Merge pull request #5 from theMomax/main

Add support for observing and modifying the selected text range.

Author: helje5

README.md

@@ -150,6 +150,32 @@ WindowGroup {
 To persist the size, the `fontSize` binding is available.
 
 
+ ### Selection and Scrolling
+ 
+ The selected text can be observed and modified via another `Binding`:
+ 
+ ```swift
+  struct ContentView: View {
+     static private let initialSource = "let a = 42\n"
+
+     @State private var source = Self.initialSource
+     @State private var selection = Self.initialSource.endIndex..<Self.initialSource.endIndex
+
+     var body: some View {
+         CodeEditor(source: $source,
+                    selection: $selection,
+                    language: .swift,
+                    theme: .ocean,
+                    autoscroll: false)
+         Button("Select All") {
+             selection = source.startIndex..<source.endIndex
+         }
+     }
+ }
+ ```
+ When `autoscroll` is `true`, the editor automatically scrolls to the respective
+ cursor position when `selection` is modfied from the outside, i.e. programatically.
+
 ### Highlightr and Shaper
 
 Based on the excellent [Highlightr](https://github.com/raspu/Highlightr).

Sources/CodeEditor/CodeEditor.swift

@@ -106,6 +106,31 @@ import Highlightr
  *
  * To persist the binding, the `fontSize` binding is available.
  *
+ * ### Selection and Scrolling
+ *
+ * The selected text can be observed and modified via another `Binding`:
+ *
+ *     struct ContentView: View {
+ *         static private let initialSource = "let a = 42\n"
+ *
+ *         @State private var source = Self.initialSource
+ *         @State private var selection = Self.initialSource.endIndex..<Self.initialSource.endIndex
+ *
+ *         var body: some View {
+ *             CodeEditor(source: $source,
+ *                        selection: $selection,
+ *                        language: .swift,
+ *                        theme: .ocean,
+ *                        autoscroll: false)
+ *             Button("Select All") {
+ *                 selection = source.startIndex..<source.endIndex
+ *             }
+ *         }
+ *     }
+ *
+ * When `autoscroll` is `true`, the editor automatically scrolls to the respective
+ * cursor position when `selection` is modfied from the outside, i.e. programatically.
+ *
  * ### Highlightr and Shaper
  *
  * Based on the excellent [Highlightr](https://github.com/raspu/Highlightr).
@@ -182,6 +207,7 @@ public struct CodeEditor: View {
    * - Parameters:
    *   - source:      A binding to a String that holds the source code to be
    *                  edited (or displayed).
+   *   - selection:   A binding to the selected range of the `source`.
    *   - language:    Optionally set a language (e.g. `.swift`), otherwise
    *                  Highlight.js will attempt to detect the language.
    *   - theme:       The name of the theme to use, defaults to "pojoaque".
@@ -200,17 +226,22 @@ public struct CodeEditor: View {
    *                  language is used.
    *   - inset:       The editor can be inset in the scroll view. Defaults to
    *                  8/8.
+   *   - autoscroll:  If enabled, the editor automatically scrolls to the respective
+   *                  region when the `selection` is changed programatically.
    */
   public init(source      : Binding<String>,
+              selection   : Binding<Range<String.Index>>? = nil,
               language    : Language?            = nil,
               theme       : ThemeName            = .default,
               fontSize    : Binding<CGFloat>?    = nil,
               flags       : Flags                = .defaultEditorFlags,
               indentStyle : IndentStyle          = .system,
               autoPairs   : [ String : String ]? = nil,
-              inset       : CGSize?              = nil)
+              inset       : CGSize?              = nil,
+              autoscroll  : Bool                 = true)
   {
     self.source      = source
+    self.selection   = selection
     self.fontSize    = fontSize
     self.language    = language
     self.themeName   = theme
@@ -220,6 +251,7 @@ public struct CodeEditor: View {
     self.autoPairs   = autoPairs
                     ?? language.flatMap({ CodeEditor.defaultAutoPairs[$0] })
                     ?? [:]
+    self.autoscroll = autoscroll
   }
 
