Support listing available video modes for a monitor (#896)

* Support listing available video modes for a monitor

* Use derivative for Windows `MonitorHandle`

* Update FEATURES.md

* Fix multiline if statement

* Add documentation for `VideoMode` type

CHANGELOG.md

@@ -40,6 +40,7 @@
 - Rename several functions to improve both internal consistency and compliance with Rust API guidelines.
 - Remove `WindowBuilder::multitouch` field, since it was only implemented on a few platforms. Multitouch is always enabled now.
 - **Breaking:** On macOS, change `ns` identifiers to use snake_case for consistency with iOS's `ui` identifiers.
+- Add `MonitorHandle::video_modes` method for retrieving supported video modes for the given monitor.
 
 # Version 0.19.1 (2019-04-08)
 

Cargo.toml

@@ -18,6 +18,7 @@ lazy_static = "1"
 libc = "0.2"
 log = "0.4"
 serde = { version = "1", optional = true, features = ["serde_derive"] }
+derivative = "1.0.2"
 
 [dev-dependencies]
 image = "0.21"
@@ -33,6 +34,7 @@ objc = "0.2.3"
 cocoa = "0.18.4"
 core-foundation = "0.6"
 core-graphics = "0.17.3"
+core-video-sys = "0.1.2"
 dispatch = "0.1.4"
 objc = "0.2.3"
 

FEATURES.md

@@ -92,6 +92,7 @@ If your PR makes notable changes to Winit's features, please update this section
 
 ### System Information
 - **Monitor list**: Retrieve the list of monitors and their metadata, including which one is primary.
+- **Video mode query**: Monitors can be queried for their supported fullscreen video modes (consisting of resolution, refresh rate, and bit depth).
 
 ### Input Handling
 - **Mouse events**: Generating mouse events associated with pointer motion, click, and scrolling events.
@@ -161,8 +162,9 @@ Legend:
 
 ### System information
 |Feature          |Windows|MacOS |Linux x11|Linux Wayland|Android|iOS    |Emscripten|
-|------------ | ----- | ---- | ------- | ----------- | ----- | ----- | -------- |
+|---------------- | ----- | ---- | ------- | ----------- | ----- | ----- | -------- |
 |Monitor list     |✔️    |✔️    |✔️       |✔️          |**N/A**|**N/A**|**N/A**   |
+|Video mode query |✔️    |✔️    |✔️       |✔️          |❌      |✔️     |❌         |
 
 ### Input handling
 |Feature                 |Windows   |MacOS   |Linux x11|Linux Wayland|Android|iOS    |Emscripten|

examples/video_modes.rs

@@ -0,0 +1,14 @@
+extern crate winit;
+
+use winit::event_loop::EventLoop;
+
+fn main() {
+    let event_loop = EventLoop::new();
+    let monitor = event_loop.primary_monitor();
+
+    println!("Listing available video modes:");
+
+    for mode in monitor.video_modes() {
+        println!("{:?}", mode);
+    }
+}

src/lib.rs

@@ -84,6 +84,8 @@ extern crate log;
 #[cfg(feature = "serde")]
 #[macro_use]
 extern crate serde;
+#[macro_use]
+extern crate derivative;
 
 #[cfg(target_os = "windows")]
 extern crate winapi;
@@ -101,6 +103,8 @@ extern crate dispatch;
 extern crate core_foundation;
 #[cfg(target_os = "macos")]
 extern crate core_graphics;
+#[cfg(target_os = "macos")]
+extern crate core_video_sys;
 #[cfg(any(target_os = "linux", target_os = "dragonfly", target_os = "freebsd", target_os = "netbsd", target_os = "openbsd"))]
 extern crate x11_dl;
 #[cfg(any(target_os = "linux", target_os = "dragonfly", target_os = "freebsd", target_os = "netbsd", target_os = "openbsd", target_os = "windows"))]

