Merge pull request #10633 from keymanapp/fix/ios/backspace-context-sy…

…nc-lazy

fix(ios): long-held backspace handling

ios/engine/KMEI/KeymanEngine/Classes/Keyboard/InputViewController.swift

@@ -144,7 +144,7 @@ open class InputViewController: UIInputViewController, KeymanWebDelegate {
   var isSystemKeyboard: Bool {
     return _isSystemKeyboard;
   }
-  
+
   // Constraints dependent upon the device's current rotation state.
   // For now, should be mostly upon keymanWeb.view.heightAnchor.
   var portraitConstraint: NSLayoutConstraint?
@@ -170,14 +170,14 @@ open class InputViewController: UIInputViewController, KeymanWebDelegate {
   var expandedHeight: CGFloat {
     return keymanWeb.keyboardHeight + activeTopBarHeight
   }
-  
+
   public convenience init() {
     // iOS will call this constructor to initialize the system keyboard app extension.
     // It's safe and there will only ever be one active instance of this class within process scope.
     // See https://developer.apple.com/library/archive/documentation/General/Conceptual/ExtensibilityPG/ExtensionOverview.html
     self.init(forSystem: true)
   }
-  
+
   public convenience init(forSystem: Bool) {
     // In-app uses of the keyboard should call this constructor for simplicity, setting `forSystem`=`false`.
     self.init(nibName: nil, bundle: nil)
@@ -189,7 +189,7 @@ open class InputViewController: UIInputViewController, KeymanWebDelegate {
     _isSystemKeyboard = true
     keymanWeb = KeymanWebViewController(storage: Storage.active)
     super.init(nibName: nibNameOrNil, bundle: nibBundleOrNil)
-    
+
     addChild(keymanWeb)
   }
 
@@ -202,7 +202,7 @@ open class InputViewController: UIInputViewController, KeymanWebDelegate {
 
     super.updateViewConstraints()
   }
-  
+
   open override func loadView() {
     let baseView = CustomInputView(frame: CGRect.zero, innerVC: keymanWeb, inputViewStyle: .keyboard)
     baseView.backgroundColor = Colors.keyboardBackground
@@ -294,18 +294,61 @@ open class InputViewController: UIInputViewController, KeymanWebDelegate {
       self.swallowBackspaceTextChange = false
       return
     }
-    
+
     let contextBeforeInput = textDocumentProxy.documentContextBeforeInput ?? ""
     let selection = textDocumentProxy.selectedText ?? ""
     let contextAfterInput = textDocumentProxy.documentContextAfterInput ?? ""
     let context = "\(contextBeforeInput)\(selection)\(contextAfterInput)"
-    let bLength = contextBeforeInput.utf16.count
-    let sLength = selection.utf16.count
+    let bLength = contextBeforeInput.unicodeScalars.count
+    let sLength = selection.unicodeScalars.count
     setContextState(text: context, range: NSMakeRange(bLength, sLength))
     // Within the app, this is triggered after every keyboard input.
     // We should NOT call .resetContext() here for this reason.
   }
-
+
+  // Pre-condition:  no text is selected.  As this is currently only called by `insertText`
+  // below, this condition is met.
+  func sendContextUpdate() {
+    let preCaretContext = textDocumentProxy.documentContextBeforeInput ?? ""
+    let postCaretContext = textDocumentProxy.documentContextAfterInput ?? ""
+
+    let updater = { (_ before: String, _ after: String) -> Void in
+      let contextWindowText = "\(before)\(after)"
+
+      let range = NSRange(location: before.unicodeScalars.count, length: 0)
+
+      self.setContextState(text: contextWindowText, range: range)
+    }
+
+    updater(preCaretContext, postCaretContext)
+
+    if preCaretContext == "" {
+      /* The `textDocumentProxy` abstraction is documented (in passing) as involving
+       * inter-process communication.  It is thus asynchronous.  Despite all attempts to prod
+       * it, the context window is only ever updated if an attempt to make an actual *edit*
+       * outside of the context window occurs.  The first such edit will NOT have
+       * available synchronous data... but a bit of an async wait will usually succeed in
+       * getting the update.
+       *
+       * 33ms seemed sufficient.  Can we go lower? (~30 Hz rate)
+       * Success with 20ms. (50 Hz rate)
+       * 1ms is not sufficient, nor is 10ms.   :(
+       *
+       * Note:  these notes were taken via Simulator, not on a physical device;
+       * there's no guarantee (yet) that the times will be the same.
+       * But something refresh-rate related is a fairly reasonable assumption.
+       */
+      DispatchQueue.main.asyncAfter(deadline: .now() + 0.033) { // 33 msec; contrast: held backspace - every 100 msec.
+
+        // Does NOT update after half a second if there's no context manipulation.
+        let preCaretAsyncContext = self.textDocumentProxy.documentContextBeforeInput ?? ""
+        let postCaretAsyncContext = self.textDocumentProxy.documentContextAfterInput ?? ""
+
+        updater(preCaretAsyncContext, postCaretAsyncContext)
+      }
+    }
+  }
+
   func insertText(_ keymanWeb: KeymanWebViewController, numCharsToDelete: Int, newText: String) {
     if keymanWeb.isSubKeysMenuVisible {
       return
@@ -318,9 +361,9 @@ open class InputViewController: UIInputViewController, KeymanWebDelegate {
       isInputClickSoundEnabled = false
       perform(#selector(self.enableInputClickSound), with: nil, afterDelay: 0.1)
     }
-    
+
     var hasDeletedSelection = false
-    
+
     if let selected = textDocumentProxy.selectedText {
       if selected.count > 0 {
         textDocumentProxy.deleteBackward()
@@ -331,14 +374,16 @@ open class InputViewController: UIInputViewController, KeymanWebDelegate {
     if numCharsToDelete <= 0 || hasDeletedSelection {
       textDocumentProxy.insertText(newText)
 
