[feat] support minimizing to the system tray on Linux when closing

src/app/daemon.cpp

@@ -128,7 +128,11 @@ bool Daemon::start(MainLoopFunc loop) {
   if (pid > 0) _exit(0);
 
   umask(0);
-  chdir("/");
+  if (chdir("/") != 0) {
+    std::cerr << "Failed to change daemon working directory to /: "
+              << std::strerror(errno) << std::endl;
+    return false;
+  }
 
   // redirect file descriptors: keep stdout/stderr if from terminal, else
   // redirect to /dev/null

src/gui/render.cpp

@@ -1374,6 +1374,10 @@ int Render::CreateMainWindow() {
 #elif defined(__APPLE__)
   tray_ = std::make_unique<MacTray>(main_window_, "CrossDesk",
                                     localization_language_index_);
+#elif defined(__linux__) && !defined(__APPLE__)
+  tray_ = std::make_unique<LinuxTray>(main_window_, "CrossDesk",
+                                      localization_language_index_,
+                                      APP_EXIT_EVENT);
 #endif
 
   ImGui_ImplSDL3_InitForSDLRenderer(main_window_, main_renderer_);
@@ -1673,20 +1677,47 @@ int Render::SetupFontAndStyle(ImFont** system_chinese_font_out) {
 }
 
 int Render::DestroyMainWindowContext() {
+  if (!main_ctx_) {
+    return 0;
+  }
+
   ImGui::SetCurrentContext(main_ctx_);
   ImGui_ImplSDLRenderer3_Shutdown();
   ImGui_ImplSDL3_Shutdown();
   ImGui::DestroyContext(main_ctx_);
+  main_ctx_ = nullptr;
 
   return 0;
 }
 
 int Render::DestroyStreamWindowContext() {
+  if (!stream_ctx_) {
+    stream_window_inited_ = false;
+    return 0;
+  }
+
   stream_window_inited_ = false;
   ImGui::SetCurrentContext(stream_ctx_);
   ImGui_ImplSDLRenderer3_Shutdown();
   ImGui_ImplSDL3_Shutdown();
   ImGui::DestroyContext(stream_ctx_);
+  stream_ctx_ = nullptr;
+
+  return 0;
+}
+
+int Render::DestroyServerWindowContext() {
+  if (!server_ctx_) {
+    server_window_inited_ = false;
+    return 0;
+  }
+
+  server_window_inited_ = false;
+  ImGui::SetCurrentContext(server_ctx_);
+  ImGui_ImplSDLRenderer3_Shutdown();
+  ImGui_ImplSDL3_Shutdown();
+  ImGui::DestroyContext(server_ctx_);
+  server_ctx_ = nullptr;
 
   return 0;
 }
@@ -1955,9 +1986,12 @@ void Render::InitializeSDL() {
     screen_height_ = dm->h;
   }
 
-  STREAM_REFRESH_EVENT = SDL_RegisterEvents(1);
-  if (STREAM_REFRESH_EVENT == (uint32_t)-1) {
-    LOG_ERROR("Failed to register custom SDL event");
+  const uint32_t custom_event_base = SDL_RegisterEvents(2);
+  if (custom_event_base == static_cast<uint32_t>(-1)) {
+    LOG_ERROR("Failed to register custom SDL events");
+  } else {
+    STREAM_REFRESH_EVENT = custom_event_base;
+    APP_EXIT_EVENT = custom_event_base + 1;
   }
 
   LOG_INFO("Screen resolution: [{}x{}]", screen_width_, screen_height_);
@@ -2031,6 +2065,10 @@ void Render::MainLoop() {
       TranslateMessage(&msg);
       DispatchMessage(&msg);
     }
+#elif defined(__linux__) && !defined(__APPLE__)
+    if (tray_) {
+      tray_->ProcessEvents();
+    }
 #endif
 
     UpdateLabels();
@@ -2041,7 +2079,11 @@ void Render::MainLoop() {
     HandleServerWindow();
     HandleWindowsServiceIntegration();
 
