Merge pull request #16634 from keymanapp/fix/mac/erratic-backspace

fix(mac): apply backspace to correct location 🍎

mac/Cartfile.resolved

@@ -1 +1 @@
-github "erikdoe/ocmock" "v3.9.1"
+github "erikdoe/ocmock" "v3.9.4"

mac/Keyman4MacIM/Keyman4MacIM.xcodeproj/project.pbxproj

@@ -731,7 +731,7 @@
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 			shellPath = /bin/sh;
-			shellScript = "# check that our PRODUCT_VERSION matches this git branch's KEYMAN_VERSION from ../../VERSION.md\n(cd .. ; ./is_same_version.sh Keyman4MacIM || exit 1 ; cd -)\n";
+			shellScript = "# check that our PRODUCT_VERSION matches this git branch's KEYMAN_VERSION from ../../VERSION.md\n# TODO: use xcode-wrap.sh (follow-up in #16712)\nexport PATH=\"/opt/homebrew/bin:/usr/local/bin:$PATH\"\necho \"BASH version inside Xcode is: $BASH_VERSION\"\n(cd .. ; ./is_same_version.sh Keyman4MacIM || exit 1 ; cd -)\n";
 			showEnvVarsInLog = 0;
 		};
 		D2FF67BB6C749BA6861F5E25 /* [CP] Check Pods Manifest.lock */ = {

mac/Keyman4MacIM/Keyman4MacIM/KMInputMethodAppDelegate.m

@@ -334,7 +334,7 @@ CGEventRef eventTapFunction(CGEventTapProxy proxy, CGEventType type, CGEventRef
     NSEvent* sysEvent = [NSEvent eventWithCGEvent:event];
     // Too many of these to be useful for most debugging sessions, but we'll keep this around to be
     // un-commented when needed.
-    os_log_debug([KMLogs keyTraceLog], "System Event: %{public}@", sysEvent);
+//    os_log_debug([KMLogs keyTraceLog], "System Event: %{public}@", sysEvent);
     
     switch (type) {
       case kCGEventFlagsChanged:

mac/Keyman4MacIM/Keyman4MacIM/KMInputMethodEventHandler.h

@@ -12,6 +12,14 @@
 #import <Foundation/Foundation.h>
 #import "KMInputMethodAppDelegate.h"
 
+// used to perform delete by inserting with replacement
+typedef struct {
+  BOOL canDeleteWithReplacement;
+  NSUInteger replacementLocation;
+  NSUInteger replacementLength;
+  NSString *replacementString;
+} ReplacementInfo;
+
 @interface KMInputMethodEventHandler : NSObject
 
 - (instancetype)initWithClient:(NSString *)clientAppId client:(id)sender;

mac/Keyman4MacIM/Keyman4MacIM/KMInputMethodEventHandler.m

@@ -37,7 +37,9 @@ CGKeyCode _keyCodeOfOriginalEvent;
 CGEventSourceRef _sourceFromOriginalEvent = nil;
 CGEventSourceRef _sourceForGeneratedEvent = nil;
 
-// This is the public initializer.
+/**
+ *  The public initializer
+ */
 - (instancetype)initWithClient:(NSString *)clientAppId client:(id) sender {
   self = [super init];
   if(self) {
@@ -109,7 +111,7 @@ CGEventSourceRef _sourceForGeneratedEvent = nil;
   }
 
   output = [self processEventWithKeymanEngine:event in:sender];
-  os_log_debug([KMLogs keyTraceLog], "keyman engine output: %{public}@", output);
+  os_log_debug([KMLogs keyTraceLog], "🅰️ keyman engine output: %{public}@", output);
 
   if (output == nil) {
     return NO;
@@ -331,52 +333,69 @@ CGEventSourceRef _sourceForGeneratedEvent = nil;
   // if we can read the text, then get the context and send it to Core
   // we do this whether the context has changed or not
   if (self.apiCompliance.canReadText) {
-    contextString = [self readContext:event forClient:client];
-    os_log_debug([KMLogs keyTraceLog], "reportContext, setting new context for compliant app (if needed)");
+    contextString = [self readContext:client outSelection:NULL];
     [self.kme setCoreContextIfNeeded:contextString];
-  } else if (self.contextChanged) {
+
+    // the context is now current, reset the flag
+    self.contextChanged = NO;
+    return;
+  }
+  
+  if (self.contextChanged) {
     // we cannot read the text but know the context has changed, so we must clear it
     os_log_debug([KMLogs keyTraceLog], "reportContext, clearing context for non-compliant app");
     [self.kme clearCoreContext];
+    
+    // the context is now current, reset the flag
+    self.contextChanged = NO;
   }
-  
-  // the context is now current, reset the flag
-  self.contextChanged = NO;
 }
 