src/monitor.rs

@@ -44,6 +44,45 @@ impl Iterator for AvailableMonitorsIter {
     }
 }
 
+/// Describes a fullscreen video mode of a monitor.
+///
+/// Can be acquired with:
+/// - [`MonitorHandle::video_modes`][monitor_get].
+///
+/// [monitor_get]: ../monitor/struct.MonitorHandle.html#method.video_modes
+#[derive(Debug, Clone, Eq, PartialEq, Hash)]
+pub struct VideoMode {
+    pub(crate) dimensions: (u32, u32),
+    pub(crate) bit_depth: u16,
+    pub(crate) refresh_rate: u16,
+}
+
+impl VideoMode {
+    /// Returns the resolution of this video mode.
+    pub fn dimensions(&self) -> PhysicalSize {
+        self.dimensions.into()
+    }
+
+    /// Returns the bit depth of this video mode, as in how many bits you have
+    /// available per color. This is generally 24 bits or 32 bits on modern
+    /// systems, depending on whether the alpha channel is counted or not.
+    ///
+    /// ## Platform-specific
+    ///
+    /// - **Wayland:** Always returns 32.
+    /// - **iOS:** Always returns 32.
+    pub fn bit_depth(&self) -> u16 {
+        self.bit_depth
+    }
+
+    /// Returns the refresh rate of this video mode. **Note**: the returned
+    /// refresh rate is an integer approximation, and you shouldn't rely on this
+    /// value to be exact.
+    pub fn refresh_rate(&self) -> u16 {
+        self.refresh_rate
+    }
+}
+
 /// Handle to a monitor.
 ///
 /// Allows you to retrieve information about a given monitor and can be used in [`Window`] creation.
@@ -88,4 +127,10 @@ impl MonitorHandle {
     pub fn hidpi_factor(&self) -> f64 {
         self.inner.hidpi_factor()
     }
+
+    /// Returns all fullscreen video modes supported by this monitor.
+    #[inline]
+    pub fn video_modes(&self) -> impl Iterator<Item = VideoMode> {
+        self.inner.video_modes()
+    }
 }

src/platform_impl/ios/monitor.rs

@@ -1,18 +1,13 @@
 use std::{
-    collections::VecDeque,
+    collections::{HashSet, VecDeque},
     fmt,
     ops::{Deref, DerefMut},
 };
 
 use dpi::{PhysicalPosition, PhysicalSize};
+use monitor::VideoMode;
 
-use platform_impl::platform::ffi::{
-    id,
-    nil,
-    CGFloat,
-    CGRect,
-    NSUInteger,
-};
+use platform_impl::platform::ffi::{id, nil, CGFloat, CGRect, CGSize, NSInteger, NSUInteger};
 
 pub struct Inner {
     uiscreen: id,
@@ -134,6 +129,27 @@ impl Inner {
             scale as f64
         }
     }
+
+    pub fn video_modes(&self) -> impl Iterator<Item = VideoMode> {
+        let refresh_rate: NSInteger = unsafe { msg_send![self.uiscreen, maximumFramesPerSecond] };
+
+        let available_modes: id = unsafe { msg_send![self.uiscreen, availableModes] };
+        let available_mode_count: NSUInteger = unsafe { msg_send![available_modes, count] };
+
+        let mut modes = HashSet::with_capacity(available_mode_count);
+
+        for i in 0..available_mode_count {
+            let mode: id = unsafe { msg_send![available_modes, objectAtIndex: i] };
+            let size: CGSize = unsafe { msg_send![mode, size] };
+            modes.insert(VideoMode {
+                dimensions: (size.width as u32, size.height as u32),
+                bit_depth: 32,
+                refresh_rate: refresh_rate as u16,
+            });
+        }
+
+        modes.into_iter()
+    }
 }
 
