If DefaultKeyBindings.dict leads you down a garden path to a multi-keystroke...

If DefaultKeyBindings.dict leads you down a garden path to a multi-keystroke combo that doesn't exist, revisit the keydown events seen along the way and replay them. Issue 3710.

sources/PTYTextView.m

@@ -1399,11 +1399,24 @@ static const int kDragThreshold = 3;
     // Hide the cursor
     [NSCursor setHiddenUntilMouseMoves:YES];
-    if ([_keyBindingEmulator handlesEvent:event]) {
+    NSMutableArray *eventsToHandle = [NSMutableArray array];
+    if ([_keyBindingEmulator handlesEvent:event extraEvents:eventsToHandle]) {
         DLog(@"iTermNSKeyBindingEmulator reports that event is handled, sending to interpretKeyEvents.");
         [self interpretKeyEvents:@[ event ]];
         return;
     }
+    [eventsToHandle addObject:event];
+    for (NSEvent *event in eventsToHandle) {
+        [self handleKeyDownEvent:event];
+    }
+}
+
+- (void)handleKeyDownEvent:(NSEvent *)event {
+    id delegate = [self delegate];
+    unsigned int modflag = [event modifierFlags];
+    unsigned short keyCode = [event keyCode];
+    BOOL rightAltPressed = (modflag & NSRightAlternateKeyMask) == NSRightAlternateKeyMask;
+    BOOL leftAltPressed = (modflag & NSAlternateKeyMask) == NSAlternateKeyMask && !rightAltPressed;
     // Should we process the event immediately in the delegate?
     if (!_hadMarkedTextBeforeHandlingKeypressEvent &&

sources/iTermNSKeyBindingEmulator.h

@@ -10,7 +10,10 @@
 @interface iTermNSKeyBindingEmulator : NSObject
-// Returns YES if the user's key bindings should handle this event.
-- (BOOL)handlesEvent:(NSEvent *)event;
+// Indicates if the event should be handled by Cocoa's regular text processing path because it has
+// a key binding. If this returns NO, then |extraEvents| may be filled in with additional events
+// to process first. That happens when a series of keys is entered which make up a multi-key binding
+// ending in an unhandleable binding.
+- (BOOL)handlesEvent:(NSEvent *)event extraEvents:(NSMutableArray *)extraEvents;
 @end

sources/iTermNSKeyBindingEmulator.m

@@ -41,7 +41,9 @@ static struct {
     { '@', NSCommandKeyMask }
 };
-@implementation iTermNSKeyBindingEmulator
+@implementation iTermNSKeyBindingEmulator {
+    NSMutableArray *_savedEvents;
+}
 + (void)initialize {
     if (self == [iTermNSKeyBindingEmulator self]) {
@@ -266,19 +268,22 @@ static struct {
 - (instancetype)init {
     self = [super init];
     if (self) {
+        _savedEvents = [[NSMutableArray alloc] init];
         _currentDict = [gRootKeyBindingsDictionary retain];
     }
     return self;
 }
 - (void)dealloc {
+    [_savedEvents release];
     [_currentDict release];
     [super dealloc];
 }
-- (BOOL)handlesEvent:(NSEvent *)event {
+- (BOOL)handlesEvent:(NSEvent *)event extraEvents:(NSMutableArray *)extraEvents {
     if (!gRootKeyBindingsDictionary) {
         DLog(@"Short-circuit DefaultKeyBindings handling because no bindings are defined");
+        [_savedEvents removeAllObjects];
         return NO;
     }
     DLog(@"Checking if default key bindings should handle %@", event);
@@ -288,6 +293,7 @@ static struct {
         DLog(@"Couldn't normalize event to key!");
         NSLog(@"WARNING: Unexpected charactersIgnoringModifiers=%@ in event %@",
               event.charactersIgnoringModifiers, event);
+        [_savedEvents removeAllObjects];
         return NO;
     }
     NSObject *obj = nil;
@@ -305,6 +311,7 @@ static struct {
         // This is part of a multi-keystroke binding. Move down the tree.
         self.currentDict = (NSDictionary *)obj;
         DLog(@"Entered multi-keystroke binding with key: %@", selectedKey);
+        [_savedEvents addObject:event];
         return YES;
     }
@@ -313,11 +320,18 @@ static struct {
     DLog(@"Default key binding is %@", obj);
     
     if (![obj isKindOfClass:[NSArray class]]) {
+        [extraEvents addObjectsFromArray:_savedEvents];
+        [_savedEvents removeAllObjects];
         return NO;
     }
     
     NSArray *theArray = (NSArray *)obj;
-    return ([theArray[0] isEqualToString:@"insertText:"]);
+    BOOL result = ([theArray[0] isEqualToString:@"insertText:"]);
+    if (!result) {
+        [extraEvents addObjectsFromArray:_savedEvents];
+    }
+    [_savedEvents removeAllObjects];
+    return result;
 }
 #pragma mark - Private