--(NSString*)readContext:(NSEvent *)event forClient:(id) client {
+/**
+ * Returns the current context string up to kMaxContext characters
+ * Also returns the results of `[client selectedRange]` in the`selection` pointer
+ */
+
+-(NSString*)readContext:(id) client outSelection:(NSRangePointer) outSelection {
   NSString *contextString = @"";
   NSAttributedString *attributedString = nil;
+  NSRange selectionRange = {0};
   
+  if (!self.apiCompliance.canReadText) {
+    os_log_debug([KMLogs keyTraceLog], "InputMethodEventHandler readContext, unable to read context: non-compliant app");
+    return contextString;
+  }
+
   // if we can read the text, then get the context for up to kMaxContext characters
-  if (self.apiCompliance.canReadText) {
-    NSRange selectionRange = [client selectedRange];
-    os_log_debug([KMLogs eventsLog], "InputMethodEventHandler readContext, canReadText: true selectionRange %{public}@: ", NSStringFromRange(selectionRange));
-    
-    NSUInteger contextLength = MIN(kMaxContext, selectionRange.location);
-    NSUInteger contextStart = selectionRange.location - contextLength;
-    
-    if (contextLength > 0) {
-      NSRange contextRange = NSMakeRange(contextStart, contextLength);
-      os_log_debug([KMLogs eventsLog], " contextRange %{public}@: client: %p", NSStringFromRange(contextRange), client);
-      attributedString = [client attributedSubstringFromRange:contextRange];
+  selectionRange = [client selectedRange];
+  os_log_debug([KMLogs keyTraceLog], "InputMethodEventHandler readContext, selectionRange %{public}@: ", NSStringFromRange(selectionRange));
       
-      // adjust string in case that we receive half of a surrogate pair at context start
-      // the API appears to always return a full code point, but this could vary by app
-      if (attributedString.length > 0) {
-        if (CFStringIsSurrogateLowCharacter([attributedString.string characterAtIndex:0])) {
-          os_log_debug([KMLogs eventsLog], " first char is low surrogate, reducing context by one character");
-          contextString = [attributedString.string substringFromIndex:1];
-        } else {
-          contextString = attributedString.string;
-          
-          //only uncomment for testing as we do not want to write context in logs
-          //os_log_debug([KMLogs keyTraceLog], " length: %lu result: %{public}@", contextString.length, contextString);
-        }
+  NSUInteger contextLength = MIN(kMaxContext, selectionRange.location);
+  NSUInteger contextStart = selectionRange.location - contextLength;
+  
+  if (contextLength > 0) {
+    NSRange contextRange = NSMakeRange(contextStart, contextLength);
+    attributedString = [client attributedSubstringFromRange:contextRange];
+    
+    // adjust string in case that we receive half of a surrogate pair at context start
+    // the API appears to always return a full code point, but this could vary by app
+    if (attributedString.length > 0) {
+      if (CFStringIsSurrogateLowCharacter([attributedString.string characterAtIndex:0])) {
+        os_log_debug([KMLogs keyTraceLog], " first char is low surrogate, reducing context by one character");
+        contextString = [attributedString.string substringFromIndex:1];
+      } else {
+        contextString = attributedString.string;
+        
+        //only uncomment for testing as we do not want to write context in logs
+        //os_log_debug([KMLogs keyTraceLog], " length: %lu result: %{public}@", contextString.length, contextString);
       }
     }
   }
   
+  // return the range of the current selection
+  if (outSelection != NULL) {
+    *outSelection = selectionRange;
+  }
   return contextString;
 }
 
