tauri-plugin-decoration 2.0.1

use tauri::plugin::{Builder, TauriPlugin};
use tauri::{Emitter, Error, Listener, Runtime, WebviewWindow};

#[cfg(target_os = "macos")]
mod traffic;

#[cfg(target_os = "linux")]
mod dconf;

#[cfg(target_os = "windows")]
mod snap;

#[cfg(target_os = "macos")]
#[macro_use]
extern crate objc;

/// Extensions to [`tauri::App`], [`tauri::AppHandle`] and [`tauri::Window`] to access the decoration APIs.
pub trait WebviewWindowExt {
    fn create_overlay_titlebar(&self) -> Result<&WebviewWindow, Error>;
    #[cfg(target_os = "macos")]
    fn set_traffic_lights_inset(&self, x: f32, y: f32) -> Result<&WebviewWindow, Error>;
    #[cfg(target_os = "macos")]
    fn make_transparent(&self) -> Result<&WebviewWindow, Error>;
    #[cfg(target_os = "macos")]
    fn set_window_level(&self, level: u32) -> Result<&WebviewWindow, Error>;
}

impl<'a> WebviewWindowExt for WebviewWindow {
    /// Create a custom titlebar overlay.
    /// This will remove the default titlebar and create a draggable area for the titlebar.
    /// On Windows, it will also create custom window controls.
    fn create_overlay_titlebar(&self) -> Result<&WebviewWindow, Error> {
        // Manage native decorations per-platform:
        // - macOS: decorations MUST stay enabled so the native traffic-light
        //   buttons exist for set_traffic_lights_inset to reposition. The
        //   frameless look comes from titleBarStyle: "Overlay" + hiddenTitle.
        // - Windows/Linux: decorations off so the custom HTML controls
        //   injected below are the only window controls.
        #[cfg(target_os = "macos")]
        self.set_decorations(true)?;
        #[cfg(any(target_os = "windows", target_os = "linux"))]
        self.set_decorations(false)?;

        let win2 = self.clone();

        self.listen("decoration-page-load", move |_event| {
            // println!("decoration-page-load event received")

            // Create a transparent draggable area for the titlebar
            let script_tb = include_str!("js/titlebar.js");

            win2.eval(script_tb)
                .unwrap_or_else(|e| println!("decoration error: {:?}", e));

            // Custom window controls for linux
            #[cfg(target_os = "linux")]
            {
                use linicon::{lookup_icon, IconType};
                use std::io::prelude::*;
                let mut control_script = include_str!("./js/linux-controls.js").to_string();

                let mut controls = Vec::new();
                if win2.is_minimizable().unwrap_or(false) {
                    controls.push("minimize".to_string());
                }

                if win2.is_maximizable().unwrap_or(false) && win2.is_resizable().unwrap_or(false) {
                    controls.push("maximize".to_string());
                }

                if win2.is_closable().unwrap_or(false) {
                    controls.push("close".to_string());
                }

                controls.push("restore".to_string());

                for control in controls.iter() {
                    if let Some(Ok(control_icon)) =
                        lookup_icon(format!("window-{}-symbolic", control))
                            .into_iter()
                            .find(|icon| match icon {
                                Ok(icon) => icon.icon_type == IconType::SVG,
                                Err(_) => false,
                            })
                    {
                        let mut icon_data = String::new();
                        if let Ok(mut f) = std::fs::File::open(&control_icon.path) {
                            let _ = f.read_to_string(&mut icon_data);
                        }

                        control_script =
                            control_script.replace(&format!("@win-{}", control), &icon_data);
                    };
                }

                controls.remove(controls.len() - 1);

                // return this string style 'appmenu:minimize,maximize,close'
                if let Ok(app_menu_config) =
                    dconf::read("/org/gnome/desktop/wm/preferences/button-layout")
                {
                    controls = app_menu_config
                        .trim_start_matches("appmenu:")
                        .split(',')
                        .map(|x| x.to_string())
                        .collect::<Vec<String>>();
                };

                let controls = format!("{:?}", controls);

                let control_script = control_script.replacen(
                    "[\"minimize\", \"maximize\", \"close\"]",
                    &controls,
                    1,
                );

                win2.eval(&control_script)
                    .unwrap_or_else(|e| println!("decoration error: {:?}", e));
            }