 // MonitorHandleExtIOS

src/platform_impl/linux/mod.rs

@@ -14,7 +14,7 @@ use icon::Icon;
 use error::{ExternalError, NotSupportedError, OsError as RootOsError};
 use event::Event;
 use event_loop::{EventLoopClosed, ControlFlow, EventLoopWindowTarget as RootELW};
-use monitor::MonitorHandle as RootMonitorHandle;
+use monitor::{MonitorHandle as RootMonitorHandle, VideoMode};
 use window::{WindowAttributes, CursorIcon};
 use self::x11::{XConnection, XError};
 use self::x11::ffi::XVisualInfo;
@@ -142,6 +142,14 @@ impl MonitorHandle {
             &MonitorHandle::Wayland(ref m) => m.hidpi_factor() as f64,
         }
     }
+
+    #[inline]
+    pub fn video_modes(&self) -> Box<dyn Iterator<Item = VideoMode>> {
+        match self {
+            MonitorHandle::X(m) => Box::new(m.video_modes()),
+            MonitorHandle::Wayland(m) => Box::new(m.video_modes()),
+        }
+    }
 }
 
 impl Window {

src/platform_impl/linux/wayland/event_loop.rs

@@ -9,6 +9,7 @@ use event_loop::{ControlFlow, EventLoopClosed, EventLoopWindowTarget as RootELW}
 use event::ModifiersState;
 use dpi::{PhysicalPosition, PhysicalSize};
 use platform_impl::platform::sticky_exit_callback;
+use monitor::VideoMode;
 
 use super::window::WindowStore;
 use super::WindowId;
@@ -584,6 +585,20 @@ impl MonitorHandle {
             .with_info(&self.proxy, |_, info| info.scale_factor)
             .unwrap_or(1)
     }
+
+    #[inline]
+    pub fn video_modes(&self) -> impl Iterator<Item = VideoMode>
+    {
+        self.mgr
+            .with_info(&self.proxy, |_, info| info.modes.clone())
+            .unwrap_or(vec![])
+            .into_iter()
+            .map(|x| VideoMode {
+                dimensions: (x.dimensions.0 as u32, x.dimensions.1 as u32),
+                refresh_rate: (x.refresh_rate as f32 / 1000.0).round() as u16,
+                bit_depth: 32
+            })
+    }
 }
 
 pub fn primary_monitor(outputs: &OutputMgr) -> MonitorHandle {

src/platform_impl/linux/x11/monitor.rs

@@ -3,6 +3,7 @@ use std::os::raw::*;
 use parking_lot::Mutex;
 
 use dpi::{PhysicalPosition, PhysicalSize};
+use monitor::VideoMode;
 use super::{util, XConnection, XError};
 use super::ffi::{
     RRCrtcChangeNotifyMask,
@@ -56,6 +57,8 @@ pub struct MonitorHandle {
     pub(crate) hidpi_factor: f64,
     /// Used to determine which windows are on this monitor
     pub(crate) rect: util::AaRect,
+    /// Supported video modes on this monitor
+    video_modes: Vec<VideoMode>,
 }
 
 impl MonitorHandle {
@@ -66,7 +69,7 @@ impl MonitorHandle {
         repr: util::MonitorRepr,
         primary: bool,
     ) -> Option<Self> {
-        let (name, hidpi_factor) = unsafe { xconn.get_output_info(resources, &repr)? };
+        let (name, hidpi_factor, video_modes) = unsafe { xconn.get_output_info(resources, &repr)? };
         let (dimensions, position) = unsafe { (repr.dimensions(), repr.position()) };
         let rect = util::AaRect::new(position, dimensions);
         Some(MonitorHandle {
@@ -77,6 +80,7 @@ impl MonitorHandle {
             position,
             primary,
             rect,
+            video_modes,
         })
     }
 
@@ -101,6 +105,11 @@ impl MonitorHandle {
     pub fn hidpi_factor(&self) -> f64 {
         self.hidpi_factor
     }
+
+    #[inline]
+    pub fn video_modes(&self) -> impl Iterator<Item = VideoMode> {
+        self.video_modes.clone().into_iter()
+    }
 }
 
 impl XConnection {

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

@@ -1,6 +1,7 @@
 use std::{env, slice};
 use std::str::FromStr;
 
+use monitor::VideoMode;
 use dpi::validate_hidpi_factor;
 use super::*;
 