@@ -508,6 +527,7 @@ CGEventSourceRef _sourceForGeneratedEvent = nil;
  * 3. generate event: generate keydown backspace events as necessary
  */
 -(BOOL)handleDeleteOnlyScenario:(CoreKeyOutput*)output keyDownEvent:(nonnull NSEvent *)event client:(id) client {
+  os_log_debug([KMLogs keyTraceLog], "🔙 handleDeleteOnlyScenario");
   
   // attempt to delete by replacing -- for compliant apps only
   if ([self handleDeleteWithReplacement:output keyDownEvent:event client:client]) {
@@ -566,35 +586,51 @@ CGEventSourceRef _sourceForGeneratedEvent = nil;
  * Ref: https://developer.apple.com/documentation/appkit/nstextinputclient/inserttext(_:replacementrange:)
  */
 -(BOOL)handleDeleteWithReplacement:(CoreKeyOutput*)output keyDownEvent:(nonnull NSEvent *)event client:(id) client {
-  BOOL handledEvent = NO;
-  NSString *context = [self readContext:event forClient:client];
-  
-  // guard: only for compliant apps with sufficient context
-  if (!(self.apiCompliance.canReplaceText) || ([context length] <= output.textToDelete.length)) {
-    os_log_debug([KMLogs keyTraceLog], "cannot replace text, non-compliant or insufficient context");
+  // guard: only for compliant apps
+  if (!self.apiCompliance.canReadText) {
+    os_log_debug([KMLogs keyTraceLog], "cannot replace text, non-compliant");
     return NO; // return without deleting/replacing
   }
-  
+
+  NSRange currentSelection = {0};
+  NSString *context = [self readContext:client outSelection:&currentSelection];
+  os_log_debug([KMLogs keyTraceLog], "handleDeleteWithReplacement, currentSelection: %{public}@: ", NSStringFromRange(currentSelection));
+
+  // guard: if text is currently selected, then accept default delete behavior of removing selected text
+  if (currentSelection.length > 0) {
+    os_log_debug([KMLogs keyTraceLog], "text is currently selected, accept default system handling to delete it");
+    return NO; // return without deleting/replacing
+  }
+
+  // guard: must have sufficient context
+  if ([context length] <= output.textToDelete.length) {
+    os_log_debug([KMLogs keyTraceLog], "cannot replace text, insufficient context");
+    return NO; // return without deleting/replacing
+  }
+
   // guard: the logic of this method depends on locating textToDelete in the context
   if (![self stringToDeleteMatchesContextSuffix:output.textToDelete context:context]) {
     os_log_debug([KMLogs keyTraceLog], "cannot replace text, textToDelete not found at end of context");
     return NO; // return without deleting/replacing
   }
 
+  // the length of the text we are to delete
   NSUInteger deletionTargetLength = output.textToDelete.length;
-  NSUInteger deletionTargetLocation = context.length-deletionTargetLength;
-  NSUInteger precedingCharacterLocation = deletionTargetLocation - 1;
+  // the location of the text we are to delete
+  NSUInteger locationOfDeletionTarget = context.length-deletionTargetLength;
 
-  // if the preceding character is the trailing half of a surrogate pair
-  // then delete by replacing with the entire surrogate pair
-  if ([self precededBySurrogatePair:precedingCharacterLocation context:context]) {
-    handledEvent = [self deleteByReplacingWithPrecedingSurrogate:precedingCharacterLocation deleteLength:deletionTargetLength context:context client:client];
-  } else {
-    // otherwise replace with only the preceding character
-    handledEvent = [self deleteByReplacingWithPrecedingCharacter:precedingCharacterLocation deleteLength:deletionTargetLength context:context client:client];
+  ReplacementInfo replacementInfo = [self evaluateForReplaceability: context textStoreLocation:currentSelection.location deleteLength:deletionTargetLength locationOfDeletionTarget:locationOfDeletionTarget];
+  
+  if (replacementInfo.canDeleteWithReplacement) {
+    id<NSTextInputClient> textInputClient = (id)client;
+    NSRange replacementRange = NSMakeRange(replacementInfo.replacementLocation, replacementInfo.replacementLength);
+
+    // perform the delete with replacement
+    os_log_debug([KMLogs keyTraceLog], "insertText with replacementString: %{public}@, replacementRange.location: %lu, replacementRange.length: %lu", replacementInfo.replacementString, replacementRange.location, replacementRange.length);
+    [textInputClient insertText:replacementInfo.replacementString replacementRange:replacementRange];
   }
-      
-  return handledEvent;
+
+  return replacementInfo.canDeleteWithReplacement;
 }
 
