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| 1 | +// |
| 2 | +// CEUndoManager.swift |
| 3 | +// CodeEditTextView |
| 4 | +// |
| 5 | +// Created by Khan Winter on 7/8/23. |
| 6 | +// |
| 7 | + |
| 8 | +import STTextView |
| 9 | +import AppKit |
| 10 | +import TextStory |
| 11 | + |
| 12 | +/// Maintains a history of edits applied to the editor and allows for undo/redo actions using those edits. |
| 13 | +/// |
| 14 | +/// This object also groups edits into sequences that make for a better undo/redo editing experience such as: |
| 15 | +/// - Breaking undo groups on newlines |
| 16 | +/// - Grouping pasted text |
| 17 | +/// |
| 18 | +/// If needed, the automatic undo grouping can be overridden using the `beginGrouping()` and `endGrouping()` methods. |
| 19 | +class CEUndoManager { |
| 20 | + /// An `UndoManager` subclass that forwards relevant actions to a `CEUndoManager`. |
| 21 | + /// Allows for objects like `STTextView` to use the `UndoManager` API |
| 22 | + /// while CETV manages the undo/redo actions. |
| 23 | + class DelegatedUndoManager: UndoManager { |
| 24 | + weak var parent: CEUndoManager? |
| 25 | + |
| 26 | + override var canUndo: Bool { parent?.canUndo ?? false } |
| 27 | + override var canRedo: Bool { parent?.canRedo ?? false } |
| 28 | + |
| 29 | + func registerMutation(_ mutation: TextMutation) { |
| 30 | + parent?.registerMutation(mutation) |
| 31 | + removeAllActions() |
| 32 | + } |
| 33 | + |
| 34 | + override func undo() { |
| 35 | + parent?.undo() |
| 36 | + } |
| 37 | + |
| 38 | + override func redo() { |
| 39 | + parent?.redo() |
| 40 | + } |
| 41 | + |
| 42 | + override func registerUndo(withTarget target: Any, selector: Selector, object anObject: Any?) { |
| 43 | + // no-op, but just in case to save resources: |
| 44 | + removeAllActions() |
| 45 | + } |
| 46 | + } |
| 47 | + |
| 48 | + /// Represents a group of mutations that should be treated as one mutation when undoing/redoing. |
| 49 | + private struct UndoGroup { |
| 50 | + struct Mutation { |
| 51 | + var mutation: TextMutation |
| 52 | + var inverse: TextMutation |
| 53 | + } |
| 54 | + |
| 55 | + var mutations: [Mutation] |
| 56 | + } |
| 57 | + |
| 58 | + public let manager: DelegatedUndoManager |
| 59 | + public var isUndoing: Bool = false |
| 60 | + public var isRedoing: Bool = false |
| 61 | + |
| 62 | + public var canUndo: Bool { |
| 63 | + !undoStack.isEmpty |
| 64 | + } |
| 65 | + public var canRedo: Bool { |
| 66 | + !redoStack.isEmpty |
| 67 | + } |
| 68 | + |
| 69 | + /// A stack of operations that can be undone. |
| 70 | + private var undoStack: [UndoGroup] = [] |
| 71 | + /// A stack of operations that can be redone. |
| 72 | + private var redoStack: [UndoGroup] = [] |
| 73 | + |
| 74 | + private unowned let textView: STTextView |
| 75 | + private(set) var isGrouping: Bool = false |
| 76 | + |
| 77 | + public init(textView: STTextView) { |
| 78 | + self.textView = textView |
| 79 | + self.manager = DelegatedUndoManager() |
| 80 | + manager.parent = self |
| 81 | + } |
| 82 | + |
| 83 | + /// Performs an undo operation if there is one available. |
| 84 | + public func undo() { |
| 85 | + guard let item = undoStack.popLast() else { |
| 86 | + return |
| 87 | + } |
| 88 | + isUndoing = true |
| 89 | + for mutation in item.mutations.reversed() { |
| 90 | + textView.applyMutationNoUndo(mutation.inverse) |
| 91 | + } |
| 92 | + redoStack.append(item) |
| 93 | + isUndoing = false |
| 94 | + } |
| 95 | + |
| 96 | + /// Performs a redo operation if there is one available. |
| 97 | + public func redo() { |
| 98 | + guard let item = redoStack.popLast() else { |
| 99 | + return |
| 100 | + } |
| 101 | + isRedoing = true |
| 102 | + for mutation in item.mutations { |
| 103 | + textView.applyMutationNoUndo(mutation.mutation) |
| 104 | + } |
| 105 | + undoStack.append(item) |
