Use EnumDisplayMonitors to enumerate monitors on Windows (#327)

* Use EnumDisplayMonitors to enumerate monitors on Windows

* Add requested changes

CHANGELOG.md

@@ -9,6 +9,9 @@
 - `MonitorId::get_position` now returns `(i32, i32)` instead of `(u32, u32)`.
 - Rewrite of the wayland backend to use wayland-client-0.11
 - Support for dead keys on wayland for keyboard utf8 input
+- Monitor enumeration on Windows is now implemented using `EnumDisplayMonitors` instead of
+`EnumDisplayDevices`. This changes the value returned by `MonitorId::get_name()`.
+- On Windows added `MonitorIdExt::hmonitor` method
 
 # Version 0.8.3 (2017-10-11)
 

src/os/windows.rs

@@ -1,5 +1,6 @@
 #![cfg(target_os = "windows")]
 
+use std::os::raw::c_void;
 use libc;
 use MonitorId;
 use Window;
@@ -37,8 +38,11 @@ impl WindowBuilderExt for WindowBuilder {
 
 /// Additional methods on `MonitorId` that are specific to Windows.
 pub trait MonitorIdExt {
-    /// Returns the name of the monitor specific to the Win32 API.
+    /// Returns the name of the monitor adapter specific to the Win32 API.
     fn native_id(&self) -> String;
+
+    /// Returns the handle of the monitor - `HMONITOR`.
+    fn hmonitor(&self) -> *mut c_void;
 }
 
 impl MonitorIdExt for MonitorId {
@@ -46,4 +50,9 @@ impl MonitorIdExt for MonitorId {
     fn native_id(&self) -> String {
         self.inner.get_native_identifier()
     }
+
+    #[inline]
+    fn hmonitor(&self) -> *mut c_void {
+        self.inner.get_hmonitor() as *mut _
+    }
 }

src/platform/windows/monitor.rs

@@ -2,7 +2,7 @@ use winapi;
 use user32;
 
 use std::collections::VecDeque;
-use std::mem;
+use std::{mem, ptr};
 
 use super::EventsLoop;
 
@@ -12,16 +12,12 @@ pub struct MonitorId {
     /// The system name of the adapter.
     adapter_name: [winapi::WCHAR; 32],
 
+    /// Monitor handle.
+    hmonitor: HMonitor,
+
     /// The system name of the monitor.
     monitor_name: String,
 
-    /// Name to give to the user.
-    readable_name: String,
-
-    /// See the `StateFlags` element here:
-    /// http://msdn.microsoft.com/en-us/library/dd183569(v=vs.85).aspx
-    flags: winapi::DWORD,
-
     /// True if this is the primary monitor.
     primary: bool,
 
@@ -32,59 +28,19 @@ pub struct MonitorId {
 
     /// The current resolution in pixels on the monitor.
     dimensions: (u32, u32),
+
+    /// DPI scaling factor.
+    hidpi_factor: f32,
 }
 
-struct DeviceEnumerator {
+// Send is not implemented for HMONITOR, we have to wrap it and implement it manually.
-    parent_device: *const winapi::WCHAR,
+// For more info see:
-    current_index: u32,
+// https://github.com/retep998/winapi-rs/issues/360
-}
+// https://github.com/retep998/winapi-rs/issues/396
+#[derive(Clone)]
+struct HMonitor(winapi::HMONITOR);
 
-impl DeviceEnumerator {
+unsafe impl Send for HMonitor {}
-    fn adapters() -> DeviceEnumerator {
-        use std::ptr;
-        DeviceEnumerator {
-            parent_device: ptr::null(),
-            current_index: 0
-        }
-    }
-
-    fn monitors(adapter_name: *const winapi::WCHAR) -> DeviceEnumerator {
-        DeviceEnumerator {
-            parent_device: adapter_name,
-            current_index: 0
-        }
-    }
-}
-
-impl Iterator for DeviceEnumerator {
-    type Item = winapi::DISPLAY_DEVICEW;
-    fn next(&mut self) -> Option<winapi::DISPLAY_DEVICEW> {
-        use std::mem;
-        loop {
-            let mut output: winapi::DISPLAY_DEVICEW = unsafe { mem::zeroed() };
-            output.cb = mem::size_of::<winapi::DISPLAY_DEVICEW>() as winapi::DWORD;
-
-            if unsafe { user32::EnumDisplayDevicesW(self.parent_device,
-                self.current_index as winapi::DWORD, &mut output, 0) } == 0
-            {
-                // the device doesn't exist, which means we have finished enumerating
-                break;
-            }
-            self.current_index += 1;
-
-            if  (output.StateFlags & winapi::DISPLAY_DEVICE_ACTIVE) == 0 ||
-                (output.StateFlags & winapi::DISPLAY_DEVICE_MIRRORING_DRIVER) != 0
-            {
-                // the device is not active
-                // the Win32 api usually returns a lot of inactive devices
-                continue;
-            }
-
-            return Some(output);
-        }
-        None
-    }
-}
 
 fn wchar_as_string(wchar: &[winapi::WCHAR]) -> String {
     String::from_utf16_lossy(wchar)
@@ -92,51 +48,45 @@ fn wchar_as_string(wchar: &[winapi::WCHAR]) -> String {
         .to_string()
 }
 
