.count,
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itemPath.item < layout(at: state).sections[itemPath.section].items.count else {
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// This occurs when getting layout attributes for initial / final animations
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return nil
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}
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guard let itemFrame = predefinedFrame ?? itemFrame(for: itemPath, kind: .cell, at: state, isFinal: true),
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let item = item(for: itemPath, kind: kind, at: state) else {
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return nil
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}
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if let cachedAttributes = cachedAttributeObjects[state]?[.cell]?[itemPath] {
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attributes = cachedAttributes
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} else {
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attributes = ChatLayoutAttributes(forCellWith: itemIndexPath)
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cachedAttributeObjects[state]?[.cell]?[itemPath] = attributes
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}
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#if DEBUG
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attributes.id = item.id
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#endif
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attributes.frame = itemFrame
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attributes.indexPath = itemIndexPath
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attributes.zIndex = 0
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attributes.alignment = item.alignment
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}
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attributes.viewSize = layoutRepresentation.viewSize
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attributes.adjustedContentInsets = layoutRepresentation.adjustedContentInset
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attributes.visibleBoundsSize = layoutRepresentation.visibleBounds.size
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attributes.layoutFrame = layoutRepresentation.layoutFrame
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attributes.additionalInsets = layoutRepresentation.settings.additionalInsets
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return attributes
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}
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func itemFrame(for itemPath: ItemPath, kind: ItemKind, at state: ModelState, isFinal: Bool = false) -> CGRect? {
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guard itemPath.section < layout(at: state).sections.count else {
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return nil
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}
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guard let item = self.item(for: itemPath, kind: kind, at: state) else {
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// This occurs when getting layout attributes for initial / final animations
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return nil
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}
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let section = layout(at: state).sections[itemPath.section]
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var itemFrame = item.frame
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let dx: CGFloat
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let visibleBounds = layoutRepresentation.visibleBounds
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let additionalInsets = layoutRepresentation.settings.additionalInsets
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switch item.alignment {
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case .leading:
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dx = additionalInsets.left
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case .trailing:
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dx = visibleBounds.size.width - itemFrame.width - additionalInsets.right
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case .center:
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let availableWidth = visibleBounds.size.width - additionalInsets.right - additionalInsets.left
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dx = additionalInsets.left + availableWidth / 2 - itemFrame.width / 2
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case .fullWidth:
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dx = additionalInsets.left
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itemFrame.size.width = layoutRepresentation.layoutFrame.size.width
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}
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itemFrame = itemFrame.offsetBy(dx: dx, dy: section.offsetY)
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if isFinal {
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itemFrame = offsetByCompensation(frame: itemFrame, at: itemPath, for: state, backward: true)
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}
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return itemFrame
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}
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func itemPath(by itemId: UUID, kind: ItemKind, at state: ModelState) -> ItemPath? {
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return layout(at: state).itemPath(by: itemId, kind: kind)
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}
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func sectionIdentifier(for index: Int, at state: ModelState) -> UUID? {
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guard index < layout(at: state).sections.count else {
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// This occurs when getting layout attributes for initial / final animations
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return nil
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}
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return layout(at: state).sections[index].id
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}
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func sectionIndex(for sectionIdentifier: UUID, at state: ModelState) -> Int? {
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guard let sectionIndex = layout(at: state).sectionIndex(by: sectionIdentifier) else {
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// This occurs when getting layout attributes for initial / final animations
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return nil
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}
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return sectionIndex
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}
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func section(at index: Int, at state: ModelState) -> SectionModel {
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guard index < layout(at: state).sections.count else {
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preconditionFailure("Section index \(index) is bigger than the amount of sections \(layout(at: state).sections.count)")
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}
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return layout(at: state).sections[index]
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}
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func itemIdentifier(for itemPath: ItemPath, kind: ItemKind, at state: ModelState) -> UUID? {
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guard itemPath.section < layout(at: state).sections.count else {
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// This occurs when getting layout attributes for initial / final animations
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return nil
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}
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let sectionModel = layout(at: state).sections[itemPath.section]
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switch kind {
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case .cell:
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guard itemPath.item < layout(at: state).sections[itemPath.section].items.count else {
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// This occurs when getting layout attributes for initial / final animations
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return nil
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}
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let rowModel = sectionModel.items[itemPath.item]
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return rowModel.id
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case .header, .footer:
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guard let item = item(for: ItemPath(item: 0, section: itemPath.section), kind: kind, at: state) else {
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return nil
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}
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return item.id
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}
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}
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func numberOfSections(at state: ModelState) -> Int {
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return layout(at: state).sections.count
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}
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func numberOfItems(in sectionIndex: Int, at state: ModelState) -> Int {
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return layout(at: state).sections[sectionIndex].items.count
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}
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func item(for itemPath: ItemPath, kind: ItemKind, at state: ModelState) -> ItemModel? {
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switch kind {
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case .header:
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guard itemPath.section < layout(at: state).sections.count,
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itemPath.item == 0 else {
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// This occurs when getting layout attributes for initial / final animations
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return nil
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}
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guard let header = layout(at: state).sections[itemPath.section].header else {
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return nil
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}
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return header
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case .footer:
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guard itemPath.section < layout(at: state).sections.count,
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itemPath.item == 0 else {
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// This occurs when getting layout attributes for initial / final animations
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return nil
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}
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guard let footer = layout(at: state).sections[itemPath.section].footer else {
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return nil
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}
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return footer
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case .cell:
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guard itemPath.section < layout(at: state).sections.count,
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itemPath.item < layout(at: state).sections[itemPath.section].count else {
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// This occurs when getting layout attributes for initial / final animations
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return nil
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! |
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}
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return layout(at: state).sections[itemPath.section].items[itemPath.item]
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}
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}
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func update(preferredSize: CGSize, alignment: ChatItemAlignment, for itemPath: ItemPath, kind: ItemKind, at state: ModelState) {
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guard var item = item(for: itemPath, kind: kind, at: state) else {
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assertionFailure("Item at index path (\(itemPath.section) - \(itemPath.item)) does not exist.")
