Improved management of multi-char keyboards

This is an alterantive to the proposal in
migueldeicaza#418 which was a follow
up to migueldeicaza#409

Rather than special casing the keyboards that way, this improves the
existing UITextInput handling and it improves the chinese, japanese
and vietnamese output - but still fails with Korean.

I could not figure out why iOS refuses to let me participate in the
composition of text, even if the system seems to do just fine on its
own (like native UITextFields).

In particular this problem as documented by Nicolas:

> Korean input: ㅇ followed by ㅜ produces 우 (as expected), but ㅇ ㅜ ㅇ produces 우ㅇ instead of 웅.

So for Korean, I add a dreaded special case.

Author: migueldeicaza

Sources/SwiftTerm/Apple/AppleTerminalView.swift

@@ -728,9 +728,6 @@ extension TerminalView {
                     let runFont = runAttributes[.font] as! TTFont
                     let startColumn = segment.column + (processedGlyphs * segment.columnWidth)
                     let endColumn = startColumn + (runGlyphsCount * segment.columnWidth)
-                    if row == 0 {
-                        print(run)
-                    }
                     var backgroundColor: TTColor?
                     if runAttributes.keys.contains(.selectionBackgroundColor) {
                         backgroundColor = runAttributes[.selectionBackgroundColor] as? TTColor
@@ -1105,7 +1102,6 @@ extension TerminalView {
         let oldPosition = terminal.buffer.yDisp
 
         let maxScrollback = terminal.buffer.lines.count - terminal.rows
-        print ("maxScrollBack: \(maxScrollback)")
         var newScrollPosition = Int (Double (maxScrollback) * toPosition)
 
         if newScrollPosition < 0 {
@@ -1114,8 +1110,7 @@ extension TerminalView {
         if newScrollPosition > maxScrollback {
             newScrollPosition = maxScrollback
         }
-        print ("newScrollpsitin: \(newScrollPosition)")
-        
+
         if newScrollPosition != oldPosition {
             scrollTo(row: newScrollPosition)
         }
@@ -1220,6 +1215,13 @@ extension TerminalView {
     public func send(data: ArraySlice<UInt8>)
     {
         ensureCaretIsVisible ()
+        #if os(iOS) || os(visionOS)
+        if TerminalView.textInputDebugEnabled {
+            let previewBytes = data.prefix(32).map { String(format: "%02X", $0) }.joined(separator: " ")
+            print("UITextInput[\(TerminalView.textInputLogCounter + 1)]: send bytes=\(data.count) [\(previewBytes)]")
+            TerminalView.textInputLogCounter += 1
+        }
+        #endif
         terminalDelegate?.send (source: self, data: data)
     }
 
@@ -1228,6 +1230,12 @@ extension TerminalView {
      * - Parameter txt: the string to send to the client
      */
     public func send (txt: String) {
+        #if os(iOS) || os(visionOS)
+        if TerminalView.textInputDebugEnabled {
+            print("UITextInput[\(TerminalView.textInputLogCounter + 1)]: send txt=\(txt.debugDescription)")
+            TerminalView.textInputLogCounter += 1
+        }
+        #endif
         let array = [UInt8] (txt.utf8)
         send (data: array[...])
     }

Sources/SwiftTerm/iOS/iOSTerminalView.swift

@@ -42,6 +42,9 @@ internal var log: Logger = Logger(subsystem: "org.tirania.SwiftTerm", category:
  * defaults, otherwise, this uses its own set of defaults colors.
  */
 open class TerminalView: UIScrollView, UITextInputTraits, UIKeyInput, UIScrollViewDelegate, TerminalDelegate {
+    public static var textInputDebugEnabled: Bool = false
+    internal static var textInputLogCounter: Int = 0
+
     struct FontSet {
         public let normal: UIFont
         let bold: UIFont
@@ -1084,14 +1087,20 @@ open class TerminalView: UIScrollView, UITextInputTraits, UIKeyInput, UIScrollVi
     }
 
     public var hasText: Bool {
-        return true
+        return !textInputStorage.isEmpty
     }
 