| 106 | + isRedoing = false |
| 107 | + } |
| 108 | + |
| 109 | + /// Clears the undo/redo stacks. |
| 110 | + public func clearStack() { |
| 111 | + undoStack.removeAll() |
| 112 | + redoStack.removeAll() |
| 113 | + } |
| 114 | + |
| 115 | + /// Registers a mutation into the undo stack. |
| 116 | + /// |
| 117 | + /// Calling this method while the manager is in an undo/redo operation will result in a no-op. |
| 118 | + /// - Parameter mutation: The mutation to register for undo/redo |
| 119 | + public func registerMutation(_ mutation: TextMutation) { |
| 120 | + if (mutation.range.length == 0 && mutation.string.isEmpty) || isUndoing || isRedoing { return } |
| 121 | + let newMutation = UndoGroup.Mutation(mutation: mutation, inverse: textView.inverseMutation(for: mutation)) |
| 122 | + if !undoStack.isEmpty, let lastMutation = undoStack.last?.mutations.last { |
| 123 | + if isGrouping || shouldContinueGroup(newMutation, lastMutation: lastMutation) { |
| 124 | + undoStack[undoStack.count - 1].mutations.append(newMutation) |
| 125 | + } else { |
| 126 | + undoStack.append(UndoGroup(mutations: [newMutation])) |
| 127 | + } |
| 128 | + } else { |
| 129 | + undoStack.append( |
| 130 | + UndoGroup(mutations: [newMutation]) |
| 131 | + ) |
| 132 | + } |
| 133 | + |
| 134 | + redoStack.removeAll() |
| 135 | + } |
| 136 | + |
| 137 | + /// Groups all incoming mutations. |
| 138 | + public func beginGrouping() { |
| 139 | + isGrouping = true |
| 140 | + } |
| 141 | + |
| 142 | + /// Stops grouping all incoming mutations. |
| 143 | + public func endGrouping() { |
| 144 | + isGrouping = false |
| 145 | + } |
| 146 | + |
| 147 | + /// Determines whether or not two mutations should be grouped. |
| 148 | + /// |
| 149 | + /// Will break group if: |
| 150 | + /// - Last mutation is delete and new is insert, and vice versa *(insert and delete)*. |
| 151 | + /// - Last mutation was not whitespace, new is whitespace *(insert)*. |
| 152 | + /// - New mutation is a newline *(insert and delete)*. |
| 153 | + /// - New mutation is not sequential with the last one *(insert and delete)*. |
| 154 | + /// |
| 155 | + /// - Parameters: |
| 156 | + /// - mutation: The current mutation. |
| 157 | + /// - lastMutation: The last mutation applied to the document. |
| 158 | + /// - Returns: Whether or not the given mutations can be grouped. |
| 159 | + private func shouldContinueGroup(_ mutation: UndoGroup.Mutation, lastMutation: UndoGroup.Mutation) -> Bool { |
| 160 | + // If last mutation was delete & new is insert or vice versa, split group |
| 161 | + if (mutation.mutation.range.length > 0 && lastMutation.mutation.range.length == 0) |
| 162 | + || (mutation.mutation.range.length == 0 && lastMutation.mutation.range.length > 0) { |
| 163 | + return false |
| 164 | + } |
| 165 | + |
| 166 | + if mutation.mutation.string.isEmpty { |
| 167 | + // Deleting |
| 168 | + return ( |
| 169 | + lastMutation.mutation.range.location == mutation.mutation.range.max |
| 170 | + && mutation.inverse.string != "\n" |
| 171 | + ) |
| 172 | + } else { |
| 173 | + // Inserting |
| 174 | + |
| 175 | + // Only attempt this check if the mutations are small enough. |
| 176 | + // If the last mutation was not whitespace, and the new one is, break the group. |
| 177 | + if lastMutation.mutation.string.count < 1024 |
| 178 | + && mutation.mutation.string.count < 1024 |
| 179 | + && !lastMutation.mutation.string.trimmingCharacters(in: .whitespaces).isEmpty |
| 180 | + && mutation.mutation.string.trimmingCharacters(in: .whitespaces).isEmpty { |
| 181 | + return false |
| 182 | + } |
| 183 | + |
| 184 | + return ( |
| 185 | + lastMutation.mutation.range.max + 1 == mutation.mutation.range.location |
| 186 | + && mutation.mutation.string != "\n" |
| 187 | + ) |
| 188 | + } |
| 189 | + } |
| 190 | +} |
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