Move AppKit (macOS) backend to winit-appkit (#4248)

winit-appkit/src/monitor.rs

@@ -0,0 +1,403 @@
+#![allow(clippy::unnecessary_cast)]
+
+use std::collections::VecDeque;
+use std::num::{NonZeroU16, NonZeroU32};
+use std::ptr::NonNull;
+use std::{fmt, ptr};
+
+use dispatch2::run_on_main;
+use dpi::{LogicalPosition, PhysicalPosition, PhysicalSize};
+use objc2::rc::Retained;
+use objc2::MainThreadMarker;
+use objc2_app_kit::NSScreen;
+use objc2_core_foundation::{CFArray, CFRetained, CFUUID};
+use objc2_core_graphics::{
+    CGDirectDisplayID, CGDisplayBounds, CGDisplayCopyAllDisplayModes, CGDisplayCopyDisplayMode,
+    CGDisplayMode, CGDisplayModelNumber, CGGetActiveDisplayList, CGMainDisplayID,
+};
+use objc2_core_video::{kCVReturnSuccess, CVDisplayLink, CVTimeFlags};
+use objc2_foundation::{ns_string, NSNumber, NSPoint, NSRect};
+use tracing::warn;
+use winit_core::monitor::{MonitorHandleProvider, VideoMode};
+
+use super::ffi;
+use super::util::cgerr;
+
+#[derive(Clone)]
+pub struct VideoModeHandle {
+    pub(crate) mode: VideoMode,
+    pub(crate) monitor: MonitorHandle,
+    pub(crate) native_mode: NativeDisplayMode,
+}
+
+impl PartialEq for VideoModeHandle {
+    fn eq(&self, other: &Self) -> bool {
+        self.monitor == other.monitor && self.mode == other.mode
+    }
+}
+
+impl Eq for VideoModeHandle {}
+
+impl std::hash::Hash for VideoModeHandle {
+    fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
+        self.monitor.hash(state);
+    }
+}
+
+impl std::fmt::Debug for VideoModeHandle {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.debug_struct("VideoModeHandle")
+            .field("mode", &self.mode)
+            .field("monitor", &self.monitor)
+            .finish()
+    }
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub struct NativeDisplayMode(pub CFRetained<CGDisplayMode>);
+
+unsafe impl Send for NativeDisplayMode {}
+unsafe impl Sync for NativeDisplayMode {}
+
+impl VideoModeHandle {
+    fn new(
+        monitor: MonitorHandle,
+        native_mode: NativeDisplayMode,
+        refresh_rate_millihertz: Option<NonZeroU32>,
+    ) -> Self {
+        unsafe {
+            // The bit-depth is basically always 32 since macOS 10.12.
+            #[allow(deprecated)]
+            let pixel_encoding =
+                CGDisplayMode::pixel_encoding(Some(&native_mode.0)).unwrap().to_string();
+            let bit_depth = if pixel_encoding.eq_ignore_ascii_case(ffi::IO32BitDirectPixels) {
+                NonZeroU16::new(32)
+            } else if pixel_encoding.eq_ignore_ascii_case(ffi::IO16BitDirectPixels) {
+                NonZeroU16::new(16)
+            } else if pixel_encoding.eq_ignore_ascii_case(ffi::kIO30BitDirectPixels) {
+                NonZeroU16::new(30)
+            } else if pixel_encoding.eq_ignore_ascii_case(ffi::kIO64BitDirectPixels) {
+                NonZeroU16::new(64)
+            } else {
+                warn!(?pixel_encoding, "unknown bit depth");
+                None
+            };
+
+            let mode = VideoMode::new(
+                PhysicalSize::new(
+                    CGDisplayMode::pixel_width(Some(&native_mode.0)) as u32,
+                    CGDisplayMode::pixel_height(Some(&native_mode.0)) as u32,
+                ),
+                bit_depth,
+                refresh_rate_millihertz,
+            );
+
+            VideoModeHandle { mode, monitor: monitor.clone(), native_mode }
+        }
+    }
+}
+
+/// `CGDirectDisplayID` is documented as:
+/// > a framebuffer, a color correction (gamma) table, and possibly an attached monitor.
+///
+/// That is, it doesn't actually represent the monitor itself. Instead, we use the UUID of the
+/// monitor, as retrieved from `CGDisplayCreateUUIDFromDisplayID` (this makes the monitor ID stable,
+/// even across reboots and video mode changes).