 /**
@@ -616,6 +652,35 @@ CGEventSourceRef _sourceForGeneratedEvent = nil;
   return doesMatch;
 }
 
+/**
+ * Evaluate whether the target can be deleted with a replacement, and, if it can, include the information
+ * that describes how to perform the replacement.
+ */
+- (ReplacementInfo)evaluateForReplaceability:(NSString*) context textStoreLocation:(NSUInteger)textStoreLocation deleteLength:(NSUInteger)deleteLength locationOfDeletionTarget:(NSUInteger)deletionLocation {
+  
+  ReplacementInfo replacementInfo;
+
+  NSUInteger precedingLocation = deletionLocation - 1;
+  os_log_debug([KMLogs keyTraceLog], "evaluateForReplaceability of deleteLength: %lu at precedingLocation: %lu", (unsigned long)deleteLength, (unsigned long)precedingLocation);
+
+  // if the preceding character is the trailing half of a surrogate pair
+  // then delete by replacing with the entire surrogate pair
+  if ([self precededBySurrogatePair:precedingLocation context:context]) {
+    replacementInfo = [self determineReplacementInfoWithPrecedingSurrogate:precedingLocation textStoreLocation:textStoreLocation deleteLength:deleteLength context:context];
+  } else {
+    // otherwise replace with only the preceding character
+    replacementInfo = [self determineReplacementInfoWithPrecedingCharacter:precedingLocation textStoreLocation:textStoreLocation deleteLength:deleteLength context:context];
+  }
+
+  if (replacementInfo.canDeleteWithReplacement) {
+    os_log_debug([KMLogs keyTraceLog], "⭐️ evaluateForReplaceability, canDeleteWithReplacement = YES, replacementString = %{public}@, replacementLength: %lu, replacementLocation: %lu", replacementInfo.replacementString, replacementInfo.replacementLength, replacementInfo.replacementLocation);
+  } else {
+    os_log_debug([KMLogs keyTraceLog], "evaluateForReplaceability, canDeleteWithReplacement = NO");
+  }
+
+  return replacementInfo;
+}
+
 /**
  * Check whether the preceding character, which is to be used for the replacement,
  * is part of a surrogate pair that is distinct from the character being deleted.
@@ -640,49 +705,53 @@ CGEventSourceRef _sourceForGeneratedEvent = nil;
 }
 
 /**
- * Replace both the text to delete and the character preceding it solely with the character that precedes it.
- * Returns YES if executing the replace/delete and NO otherwise.
+ * Determine the replacement info using the character preceding the string to be deleted.
  */
--(BOOL) deleteByReplacingWithPrecedingCharacter:(NSUInteger)precedingCharacterLocation deleteLength:(NSUInteger)deleteLength context:(NSString*) context client:(id) client {
-  
-  os_log_debug([KMLogs keyTraceLog], "deleteByReplacingWithPrecedingCharacter");
-  // get the preceding character
+-(ReplacementInfo) determineReplacementInfoWithPrecedingCharacter:(NSUInteger)precedingCharacterLocation textStoreLocation:(NSUInteger)textStoreLocation deleteLength:(NSUInteger)deleteLength context:(NSString*) context {
+  ReplacementInfo replacementInfo = {NO, 0, 0, NULL};
+
+  // get the preceding character from the context
   NSRange precedingCharacterRange = NSMakeRange(precedingCharacterLocation, 1);
   NSString *replacementString = [context substringWithRange:precedingCharacterRange];
-  
+
+  os_log_debug([KMLogs keyTraceLog], "deleteByReplacingWithPrecedingCharacter, precedingCharacterLocation = %lu, textStoreLocation = %lu, replacementString = %{public}@", precedingCharacterLocation, textStoreLocation, replacementString);
+
   // guard: if preceding character is a control character, return NO
   if ([self containsControlCharacter:replacementString]) {
     NSString *message = @"replacementString contains control characters, cannot delete with replace";
     os_log_debug([KMLogs keyTraceLog], "%@", message);
     [KMSentryHelper addDebugBreadCrumb:@"event" message:message];
-    return NO;
+    return replacementInfo;
   }
 
