api: move primary from FingerId to Pointer events

Whether the pointer event is primary or not generally matters for the
context where all input is done by the same event, so users can
_ignore_ non-primary events since they are likely from users clicking
something else with their other fingers.

Having it only on a FingerId made it useless, since it's usually used
to avoid multi-touch, but if you start mapping on touch event you
already can track things like that yourself.

Fixes #3943.

Co-authored-by: daxpedda <daxpedda@gmail.com>

src/platform_impl/apple/appkit/view.rs

@@ -657,6 +657,7 @@ declare_class!(
 
             self.queue_event(WindowEvent::PointerEntered {
                 device_id: None,
+                primary: true,
                 position,
                 kind: PointerKind::Mouse,
             });
@@ -670,6 +671,7 @@ declare_class!(
 
             self.queue_event(WindowEvent::PointerLeft {
                 device_id: None,
+                primary: true,
                 position: Some(position),
                 kind: PointerKind::Mouse,
             });
@@ -1061,6 +1063,7 @@ impl WinitView {
 
         self.queue_event(WindowEvent::PointerButton {
             device_id: None,
+            primary: true,
             state: button_state,
             position,
             button: button.into(),
@@ -1087,6 +1090,7 @@ impl WinitView {
 
         self.queue_event(WindowEvent::PointerMoved {
             device_id: None,
+            primary: true,
             position: view_point.to_physical(self.scale_factor()),
             source: PointerSource::Mouse,
         });

src/platform_impl/apple/uikit/view.rs

@@ -34,6 +34,9 @@ pub struct WinitViewState {
     rotation_last_delta: Cell<CGFloat>,
     pinch_last_delta: Cell<CGFloat>,
     pan_last_delta: Cell<CGPoint>,
+
+    primary_finger: Cell<Option<usize>>,
+    fingers: Cell<u8>,
 }
 
 declare_class!(
@@ -371,6 +374,9 @@ impl WinitView {
             rotation_last_delta: Cell::new(0.0),
             pinch_last_delta: Cell::new(0.0),
             pan_last_delta: Cell::new(CGPoint { x: 0.0, y: 0.0 }),
+
+            primary_finger: Cell::new(None),
+            fingers: Cell::new(0),
         });
         let this: Retained<Self> = unsafe { msg_send_id![super(this), initWithFrame: frame] };
 
@@ -515,12 +521,33 @@ impl WinitView {
             let window_id = window.id();
             let finger_id = RootFingerId(FingerId(touch_id));
 
+            let ivars = self.ivars();
+
             match phase {
                 UITouchPhase::Began => {
+                    let primary = if let UITouchType::Pencil = touch_type {
+                        true
+                    } else {
+                        ivars.fingers.set(ivars.fingers.get() + 1);
+                        match ivars.primary_finger.get() {
+                            Some(primary_id) => primary_id == touch_id,
+                            None => {
+                                debug_assert_eq!(
+                                    ivars.fingers.get(),
+                                    1,
+                                    "number of fingers were not counted correctly"
+                                );
+                                ivars.primary_finger.set(Some(touch_id));
+                                true
+                            },
+                        }
+                    };
+
                     touch_events.push(EventWrapper::StaticEvent(Event::WindowEvent {
                         window_id,
                         event: WindowEvent::PointerEntered {
                             device_id: None,
+                            primary,
                             position,
                             kind: if let UITouchType::Pencil = touch_type {
                                 PointerKind::Unknown
@@ -533,6 +560,7 @@ impl WinitView {
                         window_id,
                         event: WindowEvent::PointerButton {
                             device_id: None,
+                            primary,
                             state: ElementState::Pressed,
                             position,
                             button: if let UITouchType::Pencil = touch_type {
@@ -544,26 +572,44 @@ impl WinitView {
                     }));
                 },
                 UITouchPhase::Moved => {
+                    let (primary, source) = if let UITouchType::Pencil = touch_type {
+                        (true, PointerSource::Unknown)
+                    } else {
+                        (ivars.primary_finger.get().unwrap() == touch_id, PointerSource::Touch {
+                            finger_id,
+                            force,
+                        })
+                    };
+
                     touch_events.push(EventWrapper::StaticEvent(Event::WindowEvent {
                         window_id,
                         event: WindowEvent::PointerMoved {
                             device_id: None,
+                            primary,
                             position,
-                            source: if let UITouchType::Pencil = touch_type {
-                                PointerSource::Unknown
-                            } else {
-                                PointerSource::Touch { finger_id, force }
-                            },
+                            source,
                         },
                     }));
                 },
                 // 2 is UITouchPhase::Stationary and is not expected here
                 UITouchPhase::Ended | UITouchPhase::Cancelled => {
+                    let primary = if let UITouchType::Pencil = touch_type {
+                        true
+                    } else {
+                        ivars.fingers.set(ivars.fingers.get() - 1);
+                        let primary = ivars.primary_finger.get().unwrap() == touch_id;
+                        if ivars.fingers.get() == 0 {
+                            ivars.primary_finger.set(None);
+                        }
+                        primary
+                    };
+
                     if let UITouchPhase::Ended = phase {
                         touch_events.push(EventWrapper::StaticEvent(Event::WindowEvent {
                             window_id,
                             event: WindowEvent::PointerButton {
                                 device_id: None,
+                                primary,
                                 state: ElementState::Released,
                                 position,
                                 button: if let UITouchType::Pencil = touch_type {
@@ -579,6 +625,7 @@ impl WinitView {
                         window_id,
                         event: WindowEvent::PointerLeft {
                             device_id: None,
+                            primary,
                             position: Some(position),
                             kind: if let UITouchType::Pencil = touch_type {
                                 PointerKind::Unknown