Expose monitor physical size

Currently only X11 and Wayland are supported.

Author: remimimimimi

Cargo.toml

@@ -242,6 +242,7 @@ objc2-ui-kit = { version = "0.3.1", default-features = false, features = [
 # Windows
 [target.'cfg(target_os = "windows")'.dependencies]
 unicode-segmentation = "1.7.1"
+scopeguard = "1.2.0"
 windows-sys = { version = "0.59.0", features = [
     "Win32_Devices_HumanInterfaceDevice",
     "Win32_Foundation",
@@ -254,6 +255,7 @@ windows-sys = { version = "0.59.0", features = [
     "Win32_System_LibraryLoader",
     "Win32_System_Ole",
     "Win32_Security",
+    "Win32_System_Registry",
     "Win32_System_SystemInformation",
     "Win32_System_SystemServices",
     "Win32_System_Threading",

src/changelog/unreleased.md

@@ -42,6 +42,7 @@ changelog entry.
 
 ### Added
 
+- Add `MonitorHandle::physical_size()` that returns monitor physical size in millimeters.
 - Add `ActiveEventLoop::create_proxy()`.
 - On Web, add `ActiveEventLoopExtWeb::is_cursor_lock_raw()` to determine if
   `DeviceEvent::MouseMotion` is returning raw data, not OS accelerated, when using

src/monitor.rs

@@ -113,6 +113,27 @@ pub trait MonitorHandleProvider: AsAny + fmt::Debug + Send + Sync {
     #[cfg_attr(not(web_platform), doc = "detailed monitor permissions.")]
     fn position(&self) -> Option<PhysicalPosition<i32>>;
 
+    /// Returns physical size of monitor in millimeters, where the
+    /// first field of a tuple is width and the second is height.
+    ///
+    /// Returns `None` if the size of the monitor could not be determined.
+    ///
+    /// Should be used with care, since not all corner cases may be handled.
+    ///
+    /// If monitor is rotated by 90° or 270°, width and height will be swapped.
+    ///
+    /// Every major platform gets this data from
+    /// [EDID](https://en.wikipedia.org/wiki/Extended_Display_Identification_Data),
+    /// which contains display dimensions in centimeters, and
+    /// optionally higher precision in millimeters. Therefore, by
+    /// convention, we also return millimeters.
+    ///
+    /// ## Platform-specific
+    ///
+    /// - **Wayland:** Has centimeter precision.
+    /// - **iOS / Web / Android / Redox:** Unimplemented, always returns [`None`].
+    fn physical_size(&self) -> Option<(NonZeroU32, NonZeroU32)>;
+
     /// Returns the scale factor of the underlying monitor. To map logical pixels to physical
     /// pixels and vice versa, use [`Window::scale_factor`].
     ///

src/platform_impl/apple/appkit/monitor.rs

@@ -12,7 +12,8 @@ use objc2_app_kit::NSScreen;
 use objc2_core_foundation::{CFArray, CFRetained, CFUUID};
 use objc2_core_graphics::{
     CGDirectDisplayID, CGDisplayBounds, CGDisplayCopyAllDisplayModes, CGDisplayCopyDisplayMode,
-    CGDisplayMode, CGDisplayModelNumber, CGGetActiveDisplayList, CGMainDisplayID,
+    CGDisplayMode, CGDisplayModelNumber, CGDisplayScreenSize, CGGetActiveDisplayList,
+    CGMainDisplayID,
 };
 use objc2_core_video::{kCVReturnSuccess, CVDisplayLink, CVTimeFlags};
 use objc2_foundation::{ns_string, NSNumber, NSPoint, NSRect};
@@ -211,6 +212,18 @@ impl MonitorHandleProvider for MonitorHandle {
         Some(position.to_physical(self.scale_factor()))
     }
 