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return
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! |
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}
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! |
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var layout = self.layout(at: state)
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let previousFrame = item.frame
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cachedAttributesState = nil
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! |
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item.alignment = alignment
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item.calculatedSize = preferredSize
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item.calculatedOnce = true
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! |
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switch kind {
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case .header:
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! |
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layout.setAndAssemble(header: item, sectionIndex: itemPath.section)
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! |
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case .footer:
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! |
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layout.setAndAssemble(footer: item, sectionIndex: itemPath.section)
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! |
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case .cell:
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! |
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layout.setAndAssemble(item: item, sectionIndex: itemPath.section, itemIndex: itemPath.item)
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! |
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}
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! |
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storage[state] = layout
|
! |
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let frameUpdateAction = CompensatingAction.frameUpdate(previousFrame: previousFrame, newFrame: item.frame)
|
! |
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compensateOffsetIfNeeded(for: itemPath, kind: kind, action: frameUpdateAction)
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! |
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}
|
! |
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! |
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func process(changeItems: [ChangeItem]) {
|
! |
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batchUpdateCompensatingOffset = 0
|
! |
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proposedCompensatingOffset = 0
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! |
388 |
let changeItems = changeItems.sorted()
|
! |
389 |
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! |
390 |
var afterUpdateModel = layout(at: .beforeUpdate)
|
! |
391 |
resetCachedAttributeObjects()
|
! |
392 |
|
! |
393 |
changeItems.forEach { updateItem in
|
! |
394 |
switch updateItem {
|
! |
395 |
case let .sectionInsert(sectionIndex: sectionIndex):
|
! |
396 |
let items = (0..<layoutRepresentation.numberOfItems(in: sectionIndex)).map { index -> ItemModel in
|
! |
397 |
let itemIndexPath = IndexPath(item: index, section: sectionIndex)
|
! |
398 |
return ItemModel(with: layoutRepresentation.configuration(for: .cell, at: itemIndexPath.itemPath))
|
! |
399 |
}
|
! |
400 |
let header: ItemModel?
|
! |
401 |
if layoutRepresentation.shouldPresentHeader(at: sectionIndex) == true {
|
! |
402 |
let headerIndexPath = IndexPath(item: 0, section: sectionIndex)
|
! |
403 |
header = ItemModel(with: layoutRepresentation.configuration(for: .header, at: headerIndexPath.itemPath))
|
! |
404 |
} else {
|
! |
405 |
header = nil
|
! |
406 |
}
|
! |
407 |
let footer: ItemModel?
|
! |
408 |
if layoutRepresentation.shouldPresentFooter(at: sectionIndex) == true {
|
! |
409 |
let footerIndexPath = IndexPath(item: 0, section: sectionIndex)
|
! |
410 |
footer = ItemModel(with: layoutRepresentation.configuration(for: .footer, at: footerIndexPath.itemPath))
|
! |
411 |
} else {
|
! |
412 |
footer = nil
|
! |
413 |
}
|
! |
414 |
let section = SectionModel(header: header, footer: footer, items: items, collectionLayout: layoutRepresentation)
|
! |
415 |
afterUpdateModel.insertSection(section, at: sectionIndex)
|
! |
416 |
insertedSectionsIndexes.insert(sectionIndex)
|
! |
417 |
case let .itemInsert(itemIndexPath: indexPath):
|
! |
418 |
let item = ItemModel(with: layoutRepresentation.configuration(for: .cell, at: indexPath.itemPath))
|
! |
419 |
insertedIndexes.insert(indexPath)
|
! |
420 |
afterUpdateModel.insertItem(item, at: indexPath)
|
! |
421 |
case let .sectionDelete(sectionIndex: sectionIndex):
|
! |
422 |
let section = layout(at: .beforeUpdate).sections[sectionIndex]
|
! |
423 |
deletedSectionsIndexes.insert(sectionIndex)
|
! |
424 |
afterUpdateModel.removeSection(by: section.id)
|
! |
425 |
case let .itemDelete(itemIndexPath: indexPath):
|
! |
426 |
let itemId = itemIdentifier(for: indexPath.itemPath, kind: .cell, at: .beforeUpdate)!
