CODEWITHSUNDEEP
objective-ccocoamacos
smokris
smokris

Reputation: 11840

How to create an NSEvent of type NSScrollWheel?

I'd like to construct (fake) an NSEvent of type NSScrollWheel. There are NSEvent constructor methods for a few other types of NSEvents (mouseEvent, keyEvent, enterExitEvent, otherEvent), but none allows me to set, for example, deltaX.

Upvotes: 17

Views: 7216

Answers (5)

Andrew
Andrew

Reputation: 11446

We can create scrollWheel NSEvent from CGEvent:

func scrollEvent(wheel: Int32) -> NSEvent {
    CGEvent(scrollWheelEvent2Source: nil, units: .pixel, wheelCount: 1, wheel1: wheel, wheel2: 0, wheel3: 0)
        .flatMap { NSEvent(cgEvent: $0) } ?? NSEvent()
}

Upvotes: 0

Ryan Francesconi
Ryan Francesconi

Reputation: 1006

This has come up for me in 2020. I thought I'd post the Swift 5 syntax for anyone finding this answer. This override in an NSScrollView subclass will swap up/down right/left scroll behavior if the ⌘ key is down:

public override func scrollWheel(with event: NSEvent) {
    guard event.modifierFlags.contains(.command) else {
        super.scrollWheel(with: event)
        return
    }

    if let cgEvent: CGEvent = event.cgEvent?.copy() {
        cgEvent.setDoubleValueField(.scrollWheelEventDeltaAxis1, value: Double(event.scrollingDeltaX))
        cgEvent.setDoubleValueField(.scrollWheelEventDeltaAxis2, value: Double(event.scrollingDeltaY))

        if let nsEvent = NSEvent(cgEvent: cgEvent) {
            super.scrollWheel(with: nsEvent)
        }
    }
}

Upvotes: 3

Ivan Androsenko
Ivan Androsenko

Reputation: 678

Try following code:

  int scrollingDeltaX =... //custom value

//if you have some NSEvent *theEvent 
  CGEventRef cgEvent = CGEventCreateCopy(theEvent.CGEvent);

  CGEventSetIntegerValueField(cgEvent, kCGScrollWheelEventDeltaAxis2, scrollingDeltaX);

  NSEvent *newEvent = [NSEvent eventWithCGEvent:cgEvent];
  CFRelease(cgEvent);

Upvotes: 2

ughoavgfhw
ughoavgfhw

Reputation: 39905

NSEvent doesn't provide a way to do this, but you can create a CGEvent and create an NSEvent wrapper around it. The event will automatically use the current location of the cursor. See CGEventCreateScrollWheelEvent. However, posting this event using NSApplication's postEvent:atStart: doesn't work (probably because it doesn't have a window defined). You can either post the CGEvent directly to the event stream, or send the NSEvent directly to a view's scrollWheel: method.

CGWheelCount wheelCount = 2; // 1 for Y-only, 2 for Y-X, 3 for Y-X-Z
int32_t xScroll = −1; // Negative for right
int32_t yScroll = −2; // Negative for down
CGEventRef cgEvent = CGEventCreateScrollWheelEvent(NULL, kCGScrollEventUnitLine, wheelCount, yScroll, xScroll);

// You can post the CGEvent to the event stream to have it automatically sent to the window under the cursor
CGEventPost(kCGHIDEventTap, cgEvent);

NSEvent *theEvent = [NSEvent eventWithCGEvent:cgEvent];
CFRelease(cgEvent);

// Or you can send the NSEvent directly to a view
[theView scrollWheel:theEvent];

Upvotes: 13

jscs
jscs

Reputation: 64002

You can create a CGEventRef using CGEventCreateScrollWheelEvent and convert it to an NSEvent with eventWithCGEvent:. To add information to the CGEvent, use CGEventSetIntegerValueField -- among the possible fields are kCGScrollWheelEventDeltaAxis1, ...2, and ...3.

Upvotes: 2

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