-  // perform the replacement
+  // the length of the text to replace = the length of the replacement string + length of the string to delete
   NSUInteger replacementLength = [replacementString length] + deleteLength;
-  NSRange replacementRange = NSMakeRange(precedingCharacterLocation, replacementLength);
-  os_log_debug([KMLogs keyTraceLog], "replacementRange: %{public}@", NSStringFromRange(replacementRange));
-  [client insertText:replacementString replacementRange:replacementRange];
+  // the location of the replacement is the current location in the text store
+  //    minus the length of the text we are deleting
+  //    minus the length of the preceding character (the one that makes this a replacement)
+  NSUInteger replacementLocation = textStoreLocation - replacementLength;
 
-  return YES;
+  replacementInfo.canDeleteWithReplacement = YES;
+  replacementInfo.replacementString = replacementString;
+  replacementInfo.replacementLength = replacementLength;
+  replacementInfo.replacementLocation = replacementLocation;
+  return replacementInfo;
 }
 
 /**
- * Replace both the text to delete and the surrogate pair preceding it with the surrogate pair preceding it.
- * Returns YES if executing the replace/delete and NO otherwise.
+ *  Determine the replacement info using the surrogate pair preceding the string to be deleted.
  */
--(BOOL) deleteByReplacingWithPrecedingSurrogate:(NSUInteger)precedingCharacterLocation deleteLength:(NSUInteger)deleteLength context:(NSString*) context client:(id) client {
-  
-  os_log_debug([KMLogs keyTraceLog], "deleteByReplacingWithPrecedingSurrogate");
+-(ReplacementInfo) determineReplacementInfoWithPrecedingSurrogate:(NSUInteger)precedingCharacterLocation textStoreLocation:(NSUInteger)textStoreLocation deleteLength:(NSUInteger)deleteLength context:(NSString*) context {
+  ReplacementInfo replacementInfo = {NO, 0, 0, NULL};
 
   // guard: return NO if there is no character before the precedingCharacterLocation
   if (precedingCharacterLocation <= 0) {
     NSString *message = @"no characters exist before precedingCharacterLocation, so it cannot be a surrogate pair";
     os_log_debug([KMLogs keyTraceLog], "%@", message);
-    return NO;
+    return replacementInfo;
   }
 
-  // get the preceding character
+  // get the preceding character from the context
   NSRange precedingCharacterRange = NSMakeRange(precedingCharacterLocation - 1, 2);
   NSString *replacementString = [context substringWithRange:precedingCharacterRange];
 
@@ -694,18 +763,24 @@ CGEventSourceRef _sourceForGeneratedEvent = nil;
     // found preceding surrogate as expected
   } else {
     NSString *message = [NSString stringWithFormat:@"Preceding characters of string do not comprise a surrogate pair: 0x%02x, 0x%02x", (unsigned int)highCharacter, (unsigned int)lowCharacter];
-    os_log_debug([KMLogs keyTraceLog], "%@", message);
+    os_log_error([KMLogs keyTraceLog], "%@", message);
     [KMSentryHelper addDebugBreadCrumb:@"event" message:message];
-    return NO;
+    return replacementInfo;
   }
 
-  // perform the replacement
+  // the length of the text to replace = the length of the replacement string + length of the string to delete
   NSUInteger replacementLength = [replacementString length] + deleteLength;
-  NSRange replacementRange = NSMakeRange(precedingCharacterRange.location, replacementLength);
-  os_log_debug([KMLogs keyTraceLog], "replacementRange: %{public}@", NSStringFromRange(replacementRange));
-  [client insertText:replacementString replacementRange:replacementRange];
+  // the location of the replacement is the current location in the text store
+  //    minus the length of the text we are deleting
+  //    minus the length of the preceding character (the one that makes this a replacement)
+  NSUInteger replacementLocation = textStoreLocation - replacementLength;
 