|
! |
427 |
afterUpdateModel.removeItem(by: itemId)
|
! |
428 |
deletedIndexes.insert(indexPath)
|
! |
429 |
case let .sectionReload(sectionIndex: sectionIndex):
|
! |
430 |
reloadedSectionsIndexes.insert(sectionIndex)
|
! |
431 |
var section = layout(at: .beforeUpdate).sections[sectionIndex]
|
! |
432 |
|
! |
433 |
var header: ItemModel?
|
! |
434 |
if layoutRepresentation.shouldPresentHeader(at: sectionIndex) == true {
|
! |
435 |
let headerIndexPath = IndexPath(item: 0, section: sectionIndex)
|
! |
436 |
header = section.header ?? ItemModel(with: layoutRepresentation.configuration(for: .header, at: headerIndexPath.itemPath))
|
! |
437 |
header?.resetSize()
|
! |
438 |
} else {
|
! |
439 |
header = nil
|
! |
440 |
}
|
! |
441 |
section.set(header: header)
|
! |
442 |
|
! |
443 |
var footer: ItemModel?
|
! |
444 |
if layoutRepresentation.shouldPresentFooter(at: sectionIndex) == true {
|
! |
445 |
let footerIndexPath = IndexPath(item: 0, section: sectionIndex)
|
! |
446 |
footer = section.footer ?? ItemModel(with: layoutRepresentation.configuration(for: .footer, at: footerIndexPath.itemPath))
|
! |
447 |
footer?.resetSize()
|
! |
448 |
} else {
|
! |
449 |
footer = nil
|
! |
450 |
}
|
! |
451 |
section.set(footer: footer)
|
! |
452 |
|
! |
453 |
let oldItems = section.items
|
! |
454 |
let items: [ItemModel] = (0..<layoutRepresentation.numberOfItems(in: sectionIndex)).map { index in
|
! |
455 |
var newItem: ItemModel
|
! |
456 |
if index < oldItems.count {
|
! |
457 |
newItem = oldItems[index]
|
! |
458 |
} else {
|
! |
459 |
let itemIndexPath = IndexPath(item: index, section: sectionIndex)
|
! |
460 |
newItem = ItemModel(with: layoutRepresentation.configuration(for: .cell, at: itemIndexPath.itemPath))
|
! |
461 |
}
|
! |
462 |
newItem.resetSize()
|
! |
463 |
return newItem
|
! |
464 |
}
|
! |
465 |
section.set(items: items)
|
! |
466 |
afterUpdateModel.removeSection(for: sectionIndex)
|
! |
467 |
afterUpdateModel.insertSection(section, at: sectionIndex)
|
! |
468 |
case let .itemReload(itemIndexPath: indexPath):
|
! |
469 |
guard var item = self.item(for: indexPath.itemPath, kind: .cell, at: .beforeUpdate) else {
|
! |
470 |
assertionFailure("Item at index path (\(indexPath.section) - \(indexPath.item)) does not exist.")
|
! |
471 |
return
|
! |
472 |
}
|
! |
473 |
item.resetSize()
|
! |
474 |
|
! |
475 |
afterUpdateModel.replaceItem(item, at: indexPath)
|
! |
476 |
reloadedIndexes.insert(indexPath)
|
! |
477 |
case let .sectionMove(initialSectionIndex: initialSectionIndex, finalSectionIndex: finalSectionIndex):
|
! |
478 |
let section = layout(at: .beforeUpdate).sections[initialSectionIndex]
|
! |
479 |
movedSectionsIndexes.insert(finalSectionIndex)
|
! |
480 |
afterUpdateModel.removeSection(by: section.id)
|
! |
481 |
afterUpdateModel.insertSection(section, at: finalSectionIndex)
|
! |
482 |
case let .itemMove(initialItemIndexPath: initialItemIndexPath, finalItemIndexPath: finalItemIndexPath):
|
! |
483 |
let itemId = itemIdentifier(for: initialItemIndexPath.itemPath, kind: .cell, at: .beforeUpdate)!
|
! |
484 |
let item = layout(at: .beforeUpdate).sections[initialItemIndexPath.section].items[initialItemIndexPath.item]
|
! |
485 |
movedIndexes.insert(initialItemIndexPath)
|
! |
486 |
afterUpdateModel.removeItem(by: itemId)
|
! |
487 |
afterUpdateModel.insertItem(item, at: finalItemIndexPath)
|
! |
488 |
}
|
! |
489 |
}
|
! |
490 |
|
! |
491 |
afterUpdateModel = LayoutModel(sections: afterUpdateModel.sections.map { section -> SectionModel in
|
! |
492 |
var section = section
|
! |
493 |
section.assembleLayout()
|
! |
494 |
return section
|
! |
495 |
}, collectionLayout: layoutRepresentation)
|
! |
496 |
afterUpdateModel.assembleLayout()
|
! |
497 |
storage[.afterUpdate] = afterUpdateModel
|
! |
498 |
|
! |
499 |
// Calculating potential content offset changes after the updates
|
! |
500 |
insertedSectionsIndexes.sorted(by: { $0 < $1 }).forEach {
|
! |
501 |
compensateOffsetOfSectionIfNeeded(for: $0, action: .insert)
|
! |
502 |
}
|
! |
503 |
reloadedSectionsIndexes.sorted(by: { $0 < $1 }).forEach {
|
! |
504 |
let oldSection = self.section(at: $0, at: .beforeUpdate)
|
! |
505 |
guard let newSectionIndex = self.sectionIndex(for: oldSection.id, at: .afterUpdate) else {
|
! |
506 |
assertionFailure("Section with identifier \(oldSection.id) does not exist.")