@@ -101,7 +102,7 @@ impl XConnection {
         &self,
         resources: *mut ffi::XRRScreenResources,
         repr: &MonitorRepr,
-    ) -> Option<(String, f64)> {
+    ) -> Option<(String, f64, Vec<VideoMode>)> {
         let output_info = (self.xrandr.XRRGetOutputInfo)(
             self.display,
             resources,
@@ -114,6 +115,33 @@ impl XConnection {
             let _ = self.check_errors(); // discard `BadRROutput` error
             return None;
         }
+
+        let screen = (self.xlib.XDefaultScreen)(self.display);
+        let bit_depth = (self.xlib.XDefaultDepth)(self.display, screen);
+
+        let output_modes =
+            slice::from_raw_parts((*output_info).modes, (*output_info).nmode as usize);
+        let resource_modes = slice::from_raw_parts((*resources).modes, (*resources).nmode as usize);
+
+        let modes = resource_modes
+            .iter()
+            // XRROutputInfo contains an array of mode ids that correspond to
+            // modes in the array in XRRScreenResources
+            .filter(|x| output_modes.iter().any(|id| x.id == *id))
+            .map(|x| {
+                let refresh_rate = if x.dotClock > 0 && x.hTotal > 0 && x.vTotal > 0 {
+                    x.dotClock as u64 * 1000 / (x.hTotal as u64 * x.vTotal as u64)
+                } else {
+                    0
+                };
+
+                VideoMode {
+                    dimensions: (x.width, x.height),
+                    refresh_rate: (refresh_rate as f32 / 1000.0).round() as u16,
+                    bit_depth: bit_depth as u16,
+                }
+            });
+
         let name_slice = slice::from_raw_parts(
             (*output_info).name as *mut u8,
             (*output_info).nameLen as usize,
@@ -129,6 +157,6 @@ impl XConnection {
         };
 
         (self.xrandr.XRRFreeOutputInfo)(output_info);
-        Some((name, hidpi_factor))
+        Some((name, hidpi_factor, modes.collect()))
     }
 }

src/platform_impl/macos/monitor.rs

@@ -1,9 +1,18 @@
 use std::{collections::VecDeque, fmt};
 
-use cocoa::{appkit::NSScreen, base::{id, nil}, foundation::{NSString, NSUInteger}};
-use core_graphics::display::{CGDirectDisplayID, CGDisplay, CGDisplayBounds};
+use cocoa::{
+    appkit::NSScreen,
+    base::{id, nil},
+    foundation::{NSString, NSUInteger},
+};
+use core_graphics::display::{CGDirectDisplayID, CGDisplay, CGDisplayBounds, CGDisplayMode};
+use core_video_sys::{
+    kCVReturnSuccess, kCVTimeIsIndefinite, CVDisplayLinkCreateWithCGDisplay,
+    CVDisplayLinkGetNominalOutputVideoRefreshPeriod, CVDisplayLinkRelease,
+};
 
 use dpi::{PhysicalPosition, PhysicalSize};
+use monitor::VideoMode;
 use platform_impl::platform::util::IdRef;
 
 #[derive(Clone, PartialEq)]
@@ -93,6 +102,44 @@ impl MonitorHandle {
         unsafe { NSScreen::backingScaleFactor(screen) as f64 }
     }
 
+    pub fn video_modes(&self) -> impl Iterator<Item = VideoMode> {
+        let cv_refresh_rate = unsafe {
+            let mut display_link = std::ptr::null_mut();
+            assert_eq!(
+                CVDisplayLinkCreateWithCGDisplay(self.0, &mut display_link),
+                kCVReturnSuccess
+            );
+            let time = CVDisplayLinkGetNominalOutputVideoRefreshPeriod(display_link);
+            CVDisplayLinkRelease(display_link);
+
+            // This value is indefinite if an invalid display link was specified
+            assert!(time.flags & kCVTimeIsIndefinite == 0);
+
+            time.timeScale as i64 / time.timeValue
+        };
+
+        CGDisplayMode::all_display_modes(self.0, std::ptr::null())
+            .expect("failed to obtain list of display modes")
+            .into_iter()
+            .map(move |mode| {
+                let cg_refresh_rate = mode.refresh_rate().round() as i64;
+
+                // CGDisplayModeGetRefreshRate returns 0.0 for any display that
+                // isn't a CRT
+                let refresh_rate = if cg_refresh_rate > 0 {
+                    cg_refresh_rate
+                } else {
+                    cv_refresh_rate
+                };
+
+                VideoMode {
+                    dimensions: (mode.width() as u32, mode.height() as u32),
+                    refresh_rate: refresh_rate as u16,
+                    bit_depth: mode.bit_depth() as u16,
+                }
+            })
+    }
+
     pub(crate) fn ns_screen(&self) -> Option<id> {
         unsafe {
             let native_id = self.native_identifier();

