Allow tone key to revise prior reading (#753)

McBopomofoTests/KeyHandlerBopomofoTests.swift

@@ -2706,3 +2706,51 @@ extension KeyHandlerBopomofoTests {
         }
     }
 }
+
+extension KeyHandlerBopomofoTests {
+
+    func checkChangingReadingUsingToneKey(input: String, expected: String) {
+        let associatedPhrasesEnabled = Preferences.associatedPhrasesEnabled
+        let allowChangingPriorTone = Preferences.allowChangingPriorTone
+        Preferences.associatedPhrasesEnabled = false
+        Preferences.allowChangingPriorTone = true
+
+        defer {
+            Preferences.associatedPhrasesEnabled = associatedPhrasesEnabled
+            Preferences.allowChangingPriorTone = allowChangingPriorTone
+        }
+
+        var state: InputState = InputState.Empty()
+        let keys = Array(input).map {
+            String($0)
+        }
+        for key in keys {
+            let input = KeyHandlerInput(
+                inputText: key, keyCode: 0, charCode: charCode(key), flags: [],
+                isVerticalMode: false)
+            handler.handle(input: input, state: state) { newState in
+                state = newState
+            } errorCallback: {
+            }
+        }
+        XCTAssertTrue(state is InputState.Inputting, "\(state)")
+        if let state = state as? InputState.Inputting {
+            XCTAssertEqual(state.composingBuffer, expected)
+        }
+    }
+
+    // Input 小麥 then change to tone 3
+    func testChangingReadingUsingToneKey1() {
+        checkChangingReadingUsingToneKey(input: "vul3a943", expected: "小買")
+    }
+
+    // Input 小麥 then change to tone 4
+    func testChangingReadingUsingToneKey2() {
+        checkChangingReadingUsingToneKey(input: "vul3a946", expected: "小埋")
+    }
+
+    // Input 小麥 then change to tone 5
+    func testChangingReadingUsingToneKey3() {
+        checkChangingReadingUsingToneKey(input: "vul3a947", expected: "小麥˙")
+    }
+}

Source/Engine/Mandarin/Mandarin.h

@@ -482,3 +482,4 @@ class BopomofoReadingBuffer {
 }  // namespace Formosa
 
 #endif  // SRC_ENGINE_MANDARIN_MANDARIN_H_
+

Source/KeyHandler.mm

@@ -450,7 +450,8 @@ - (BOOL)handleInput:(KeyHandlerInput *)input state:(InputState *)inState stateCa
     // MARK: Handle BPMF Keys
 
     // see if it's valid BPMF reading
-    if (!skipBpmfHandling && _bpmfReadingBuffer->isValidKey((char)charCode)) {
+    bool isValidKey = _bpmfReadingBuffer->isValidKey((char)charCode);
+    if (!skipBpmfHandling && isValidKey) {
         _bpmfReadingBuffer->combineKey((char)charCode);
         keyConsumedByReading = YES;
 
@@ -463,7 +464,38 @@ - (BOOL)handleInput:(KeyHandlerInput *)input state:(InputState *)inState stateCa
         }
     }
 
-    BOOL composeReading = _bpmfReadingBuffer->isValidKey((char)charCode) && _bpmfReadingBuffer->hasToneMarker() && !_bpmfReadingBuffer->hasToneMarkerOnly();
+    // Issue 753
+    //
+    // This allows users to use tone key to change an existing reading before
+    // the current cursor.
+    if (_bpmfReadingBuffer->hasToneMarkerOnly() &&
+        _grid->readings().size() > 0 &&
+        _grid->cursor() > 0 &&
+        Preferences.allowChangingPriorTone) {
+        size_t cursor = _grid->cursor() - 1;
+        const std::string& reading = _grid->readings()[cursor];
+        if (!reading.empty() && reading[0] != '_') {
+            Formosa::Mandarin::BopomofoReadingBuffer tmpBuffer(_bpmfReadingBuffer->keyboardLayout());
+            Formosa::Mandarin::BopomofoSyllable syllable = Formosa::Mandarin::BopomofoSyllable::FromComposedString(reading);
+            std::string keys = _bpmfReadingBuffer->keyboardLayout()->keySequenceFromSyllable(syllable);
+            for (char k:keys) {
+                tmpBuffer.combineKey(k);
+            }
+            tmpBuffer.combineKey((char)charCode);
+            std::string newReading = tmpBuffer.syllable().composedString();
+            if (_languageModel->hasUnigrams(newReading)) {
+                _bpmfReadingBuffer->clear();
+                _grid->deleteReadingBeforeCursor();
+                _grid->insertReading(newReading);
+                [self _walk];
+                InputStateInputting *inputting = (InputStateInputting *)[self buildInputtingState];
+                stateCallback(inputting);
+                return YES;
+            }
+        }
+    }
+
+    BOOL composeReading = isValidKey && _bpmfReadingBuffer->hasToneMarker() && !_bpmfReadingBuffer->hasToneMarkerOnly();
 
     // see if we have composition if Enter/Space is hit and buffer is not empty
     // this is bit-OR'ed so that the tone marker key is also taken into account

Source/Preferences.swift

@@ -74,6 +74,7 @@ private let kBig5InputEnabledKey = "Big5InputEnabled"
 let kBeepUponInputErrorKey = "BeepUponInputError"
 
 private let kEnableUserPhrasesInPlainBopomofo = "EnableUserPhrasesInPlainBopomofo"
+private let kAllowChangingPriorTone = "AllowChangingPriorTone"
 
 // MARK: Property wrappers
 
@@ -570,6 +571,11 @@ extension Preferences {
     @objc static var enableUserPhrasesInPlainBopomofo: Bool
 }
 
+extension Preferences {
+    @UserDefault(key: kAllowChangingPriorTone, defaultValue: false)
+    @objc static var allowChangingPriorTone: Bool
+}
+
 extension Preferences {
     static func createReport() -> String {
         var lines: [String] = []