|
! |
507 |
return
|
! |
508 |
}
|
! |
509 |
let newSection = self.section(at: newSectionIndex, at: .afterUpdate)
|
! |
510 |
compensateOffsetOfSectionIfNeeded(for: $0, action: .frameUpdate(previousFrame: oldSection.frame, newFrame: newSection.frame))
|
! |
511 |
}
|
! |
512 |
deletedSectionsIndexes.sorted(by: { $0 < $1 }).forEach {
|
! |
513 |
compensateOffsetOfSectionIfNeeded(for: $0, action: .delete)
|
! |
514 |
}
|
! |
515 |
|
! |
516 |
reloadedIndexes.sorted(by: { $0 < $1 }).forEach {
|
! |
517 |
guard let oldItem = self.item(for: $0.itemPath, kind: .cell, at: .beforeUpdate),
|
! |
518 |
let newItemIndexPath = self.itemPath(by: oldItem.id, kind: .cell, at: .afterUpdate),
|
! |
519 |
let newItem = self.item(for: newItemIndexPath, kind: .cell, at: .afterUpdate) else {
|
|
520 |
assertionFailure("Internal inconsistency")
|
! |
521 |
return
|
! |
522 |
}
|
! |
523 |
compensateOffsetIfNeeded(for: $0.itemPath, kind: .cell, action: .frameUpdate(previousFrame: oldItem.frame, newFrame: newItem.frame))
|
! |
524 |
}
|
! |
525 |
|
! |
526 |
insertedIndexes.sorted(by: { $0 < $1 }).forEach {
|
! |
527 |
compensateOffsetIfNeeded(for: $0.itemPath, kind: .cell, action: .insert)
|
! |
528 |
}
|
! |
529 |
deletedIndexes.sorted(by: { $0 < $1 }).forEach {
|
! |
530 |
compensateOffsetIfNeeded(for: $0.itemPath, kind: .cell, action: .delete)
|
! |
531 |
}
|
! |
532 |
|
! |
533 |
totalProposedCompensatingOffset = proposedCompensatingOffset
|
! |
534 |
}
|
! |
535 |
|
! |
536 |
func commitUpdates() {
|
! |
537 |
insertedIndexes = []
|
! |
538 |
insertedSectionsIndexes = []
|
! |
539 |
|
! |
540 |
reloadedIndexes = []
|
! |
541 |
reloadedSectionsIndexes = []
|
|
542 |
|
! |
543 |
movedIndexes = []
|
! |
544 |
movedSectionsIndexes = []
|
! |
545 |
|
! |
546 |
deletedIndexes = []
|
! |
547 |
deletedSectionsIndexes = []
|
! |
548 |
|
! |
549 |
storage[.beforeUpdate] = layout(at: .afterUpdate)
|
! |
550 |
storage[.afterUpdate] = nil
|
! |
551 |
|
! |
552 |
totalProposedCompensatingOffset = 0
|
! |
553 |
|
! |
554 |
cachedAttributeObjects[.beforeUpdate] = cachedAttributeObjects[.afterUpdate]
|
! |
555 |
resetCachedAttributeObjects(at: .afterUpdate)
|
! |
556 |
}
|
! |
557 |
|
! |
558 |
func contentSize(for state: ModelState) -> CGSize {
|
|
559 |
let contentHeight = self.contentHeight(at: state)
|
! |
560 |
guard contentHeight != 0 else {
|
! |
561 |
return .zero
|
! |
562 |
}
|
! |
563 |
// This is a workaround for `layoutAttributesForElementsInRect:` not getting invoked enough
|
! |
564 |
// times if `collectionViewContentSize.width` is not smaller than the width of the collection
|
! |
565 |
// view, minus horizontal insets. This results in visual defects when performing batch
|
! |
566 |
// updates. To work around this, we subtract 0.0001 from our content size width calculation;
|
! |
567 |
// this small decrease in `collectionViewContentSize.width` is enough to work around the
|
! |
568 |
// incorrect, internal collection view `CGRect` checks, without introducing any visual
|
! |
569 |
// differences for elements in the collection view.
|
! |
570 |
// See https://openradar.appspot.com/radar?id=5025850143539200 for more details.
