Don't change cursor on mouse move while mouse button is held down

gpui/src/platform/event.rs

@@ -24,5 +24,6 @@ pub enum Event {
     },
     MouseMoved {
         position: Vector2F,
+        left_mouse_down: bool,
     },
 }

gpui/src/platform/mac/event.rs

@@ -6,8 +6,8 @@ use cocoa::appkit::{
     NSUpArrowFunctionKey as ARROW_UP_KEY,
 };
 use cocoa::{
-    appkit::{NSEvent as _, NSEventModifierFlags, NSEventType},
-    base::{id, YES},
+    appkit::{NSEvent, NSEventModifierFlags, NSEventType},
+    base::{id, nil, YES},
     foundation::NSString as _,
 };
 use std::{ffi::CStr, os::raw::c_char};
@@ -116,6 +116,7 @@ impl Event {
                     native_event.locationInWindow().x as f32,
                     window_height - native_event.locationInWindow().y as f32,
                 ),
+                left_mouse_down: NSEvent::pressedMouseButtons(nil) & 1 != 0,
             }),
             _ => None,
         }