Desktop: Add fullscreen window mode (#3625)

desktop/src/app.rs

@@ -352,6 +352,11 @@ impl App {
 					window.toggle_maximize();
 				}
 			}
+			DesktopFrontendMessage::WindowFullscreen => {
+				if let Some(window) = &mut self.window {
+					window.toggle_fullscreen();
+				}
+			}
 			DesktopFrontendMessage::WindowDrag => {
 				if let Some(window) = &self.window {
 					window.start_drag();

desktop/src/window.rs

@@ -1,13 +1,13 @@
+use crate::consts::APP_NAME;
+use crate::event::AppEventScheduler;
+use crate::wrapper::messages::MenuItem;
 use std::collections::HashMap;
 use std::sync::Arc;
 use winit::cursor::{CursorIcon, CustomCursor, CustomCursorSource};
 use winit::event_loop::ActiveEventLoop;
+use winit::monitor::Fullscreen;
 use winit::window::{Window as WinitWindow, WindowAttributes};
 
-use crate::consts::APP_NAME;
-use crate::event::AppEventScheduler;
-use crate::wrapper::messages::MenuItem;
-
 pub(crate) trait NativeWindow {
 	fn init() {}
 	fn configure(attributes: WindowAttributes, event_loop: &dyn ActiveEventLoop) -> WindowAttributes;
@@ -111,6 +111,9 @@ impl Window {
 	}
 
 	pub(crate) fn toggle_maximize(&self) {
+		if self.is_fullscreen() {
+			return;
+		}
 		self.winit_window.set_maximized(!self.winit_window.is_maximized());
 	}
 
@@ -118,11 +121,22 @@ impl Window {
 		self.winit_window.is_maximized()
 	}
 
+	pub(crate) fn toggle_fullscreen(&mut self) {
+		if self.is_fullscreen() {
+			self.winit_window.set_fullscreen(None);
+		} else {
+			self.winit_window.set_fullscreen(Some(Fullscreen::Borderless(None)));
+		}
+	}
+
 	pub(crate) fn is_fullscreen(&self) -> bool {
 		self.winit_window.fullscreen().is_some()
 	}
 
 	pub(crate) fn start_drag(&self) {
+		if self.is_fullscreen() {
+			return;
+		}
 		let _ = self.winit_window.drag_window();
 	}
 

desktop/src/window/win/native_handle.rs

@@ -210,10 +210,10 @@ unsafe fn ensure_helper_class() {
 // Main window message handler, called on the UI thread for every message the main window receives.
 unsafe extern "system" fn main_window_handle_message(hwnd: HWND, msg: u32, wparam: WPARAM, lparam: LPARAM) -> LRESULT {
 	if msg == WM_NCCALCSIZE && wparam.0 != 0 {
-		// When maximized, shrink to visible frame so content doesn't extend beyond it.
-		if unsafe { IsZoomed(hwnd).as_bool() } {
-			let params = unsafe { &mut *(lparam.0 as *mut NCCALCSIZE_PARAMS) };
+		let params = unsafe { &mut *(lparam.0 as *mut NCCALCSIZE_PARAMS) };
 
+		// When maximized, shrink to visible frame so content doesn't extend beyond it.
+		if unsafe { IsZoomed(hwnd).as_bool() } && !is_effectively_fullscreen(params.rgrc[0]) {
 			let dpi = unsafe { GetDpiForWindow(hwnd) };
 			let size = unsafe { GetSystemMetricsForDpi(SM_CXSIZEFRAME, dpi) };
 			let pad = unsafe { GetSystemMetricsForDpi(SM_CXPADDEDBORDER, dpi) };
@@ -366,3 +366,27 @@ unsafe fn calculate_resize_direction(helper: HWND, lparam: LPARAM) -> Option<u32
 		_ => None,
 	}
 }
+
+// Check if the rect is effectively fullscreen, meaning it would cover the entire monitor.
+// We need to use this heuristic because Windows doesn't provide a way to check for fullscreen state.
+fn is_effectively_fullscreen(rect: RECT) -> bool {
+	let hmon = unsafe { MonitorFromRect(&rect, MONITOR_DEFAULTTONEAREST) };
+	if hmon.is_invalid() {
+		return false;
+	}
+
+	let mut monitor_info = MONITORINFO {
+		cbSize: std::mem::size_of::<MONITORINFO>() as u32,
+		..Default::default()
+	};
+	if !unsafe { GetMonitorInfoW(hmon, &mut monitor_info) }.as_bool() {
+		return false;
+	}
+
+	// Allow a tiny tolerance for DPI / rounding issues
+	const EPS: i32 = 1;
+	(rect.left - monitor_info.rcMonitor.left).abs() <= EPS
+		&& (rect.top - monitor_info.rcMonitor.top).abs() <= EPS
+		&& (rect.right - monitor_info.rcMonitor.right).abs() <= EPS
+		&& (rect.bottom - monitor_info.rcMonitor.bottom).abs() <= EPS
+}

desktop/wrapper/src/intercept_frontend_message.rs

@@ -148,6 +148,9 @@ pub(super) fn intercept_frontend_message(dispatcher: &mut DesktopWrapperMessageD
 		FrontendMessage::WindowMaximize => {
 			dispatcher.respond(DesktopFrontendMessage::WindowMaximize);
 		}
+		FrontendMessage::WindowFullscreen => {
+			dispatcher.respond(DesktopFrontendMessage::WindowFullscreen);
+		}
 		FrontendMessage::WindowDrag => {
 			dispatcher.respond(DesktopFrontendMessage::WindowDrag);
 		}

desktop/wrapper/src/messages.rs

@@ -69,6 +69,7 @@ pub enum DesktopFrontendMessage {
 	WindowClose,
 	WindowMinimize,
 	WindowMaximize,
+	WindowFullscreen,
 	WindowDrag,
 	WindowHide,
 	WindowHideOthers,