-  return YES;
+  replacementInfo.canDeleteWithReplacement = YES;
+  replacementInfo.replacementString = replacementString;
+  replacementInfo.replacementLength = replacementLength;
+  replacementInfo.replacementLocation = replacementLocation;
+  
+  return replacementInfo;
 }
 
 -(BOOL) containsControlCharacter:(NSString*)text {

mac/Keyman4MacIM/Keyman4MacIM/TextApiCompliance.m

@@ -377,8 +377,12 @@ NSString *const kKMLegacyApps = @"KMLegacyApps";
                             [clientAppId isEqual: @"com.google.Chrome"] ||
                             // 2023-12-13[sgs]: must hard-code for Chrome because Google Docs returns relative but incorrect location so no way to auto-detect
                             [clientAppId hasPrefix: @"net.java"] ||
-                            [clientAppId isEqual: @"com.Keyman.test.legacyInput"]
+                            [clientAppId isEqual: @"com.Keyman.test.legacyInput"] ||
                             /*||[clientAppId isEqual: @"ro.sync.exml.Oxygen"] - Oxygen has worse problems */
+                            [clientAppId isEqual: @"com.tinyspeck.slackmacgap"] ||
+                            // #16731 2026-09-24[sgs]: Slack does double backspace when inserting with replacement
+                            [clientAppId isEqual: @"com.microsoft.VSCode"]
+                            // #16731 2026-09-24[sgs]: VSCode does double backspace when inserting with replacement
                             );
   
   os_log_debug([KMLogs complianceLog], "containedInHardCodedNoncompliantAppList: for app %{public}@: %{public}@", clientAppId, isAppNonCompliant?@"yes":@"no");

mac/Keyman4MacIM/KeymanTests/InputMethodTests.m

@@ -23,6 +23,7 @@ id testClient = nil;
 @interface InputMethodTests : XCTestCase
 @end
 
+// redeclare private properties and functions to expose for testing
 @interface KMInputMethodEventHandler (Testing)
 @property (nonatomic, retain) TextApiCompliance* apiCompliance;
 @property (nonatomic, retain) NSString* clientApplicationId;
@@ -30,7 +31,10 @@ id testClient = nil;
 - (instancetype)initWithClient:(NSString *)clientAppId client:(id) sender;
 - (NSRange) calculateInsertRangeForDeletedText:(NSString*)textToDelete selectionRange:(NSRange) selection;
 - (void)checkTextApiCompliance:(id)client;
-
+- (ReplacementInfo)evaluateForReplaceability:(NSString*) context
+                           textStoreLocation:(NSUInteger)textStoreLocation
+                                deleteLength:(NSUInteger)deleteLength
+                    locationOfDeletionTarget:(NSUInteger)deletionLocation;
 @end
 
 @implementation InputMethodTests
@@ -92,6 +96,134 @@ id testClient = nil;
   XCTAssertTrue(correctResult, @"insert or replacement range expected to be {1,2}");
 }
 