     /*
-        Soft keyboard input. Hardware keyboard input is handled in pressesBegan.
+        Soft keyboard input. Hardware keyboard text input is delivered here; special keys are handled in pressesBegan.
     */
     open func insertText(_ text: String) {
-        uitiLog("insertText(\"\(text)\") textInputStorage:\"\(textInputStorage)\"")
+        //uitiLog("insertText(\(text.debugDescription)) \(textInputStateDescription())")
+
+        if tryComposeKoreanFinal(text) {
+            return
+        }
+
+        beginTextInputEdit()
 
         let rangeToReplace = _markedTextRange ?? _selectedTextRange
         let rangeStartIndex = rangeToReplace.startPosition.offset
@@ -1100,6 +1109,8 @@ open class TerminalView: UIScrollView, UITextInputTraits, UIKeyInput, UIScrollVi
         let insertedPosition = TextPosition(offset: rangeStartIndex + text.count)
         _selectedTextRange = TextRange(from: insertedPosition, to: insertedPosition)
 
+        endTextInputEdit()
+
         if terminalAccessory?.controlModifier ?? false {
             self.send(applyControlToEventCharacters(text))
             terminalAccessory?.controlModifier = false
@@ -1115,14 +1126,77 @@ open class TerminalView: UIScrollView, UITextInputTraits, UIKeyInput, UIScrollVi
         queuePendingDisplay()
     }
 
+    // this is necessary because something in the iOS IME seems to prevent
+    // the sequence  "ㅇ", "ㅜ", "ㅇ" from becoming "웅", and instead
+    // it becomes "우" followed by "ㅇ"
+    private func tryComposeKoreanFinal(_ text: String) -> Bool {
+        guard let language = textInputMode?.primaryLanguage, language.hasPrefix("ko") else { return false }
+        guard _markedTextRange == nil else { return false }
+        guard _selectedTextRange.isEmpty, _selectedTextRange.endPosition.offset == textInputStorage.count else { return false }
+        guard text.count == 1, let jamo = text.first else { return false }
+        guard let finalIndex = koreanFinalIndex[jamo] else { return false }
+        guard let lastChar = textInputStorage.last else { return false }
+        guard let composed = composeHangulSyllable(base: lastChar, finalIndex: finalIndex) else { return false }
+
+        uitiLog("koreanComposeFinal base:\(lastChar) jamo:\(jamo) -> \(composed)")
+
+        beginTextInputEdit()
+        textInputStorage.removeLast()
+        textInputStorage.append(composed)
+        let newOffset = textInputStorage.count
+        _markedTextRange = nil
+        _selectedTextRange = TextRange(from: TextPosition(offset: newOffset), to: TextPosition(offset: newOffset))
+        endTextInputEdit()
+
+        send([backspaceSendsControlH ? 8 : 0x7f])
+        send(txt: String(composed))
+        queuePendingDisplay()
+        return true
+    }
+
+    private let koreanFinalIndex: [Character: Int] = [
+        "ㄱ": 1, "ㄲ": 2, "ㄳ": 3,
+        "ㄴ": 4, "ㄵ": 5, "ㄶ": 6,
+        "ㄷ": 7,
+        "ㄹ": 8, "ㄺ": 9, "ㄻ": 10, "ㄼ": 11, "ㄽ": 12, "ㄾ": 13, "ㄿ": 14, "ㅀ": 15,
+        "ㅁ": 16,
+        "ㅂ": 17, "ㅄ": 18,
+        "ㅅ": 19, "ㅆ": 20,
+        "ㅇ": 21,
+        "ㅈ": 22,
+        "ㅊ": 23,
+        "ㅋ": 24,
+        "ㅌ": 25,
+        "ㅍ": 26,
+        "ㅎ": 27
+    ]
+
+    private func composeHangulSyllable(base: Character, finalIndex: Int) -> Character? {
+        guard finalIndex > 0 && finalIndex < 28 else { return nil }
+        guard let scalar = base.unicodeScalars.first, base.unicodeScalars.count == 1 else { return nil }
+        let scalarValue = Int(scalar.value)
+        let sBase = 0xAC00
+        let sEnd = 0xD7A3
+        guard scalarValue >= sBase && scalarValue <= sEnd else { return nil }
+        let vCount = 21
+        let tCount = 28
+        let sIndex = scalarValue - sBase
+        let lIndex = sIndex / (vCount * tCount)
+        let vIndex = (sIndex % (vCount * tCount)) / tCount
+        let tIndex = sIndex % tCount
+        guard tIndex == 0 else { return nil }
+        let newScalarValue = sBase + (lIndex * vCount + vIndex) * tCount + finalIndex
+        guard let newScalar = UnicodeScalar(newScalarValue) else { return nil }
+        return Character(newScalar)
+    }
+
     func ensureCaretIsVisible ()
     {
         contentOffset = CGPoint (x: 0, y: CGFloat (terminal.buffer.lines.count-terminal.rows)*cellDimension.height)
     }
 
     public func deleteBackward() {
-        uitiLog("deleteBackward() textInputStorage:\"\(textInputStorage)\" markedTextRange:\"\(_markedTextRange)\" selectedTextRange:\"\(_selectedTextRange)\"")
-        inputDelegate?.selectionWillChange(self)
+        uitiLog("deleteBackward() \(textInputStateDescription())")
 