|
! |
571 |
let contentSize = CGSize(width: layoutRepresentation.visibleBounds.size.width - 0.0001, height: contentHeight)
|
|
572 |
return contentSize
|
! |
573 |
}
|
! |
574 |
|
! |
575 |
func offsetByTotalCompensation(attributes: UICollectionViewLayoutAttributes?, for state: ModelState, backward: Bool = false) {
|
! |
576 |
guard layoutRepresentation.keepContentOffsetAtBottomOnBatchUpdates,
|
! |
577 |
state == .afterUpdate,
|
! |
578 |
let attributes = attributes else {
|
! |
579 |
return
|
|
580 |
}
|
! |
581 |
if backward, isLayoutBiggerThanVisibleBounds(at: .afterUpdate) {
|
! |
582 |
attributes.frame = attributes.frame.offsetBy(dx: 0, dy: totalProposedCompensatingOffset * -1)
|
! |
583 |
} else if !backward, isLayoutBiggerThanVisibleBounds(at: .afterUpdate) {
|
! |
584 |
attributes.frame = attributes.frame.offsetBy(dx: 0, dy: totalProposedCompensatingOffset)
|
|
585 |
}
|
! |
586 |
}
|
! |
587 |
|
! |
588 |
func layout(at state: ModelState) -> LayoutModel {
|
! |
589 |
guard let layout = storage[state] else {
|
! |
590 |
assertionFailure("Internal inconsistency. Layout at \(state) is missing.")
|
! |
591 |
return LayoutModel(sections: [], collectionLayout: layoutRepresentation)
|
! |
592 |
}
|
! |
593 |
return layout
|
! |
594 |
}
|
! |
595 |
|
! |
596 |
func isLayoutBiggerThanVisibleBounds(at state: ModelState, withFullCompensation: Bool = false) -> Bool {
|
! |
597 |
let visibleBoundsHeight = layoutRepresentation.visibleBounds.height + (withFullCompensation ? batchUpdateCompensatingOffset + proposedCompensatingOffset : 0)
|
! |
598 |
return contentHeight(at: state).rounded() > visibleBoundsHeight.rounded()
|
! |
599 |
}
|
! |
600 |
|
! |
601 |
private func allAttributes(at state: ModelState, visibleRect: CGRect? = nil) -> [ChatLayoutAttributes] {
|
! |
602 |
let layout = self.layout(at: state)
|
! |
603 |
|
! |
604 |
if let visibleRect = visibleRect {
|
! |
605 |
enum TraverseState {
|
! |
606 |
case notFound
|
! |
607 |
case found
|
! |
608 |
case done
|
! |
609 |
}
|
! |
610 |
|
! |
611 |
var traverseState: TraverseState = .notFound
|
! |
612 |
|
! |
613 |
func check(rect: CGRect) -> Bool {
|
! |
614 |
switch traverseState {
|
! |
615 |
case .notFound:
|
! |
616 |
if visibleRect.intersects(rect) {
|
! |
617 |
traverseState = .found
|
! |
618 |
return true
|
! |
619 |
} else {
|
! |
620 |
return false
|
! |
621 |
}
|
! |
622 |
case .found:
|
! |
623 |
if visibleRect.intersects(rect) {
|
! |
624 |
return true
|
! |
625 |
} else {
|
! |
626 |
if rect.minY > visibleRect.maxY + batchUpdateCompensatingOffset + proposedCompensatingOffset {
|
! |
627 |
traverseState = .done
|
! |
628 |
}
|
! |
629 |
return false
|
! |
630 |
}
|
! |
631 |
case .done:
|
! |
632 |
return false
|
! |
633 |
}
|
! |
634 |
}
|
! |
635 |
|
! |
636 |
var allRects = [(frame: CGRect, indexPath: ItemPath, kind: ItemKind)]()
|
! |
637 |
// I dont think there can be more then a 200 elements on the screen simultaneously
|
! |
638 |
allRects.reserveCapacity(200)
|
! |
639 |
for sectionIndex in 0..<layout.sections.count {
|
! |
640 |
let section = layout.sections[sectionIndex]
|
! |
641 |
let sectionPath = ItemPath(item: 0, section: sectionIndex)
|
! |
642 |
if let headerFrame = itemFrame(for: sectionPath, kind: .header, at: state, isFinal: true),
|
! |
643 |
check(rect: headerFrame) {
|
! |
644 |
allRects.append((frame: headerFrame, indexPath: sectionPath, kind: .header))
|
! |
645 |
}
|
! |
646 |
guard traverseState != .done else {
|
! |
647 |
break
|
! |
648 |
}
|
! |
649 |
|
! |
650 |
var startingIndex = 0
|
! |
651 |
// If header is not visible
|
! |
652 |
if traverseState == .notFound, !section.items.isEmpty {
|
! |
653 |
func predicate(itemIndex: Int) -> ComparisonResult {
|
! |
654 |
let itemPath = ItemPath(item: itemIndex, section: sectionIndex)
|
! |
655 |
guard let itemFrame = itemFrame(for: itemPath, kind: .cell, at: state, isFinal: true) else {
|
! |
656 |
return .orderedDescending
|
! |
657 |
}
|
! |
658 |
if itemFrame.intersects(visibleRect) {
|
! |
659 |
return .orderedSame
|
! |
660 |
}
|
! |
661 |
if itemFrame.minY > visibleRect.maxY {
|
! |
662 |
return .orderedDescending