+///
+/// NOTE: I'd be perfectly valid to store `[u8; 16]` in here instead, we only store `CFUUID` to
+/// avoid having to re-create it when we want to fetch the display ID.
+#[derive(Clone, PartialEq, Eq, Hash)]
+pub struct MonitorHandle(CFRetained<CFUUID>);
+
+impl MonitorHandle {
+    /// Internal comparisons of [`MonitorHandle`]s are done first requesting a UUID for the handle.
+    fn uuid(&self) -> u128 {
+        u128::from_ne_bytes(self.0.uuid_bytes().into())
+    }
+
+    fn display_id(&self) -> CGDirectDisplayID {
+        unsafe { ffi::CGDisplayGetDisplayIDFromUUID(&self.0) }
+    }
+
+    #[track_caller]
+    pub(crate) fn new(display_id: CGDirectDisplayID) -> Option<Self> {
+        // kCGNullDirectDisplay
+        if display_id == 0 {
+            // `CGDisplayCreateUUIDFromDisplayID` checks kCGNullDirectDisplay internally.
+            warn!("constructing monitor from invalid display ID 0; falling back to main monitor");
+        }
+        // SAFETY: Valid to call.
+        let ptr = unsafe { ffi::CGDisplayCreateUUIDFromDisplayID(display_id) };
+        let ptr = NonNull::new(ptr)?;
+        // SAFETY: `CGDisplayCreateUUIDFromDisplayID` is a "create" function, so the pointer has
+        // +1 retain count.
+        let uuid = unsafe { CFRetained::from_raw(ptr) };
+        Some(Self(uuid))
+    }
+
+    fn refresh_rate_millihertz(&self) -> Option<NonZeroU32> {
+        let current_display_mode =
+            NativeDisplayMode(unsafe { CGDisplayCopyDisplayMode(self.display_id()) }.unwrap());
+        refresh_rate_millihertz(self.display_id(), &current_display_mode)
+    }
+
+    pub fn video_mode_handles(&self) -> impl Iterator<Item = VideoModeHandle> {
+        let refresh_rate_millihertz = self.refresh_rate_millihertz();
+        let monitor = self.clone();
+
+        let array = unsafe { CGDisplayCopyAllDisplayModes(self.display_id(), None) };
+        let modes = if let Some(array) = array {
+            // SAFETY: `CGDisplayCopyAllDisplayModes` is documented to return an array of
+            // display modes.
+            unsafe { CFRetained::cast_unchecked::<CFArray<CGDisplayMode>>(array) }
+        } else {
+            // Occasionally, certain CalDigit Thunderbolt Hubs report a spurious monitor during
+            // sleep/wake/cycling monitors. It tends to have null or 1 video mode only.
+            // See <https://github.com/bevyengine/bevy/issues/17827>.
+            warn!(monitor = ?self, "failed to get a list of display modes");
+            CFArray::empty()
+        };
+
+        modes.into_iter().map(move |mode| {
+            let cg_refresh_rate_hertz = unsafe { CGDisplayMode::refresh_rate(Some(&mode)) };
+
+            // CGDisplayModeGetRefreshRate returns 0.0 for any display that
+            // isn't a CRT
+            let refresh_rate_millihertz = if cg_refresh_rate_hertz > 0.0 {
+                NonZeroU32::new((cg_refresh_rate_hertz * 1000.0).round() as u32)
+            } else {
+                refresh_rate_millihertz
+            };
+
+            VideoModeHandle::new(monitor.clone(), NativeDisplayMode(mode), refresh_rate_millihertz)
+        })
+    }
+
+    pub(crate) fn ns_screen(&self, mtm: MainThreadMarker) -> Option<Retained<NSScreen>> {
+        let uuid = self.uuid();
+        NSScreen::screens(mtm).into_iter().find(|screen| {
+            let other_native_id = get_display_id(screen);
+            if let Some(other) = MonitorHandle::new(other_native_id) {
+                uuid == other.uuid()
+            } else {
+                // Display ID was just fetched from live NSScreen, but can still result in `None`
+                // with certain Thunderbolt docked monitors.