   /**
@@ -268,23 +300,27 @@ public struct CodeEditor: View {
   }
 
   private var source      : Binding<String>
+  private var selection   : Binding<Range<String.Index>>?
   private var fontSize    : Binding<CGFloat>?
   private let language    : Language?
   private let themeName   : ThemeName
   private let flags       : Flags
   private let indentStyle : IndentStyle
   private let autoPairs   : [ String : String ]
   private let inset       : CGSize
+  private let autoscroll  : Bool
 
   public var body: some View {
     UXCodeTextViewRepresentable(source      : source,
+                                selection   : selection,
                                 language    : language,
                                 theme       : themeName,
                                 fontSize    : fontSize,
                                 flags       : flags,
                                 indentStyle : indentStyle,
                                 autoPairs   : autoPairs,
-                                inset       : inset)
+                                inset       : inset,
+                                autoscroll  : autoscroll)
   }
 }
 

Sources/CodeEditor/UXCodeTextView.swift

@@ -264,7 +264,7 @@ protocol UXCodeTextViewDelegate: UXTextViewDelegate {
 
 extension UXTextView {
 
-  fileprivate var swiftSelectedRange : Range<String.Index> {
+  var swiftSelectedRange : Range<String.Index> {
     let s = self.string
     guard !s.isEmpty else { return s.startIndex..<s.startIndex }
     #if os(macOS)

Sources/CodeEditor/UXCodeTextViewRepresentable.swift

@@ -41,35 +41,50 @@ struct UXCodeTextViewRepresentable : UXViewRepresentable {
    *                  the opening character. For example: `[ "<": ">" ]` would
    *                  automatically insert the closing ">" if the user enters
    *                  "<".
+   *   - autoscroll:  If enabled, the editor automatically scrolls to the respective
+   *                  region when the `selection` is changed programatically.
    */
   public init(source      : Binding<String>,
+              selection   : Binding<Range<String.Index>>?,
               language    : CodeEditor.Language?,
               theme       : CodeEditor.ThemeName,
               fontSize    : Binding<CGFloat>?,
               flags       : CodeEditor.Flags,
               indentStyle : CodeEditor.IndentStyle,
               autoPairs   : [ String : String ],
-              inset       : CGSize)
+              inset       : CGSize,
+              autoscroll  : Bool)
   {
     self.source      = source
+    self.selection = selection
     self.fontSize    = fontSize
     self.language    = language
     self.themeName   = theme
     self.flags       = flags
     self.indentStyle = indentStyle
     self.autoPairs   = autoPairs
     self.inset       = inset
+    self.autoscroll = autoscroll
   }
 
   private var source      : Binding<String>
+  private var selection   : Binding<Range<String.Index>>?
   private var fontSize    : Binding<CGFloat>?
   private let language    : CodeEditor.Language?
   private let themeName   : CodeEditor.ThemeName
   private let flags       : CodeEditor.Flags
   private let indentStyle : CodeEditor.IndentStyle
   private let inset       : CGSize
   private let autoPairs   : [ String : String ]
-  
+  private let autoscroll  : Bool
+
+  // The inner `value` is true, exactly when execution is inside
+  // the `updateTextView(_:)` method. The `Coordinator` can use this
+  // value to guard against update cycles.
+  // This needs to be a `State`, as the `UXCodeTextViewRepresentable`
+  // might be destructed and recreated in between calls to `makeCoordinator()`
+  // and `updateTextView(_:)`.
+  @State private var isCurrentlyUpdatingView = ReferenceTypeBool(value: false)
 
   // MARK: - TextView Delegate  Coordinator
 
@@ -92,15 +107,66 @@ struct UXCodeTextViewRepresentable : UXViewRepresentable {
           assertionFailure("unexpected notification object")
           return
         }
-        parent.source.wrappedValue = textView.string
+        textViewDidChange(textView: textView)
       }    
     #elseif os(iOS)
       public func textViewDidChange(_ textView: UITextView) {
-        parent.source.wrappedValue = textView.string
+        textViewDidChange(textView: textView)
+      }
+    #else
+      #error("Unsupported OS")
+    #endif
+      
+    private func textViewDidChange(textView: UXTextView) {
+      // This function may be called as a consequence of updating the text string
+      //  in UXCodeTextViewRepresentable/updateTextView(_:)`.
+      // Since this function might update the `parent.source` `Binding`, which in
+      // turn might update a `State`, this would lead to undefined behavior.
+      // (Changing a `State` during a `View` update is not permitted).
+      guard !parent.isCurrentlyUpdatingView.value else {
+        return
+      }
+      
+      parent.source.wrappedValue = textView.string
+    }
+      
+    #if os(macOS)
+      public func textViewDidChangeSelection(_ notification: Notification) {
+        guard let textView = notification.object as? UXTextView else {
+          assertionFailure("unexpected notification object")
+          return
+        }
+        
+        textViewDidChangeSelection(textView: textView as! UXCodeTextView)
+      }
+    #elseif os(iOS)
+      public func textViewDidChangeSelection(_ textView: UITextView) {
+        textViewDidChangeSelection(textView: textView as! UXCodeTextView)
       }
     #else
       #error("Unsupported OS")
     #endif
+      
+    private func textViewDidChangeSelection(textView: UXCodeTextView) {
+      // This function may be called as a consequence of updating the selected
+      // range in UXCodeTextViewRepresentable/updateTextView(_:)`.
+      // Since this function might update the `parent.selection` `Binding`, which in
+      // turn might update a `State`, this would lead to undefined behavior.
+      // (Changing a `State` during a `View` update is not permitted).
+      guard !parent.isCurrentlyUpdatingView.value else {
+        return
+      }
+      
+      guard let selection = parent.selection else {
+        return
+      }
+
+      let range = textView.swiftSelectedRange
+      
+      if selection.wrappedValue != range {
+        selection.wrappedValue = range
+      }
+    }
 