+- (void)testEvaluateReplacement_precededByControlCharacter_canReplaceFalse {
+  NSString *context = @"test\ta";
+  NSUInteger storeLocation = 100;
+  NSUInteger deletionLength = 1;
+  NSUInteger locationOfDeletion = 5;
+
+  ReplacementInfo replacementInfo = [testEventHandler evaluateForReplaceability: context textStoreLocation:storeLocation deleteLength:deletionLength locationOfDeletionTarget:locationOfDeletion];
+  XCTAssertFalse(replacementInfo.canDeleteWithReplacement, @"target preceded by control character, canDelete should be false");
+}
+
+- (void)testEvaluateReplacement_precededByLatinCharacter_canReplaceTrue {
+  NSString *context = @"testxa";
+  NSUInteger storeLocation = 100;
+  NSUInteger deletionLength = 1;
+  NSUInteger locationOfDeletion = 5;
+  
+  ReplacementInfo replacementInfo = [testEventHandler evaluateForReplaceability: context textStoreLocation:storeLocation deleteLength:deletionLength locationOfDeletionTarget:locationOfDeletion];
+  
+  XCTAssertTrue([replacementInfo.replacementString isEqualToString:@"x"], @"replacementString should be == 'x'");
+  XCTAssertTrue(replacementInfo.replacementLength == 2, @"replacementLength should be 2");
+}
+
+- (void)testEvaluateReplacement_lowStoreLocation_correctReplacementLocation {
+  NSString *context = @"testxa";
+  NSUInteger storeLocation = 10;
+  NSUInteger deletionLength = 1;
+  NSUInteger locationOfDeletion = 5;
+  
+  ReplacementInfo replacementInfo = [testEventHandler evaluateForReplaceability: context textStoreLocation:storeLocation deleteLength:deletionLength locationOfDeletionTarget:locationOfDeletion];
+  
+  XCTAssertTrue(replacementInfo.replacementLocation==8, @"replacementLocation should be 8");
+}
+
+- (void)testEvaluateReplacement_highStoreLocation_correctReplacementLocation {
+  NSString *context = @"testxa";
+  NSUInteger storeLocation = 1000;
+  NSUInteger deletionLength = 1;
+  NSUInteger locationOfDeletion = 5;
+  
+  ReplacementInfo replacementInfo = [testEventHandler evaluateForReplaceability: context textStoreLocation:storeLocation deleteLength:deletionLength locationOfDeletionTarget:locationOfDeletion];
+  
+  XCTAssertTrue(replacementInfo.replacementLocation==998, @"replacementLocation should be 998");
+}
+
+// Uses Malar Tirhuta script
+- (void)testEvaluateReplacement_latinCharacterPrecededBySurrogatePair_replacementLengthThree {
+  NSString *context = @"test.𑒏a";    // 𑒏 : U+1148F : TIRHUTA LETTER
+  NSString *stringToDelete = @"a";
+  
+  NSRange range = [context rangeOfString:stringToDelete];
+  
+  NSUInteger storeLocation = 100;
+  NSUInteger deletionLength = stringToDelete.length;
+  NSUInteger locationOfDeletion = range.location;
+  
+  ReplacementInfo replacementInfo = [testEventHandler evaluateForReplaceability: context textStoreLocation:storeLocation deleteLength:deletionLength locationOfDeletionTarget:locationOfDeletion];
+  
+  XCTAssertTrue([replacementInfo.replacementString isEqualToString:@"𑒏"], @"replacementString is incorrect");
+  XCTAssertTrue(replacementInfo.replacementLength == 3, @"replacementLength should == 3");
+}
+
+- (void)testEvaluateReplacement_surrogatePairPrecededByLatinCharacter_replacementLengthThree {
+  NSString *context = @"test.a𑒏";    // 𑒏 : U+1148F : TIRHUTA LETTER
+  NSString *stringToDelete = @"𑒏";
+  
+  NSRange range = [context rangeOfString:stringToDelete];
+  
+  NSUInteger storeLocation = 100;
+  NSUInteger deletionLength = stringToDelete.length;
+  NSUInteger locationOfDeletion = range.location;
+  
+  ReplacementInfo replacementInfo = [testEventHandler evaluateForReplaceability: context textStoreLocation:storeLocation deleteLength:deletionLength locationOfDeletionTarget:locationOfDeletion];
+  
+  XCTAssertTrue([replacementInfo.replacementString isEqualToString:@"a"], @"replacementString is incorrect");
+  XCTAssertTrue(replacementInfo.replacementLength == 3, @"replacementLength should == 3");
+}
+
+- (void)testEvaluateReplacement_latinCharacterPrecededByEmoji_replacementLengthThree {
+  NSString *context = @"test🏁a";
+  NSString *stringToDelete = @"a";
+  
+  NSRange range = [context rangeOfString:stringToDelete];
+  
+  NSUInteger storeLocation = 100;
+  NSUInteger deletionLength = stringToDelete.length;
+  NSUInteger locationOfDeletion = range.location;
+  
+  ReplacementInfo replacementInfo = [testEventHandler evaluateForReplaceability: context textStoreLocation:storeLocation deleteLength:deletionLength locationOfDeletionTarget:locationOfDeletion];
+  
+  XCTAssertTrue([replacementInfo.replacementString isEqualToString:@"🏁"], @"replacementString should be == '🏁'");
+  XCTAssertTrue(replacementInfo.replacementLength == 3, @"replacementLength should == 3");
+}
+
+- (void)testEvaluateReplacement_emojiPrecededByLatinCharacter_replacementLengthThree {
+  NSString *context = @"testa🏁";
+  NSString *stringToDelete = @"🏁";
+  
+  NSRange range = [context rangeOfString:stringToDelete];
+  
+  NSUInteger storeLocation = 100;
+  NSUInteger deletionLength = stringToDelete.length;
+  NSUInteger locationOfDeletion = range.location;
+  
+  ReplacementInfo replacementInfo = [testEventHandler evaluateForReplaceability: context textStoreLocation:storeLocation deleteLength:deletionLength locationOfDeletionTarget:locationOfDeletion];
+  
+  XCTAssertTrue([replacementInfo.replacementString isEqualToString:@"a"], @"replacementString should be == 'a'");
+  XCTAssertTrue(replacementInfo.replacementLength == 3, @"replacementLength should == 3");
+}
+
+// Note: though this test checks the calculation, deleting the jolly roger emoji will currently not behave as expected.
+// Keyman core instructs only part of the emoji to be deleted. The same happens with emoji with skin tones.
+// See #4956 for context
+- (void)testEvaluateReplacement_jollyRogerPrecededByLatinCharacter_replacementLengthSix {
+  NSString *context = @"testa🏴‍☠️";
+  NSString *stringToDelete = @"🏴‍☠️";
+  
+  NSRange range = [context rangeOfString:stringToDelete];
+  
+  NSUInteger storeLocation = 100;
+  NSUInteger deletionLength = stringToDelete.length;
+  NSUInteger locationOfDeletion = range.location;
+  
+  ReplacementInfo replacementInfo = [testEventHandler evaluateForReplaceability: context textStoreLocation:storeLocation deleteLength:deletionLength locationOfDeletionTarget:locationOfDeletion];
+  
+  XCTAssertTrue([replacementInfo.replacementString isEqualToString:@"a"], @"replacementString should be == 'a'");
+  XCTAssertTrue(replacementInfo.replacementLength == 6, @"replacementLength should == 6");
+}
+
 /**
  * test compliance check of a KMInputMethodEventHandler with a nil client application ID
  * not sure if this can ever happen, but the lifecycle of the input method is not 100% clear,