+    fn physical_size(&self) -> Option<(NonZeroU32, NonZeroU32)> {
+        let size_float = unsafe { CGDisplayScreenSize(self.display_id()) };
+        if size_float.width > 0.0 && size_float.height > 0.0 {
+            Some((
+                NonZeroU32::new(size_float.width.round() as u32)?,
+                NonZeroU32::new(size_float.height.round() as u32)?,
+            ))
+        } else {
+            None
+        }
+    }
+
     fn scale_factor(&self) -> f64 {
         run_on_main(|mtm| {
             match self.ns_screen(mtm) {

src/platform_impl/apple/uikit/monitor.rs

@@ -110,6 +110,13 @@ impl MonitorHandleProvider for MonitorHandle {
         Some((bounds.origin.x as f64, bounds.origin.y as f64).into())
     }
 
+    fn physical_size(&self) -> Option<(NonZeroU32, NonZeroU32)> {
+        // NOTE: There is no way to query the PPI on iOS.
+        // TODO(madsmtm): Use a hardcoded mapping of device models to PPI.
+        // <https://stackoverflow.com/a/28573791>
+        None
+    }
+
     fn scale_factor(&self) -> f64 {
         self.ui_screen.get_on_main(|ui_screen| ui_screen.nativeScale()) as f64
     }

src/platform_impl/linux/wayland/output.rs

@@ -51,6 +51,16 @@ impl CoreMonitorHandle for MonitorHandle {
         }))
     }
 
+    fn physical_size(&self) -> Option<(NonZeroU32, NonZeroU32)> {
+        let output_data = self.proxy.data::<OutputData>().unwrap();
+        let (width_mm, height_mm) = output_data.with_output_info(|oi| oi.physical_size);
+
+        Some((
+            NonZeroU32::new(width_mm.try_into().ok()?)?,
+            NonZeroU32::new(height_mm.try_into().ok()?)?,
+        ))
+    }
+
     fn scale_factor(&self) -> f64 {
         let output_data = self.proxy.data::<OutputData>().unwrap();
         output_data.scale_factor() as f64

src/platform_impl/linux/x11/monitor.rs

@@ -1,7 +1,7 @@
 use std::num::NonZeroU32;
 
 use x11rb::connection::RequestConnection;
-use x11rb::protocol::randr::{self, ConnectionExt as _};
+use x11rb::protocol::randr::{self, ConnectionExt as _, Rotation};
 use x11rb::protocol::xproto;
 
 use super::{util, X11Error, XConnection};
@@ -41,6 +41,8 @@ pub struct MonitorHandle {
     pub(crate) position: (i32, i32),
     /// If the monitor is the primary one
     primary: bool,
+    /// The physical size of a monitor in millimeters.
+    pub(crate) physical_size: Option<(NonZeroU32, NonZeroU32)>,
     /// The DPI scale factor
     pub(crate) scale_factor: f64,
     /// Used to determine which windows are on this monitor
@@ -66,6 +68,10 @@ impl MonitorHandleProvider for MonitorHandle {
         Some(self.position.into())
     }
 
+    fn physical_size(&self) -> Option<(NonZeroU32, NonZeroU32)> {
+        self.physical_size
+    }
+
     fn scale_factor(&self) -> f64 {
         self.scale_factor
     }
@@ -125,19 +131,46 @@ impl MonitorHandle {
         crtc: &randr::GetCrtcInfoReply,
         primary: bool,
     ) -> Option<Self> {
-        let (name, scale_factor, video_modes) = xconn.get_output_info(resources, crtc)?;
+        let (name, mut physical_size, scale_factor, video_modes) =
+            xconn.get_output_info(resources, crtc)?;
+
+        let rotation = xconn
+            .xcb_connection()
+            .randr_get_crtc_info(id, x11rb::CURRENT_TIME)
+            .ok()?
+            .reply()
+            .ok()?
+            .rotation;
+
+        // By default, X11 window system is the only that does not
+        // swap width and height when display is rotated. To match
+        // behaviour with Windows and MacOS we do this manually.
+        if matches!(rotation, Rotation::ROTATE90 | Rotation::ROTATE270) {
+            physical_size = physical_size.map(|(width_mm, height_mm)| (height_mm, width_mm));
+        }
+
         let dimensions = (crtc.width as u32, crtc.height as u32);
         let position = (crtc.x as i32, crtc.y as i32);
 
         let rect = util::AaRect::new(position, dimensions);
 
