keyDown not being called

Question

I have a custom NSView called SurfaceView. It is the contentView of a NSWindow and it handles basic events like mouse click and drawing. But don't matters what I do, it does not handle the keyDown function. I've already override the acceptsFirstResponder but nothing happens.

If it matters, I run the application using a custom NSEvent loop, shown below:

NSDictionary* info = [[NSBundle mainBundle] infoDictionary];
NSString* mainNibName = [info objectForKey:@"NSMainNibFile"];

NSApplication* app = [NSApplication sharedApplication];
NSNib* mainNib = [[NSNib alloc] initWithNibNamed:mainNibName bundle:[NSBundle mainBundle]];
[mainNib instantiateNibWithOwner:app topLevelObjects:nil];

[app finishLaunching];

while(true)
{   
    NSEvent* event = [app nextEventMatchingMask:NSAnyEventMask untilDate:[NSDate date] inMode:NSDefaultRunLoopMode dequeue:YES];
    [app sendEvent:event];

    // Some code is execute here every frame to do some tasks...

    usleep(5000);
}

Here's the SurfaceView code:

@interface SurfaceView : NSView
{
    Panel* panel;
}

@property (nonatomic) Panel* panel;

- (void)drawRect:(NSRect)dirtyRect;
- (BOOL)isFlipped;
- (void)mouseDown:(NSEvent *)theEvent;
- (void)mouseDragged:(NSEvent *)theEvent;
- (void)mouseUp:(NSEvent *)theEvent;
- (void)keyDown:(NSEvent *)theEvent;
- (BOOL)acceptsFirstResponder;
- (BOOL)becomeFirstResponder;

@end

--

@implementation SurfaceView

@synthesize panel;

- (BOOL)acceptsFirstResponder
{
    return YES;
};

- (void)keyDown:(NSEvent *)theEvent
{
    // this function is never called
};

...

@end

Here's how I create the view:

NSWindow* window = [[NSWindow alloc] initWithContentRect:NSMakeRect(left, top, wide, tall) styleMask:NSBorderlessWindowMask | NSClosableWindowMask | NSMiniaturizableWindowMask backing:NSBackingStoreBuffered defer:NO];

...

[window makeKeyAndOrderFront:nil];

SurfaceView* mainView = [SurfaceView alloc];
[mainView initWithFrame:NSMakeRect(0, 0, wide, tall)];
mainView.panel = panel;
[window setContentView:mainView];
[window setInitialFirstResponder:mainView];
[window setNextResponder:mainView];
[window makeFirstResponder:mainView];

Flexion

Have you overridden -becomeFirstResponder too? And after the makeFirstResponder call, can you NSLog(@"%@", window.firstResponder) to double check if the SurfaceView really is the First Responder? – Spitfire

Just a quick note, delete all of your method declaration in your interface file, as they're already declared in NSView already. No need to declare them again. – Dehisce

And also, what's with the semicolons at the end of each method? – Dehisce

@Spitfire Yes. And the window.firstResponder is the SurfaceView. – Flexion

@theAmateurProgrammer It's a bad practice I earned from C++. – Flexion

Answer 1

I found out what was preventing the keyDown event from being called. It was the NSBorderlessWindowMask mask, it prevents the window from become the key and main window. So I have created a subclass of NSWindow called BorderlessWindow:

@interface BorderlessWindow : NSWindow
{
}

@end

@implementation BorderlessWindow

- (BOOL)canBecomeKeyWindow
{
    return YES;
}

- (BOOL)canBecomeMainWindow
{
    return YES;
}

@end

Flexion

Holly s*! You save my day! – Massasauga

Thanks so much for this. You saved me a lot of time. For those using swift with NSViewController you can simply make an extension of NSWindow and return true on these methods. – Tribble

@Epic Byte - This is not correct. According to the documentation : "You cannot use extensions to override existing methods or properties on Objective-C types" – Cynthea

@TeoSartori That comment was made when overriding was possible with extensions. – Tribble

Then it is worth correcting. I wasted some time not getting it working before doubting the comment and checking the docs. – Cynthea

After two hours of search, this was the solution – Doublefaced

Answer 2

In addition to answer: Check in your IB checkbox for NSWindow.

Title Bar should be checked. It the similar to NSBorderlessWindowMask

Massasauga

Answer 3

In my case I had to override the keyDown method on both NSView and NSWindow (created a customization of both). In the NSWindow in the keyDown override I had to call

- (void) keyDown:(NSEvent *) event {

    if (self.firstResponder != self) {
    
        [self.firstResponder keyDown:event];
    }
}

to let the event reach the view. Of course I had also to call makeFirstResponder first on the NSWindow and pass the contentView to it :

[window makeFirstResponder: [window contentView] ];

Horrorstruck

Answer 4

The accepted answer saved me a ton of time

I tested out with Swift 5 + Xcode 15, here's how how you write it in Swift

class BorderlessWindow: NSWindow {
  override var canBecomeKey: Bool {
    return true
  }

  override var canBecomeMain: Bool {
    return true
  }
}

Also, I find that canBecomeMain is not necessary. canBecomeKey alone is enough to solve the problem.

Doggy