windows: Support multi-monitor (#11699)

Zed can detect changes in monitor connections and disconnections and
provide corresponding feedback. For example, if the current window's
display monitor is disconnected, the window will be moved to the primary
monitor. And now Zed always opens on the monitor specified in
`WindowParams`.

Release Notes:

- N/A

crates/gpui/src/platform/windows/display.rs

@@ -108,6 +108,22 @@ impl WindowsDisplay {
         Some(WindowsDisplay::new_with_handle(monitor))
     }
 
+    /// Check if the center point of given bounds is inside this monitor
+    pub fn check_given_bounds(&self, bounds: Bounds<DevicePixels>) -> bool {
+        let center = bounds.center();
+        let center = POINT {
+            x: center.x.0,
+            y: center.y.0,
+        };
+        let monitor = unsafe { MonitorFromPoint(center, MONITOR_DEFAULTTONULL) };
+        if monitor.is_invalid() {
+            false
+        } else {
+            let display = WindowsDisplay::new_with_handle(monitor);
+            display.uuid == self.uuid
+        }
+    }
+
     pub fn displays() -> Vec<Rc<dyn PlatformDisplay>> {
         available_monitors()
             .into_iter()
@@ -135,6 +151,11 @@ impl WindowsDisplay {
             .then(|| devmode.dmDisplayFrequency)
         })
     }
+
+    /// Check if this monitor is still online
+    pub fn is_connected(hmonitor: HMONITOR) -> bool {
+        available_monitors().iter().contains(&hmonitor)
+    }
 }
 
 impl PlatformDisplay for WindowsDisplay {

crates/gpui/src/platform/windows/events.rs

@@ -39,6 +39,7 @@ pub(crate) fn handle_msg(
         WM_TIMER => handle_timer_msg(handle, wparam, state_ptr),
         WM_NCCALCSIZE => handle_calc_client_size(handle, wparam, lparam, state_ptr),
         WM_DPICHANGED => handle_dpi_changed_msg(handle, wparam, lparam, state_ptr),
+        WM_DISPLAYCHANGE => handle_display_change_msg(handle, state_ptr),
         WM_NCHITTEST => handle_hit_test_msg(handle, msg, wparam, lparam, state_ptr),
         WM_PAINT => handle_paint_msg(handle, state_ptr),
         WM_CLOSE => handle_close_msg(state_ptr),
@@ -112,6 +113,8 @@ fn handle_move_msg(
     {
         // center of the window may have moved to another monitor
         let monitor = unsafe { MonitorFromWindow(handle, MONITOR_DEFAULTTONULL) };
+        // minimize the window can trigger this event too, in this case,
+        // monitor is invalid, we do nothing.
         if !monitor.is_invalid() && lock.display.handle != monitor {
             // we will get the same monitor if we only have one
             lock.display = WindowsDisplay::new_with_handle(monitor);
@@ -775,6 +778,41 @@ fn handle_dpi_changed_msg(
     Some(0)
 }
 
+/// The following conditions will trigger this event:
+/// 1. The monitor on which the window is located goes offline or changes resolution.
+/// 2. Another monitor goes offline, is plugged in, or changes resolution.
+///
+/// In either case, the window will only receive information from the monitor on which
+/// it is located.
+///
+/// For example, in the case of condition 2, where the monitor on which the window is
+/// located has actually changed nothing, it will still receive this event.
+fn handle_display_change_msg(handle: HWND, state_ptr: Rc<WindowsWindowStatePtr>) -> Option<isize> {
+    // NOTE:
+    // Even the `lParam` holds the resolution of the screen, we just ignore it.
+    // Because WM_DPICHANGED, WM_MOVE, WM_SIEZ will come first, window reposition and resize
+    // are handled there.
+    // So we only care about if monitor is disconnected.
+    let previous_monitor = state_ptr.as_ref().state.borrow().display;
+    if WindowsDisplay::is_connected(previous_monitor.handle) {
+        // we are fine, other display changed
+        return None;
+    }
+    // display disconnected
+    // in this case, the OS will move our window to another monitor, and minimize it.
+    // we deminimize the window and query the monitor after moving
+    unsafe { ShowWindow(handle, SW_SHOWNORMAL) };
+    let new_monitor = unsafe { MonitorFromWindow(handle, MONITOR_DEFAULTTONULL) };
+    // all monitors disconnected
+    if new_monitor.is_invalid() {
+        log::error!("No monitor detected!");
+        return None;
+    }
+    let new_display = WindowsDisplay::new_with_handle(new_monitor);
+    state_ptr.as_ref().state.borrow_mut().display = new_display;
+    Some(0)
+}
+
 fn handle_hit_test_msg(
     handle: HWND,
     msg: u32,

crates/gpui/src/platform/windows/window.rs

@@ -258,13 +258,17 @@ impl WindowsWindow {
         );
         let dwstyle = WS_THICKFRAME | WS_SYSMENU | WS_MAXIMIZEBOX | WS_MINIMIZEBOX;
         let hinstance = get_module_handle();
+        let display = if let Some(display_id) = params.display_id {
+            // if we obtain a display_id, then this ID must be valid.
+            WindowsDisplay::new(display_id).unwrap()
+        } else {
+            WindowsDisplay::primary_monitor().unwrap()
+        };
         let mut context = WindowCreateContext {
             inner: None,
             handle,
             hide_title_bar,
-            // todo(windows) move window to target monitor
-            // options.display_id
-            display: WindowsDisplay::primary_monitor().unwrap(),
+            display,
             transparent: params.window_background != WindowBackgroundAppearance::Opaque,
             executor,
             mouse_wheel_settings,
@@ -297,10 +301,16 @@ impl WindowsWindow {
                 ..Default::default()
             };
             GetWindowPlacement(raw_hwnd, &mut placement).log_err();
-            placement.rcNormalPosition.left = params.bounds.left().0;
-            placement.rcNormalPosition.right = params.bounds.right().0;
-            placement.rcNormalPosition.top = params.bounds.top().0;
-            placement.rcNormalPosition.bottom = params.bounds.bottom().0;
+            // the bounds may be not inside the display
+            let bounds = if display.check_given_bounds(params.bounds) {
+                params.bounds
+            } else {
+                display.default_bounds()
+            };
+            placement.rcNormalPosition.left = bounds.left().0;
+            placement.rcNormalPosition.right = bounds.right().0;
+            placement.rcNormalPosition.top = bounds.top().0;
+            placement.rcNormalPosition.bottom = bounds.bottom().0;
             SetWindowPlacement(raw_hwnd, &placement).log_err();
         }
         unsafe { ShowWindow(raw_hwnd, SW_SHOW).ok().log_err() };