            // On Windows, create custom window controls and install
            // the native Snap Layout overlay.
            #[cfg(target_os = "windows")]
            {
                let mut controls = Vec::new();
                let mut right_index: u32 = 0;
                let mut has_maximize = false;

                if win2.is_minimizable().unwrap_or(false) {
                    controls.push("minimize");
                    right_index += 1;
                }

                if win2.is_maximizable().unwrap_or(false) && win2.is_resizable().unwrap_or(false) {
                    controls.push("maximize");
                    has_maximize = true;
                    right_index += 1;
                }

                if win2.is_closable().unwrap_or(false) {
                    controls.push("close");
                }

                let script_controls = include_str!("js/controls.js");
                let controls = format!("{:?}", controls);

                // this line finds ["minimize", "maximize", "close"] in the file
                // and replaces it with only the controls enabled for the window
                let script_controls = script_controls.replacen(
                    "[\"minimize\", \"maximize\", \"close\"]",
                    &controls,
                    1,
                );

                win2.eval(script_controls.as_str())
                    .unwrap_or_else(|e| println!("decoration error: {:?}", e));

                // Install the native Win32 child HWND overlay for Snap Layout.
                // The overlay returns HTMAXBUTTON from WM_NCHITTEST, which is
                // the Windows-supported path for showing the Snap Layout
                // flyout on Windows 11 — no keyboard or mouse simulation.
                if has_maximize {
                    let snap_win = win2.clone();
                    if let Err(e) = snap::install(
                        &snap_win,
                        32,
                        58,
                        right_index.saturating_sub(1),
                    ) {
                        eprintln!("decoration: failed to install snap overlay: {:?}", e);
                    }
                }

                // Unlisten the page-load event when the window closes so the
                // listener doesn't leak across navigations/reloads. We use
                // once-only registration via a flag stored on the window to
                // avoid stacking duplicate on_window_event handlers on every
                // page load.
                let win3 = win2.clone();
                let event_id = _event.id();
                win2.on_window_event(move |eve| match eve {
                    tauri::WindowEvent::CloseRequested { .. } => {
                        win3.unlisten(event_id);
                        #[cfg(target_os = "windows")]
                        let _ = snap::uninstall(&win3);
                    }
                    _ => {}
                });
            }
        });

        Ok(self)
    }

    /// Position the macOS traffic-light buttons (close/minimize/zoom).
    ///
    /// The two parameters control different things because the buttons are
    /// native OS controls positioned within an AppKit titlebar container:
    ///
    /// - `x` — **horizontal position**, in points from the left edge of the
    ///   window's content. The first button is placed at `x`, and each
    ///   subsequent button is placed `20pt` to its right. This is a direct
    ///   offset.
    ///
    /// - `y` — **titlebar container height**, in points, added on top of the
    ///   button height (`container_height = button_height + y`). The buttons
    ///   are then **vertically centered** within that container. This is an
    ///   *indirect* control: increasing `y` makes the container taller and
    ///   pushes the centered buttons down from the window's top edge;
    ///   decreasing it pulls them up. It does *not* offset the buttons off
    ///   center within the container.
    ///
    /// As a side effect, this method exposes the right edge of the last
    /// button to the webview as the `--decoration-traffic-light-left` CSS
    /// custom property so app content can avoid overlapping the cluster.
    ///
    /// This is only available on macOS.
    #[cfg(target_os = "macos")]
    fn set_traffic_lights_inset(&self, x: f32, y: f32) -> Result<&WebviewWindow, Error> {
        ensure_main_thread(self, move |win| {
            let ns_window = win.ns_window()?;
            let ns_window_handle = traffic::UnsafeWindowHandle(ns_window);

            // Store the custom position in the window state
            traffic::update_traffic_light_positions(win, x.into(), y.into());