mac/KeymanEngine4Mac/KeymanEngine4Mac.xcodeproj/project.pbxproj

@@ -473,7 +473,7 @@
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 			shellPath = /bin/sh;
-			shellScript = "# check that our PRODUCT_VERSION matches this git branch's KEYMAN_VERSION from ../../VERSION.md\n(cd .. ; ./is_same_version.sh KeymanEngine4Mac || exit 1 ; cd -)\n";
+			shellScript = "# check that our PRODUCT_VERSION matches this git branch's KEYMAN_VERSION from ../../VERSION.md\n# TODO: use xcode-wrap.sh (follow-up in #16712)\nexport PATH=\"/opt/homebrew/bin:/usr/local/bin:$PATH\"\necho \"BASH version inside Xcode is: $BASH_VERSION\"\n(cd .. ; ./is_same_version.sh KeymanEngine4Mac || exit 1 ; cd -)\n";
 			showEnvVarsInLog = 0;
 		};
 		E2588F2F1F2647A50061C9C4 /* ShellScript */ = {

mac/KeymanEngine4Mac/KeymanEngine4Mac/CoreWrapper/CoreWrapper.m

@@ -275,7 +275,9 @@ const int CORE_ENVIRONMENT_ARRAY_LENGTH = 6;
 -(void)setContextIfNeeded:(NSString*)context {
   unichar const * unicharContext = [self.coreHelper createUnicharStringFromNSString:context];
   km_core_status result = km_core_state_context_set_if_needed(self.coreState, unicharContext);
-  os_log_debug([KMELogs coreLog], "setContextIfNeeded, context=%{public}@, km_core_state_context_set_if_needed result=%d", context, result);
+  
+  // only uncomment for debugging to avoid logging context
+  //os_log_debug([KMELogs coreLog], "setContextIfNeeded, context=%{public}@, km_core_state_context_set_if_needed result=%d", context, result);
 }
 
 -(NSString*)contextDebug {