+                warn!(other_native_id, "comparing against screen with invalid display ID");
+                false
+            }
+        })
+    }
+}
+
+impl MonitorHandleProvider for MonitorHandle {
+    fn id(&self) -> u128 {
+        self.uuid()
+    }
+
+    fn native_id(&self) -> u64 {
+        self.display_id() as _
+    }
+
+    // TODO: Be smarter about this:
+    //
+    // <https://github.com/glfw/glfw/blob/57cbded0760a50b9039ee0cb3f3c14f60145567c/src/cocoa_monitor.m#L44-L126>
+    fn name(&self) -> Option<std::borrow::Cow<'_, str>> {
+        let screen_num = unsafe { CGDisplayModelNumber(self.display_id()) };
+        Some(format!("Monitor #{screen_num}").into())
+    }
+
+    fn position(&self) -> Option<PhysicalPosition<i32>> {
+        // This is already in screen coordinates. If we were using `NSScreen`,
+        // then a conversion would've been needed:
+        // flip_window_screen_coordinates(self.ns_screen(mtm)?.frame())
+        let bounds = unsafe { CGDisplayBounds(self.display_id()) };
+        let position = LogicalPosition::new(bounds.origin.x, bounds.origin.y);
+        Some(position.to_physical(self.scale_factor()))
+    }
+
+    fn scale_factor(&self) -> f64 {
+        run_on_main(|mtm| {
+            match self.ns_screen(mtm) {
+                Some(screen) => screen.backingScaleFactor() as f64,
+                None => 1.0, // default to 1.0 when we can't find the screen
+            }
+        })
+    }
+
+    fn current_video_mode(&self) -> Option<VideoMode> {
+        let mode =
+            NativeDisplayMode(unsafe { CGDisplayCopyDisplayMode(self.display_id()) }.unwrap());
+        let refresh_rate_millihertz = refresh_rate_millihertz(self.display_id(), &mode);
+        Some(VideoModeHandle::new(self.clone(), mode, refresh_rate_millihertz).mode)
+    }
+
+    fn video_modes(&self) -> Box<dyn Iterator<Item = VideoMode>> {
+        Box::new(self.video_mode_handles().map(|mode| mode.mode))
+    }
+}
+
+pub fn available_monitors() -> VecDeque<MonitorHandle> {
+    let mut expected_count = 0;
+    let res = cgerr(unsafe { CGGetActiveDisplayList(0, ptr::null_mut(), &mut expected_count) });
+    if res.is_err() {
+        return VecDeque::with_capacity(0);
+    }
+
+    let mut displays: Vec<CGDirectDisplayID> = vec![0; expected_count as usize];
+    let mut actual_count = 0;
+    let res = cgerr(unsafe {
+        CGGetActiveDisplayList(expected_count, displays.as_mut_ptr(), &mut actual_count)
+    });
+    displays.truncate(actual_count as usize);
+
+    if res.is_err() {
+        return VecDeque::with_capacity(0);
+    }
+
+    let mut monitors = VecDeque::with_capacity(displays.len());
+    for display in displays {
+        // Display ID just fetched from `CGGetActiveDisplayList`, should be fine to unwrap.
+        monitors.push_back(MonitorHandle::new(display).expect("invalid display ID"));
+    }
+    monitors
+}
+
+pub fn primary_monitor() -> MonitorHandle {
+    // Display ID just fetched from `CGMainDisplayID`, should be fine to unwrap.
+    MonitorHandle::new(unsafe { CGMainDisplayID() }).expect("invalid display ID")
+}
+
+impl fmt::Debug for MonitorHandle {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("MonitorHandle")
+            .field("name", &self.name())
+            .field("uuid", &self.uuid())
+            .field("display_id", &self.display_id())
+            .field("position", &self.position())
+            .field("scale_factor", &self.scale_factor())
+            .finish_non_exhaustive()
+    }
+}
+
+pub(crate) fn get_display_id(screen: &NSScreen) -> u32 {
+    let key = ns_string!("NSScreenNumber");
+
+    objc2::rc::autoreleasepool(|_| {
+        let device_description = screen.deviceDescription();
+
+        // Retrieve the CGDirectDisplayID associated with this screen
+        //
+        // The value from @"NSScreenNumber" in deviceDescription is guaranteed
+        // to be an NSNumber. See documentation for details:
+        // <https://developer.apple.com/documentation/appkit/nsscreen/1388360-devicedescription?language=objc>
+        let obj = device_description
+            .objectForKey(key)
+            .expect("failed getting screen display id from device description")
+            .downcast::<NSNumber>()
+            .expect("NSScreenNumber must be NSNumber");
+
+        obj.as_u32()
+    })
+}
+
+/// Core graphics screen coordinates are relative to the top-left corner of
+/// the so-called "main" display, with y increasing downwards - which is
+/// exactly what we want in Winit.