|
! |
663 |
}
|
! |
664 |
return .orderedAscending
|
! |
665 |
}
|
! |
666 |
|
! |
667 |
// Find if any of the items of the section is visible
|
! |
668 |
if [ComparisonResult.orderedSame, .orderedDescending].contains(predicate(itemIndex: section.items.count - 1)),
|
! |
669 |
let firstMatchingIndex = Array(0...section.items.count - 1).binarySearch(predicate: predicate) {
|
! |
670 |
// Find first item that is visible
|
! |
671 |
startingIndex = firstMatchingIndex
|
! |
672 |
for itemIndex in (0..<firstMatchingIndex).reversed() {
|
! |
673 |
let itemPath = ItemPath(item: itemIndex, section: sectionIndex)
|
! |
674 |
guard let itemFrame = itemFrame(for: itemPath, kind: .cell, at: state, isFinal: true) else {
|
! |
675 |
continue
|
! |
676 |
}
|
! |
677 |
guard itemFrame.maxY >= visibleRect.minY else {
|
! |
678 |
break
|
! |
679 |
}
|
! |
680 |
startingIndex = itemIndex
|
! |
681 |
}
|
! |
682 |
} else {
|
! |
683 |
// Otherwise we can safely skip all the items in the section and go to footer.
|
! |
684 |
startingIndex = section.items.count
|
! |
685 |
}
|
! |
686 |
}
|
! |
687 |
|
! |
688 |
if startingIndex < section.items.count {
|
! |
689 |
for itemIndex in startingIndex..<section.items.count {
|
! |
690 |
let itemPath = ItemPath(item: itemIndex, section: sectionIndex)
|
! |
691 |
if let itemFrame = self.itemFrame(for: itemPath, kind: .cell, at: state, isFinal: true),
|
! |
692 |
check(rect: itemFrame) {
|
! |
693 |
if state == .beforeUpdate || isAnimatedBoundsChange {
|
! |
694 |
allRects.append((frame: itemFrame, indexPath: itemPath, kind: .cell))
|
! |
695 |
} else {
|
! |
696 |
var itemWasVisibleBefore: Bool {
|
! |
697 |
guard let itemIdentifier = self.itemIdentifier(for: itemPath, kind: .cell, at: .afterUpdate),
|
! |
698 |
let initialIndexPath = self.itemPath(by: itemIdentifier, kind: .cell, at: .beforeUpdate),
|
! |
699 |
let item = self.item(for: initialIndexPath, kind: .cell, at: .beforeUpdate),
|
! |
700 |
item.calculatedOnce == true,
|
! |
701 |
let itemFrame = self.itemFrame(for: initialIndexPath, kind: .cell, at: .beforeUpdate, isFinal: false),
|
! |
702 |
itemFrame.intersects(layoutRepresentation.visibleBounds.offsetBy(dx: 0, dy: -totalProposedCompensatingOffset)) else {
|
! |
703 |
return false
|
! |
704 |
}
|
! |
705 |
return true
|
! |
706 |
}
|
! |
707 |
var itemWillBeVisible: Bool {
|
! |
708 |
let offsetVisibleBounds = layoutRepresentation.visibleBounds.offsetBy(dx: 0, dy: proposedCompensatingOffset + batchUpdateCompensatingOffset)
|
! |
709 |
if insertedIndexes.contains(itemPath.indexPath),
|
! |
710 |
let itemFrame = self.itemFrame(for: itemPath, kind: .cell, at: state, isFinal: true),
|
! |
711 |
itemFrame.intersects(offsetVisibleBounds) {
|
! |
712 |
return true
|
! |
713 |
}
|
! |
714 |
if let itemIdentifier = self.itemIdentifier(for: itemPath, kind: .cell, at: .afterUpdate),
|
! |
715 |
let initialIndexPath = self.itemPath(by: itemIdentifier, kind: .cell, at: .beforeUpdate)?.indexPath,
|
! |
716 |
movedIndexes.contains(initialIndexPath) || reloadedIndexes.contains(initialIndexPath),
|
! |
717 |
let itemFrame = self.itemFrame(for: itemPath, kind: .cell, at: state, isFinal: true),
|
! |
718 |
itemFrame.intersects(offsetVisibleBounds) {
|
! |
719 |
return true
|
! |
720 |
}
|
! |
721 |
return false
|
! |
722 |
}
|
! |
723 |
if itemWillBeVisible || itemWasVisibleBefore {
|
! |
724 |
allRects.append((frame: itemFrame, indexPath: itemPath, kind: .cell))
|
! |
725 |
}
|
! |
726 |
}
|
! |
727 |
}
|
! |
728 |
guard traverseState != .done else {
|
! |
729 |
break
|
! |
730 |
}
|
! |
731 |
}
|
! |
732 |
}
|
! |
733 |
|
! |
734 |
if let footerFrame = itemFrame(for: sectionPath, kind: .footer, at: state, isFinal: true),
|
! |
735 |
check(rect: footerFrame) {
|
! |
736 |
allRects.append((frame: footerFrame, indexPath: sectionPath, kind: .footer))
|
! |
737 |
}
|
! |
738 |
}
|
! |
739 |
|
! |
740 |
return allRects.compactMap { frame, path, kind -> ChatLayoutAttributes? in
|
! |
741 |
return self.itemAttributes(for: path, kind: kind, predefinedFrame: frame, at: state)
|
! |
742 |
}
|
! |
743 |
} else {
|
! |
744 |
// Debug purposes only.
