fix(macOS): cursor_position returns incorrect position (#711)

* On macOS, fix `cursor_position` returns incorrect position

* Add proper error handling

* Restore example

.changes/cursor.md

@@ -0,0 +1,6 @@
+---
+"tao": patch
+---
+
+On macOS, Fix `cursor_position` return incorrect position.
+

src/platform_impl/macos/util/mod.rs

@@ -17,7 +17,11 @@ use cocoa::{
   base::{id, nil},
   foundation::{NSAutoreleasePool, NSPoint, NSRect, NSString, NSUInteger},
 };
-use core_graphics::display::CGDisplay;
+use core_graphics::{
+  display::CGDisplay,
+  event::CGEvent,
+  event_source::{CGEventSource, CGEventSourceStateID},
+};
 use objc::runtime::{Class, Object, Sel, BOOL, YES};
 
 use crate::{
@@ -124,11 +128,17 @@ pub fn window_position(position: LogicalPosition<f64>) -> NSPoint {
   )
 }
 
+// FIXME: This is actually logical position.
 pub fn cursor_position() -> Result<PhysicalPosition<f64>, ExternalError> {
-  unsafe {
-    let pt: NSPoint = msg_send![class!(NSEvent), mouseLocation];
-    Ok((pt.x, pt.y).into())
+  if let Ok(s) = CGEventSource::new(CGEventSourceStateID::CombinedSessionState) {
+    if let Ok(e) = CGEvent::new(s) {
+      let pt = e.location();
+      let pos = PhysicalPosition::new(pt.x, pt.y);
+      return Ok(pos);
+    }
   }
+
+  return Err(ExternalError::Os(os_error!(super::OsError::CGError(0))));
 }
 
 pub unsafe fn ns_string_id_ref(s: &str) -> IdRef {