+      sendContextUpdate()
       return
     }
 
     if numCharsToDelete > 0 && textDocumentProxy.documentContextBeforeInput == nil {
       textDocumentProxy.deleteBackward()
+      sendContextUpdate()
       return
     }
-    
+
     for _ in 0..<numCharsToDelete {
       let oldContext = textDocumentProxy.documentContextBeforeInput ?? ""
       textDocumentProxy.deleteBackward()
@@ -378,6 +423,8 @@ open class InputViewController: UIInputViewController, KeymanWebDelegate {
     if !newText.isEmpty {
       textDocumentProxy.insertText(newText)
     }
+
+    sendContextUpdate()
   }
 
   func menuKeyUp(_ keymanWeb: KeymanWebViewController) {
@@ -411,7 +458,7 @@ open class InputViewController: UIInputViewController, KeymanWebDelegate {
   func updateShowBannerSetting() {
     keymanWeb.updateShowBannerSetting()
   }
-  
+
   func updateSpacebarText() {
     keymanWeb.updateSpacebarText()
   }
@@ -452,7 +499,7 @@ open class InputViewController: UIInputViewController, KeymanWebDelegate {
     // If 'isSystemKeyboard' is true, always show the top bar.
     return isTopBarActive ? CGFloat(InputViewController.topBarHeight) : 0
   }
-  
+
   public var kmwHeight: CGFloat {
     return keymanWeb.keyboardHeight
   }
@@ -468,12 +515,12 @@ open class InputViewController: UIInputViewController, KeymanWebDelegate {
     self.updateViewConstraints()
     fixLayout()
   }
-  
+
   func fixLayout() {
     view.setNeedsLayout()
     view.layoutIfNeeded()
   }
-  
+
   open override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {
     super.viewWillTransition(to: size, with: coordinator)
 
@@ -507,7 +554,7 @@ open class InputViewController: UIInputViewController, KeymanWebDelegate {
       keymanWeb.shouldReload = false
     }
   }
-  
+
   func setKeyboard(_ kb: InstallableKeyboard) throws {
     try keymanWeb.setKeyboard(kb)
   }
@@ -519,19 +566,19 @@ open class InputViewController: UIInputViewController, KeymanWebDelegate {
   internal var shouldReload: Bool {
     return keymanWeb.shouldReload
   }
-    
+
   func registerLexicalModel(_ lm: InstallableLexicalModel) throws {
     try keymanWeb.registerLexicalModel(lm)
   }
-  
+
   func deregisterLexicalModel(_ lm: InstallableLexicalModel) {
     keymanWeb.deregisterLexicalModel(lm)
   }
-  
+
   func showHelpBubble() {
     keymanWeb.showHelpBubble()
   }
-  
+
   func showHelpBubble(afterDelay delay: TimeInterval) {
     keymanWeb.showHelpBubble(afterDelay: delay)
   }
@@ -543,53 +590,60 @@ open class InputViewController: UIInputViewController, KeymanWebDelegate {
     os_log("%{public}s", log: KeymanEngineLogger.ui, type: .info, message)
     SentryManager.breadcrumb(message)
   }
-  
+
   func resetContext() {
     keymanWeb.resetContext()
   }
 
   internal func setSentryState(enabled: Bool) {
     keymanWeb.setSentryState(enabled: enabled)
   }
-
+
+  /**
+   * Facilitates context synchronization with the KMW-app/webview side.
+   *
+   * The range's components should be SMP-aware, as the embedded engine
+   * will be expecting SMP-aware measurements.  Swift's `.unicodeScalars`
+   * property on `String`s lines up best with this.
+   */
   func setContextState(text: String?, range: NSRange) {
     // Check for any LTR or RTL marks at the context's start; if they exist, we should
     // offset the selection range.
     let characterOrderingChecks = [ "\u{200e}" /*LTR*/, "\u{202e}" /*RTL 1*/, "\u{200f}" /*RTL 2*/ ]
     var offsetPrefix = false;
-    
+
     let context = text ?? ""
-    
+
     for codepoint in characterOrderingChecks {
       if(context.hasPrefix(codepoint)) {
         offsetPrefix = true;
         break;
       }
     }
-    
+
     var selRange = range;
     if(offsetPrefix) { // If we have a character ordering mark, offset range location to hide it.
       selRange = NSRange(location: selRange.location - 1, length: selRange.length)
     }
-    
+
     keymanWeb.setText(context)
     if range.location != NSNotFound {
       keymanWeb.setCursorRange(selRange)
     }
   }
-  
+
   func resetKeyboardState() {
     keymanWeb.resetKeyboardState()
   }
 
   func endEditing(_ force: Bool) {
     keymanWeb.view.endEditing(force)
   }
-  
+
   func dismissKeyboardMenu() {
     keymanWeb.dismissKeyboardMenu()
   }
-  
+
   open func setBannerImage(to path: String) {
     keymanWeb.setBannerImage(to: path)
   }

web/src/app/webview/src/contextManager.ts

@@ -36,7 +36,11 @@ class ContextHost extends Mock {
   // changing the context's text.
   setText(text: string): void {
     this.text = text;
-    this.setSelection(this.text._kmwLength());
+    // Regardless of keyboard, we should check the SMP-aware length of the string.
+    // Our host app will not know whether or not the keyboard uses SMP chars,
+    // and we want a consistent interface for context synchronization between
+    // host app + app/webview KMW.
+    this.setSelection(this.text.kmwLength());
   }
 }