|
! |
745 |
var attributes = [ChatLayoutAttributes]()
|
! |
746 |
attributes.reserveCapacity(layout.sections.count * 1000)
|
! |
747 |
layout.sections.enumerated().forEach { sectionIndex, section in
|
! |
748 |
let sectionPath = ItemPath(item: 0, section: sectionIndex)
|
! |
749 |
if let headerAttributes = self.itemAttributes(for: sectionPath, kind: .header, at: state) {
|
|
750 |
attributes.append(headerAttributes)
|
! |
751 |
}
|
! |
752 |
if let footerAttributes = self.itemAttributes(for: sectionPath, kind: .footer, at: state) {
|
! |
753 |
attributes.append(footerAttributes)
|
! |
754 |
}
|
! |
755 |
section.items.enumerated().forEach { itemIndex, _ in
|
! |
756 |
let itemPath = ItemPath(item: itemIndex, section: sectionIndex)
|
! |
757 |
if let itemAttributes = self.itemAttributes(for: itemPath, kind: .cell, at: state) {
|
! |
758 |
attributes.append(itemAttributes)
|
! |
759 |
}
|
! |
760 |
}
|
! |
761 |
}
|
! |
762 |
|
! |
763 |
return attributes
|
! |
764 |
}
|
! |
765 |
}
|
! |
766 |
|
! |
767 |
private func compensateOffsetIfNeeded(for itemPath: ItemPath, kind: ItemKind, action: CompensatingAction) {
|
! |
768 |
guard layoutRepresentation.keepContentOffsetAtBottomOnBatchUpdates else {
|
! |
769 |
return
|
! |
770 |
}
|
! |
771 |
let minY = (layoutRepresentation.visibleBounds.lowerPoint.y + batchUpdateCompensatingOffset + proposedCompensatingOffset).rounded()
|
! |
772 |
switch action {
|
! |
773 |
case .insert:
|
! |
774 |
guard isLayoutBiggerThanVisibleBounds(at: .afterUpdate),
|
! |
775 |
let itemFrame = itemFrame(for: itemPath, kind: kind, at: .afterUpdate) else {
|
! |
776 |
return
|
! |
777 |
}
|
! |
778 |
if itemFrame.minY.rounded() - layoutRepresentation.settings.interItemSpacing <= minY {
|
! |
779 |
proposedCompensatingOffset += itemFrame.height + layoutRepresentation.settings.interItemSpacing
|
! |
780 |
}
|
! |
781 |
case let .frameUpdate(previousFrame, newFrame):
|
! |
782 |
guard isLayoutBiggerThanVisibleBounds(at: .afterUpdate, withFullCompensation: true) else {
|
! |
783 |
return
|
! |
784 |
}
|
|
785 |
if newFrame.minY.rounded() <= minY {
|
! |
786 |
batchUpdateCompensatingOffset += newFrame.height - previousFrame.height
|
! |
787 |
}
|
! |
788 |
case .delete:
|
! |
789 |
guard isLayoutBiggerThanVisibleBounds(at: .beforeUpdate),
|
! |
790 |
let deletedFrame = itemFrame(for: itemPath, kind: kind, at: .beforeUpdate) else {
|
! |
791 |
return
|
! |
792 |
}
|
! |
793 |
if deletedFrame.minY.rounded() <= minY {
|
! |
794 |
// Changing content offset for deleted items using `invalidateLayout(with:) causes UI glitches.
|
! |
795 |
// So we are using targetContentOffset(forProposedContentOffset:) which is going to be called after.