+unsafe extern "system" fn monitor_enum_proc(hmonitor: winapi::HMONITOR, _: winapi::HDC, place: winapi::LPRECT, data: winapi::LPARAM) -> winapi::BOOL {
+    let monitors = data as *mut VecDeque<MonitorId>;
+
+    let place = *place;
+    let position = (place.left as i32, place.top as i32);
+    let dimensions = ((place.right - place.left) as u32, (place.bottom - place.top) as u32);
+
+    let mut monitor_info: winapi::MONITORINFOEXW = mem::zeroed();
+    monitor_info.cbSize = mem::size_of::<winapi::MONITORINFOEXW>() as winapi::DWORD;
+    if user32::GetMonitorInfoW(hmonitor, &mut monitor_info as *mut winapi::MONITORINFOEXW as *mut winapi::MONITORINFO) == 0 {
+        // Some error occurred, just skip this monitor and go on.
+        return winapi::TRUE;
+    }
+
+    (*monitors).push_back(MonitorId {
+        adapter_name: monitor_info.szDevice,
+        hmonitor: HMonitor(hmonitor),
+        monitor_name: wchar_as_string(&monitor_info.szDevice),
+        primary: monitor_info.dwFlags & winapi::MONITORINFOF_PRIMARY != 0,
+        position,
+        dimensions,
+        hidpi_factor: 1.0,
+    });
+
+    // TRUE means continue enumeration.
+    winapi::TRUE
+}
+
 impl EventsLoop {
     pub fn get_available_monitors(&self) -> VecDeque<MonitorId> {
-        // return value
+        unsafe {
-        let mut result = VecDeque::new();
+            let mut result: VecDeque<MonitorId> = VecDeque::new();
-
+            user32::EnumDisplayMonitors(ptr::null_mut(), ptr::null_mut(), Some(monitor_enum_proc), &mut result as *mut _ as winapi::LPARAM);
-        for adapter in DeviceEnumerator::adapters() {
-            // getting the position
-            let (position, dimensions) = unsafe {
-                let mut dev: winapi::DEVMODEW = mem::zeroed();
-                dev.dmSize = mem::size_of::<winapi::DEVMODEW>() as winapi::WORD;
-
-                if user32::EnumDisplaySettingsExW(adapter.DeviceName.as_ptr(), 
-                    winapi::ENUM_CURRENT_SETTINGS,
-                    &mut dev, 0) == 0
-                {
-                    continue;
-                }
-
-                let point: &winapi::POINTL = mem::transmute(&dev.union1);
-                let position = (point.x as i32, point.y as i32);
-
-                let dimensions = (dev.dmPelsWidth as u32, dev.dmPelsHeight as u32);
-
-                (position, dimensions)
-            };
-
-            for (num, monitor) in DeviceEnumerator::monitors(adapter.DeviceName.as_ptr()).enumerate() {
-                // adding to the resulting list
-                result.push_back(MonitorId {
-                    adapter_name: adapter.DeviceName,
-                    monitor_name: wchar_as_string(&monitor.DeviceName),
-                    readable_name: wchar_as_string(&monitor.DeviceString),
-                    flags: monitor.StateFlags,
-                    primary: (adapter.StateFlags & winapi::DISPLAY_DEVICE_PRIMARY_DEVICE) != 0 &&
-                            num == 0,
-                    position: position,
-                    dimensions: dimensions,
-                });
-            }
-        }
             result
         }
+    }
 
     pub fn get_primary_monitor(&self) -> MonitorId {
-        // we simply get all available monitors and return the one with the `PRIMARY_DEVICE` flag
+        // we simply get all available monitors and return the one with the `MONITORINFOF_PRIMARY` flag
         // TODO: it is possible to query the win32 API for the primary monitor, this should be done
         //  instead
         for monitor in self.get_available_monitors().into_iter() {
@@ -153,7 +103,7 @@ impl MonitorId {
     /// See the docs if the crate root file.
     #[inline]
     pub fn get_name(&self) -> Option<String> {
-        Some(self.readable_name.clone())
+        Some(self.monitor_name.clone())
     }
 
     /// See the docs of the crate root file.
@@ -162,10 +112,16 @@ impl MonitorId {
         self.monitor_name.clone()
     }
 
-    /// See the docs if the crate root file.
+    /// See the docs of the crate root file.
+    #[inline]
+    pub fn get_hmonitor(&self) -> winapi::HMONITOR {
+        self.hmonitor.0
+    }
+
+    /// See the docs of the crate root file.
     #[inline]
     pub fn get_dimensions(&self) -> (u32, u32) {
-        // TODO: retreive the dimensions every time this is called
+        // TODO: retrieve the dimensions every time this is called
         self.dimensions
     }
 
@@ -184,6 +140,6 @@ impl MonitorId {
 
     #[inline]
     pub fn get_hidpi_factor(&self) -> f32 {
-        1.0
+        self.hidpi_factor
     }
 }