         // after backward deletion, marked range is always cleared, and length of selected range is always zero
         let rangeToDelete = _markedTextRange ?? _selectedTextRange
@@ -1140,12 +1214,15 @@ open class TerminalView: UIScrollView, UITextInputTraits, UIKeyInput, UIScrollVi
                 return
             }
 
+            beginTextInputEdit()
+
             rangeStartIndex -= 1
             textInputStorage.remove(at: textInputStorage.index(textInputStorage.startIndex, offsetBy: rangeStartIndex))
             rangeStartPosition = TextPosition(offset: rangeStartIndex)
 
             self.send ([backspaceSendsControlH ? 8 : 0x7f])
         } else {
+            beginTextInputEdit()
             // Send as many backspaces that are in the range to delete. When on auto-repeat, after a some time
             // pressing the backspace, it will delete chunks of text at a time.
             let oldText = textInputStorage[rangeToDelete.fullRange(in: textInputStorage)]
@@ -1160,7 +1237,7 @@ open class TerminalView: UIScrollView, UITextInputTraits, UIKeyInput, UIScrollVi
         _markedTextRange = nil
         _selectedTextRange = TextRange(from: rangeStartPosition, to: rangeStartPosition)
 
-        inputDelegate?.selectionDidChange(self)
+        endTextInputEdit()
     }
 
     enum SendData {
@@ -1211,9 +1288,15 @@ open class TerminalView: UIScrollView, UITextInputTraits, UIKeyInput, UIScrollVi
 
     public override func pressesBegan(_ presses: Set<UIPress>, with event: UIPressesEvent?) {
         var didHandleEvent = false
+
+        if _markedTextRange != nil {
+            super.pressesBegan(presses, with: event)
+            return
+        }
 
         for press in presses {
             guard let key = press.key else { continue }
+            uitiLog("pressesBegan keyCode:\(key.keyCode) chars:\(key.characters.debugDescription) ignoring:\(key.charactersIgnoringModifiers.debugDescription) modifiers:\(key.modifierFlags)")
 
             var data: SendData? = nil
 
@@ -1281,19 +1364,13 @@ open class TerminalView: UIScrollView, UITextInputTraits, UIKeyInput, UIScrollVi
             case .keyboardDeleteForward:
                 data = .bytes (EscapeSequences.cmdDelKey)
 
-            case .keyboardDeleteOrBackspace:
-                data = .bytes ([backspaceSendsControlH ? 8 : 0x7f])
-                
             case .keyboardEscape:
                 data = .bytes ([0x1b])
 
             case .keyboardInsert:
                 print (".keyboardInsert ignored")
                 break
 
-            case .keyboardReturn:
-                data = .bytes (returnByteSequence)
-                
             case .keyboardTab:
                 data = .bytes ([9])
 
@@ -1331,16 +1408,6 @@ open class TerminalView: UIScrollView, UITextInputTraits, UIKeyInput, UIScrollVi
                     optionAsMetaKey.toggle()
                 } else if key.modifierFlags.contains (.alternate) && optionAsMetaKey {
                     data = .text("\u{1b}\(key.charactersIgnoringModifiers)")
-                } else if !key.modifierFlags.contains (.command){
-                    if let keyboardLanguage = self.textInputMode?.primaryLanguage {
-                        // Is the keyboard language one of the multi-input languages? Chinese, Japanese, Korean and Hindi-Transliteration
-                        // If so, do not process the input yet (we'll do it later in unmarkText())
-                        if (!keyboardLanguage.hasPrefix("hi") && !keyboardLanguage.hasPrefix("zh") && !keyboardLanguage.hasPrefix("ja") && !keyboardLanguage.hasPrefix("ko")) {
-                            if key.characters.count > 0 {
-                                data = .text (key.characters)
-                            }
-                        }
-                    }
                 }
             }
             if let sendableData = data {