Change create_custom_cursor() to return Result (#3844)

src/platform_impl/apple/appkit/cursor.rs

@@ -11,7 +11,9 @@ use objc2_foundation::{
     NSString,
 };
 
+use super::OsError;
 use crate::cursor::{CursorImage, OnlyCursorImageSource};
+use crate::error::ExternalError;
 use crate::window::CursorIcon;
 
 #[derive(Clone, Debug, PartialEq, Eq, Hash)]
@@ -23,12 +25,12 @@ unsafe impl Send for CustomCursor {}
 unsafe impl Sync for CustomCursor {}
 
 impl CustomCursor {
-    pub(crate) fn new(cursor: OnlyCursorImageSource) -> CustomCursor {
-        Self(cursor_from_image(&cursor.0))
+    pub(crate) fn new(cursor: OnlyCursorImageSource) -> Result<CustomCursor, ExternalError> {
+        cursor_from_image(&cursor.0).map(Self)
     }
 }
 
-pub(crate) fn cursor_from_image(cursor: &CursorImage) -> Retained<NSCursor> {
+pub(crate) fn cursor_from_image(cursor: &CursorImage) -> Result<Retained<NSCursor>, ExternalError> {
     let width = cursor.width;
     let height = cursor.height;
 
@@ -45,8 +47,8 @@ pub(crate) fn cursor_from_image(cursor: &CursorImage) -> Retained<NSCursor> {
             NSDeviceRGBColorSpace,
             width as isize * 4,
             32,
-        ).unwrap()
-    };
+        )
+    }.ok_or_else(|| ExternalError::Os(os_error!(OsError::CreationError("parent view should be installed in a window"))))?;
     let bitmap_data = unsafe { slice::from_raw_parts_mut(bitmap.bitmapData(), cursor.rgba.len()) };
     bitmap_data.copy_from_slice(&cursor.rgba);
 
@@ -57,7 +59,7 @@ pub(crate) fn cursor_from_image(cursor: &CursorImage) -> Retained<NSCursor> {
 
     let hotspot = NSPoint::new(cursor.hotspot_x as f64, cursor.hotspot_y as f64);
 
-    NSCursor::initWithImage_hotSpot(NSCursor::alloc(), &image, hotspot)
+    Ok(NSCursor::initWithImage_hotSpot(NSCursor::alloc(), &image, hotspot))
 }
 
 pub(crate) fn default_cursor() -> Retained<NSCursor> {

src/platform_impl/apple/appkit/event_loop.rs

@@ -28,7 +28,7 @@ use super::event::dummy_event;
 use super::monitor::{self, MonitorHandle};
 use super::observer::setup_control_flow_observers;
 use crate::application::ApplicationHandler;
-use crate::error::EventLoopError;
+use crate::error::{EventLoopError, ExternalError};
 use crate::event_loop::{ActiveEventLoop as RootWindowTarget, ControlFlow, DeviceEvents};
 use crate::platform::macos::ActivationPolicy;
 use crate::platform::pump_events::PumpStatus;
@@ -85,8 +85,11 @@ impl ActiveEventLoop {
         &self.delegate
     }
 
-    pub fn create_custom_cursor(&self, source: CustomCursorSource) -> RootCustomCursor {
-        RootCustomCursor { inner: CustomCursor::new(source.inner) }
+    pub fn create_custom_cursor(
+        &self,
+        source: CustomCursorSource,
+    ) -> Result<RootCustomCursor, ExternalError> {
+        Ok(RootCustomCursor { inner: CustomCursor::new(source.inner)? })
     }
 
     #[inline]

src/platform_impl/apple/uikit/event_loop.rs

@@ -21,7 +21,7 @@ use super::app_delegate::AppDelegate;
 use super::app_state::{AppState, EventLoopHandler};
 use super::{app_state, monitor, MonitorHandle};
 use crate::application::ApplicationHandler;
-use crate::error::EventLoopError;
+use crate::error::{EventLoopError, ExternalError, NotSupportedError};
 use crate::event::Event;
 use crate::event_loop::{ActiveEventLoop as RootActiveEventLoop, ControlFlow, DeviceEvents};
 use crate::window::{CustomCursor, CustomCursorSource, Theme};
@@ -36,9 +36,11 @@ impl ActiveEventLoop {
         EventLoopProxy::new(AppState::get_mut(self.mtm).proxy_wake_up())
     }
 
-    pub fn create_custom_cursor(&self, source: CustomCursorSource) -> CustomCursor {
-        let _ = source.inner;
-        CustomCursor { inner: super::PlatformCustomCursor }
+    pub fn create_custom_cursor(
+        &self,
+        _source: CustomCursorSource,
+    ) -> Result<CustomCursor, ExternalError> {
+        Err(ExternalError::NotSupported(NotSupportedError::new()))
     }
 
     pub fn available_monitors(&self) -> VecDeque<MonitorHandle> {