fix(mac): standardize interaction between OSK and physical keyboard

mac/Keyman4MacIM/Keyman4MacIM/KMInputMethodAppDelegate.m

@@ -944,6 +944,7 @@ - (void)registerConfigurationWindow:(NSWindowController *)window {
 }
 
 - (void)showOSK {
+  [self.oskWindow prepareToShowOsk];
   [[self.oskWindow window] makeKeyAndOrderFront:nil];
   [[self.oskWindow window] setLevel:NSStatusWindowLevel];
   [[self.oskWindow window] setTitle:self.oskWindowTitle];
@@ -1242,13 +1243,32 @@ - (NSEventModifierFlags) determineModifiers {
   NSEventModifierFlags modifierFlags = 0;
 
   if (self.receivedKeyDownFromOsk) {
+    /**
+     * the event was generated from the OSK, so use the oskEventModifiers in effect at time of event generation
+     */
     modifierFlags = self.oskEventModifiers;
     os_log_debug([KMLogs eventsLog], "--- use modifiers from OSK, oskEventModifiers: 0x%lX", (unsigned long)modifierFlags);
     self.oskEventModifiers = 0;
-  } else {
+  } else { 
+    /**
+     * the event originated from the physical keyboard, use the modifiers on kCGEventFlagsChanged events
+     */
     NSEventModifierFlags originalModifiers = self.currentModifiers;
     modifierFlags = [self.modifierMapping adjustModifiers:originalModifiers];
     os_log_debug([KMLogs eventsLog], "--- use adjusted modifiers from current state: 0x%lX", (unsigned long)modifierFlags);
+
+    /**
+     * If the OSK is open, then we also need to apply its modifiers, if any, to this event originating from the physical keyboard.
+     * If the OSK is closed, its modifiers will be zero.
+     */
+    NSEventModifierFlags oskModifiers = [self.oskWindow getOskEventModifierFlags];
+    if (oskModifiers != 0) {
+      os_log_debug([KMLogs eventsLog], "--- modifiers from OSK to apply to physical keyboard event: 0x%lX", (unsigned long)oskModifiers);
+
+      // combine osk modifiers with adjusted modifiers
+      modifierFlags = oskModifiers | modifierFlags;
+      os_log_debug([KMLogs eventsLog], "--- combined modifiers to apply to physical keyboard event: 0x%lX", (unsigned long)modifierFlags);
+    }
   }
 
   return modifierFlags;

mac/Keyman4MacIM/Keyman4MacIM/OnScreenKeyboard/OSKWindowController.h

@@ -13,6 +13,8 @@
 
 @property (nonatomic, weak) IBOutlet OSKView *oskView;
 
+- (void)prepareToShowOsk;
 - (void)resetOSK;
+- (NSEventModifierFlags)getOskEventModifierFlags;
 
 @end

mac/Keyman4MacIM/Keyman4MacIM/OnScreenKeyboard/OSKWindowController.m

@@ -66,9 +66,16 @@ - (void)windowDidResize:(NSNotification *)notification {
   [self.oskView resizeOSKLayout];
 }
 
+- (void)prepareToShowOsk {
+  os_log_info([KMLogs oskLog], "OSKWindowController prepareToShowOsk");
+}
+
 - (void)windowWillClose:(NSNotification *)notification {
+  os_log_debug([KMLogs oskLog], "OSKWindowController windowWillClose");
   [KMSettingsRepository.shared writeShowOskOnActivate:NO];
-  os_log_debug([KMLogs oskLog], "OSKWindowController windowWillClose, updating settings writeShowOsk to NO");
+
+  // whenever the OSK is closing clear all of its modifier keys
+  [self.oskView clearOskModifiers];
 }
 
 - (void)helpAction:(id)sender {
@@ -97,6 +104,16 @@ - (void)resetOSK {
   }
 }
 
+/**
+ * returns current event flags representing the state of the modifiers on the OSK or zero if OSK is closed
+ */
+- (NSEventModifierFlags)getOskEventModifierFlags {
+  if (self.window.isVisible) {
+    return [self.oskView getOskEventModifierFlags];
+  } else {
+    return 0;
+  }
+}
 - (void)startTimerWithTimeInterval:(NSTimeInterval)interval {
   if (_modFlagsTimer == nil) {
     TimerTarget *timerTarget = [[TimerTarget alloc] init];

mac/KeymanEngine4Mac/KeymanEngine4Mac/KME/OnScreenKeyboard/OSKView.h

@@ -25,6 +25,8 @@
 - (void)setOskOptionState:(BOOL)oskAltState;
 - (void)setPhysicalControlState:(BOOL)ctrlState;
 - (void)setOskControlState:(BOOL)oskCtrlState;
+- (void)clearOskModifiers;
+- (NSEventModifierFlags)getOskEventModifierFlags;
 - (void)resetOSK;
 - (void)resizeOSKLayout;
 - (int64_t)createOskEventUserData;