     var allowCopy: Bool {
       return parent.flags.contains(.selectable)
@@ -113,6 +179,11 @@ struct UXCodeTextViewRepresentable : UXViewRepresentable {
   }
 
   private func updateTextView(_ textView: UXCodeTextView) {
+    isCurrentlyUpdatingView.value = true
+    defer {
+      isCurrentlyUpdatingView.value = false
+    }
+      
     if let binding = fontSize {
       textView.applyNewTheme(themeName, andFontSize: binding.wrappedValue)
     }
@@ -136,6 +207,25 @@ struct UXCodeTextViewRepresentable : UXViewRepresentable {
       }
     }
 
+    if let selection = selection {
+      let range = selection.wrappedValue
+      
+      if range != textView.swiftSelectedRange {
+        let nsrange = NSRange(range, in: textView.string)
+        #if os(macOS)
+          textView.setSelectedRange(nsrange)
+        #elseif os(iOS)
+          textView.selectedRange = nsrange
+        #else
+          #error("Unsupported OS")
+        #endif
+        
+        if autoscroll {
+          textView.scrollRangeToVisible(nsrange)
+        }
+      }
+    }
+    
     textView.isEditable   = flags.contains(.editable)
     textView.isSelectable = flags.contains(.selectable)
   }
@@ -197,28 +287,44 @@ struct UXCodeTextViewRepresentable : UXViewRepresentable {
   #endif // iOS
 }
 
+extension UXCodeTextViewRepresentable {
+  // A wrapper around a `Bool` that enables updating
+  // the wrapped value during `View` renders.
+  private class ReferenceTypeBool {
+    var value: Bool
+      
+    init(value: Bool) {
+      self.value = value
+    }
+  }
+}
+
 struct UXCodeTextViewRepresentable_Previews: PreviewProvider {
 
   static var previews: some View {
 
     UXCodeTextViewRepresentable(source      : .constant("let a = 5"),
+                                selection   : nil,
                                 language    : nil,
                                 theme       : .pojoaque,
                                 fontSize    : nil,
                                 flags       : [ .selectable ],
                                 indentStyle : .system,
                                 autoPairs   : [:],
-                                inset       : .init(width: 8, height: 8))
+                                inset       : .init(width: 8, height: 8),
+                                autoscroll  : false)
       .frame(width: 200, height: 100)
 
     UXCodeTextViewRepresentable(source: .constant("let a = 5"),
+                                selection   : nil,
                                 language    : .swift,
                                 theme       : .pojoaque,
                                 fontSize    : nil,
                                 flags       : [ .selectable ],
                                 indentStyle : .system,
                                 autoPairs   : [:],
-                                inset       : .init(width: 8, height: 8))
+                                inset       : .init(width: 8, height: 8),
+                                autoscroll  : false)
       .frame(width: 200, height: 100)
 
     UXCodeTextViewRepresentable(
@@ -228,13 +334,15 @@ struct UXCodeTextViewRepresentable_Previews: PreviewProvider {
         \bye
         """#
       ),
+      selection   : nil,
       language    : .tex,
       theme       : .pojoaque,
       fontSize    : nil,
       flags       : [ .selectable ],
       indentStyle : .system,
       autoPairs   : [:],
-      inset       : .init(width: 8, height: 8)
+      inset       : .init(width: 8, height: 8),
+      autoscroll  : false
     )
     .frame(width: 540, height: 200)
   }