-        Some(MonitorHandle { id, name, scale_factor, position, primary, rect, video_modes })
+        Some(MonitorHandle {
+            id,
+            name,
+            physical_size,
+            scale_factor,
+            position,
+            primary,
+            rect,
+            video_modes,
+        })
     }
 
     pub fn dummy() -> Self {
         MonitorHandle {
             id: 0,
             name: "<dummy monitor>".into(),
+            physical_size: None,
             scale_factor: 1.0,
             position: (0, 0),
             primary: true,

src/platform_impl/linux/x11/util/randr.rs

@@ -1,4 +1,4 @@
-use std::num::NonZeroU16;
+use std::num::{NonZeroU16, NonZeroU32};
 use std::str::FromStr;
 use std::{env, str};
 
@@ -10,6 +10,8 @@ use crate::dpi::validate_scale_factor;
 use crate::monitor::VideoMode;
 use crate::platform_impl::platform::x11::{monitor, VideoModeHandle};
 
+pub type OutputInfo = (String, Option<(NonZeroU32, NonZeroU32)>, f64, Vec<VideoModeHandle>);
+
 /// Represents values of `WINIT_HIDPI_FACTOR`.
 pub enum EnvVarDPI {
     Randr,
@@ -59,7 +61,7 @@ impl XConnection {
         &self,
         resources: &monitor::ScreenResources,
         crtc: &randr::GetCrtcInfoReply,
-    ) -> Option<(String, f64, Vec<VideoModeHandle>)> {
+    ) -> Option<OutputInfo> {
         let output_info = match self
             .xcb_connection()
             .randr_get_output_info(crtc.outputs[0], x11rb::CURRENT_TIME)
@@ -127,6 +129,10 @@ impl XConnection {
             },
         );
 
+        let physical_size = NonZeroU32::new(output_info.mm_width).and_then(|mm_width| {
+            NonZeroU32::new(output_info.mm_height).map(|mm_height| (mm_width, mm_height))
+        });
+
         let scale_factor = match dpi_env {
             EnvVarDPI::Randr => calc_dpi_factor(
                 (crtc.width.into(), crtc.height.into()),
@@ -153,7 +159,7 @@ impl XConnection {
             },
         };
 
-        Some((name, scale_factor, modes))
+        Some((name, physical_size, scale_factor, modes))
     }
 
     pub fn set_crtc_config(

src/platform_impl/web/monitor.rs

@@ -4,7 +4,7 @@ use std::fmt::{self, Debug, Formatter};
 use std::future::Future;
 use std::hash::{Hash, Hasher};
 use std::mem;
-use std::num::NonZeroU16;
+use std::num::{NonZeroU16, NonZeroU32};
 use std::ops::{Deref, DerefMut};
 use std::pin::Pin;
 use std::rc::{Rc, Weak};
@@ -128,6 +128,21 @@ impl MonitorHandleProvider for MonitorHandle {
         self.id.unwrap_or_default()
     }
 
+    fn physical_size(&self) -> Option<(NonZeroU32, NonZeroU32)> {
+        // NOTE: Browsers expose only CSS-pixel which is different
+        // from the actual pixel. CSS mm also means logical
+        // millimeters, and not an actual millimeter and equivalent to
+        // approximately 3.78px. There are couple of ways to solve
+        // this problem. First one is to stick with approximation, and
+        // other is to explicitly ask user. Both are non-ideal, so no
+        // implementation provided.
+        // References:
+        //
+        //   [1] <https://developer.mozilla.org/en-US/docs/Web/CSS/length#px>
+        //   [2] <https://stackoverflow.com/questions/75533347/how-can-i-get-the-physical-size-of-a-pixel-in-millimeters-at-a-specific-window>
+        None
+    }
+
     fn scale_factor(&self) -> f64 {
         self.inner.queue(|inner| inner.scale_factor())
     }