            // Apply the position immediately. position_traffic_lights returns
            // the right-edge x of the last traffic-light button so we can
            // expose it to the webview as a CSS custom property. Apps can then
            // offset their own titlebar content (e.g. menu bars) with a single
            // line of CSS: `padding-left: var(--decoration-traffic-light-left, 0px)`.
            let cluster_right_edge =
                traffic::position_traffic_lights(ns_window_handle, x.into(), y.into());

            if cluster_right_edge > 0.0 {
                // Add a small breathing gap after the last button.
                let left_clearance = cluster_right_edge + 8.0;
                let script = format!(
                    "document.documentElement.style.setProperty(\
                     '--decoration-traffic-light-left','{0}px')",
                    left_clearance
                );
                if let Err(e) = win.eval(&script) {
                    eprintln!(
                        "decoration: failed to expose traffic-light CSS var: {:?}",
                        e
                    );
                }
            }

            Ok(win)
        })
    }

    /// Set the window background to transparent.
    /// This helper function is different from Tauri's default
    /// as it doesn't use the `transparent` flag or macOS Private APIs.
    #[cfg(target_os = "macos")]
    fn make_transparent(&self) -> Result<&WebviewWindow, Error> {
        use cocoa::{
            appkit::NSColor,
            base::{id, nil},
            foundation::NSString,
        };

        // Make webview background transparent
        self.with_webview(|webview| unsafe {
            let id = webview.inner() as *mut objc::runtime::Object;
            let no: id = msg_send![class!(NSNumber), numberWithBool:0];
            let _: id =
                msg_send![id, setValue:no forKey: NSString::alloc(nil).init_str("drawsBackground")];
        })?;

        // Make window background transparent
        ensure_main_thread(self, move |win| {
            let ns_win = win.ns_window()? as id;
            unsafe {
                let win_bg_color =
                    NSColor::colorWithSRGBRed_green_blue_alpha_(nil, 0.0, 0.0, 0.0, 0.0);
                let _: id = msg_send![ns_win, setBackgroundColor: win_bg_color];
            }
            Ok(win)
        })
    }

    /// Set the window level.
    /// This will set the window level to the specified value.
    /// NSWindowLevel values can be found [here](https://developer.apple.com/documentation/appkit/nswindowlevel?language=objc).
    /// This is only available on macOS.
    #[cfg(target_os = "macos")]
    fn set_window_level(&self, level: u32) -> Result<&WebviewWindow, Error> {
        ensure_main_thread(self, move |win| {
            let ns_win = win.ns_window()? as cocoa::base::id;
            unsafe {
                let _: () = msg_send![ns_win, setLevel: level];
            }
            Ok(win)
        })
    }
}

pub fn init<R: Runtime>() -> TauriPlugin<R> {
    Builder::new("decoration")
        .on_page_load(|win, _payload: &tauri::webview::PageLoadPayload| {
            match win.emit("decoration-page-load", ()) {
                Ok(_) => {}
                Err(e) => println!("decoration error: {:?}", e),
            }
        })
        .on_window_ready(|_win| {
            #[cfg(target_os = "macos")]
            traffic::setup_traffic_light_positioner(_win);
            return;
        })
        .build()
}

#[cfg(target_os = "macos")]
fn is_main_thread() -> bool {
    // pthread_main_np() is the reliable way to check if we're on the main
    // thread on macOS. Checking the thread name is fragile because Tauri
    // doesn't guarantee the main thread is named "main".
    extern "C" {
        fn pthread_main_np() -> i32;
    }
    unsafe { pthread_main_np() != 0 }
}

#[cfg(target_os = "macos")]
fn ensure_main_thread<F>(
    win: &WebviewWindow,
    main_action: F,
) -> Result<&WebviewWindow, tauri::Error>
where
    F: FnOnce(&WebviewWindow) -> Result<&WebviewWindow, Error> + Send + 'static,
{
    match is_main_thread() {
        true => {
            main_action(win)?;
            Ok(win)
        }
        false => {
            let win2 = win.clone();

            match win.run_on_main_thread(move || {
                // Don't unwrap — panicking inside run_on_main_thread is
                // silently swallowed and can stop controls from rendering.
                if let Err(e) = main_action(&win2) {
                    eprintln!("decoration: main_thread action failed: {:?}", e);
                }
            }) {
                Ok(_) => Ok(win),
                Err(e) => Err(e),
            }
        }
    }
}