cocoa: distinguish between horizontal and vertical scroll

we need to switch the x and y deltas when Shift is being held because
macOS switches them around. otherwise we would get a horizontal scroll
on a vertical one and vice versa.

additional we switch from deltaX/Y to scrollingDeltaX/Y since the Apple
docs suggest it's the preferred way now. in my tests both reported the
same values on imprecise scrolls though.

1 files changed, 12 insertions, 2 deletions

diff --git a/video/out/cocoa/events_view.m b/video/out/cocoa/events_view.m
index b9b2bbb9b9..3162e5e9c9 100644
--- a/video/out/cocoa/events_view.m
+++ b/video/out/cocoa/events_view.m
@@ -268,8 +268,18 @@
         [self preciseScroll:event];
     } else {
         const int modifiers = [event modifierFlags];
-        const int mpkey = ([event deltaX] + [event deltaY]) > 0 ?
-                            MP_MOUSE_BTN3 : MP_MOUSE_BTN4;
+        const float deltaX = (modifiers & NSEventModifierFlagShift) ?
+                             [event scrollingDeltaY] : [event scrollingDeltaX];
+        const float deltaY = (modifiers & NSEventModifierFlagShift) ?
+                             [event scrollingDeltaX] : [event scrollingDeltaY];
+        int mpkey;
+
+        if (fabs(deltaY) >= fabs(deltaX)) {
+            mpkey = deltaY > 0 ? MP_MOUSE_BTN3 : MP_MOUSE_BTN4;
+        } else {
+            mpkey = deltaX > 0 ? MP_MOUSE_BTN5 : MP_MOUSE_BTN6;
+        }
+
         [self.adapter putKey:mpkey withModifiers:modifiers];
     }
 }