+///
+/// However, `NSWindow` and `NSScreen` changes these coordinates to:
+/// 1. Be relative to the bottom-left corner of the "main" screen.
+/// 2. Be relative to the bottom-left corner of the window/screen itself.
+/// 3. Have y increasing upwards.
+///
+/// This conversion happens to be symmetric, so we only need this one function
+/// to convert between the two coordinate systems.
+pub(crate) fn flip_window_screen_coordinates(frame: NSRect) -> NSPoint {
+    // It is intentional that we use `CGMainDisplayID` (as opposed to
+    // `NSScreen::mainScreen`), because that's what the screen coordinates
+    // are relative to, no matter which display the window is currently on.
+    let main_screen_height = unsafe { CGDisplayBounds(CGMainDisplayID()) }.size.height;
+
+    let y = main_screen_height - frame.size.height - frame.origin.y;
+    NSPoint::new(frame.origin.x, y)
+}
+
+fn refresh_rate_millihertz(id: CGDirectDisplayID, mode: &NativeDisplayMode) -> Option<NonZeroU32> {
+    unsafe {
+        let refresh_rate = CGDisplayMode::refresh_rate(Some(&mode.0));
+        if refresh_rate > 0.0 {
+            return NonZeroU32::new((refresh_rate * 1000.0).round() as u32);
+        }
+
+        let mut display_link = std::ptr::null_mut();
+        #[allow(deprecated)]
+        if CVDisplayLink::create_with_cg_display(id, NonNull::from(&mut display_link))
+            != kCVReturnSuccess
+        {
+            return None;
+        }
+        let display_link = CFRetained::from_raw(NonNull::new(display_link).unwrap());
+        #[allow(deprecated)]
+        let time = display_link.nominal_output_video_refresh_period();
+
+        // This value is indefinite if an invalid display link was specified
+        if time.flags & CVTimeFlags::IsIndefinite.0 != 0 {
+            return None;
+        }
+
+        (time.timeScale as i64)
+            .checked_div(time.timeValue)
+            .map(|v| (v * 1000) as u32)
+            .and_then(NonZeroU32::new)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn uuid_stable() {
+        let handle_a = MonitorHandle::new(1).unwrap();
+        let handle_b = MonitorHandle::new(1).unwrap();
+        assert_eq!(handle_a, handle_b);
+        assert_eq!(handle_a.display_id(), handle_b.display_id());
+        assert_eq!(handle_a.uuid(), handle_b.uuid());
+
+        let handle_a = primary_monitor();
+        let handle_b = primary_monitor();
+        assert_eq!(handle_a, handle_b);
+        assert_eq!(handle_a.display_id(), handle_b.display_id());
+        assert_eq!(handle_a.uuid(), handle_b.uuid());
+    }
+
+    /// Test the MonitorHandle::new fallback.
+    #[test]
+    fn monitorhandle_from_zero() {
+        let handle0 = MonitorHandle::new(0).unwrap();
+        let handle1 = MonitorHandle::new(1).unwrap();
+        assert_eq!(handle0, handle1);
+        assert_eq!(handle0.display_id(), handle1.display_id());
+        assert_eq!(handle0.uuid(), handle1.uuid());
+    }
+
+    #[test]
+    fn from_invalid_id() {
+        // Assume there are never this many monitors connected.
+        assert!(MonitorHandle::new(10000).is_none());
+    }
+
+    /// Test that calling `CGDisplayGetDisplayIDFromUUID` on an invalid UUID returns an invalid
+    /// display ID.
+    #[test]
+    fn invalid_monitor_handle() {
+        // `CGMainDisplayID` must be called to avoid:
+        // ```
+        // Assertion failed: (did_initialize), function CGS_REQUIRE_INIT, file CGInitialization.c, line 44.
+        // ```
+        // See https://github.com/JXA-Cookbook/JXA-Cookbook/issues/27#issuecomment-277517668
+        let _ = unsafe { CGMainDisplayID() };
+
+        let handle = MonitorHandle(CFUUID::new(None).unwrap());
+        assert_eq!(handle.display_id(), 0);
+    }
+}