feat: add EventLoopBuilderExtUnix::with_app_id on Linux (#912)

closes #910

.changes/app_id_gtk.md

@@ -0,0 +1,5 @@
+---
+"tao": "patch"
+---
+
+Add `EventLoopBuilderExtUnix::with_app_id` on Linux to allow setting a unique app id for the underlying gtk application.

src/platform/unix.rs

@@ -38,6 +38,11 @@ pub trait EventLoopBuilderExtUnix {
   /// terminates. Attempting to use a `Window` after its parent thread terminates has
   /// unspecified, although explicitly not undefined, behavior.
   fn with_any_thread(&mut self, any_thread: bool) -> &mut Self;
+
+  /// Set the gtk application id.
+  ///
+  /// If no application ID is given then some features (most notably application uniqueness) will be disabled.
+  fn with_app_id<S: Into<String>>(&mut self, id: S) -> &mut Self;
 }
 
 impl<T> EventLoopBuilderExtUnix for EventLoopBuilder<T> {
@@ -46,6 +51,11 @@ impl<T> EventLoopBuilderExtUnix for EventLoopBuilder<T> {
     self.platform_specific.any_thread = any_thread;
     self
   }
+
+  fn with_app_id<S: Into<String>>(&mut self, id: S) -> &mut Self {
+    self.platform_specific.app_id = Some(id.into());
+    self
+  }
 }
 
 /// Additional methods on `Window` that are specific to Unix.

src/platform_impl/linux/event_loop.rs

@@ -171,9 +171,10 @@ pub struct EventLoop<T: 'static> {
   run_device_thread: Option<Rc<AtomicBool>>,
 }
 
-#[derive(Default, Debug, Copy, Clone, PartialEq, Eq, Hash)]
+#[derive(Default, Debug, Clone, PartialEq, Eq, Hash)]
 pub(crate) struct PlatformSpecificEventLoopAttributes {
   pub(crate) any_thread: bool,
+  pub(crate) app_id: Option<String>,
 }
 
 impl<T: 'static> EventLoop<T> {
@@ -184,13 +185,15 @@ impl<T: 'static> EventLoop<T> {
 
     let context = MainContext::default();
     context
-      .with_thread_default(|| EventLoop::new_gtk().expect("Failed to initialize gtk backend!"))
+      .with_thread_default(|| {
+        EventLoop::new_gtk(attrs.app_id.as_deref()).expect("Failed to initialize gtk backend!")
+      })
       .expect("Failed to initialize gtk backend!")
   }
 
-  fn new_gtk() -> Result<EventLoop<T>, Box<dyn Error>> {
+  fn new_gtk(app_id: Option<&str>) -> Result<EventLoop<T>, Box<dyn Error>> {
     let context = MainContext::default();
-    let app = gtk::Application::new(None, gio::ApplicationFlags::empty());
+    let app = gtk::Application::new(app_id, gio::ApplicationFlags::empty());
     let app_ = app.clone();
     let cancellable: Option<&Cancellable> = None;
     app.register(cancellable)?;

src/platform_impl/linux/icon.rs

@@ -2,8 +2,6 @@
 // Copyright 2021-2023 Tauri Programme within The Commons Conservancy
 // SPDX-License-Identifier: Apache-2.0
 
-use std::{fs::File, io::BufWriter, path::Path};
-
 use gtk::gdk_pixbuf::{Colorspace, Pixbuf};
 
 use crate::window::BadIcon;