Fixes navigation between word boundaries (#348)

Author: simonbs

Sources/Runestone/TextView/Core/TextInputStringTokenizer.swift

@@ -3,6 +3,10 @@ import UIKit
 final class TextInputStringTokenizer: UITextInputStringTokenizer {
     var lineManager: LineManager
     var stringView: StringView
+    // Used to ensure we can workaround bug where multi-stage input, like when entering Korean text
+    // does not work properly. If we do not treat navigation between word boundies as a special case then
+    // navigating with Shift + Option + Arrow Keys followed by Shift + Arrow Keys will not work correctly.
+    var didCallPositionFromPositionToWordBoundary = false
 
     private let lineControllerStorage: LineControllerStorage
     private var newlineCharacters: [Character] {
@@ -206,6 +210,7 @@ private extension TextInputStringTokenizer {
         guard let indexedPosition = position as? IndexedPosition else {
             return nil
         }
+        didCallPositionFromPositionToWordBoundary = true
         let location = indexedPosition.index
         let alphanumerics = CharacterSet.alphanumerics
         if direction.isForward {

Sources/Runestone/TextView/Core/TextInputView.swift

@@ -47,6 +47,16 @@ final class TextInputView: UIView, UITextInput {
                     shouldNotifyInputDelegate = true
                     didCallPositionFromPositionInDirectionWithOffset = false
                 }
+                // This is a consequence of our workaround that ensures multi-stage input, such as when entering Korean,
+                // works correctly. The workaround causes bugs when selecting words using Shift + Option + Arrow Keys
+                // followed by Shift + Arrow Keys if we do not treat it as a special case.
+                // The consequence of not having this workaround is that Shift + Arrow Keys may adjust the wrong end of
+                // the selected text when followed by navigating between word boundaries usign Shift + Option + Arrow Keys.
+                if customTokenizer.didCallPositionFromPositionToWordBoundary && !didCallDeleteBackward {
+                    shouldNotifyInputDelegate = true
+                    customTokenizer.didCallPositionFromPositionToWordBoundary = false
+                }
+                didCallDeleteBackward = false
                 notifyInputDelegateAboutSelectionChangeInLayoutSubviews = !shouldNotifyInputDelegate
                 if shouldNotifyInputDelegate {
                     inputDelegate?.selectionWillChange(self)
@@ -594,6 +604,7 @@ final class TextInputView: UIView, UITextInput {
     private var notifyInputDelegateAboutSelectionChangeInLayoutSubviews = false
     private var notifyDelegateAboutSelectionChangeInLayoutSubviews = false
     private var didCallPositionFromPositionInDirectionWithOffset = false
+    private var didCallDeleteBackward = false
     private var hasDeletedTextWithPendingLayoutSubviews = false
     private var preserveUndoStackWhenSettingString = false
     private var cancellables: [AnyCancellable] = []
@@ -1116,6 +1127,7 @@ extension TextInputView {
     }
 
     func deleteBackward() {
+        didCallDeleteBackward = true
         guard let selectedRange = markedRange ?? selectedRange, selectedRange.length > 0 else {
             return
         }