src/platform_impl/windows/monitor.rs

@@ -1,21 +1,25 @@
-use winapi::shared::minwindef::{BOOL, DWORD, LPARAM, TRUE};
+use winapi::shared::minwindef::{BOOL, DWORD, LPARAM, TRUE, WORD};
 use winapi::shared::windef::{HDC, HMONITOR, HWND, LPRECT, POINT};
 use winapi::um::winnt::LONG;
-use winapi::um::winuser;
+use winapi::um::{wingdi, winuser};
 
-use std::{mem, ptr, io};
-use std::collections::VecDeque;
+use std::collections::{HashSet, VecDeque};
+use std::{io, mem, ptr};
 
-use super::{EventLoop, util};
+use super::{util, EventLoop};
 use dpi::{PhysicalPosition, PhysicalSize};
+use monitor::VideoMode;
 use platform_impl::platform::dpi::{dpi_to_scale_factor, get_monitor_dpi};
 use platform_impl::platform::window::Window;
 
 /// Win32 implementation of the main `MonitorHandle` object.
-#[derive(Debug, Clone)]
+#[derive(Derivative)]
+#[derivative(Debug, Clone)]
 pub struct MonitorHandle {
     /// Monitor handle.
     hmonitor: HMonitor,
+    #[derivative(Debug = "ignore")]
+    monitor_info: winuser::MONITORINFOEXW,
     /// The system name of the monitor.
     monitor_name: String,
     /// True if this is the primary monitor.
@@ -130,6 +134,7 @@ impl MonitorHandle {
             position: (place.left as i32, place.top as i32),
             dimensions,
             hidpi_factor: dpi_to_scale_factor(get_monitor_dpi(hmonitor).unwrap_or(96)),
+            monitor_info,
         }
     }
 
@@ -170,4 +175,39 @@ impl MonitorHandle {
     pub fn hidpi_factor(&self) -> f64 {
         self.hidpi_factor
     }
+
+    #[inline]
+    pub fn video_modes(&self) -> impl Iterator<Item = VideoMode> {
+        // EnumDisplaySettingsExW can return duplicate values (or some of the
+        // fields are probably changing, but we aren't looking at those fields
+        // anyway), so we're using a HashSet deduplicate
+        let mut modes = HashSet::new();
+        let mut i = 0;
+
+        loop {
+            unsafe {
+                let device_name = self.monitor_info.szDevice.as_ptr();
+                let mut mode: wingdi::DEVMODEW = mem::zeroed();
+                mode.dmSize = mem::size_of_val(&mode) as WORD;
+                if winuser::EnumDisplaySettingsExW(device_name, i, &mut mode, 0) == 0 {
+                    break;
+                }
+                i += 1;
+
+                const REQUIRED_FIELDS: DWORD = wingdi::DM_BITSPERPEL
+                    | wingdi::DM_PELSWIDTH
+                    | wingdi::DM_PELSHEIGHT
+                    | wingdi::DM_DISPLAYFREQUENCY;
+                assert!(mode.dmFields & REQUIRED_FIELDS == REQUIRED_FIELDS);
+
+                modes.insert(VideoMode {
+                    dimensions: (mode.dmPelsWidth, mode.dmPelsHeight),
+                    bit_depth: mode.dmBitsPerPel as u16,
+                    refresh_rate: mode.dmDisplayFrequency as u16,
+                });
+            }
+        }
+
+        modes.into_iter()
+    }
 }