|
! |
796 |
proposedCompensatingOffset -= (deletedFrame.height + layoutRepresentation.settings.interItemSpacing)
|
! |
797 |
}
|
! |
798 |
}
|
! |
799 |
|
! |
800 |
}
|
! |
801 |
|
! |
802 |
private func compensateOffsetOfSectionIfNeeded(for sectionIndex: Int, action: CompensatingAction) {
|
! |
803 |
guard layoutRepresentation.keepContentOffsetAtBottomOnBatchUpdates else {
|
! |
804 |
return
|
! |
805 |
}
|
! |
806 |
let minY = (layoutRepresentation.visibleBounds.lowerPoint.y + batchUpdateCompensatingOffset + proposedCompensatingOffset).rounded()
|
! |
807 |
switch action {
|
! |
808 |
case .insert:
|
! |
809 |
guard isLayoutBiggerThanVisibleBounds(at: .afterUpdate),
|
! |
810 |
sectionIndex < layout(at: .afterUpdate).sections.count else {
|
! |
811 |
return
|
! |
812 |
}
|
! |
813 |
let section = layout(at: .afterUpdate).sections[sectionIndex]
|
! |
814 |
|
! |
815 |
if section.offsetY.rounded() - layoutRepresentation.settings.interSectionSpacing <= minY {
|
! |
816 |
proposedCompensatingOffset += section.height + layoutRepresentation.settings.interSectionSpacing
|
! |
817 |
}
|
! |
818 |
case let .frameUpdate(previousFrame, newFrame):
|
! |
819 |
guard sectionIndex < layout(at: .afterUpdate).sections.count,
|
! |
820 |
isLayoutBiggerThanVisibleBounds(at: .afterUpdate, withFullCompensation: true) else {
|
! |
821 |
return
|
! |
822 |
}
|
! |
823 |
if newFrame.minY.rounded() <= minY {
|
|
824 |
batchUpdateCompensatingOffset += newFrame.height - previousFrame.height
|
|
825 |
}
|
|
826 |
case .delete:
|
|
827 |
guard isLayoutBiggerThanVisibleBounds(at: .afterUpdate),
|
! |
828 |
sectionIndex < layout(at: .afterUpdate).sections.count else {
|
! |
829 |
return
|
! |
830 |
}
|
! |
831 |
let section = layout(at: .beforeUpdate).sections[sectionIndex]
|
! |
832 |
if section.locationHeight.rounded() <= minY {
|
! |
833 |
// Changing content offset for deleted items using `invalidateLayout(with:) causes UI glitches.
|
! |
834 |
// So we are using targetContentOffset(forProposedContentOffset:) which is going to be called after.
|
! |
835 |
proposedCompensatingOffset -= (section.height + layoutRepresentation.settings.interSectionSpacing)
|
|
836 |
}
|
|
837 |
}
|
|
838 |
|
|
839 |
}
|
|
840 |
|
! |
841 |
private func offsetByCompensation(frame: CGRect,
|
! |
842 |
at itemPath: ItemPath,
|
! |
843 |
for state: ModelState,
|
! |
844 |
backward: Bool = false) -> CGRect {
|
! |
845 |
guard layoutRepresentation.keepContentOffsetAtBottomOnBatchUpdates,
|
! |
846 |
state == .afterUpdate,
|
! |
847 |
isLayoutBiggerThanVisibleBounds(at: .afterUpdate) else {
|
! |
848 |
return frame
|
! |
849 |
}
|
! |
850 |
return frame.offsetBy(dx: 0, dy: proposedCompensatingOffset * (backward ? -1 : 1))
|
! |
851 |
}
|
! |
852 |
|
! |
853 |
}
|
! |
854 |
|
! |
855 |
extension RandomAccessCollection where Index == Int {
|
! |
856 |
|
|
857 |
func binarySearch(predicate: (Element) -> ComparisonResult) -> Index? {
|
|
858 |
var lowerBound = startIndex
|
|
859 |
var upperBound = endIndex
|
|
860 |
|
|
861 |
while lowerBound < upperBound {
|
|
862 |
let midIndex = lowerBound + (upperBound - lowerBound) / 2
|
|
863 |
if predicate(self[midIndex]) == .orderedSame {
|
|
864 |
return midIndex
|
|
865 |
} else if predicate(self[midIndex]) == .orderedAscending {
|
|
866 |
lowerBound = midIndex + 1
|
|
867 |
} else {
|
|
868 |
upperBound = midIndex
|
|
869 |
}
|
|
870 |
}
|
|
871 |
return nil
|
|
872 |
}
|
|
873 |
|
|
874 |
func binarySearchRange(predicate: (Element) -> ComparisonResult) -> [Element] {
|
|
875 |
guard let firstMatchingIndex = binarySearch(predicate: predicate) else {
|
|
876 |
return []
|
|
877 |
}
|
|
878 |
|
|
879 |
var startingIndex = firstMatchingIndex
|
|
880 |
for index in (0..<firstMatchingIndex).reversed() {
|
|
881 |
let attributes = self[index]
|
|
882 |
guard predicate(attributes) == .orderedSame else {
|
|
883 |
break
|
|
884 |
}
|
|
885 |
startingIndex = index
|
|
886 |
}
|
|
887 |
|
|
888 |
var lastIndex = firstMatchingIndex
|
|
889 |
for index in (firstMatchingIndex + 1)..<count {
|
|
890 |
let attributes = self[index]
|
|
891 |
guard predicate(attributes) == .orderedSame else {
|
|
892 |
break
|
|
893 |
}
|
|
894 |
lastIndex = index
|
|
895 |
}
|
|
896 |
return Array(self[startingIndex...lastIndex])
|
|
897 |
}
|
|
898 |
|
|
899 |
}
|
|