-    DrawMainWindow();
+    const bool main_window_visible =
+        main_window_ && !(SDL_GetWindowFlags(main_window_) & SDL_WINDOW_HIDDEN);
+    if (main_window_visible) {
+      DrawMainWindow();
+    }
     if (stream_window_inited_) {
       DrawStreamWindow();
     }
@@ -2066,6 +2108,12 @@ bool Render::MinimizeMainWindowToTray() {
 
   tray_->MinimizeToTray();
   return true;
+#elif defined(__linux__) && !defined(__APPLE__)
+  if (!tray_) {
+    return false;
+  }
+
+  return tray_->MinimizeToTray();
 #else
   return false;
 #endif
@@ -2407,6 +2455,7 @@ void Render::HandleServerWindow() {
 
   if (need_to_destroy_server_window_) {
     DestroyServerWindow();
+    DestroyServerWindowContext();
     need_to_destroy_server_window_ = false;
   }
 }
@@ -2447,6 +2496,27 @@ void Render::Cleanup() {
   WaitForThumbnailSaveTasks();
 
   AudioDeviceDestroy();
+#if defined(_WIN32) || defined(__APPLE__) || defined(__linux__)
+  tray_.reset();
+#endif
+
+  if (stream_window_created_) {
+    if (stream_window_) {
+      SDL_SetWindowMouseGrab(stream_window_, false);
+    }
+    DestroyStreamWindow();
+  }
+  if (stream_ctx_) {
+    DestroyStreamWindowContext();
+  }
+
+  if (server_window_created_) {
+    DestroyServerWindow();
+  }
+  if (server_ctx_) {
+    DestroyServerWindowContext();
+  }
+
   DestroyMainWindowContext();
   DestroyMainWindow();
   SDL_Quit();
@@ -2860,6 +2930,20 @@ void Render::ProcessSdlEvent(const SDL_Event& event) {
     }
   }
 
+  if (APP_EXIT_EVENT != 0 && event.type == APP_EXIT_EVENT) {
+    LOG_INFO("Quit program from system tray");
+    if (stream_window_) {
+      SDL_SetWindowMouseGrab(stream_window_, false);
+    }
+#if defined(__linux__) && !defined(__APPLE__)
+    if (tray_) {
+      tray_->RemoveTrayIcon();
+    }
+#endif
+    exit_ = true;
+    return;
+  }
+
   switch (event.type) {
     case SDL_EVENT_QUIT:
       if (stream_window_inited_) {

src/gui/render.h

@@ -41,6 +41,8 @@
 #include "win_tray.h"
 #elif defined(__APPLE__)
 #include "mac_tray.h"
+#elif defined(__linux__)
+#include "linux_tray.h"
 #endif
 
 namespace crossdesk {
@@ -515,6 +517,8 @@ class Render {
   std::unique_ptr<WinTray> tray_;
 #elif defined(__APPLE__)
   std::unique_ptr<MacTray> tray_;
+#elif defined(__linux__)
+  std::unique_ptr<LinuxTray> tray_;
 #endif
 
   // main window properties
@@ -596,6 +600,7 @@ class Render {
   SDL_Event last_mouse_event{};
   SDL_AudioStream* output_stream_ = nullptr;
   uint32_t STREAM_REFRESH_EVENT = 0;
+  uint32_t APP_EXIT_EVENT = 0;
 #if _WIN32
   std::atomic<bool> pending_windows_service_sas_{false};
   bool local_service_status_received_ = false;

src/gui/toolbars/title_bar.cpp

@@ -300,13 +300,12 @@ int Render::TitleBar(bool main_window) {
   }
 
   if (close_button_clicked) {
-    if (main_window && MinimizeMainWindowToTray()) {
-      return 0;
+    const bool minimized_to_tray = main_window && MinimizeMainWindowToTray();
+    if (!minimized_to_tray) {
+      SDL_Event event;
+      event.type = SDL_EVENT_QUIT;
+      SDL_PushEvent(&event);
     }
-
-    SDL_Event event;
-    event.type = SDL_EVENT_QUIT;
-    SDL_PushEvent(&event);
   }
 
   draw_list->AddLine(ImVec2(xmark_pos_x - xmark_size / 2 - 0.25f,

src/gui/tray/linux_tray.h

@@ -0,0 +1,40 @@
+/*
+ * @Author: DI JUNKUN
+ * @Date: 2026-06-23
+ * Copyright (c) 2026 by DI JUNKUN, All Rights Reserved.
+ */
+
+#ifndef _LINUX_TRAY_H_
+#define _LINUX_TRAY_H_
+
+#if defined(__linux__) && !defined(__APPLE__)
+
+#include <cstdint>
+#include <memory>
+#include <string>
+
+struct SDL_Window;
+
+namespace crossdesk {
+
+struct LinuxTrayImpl;
+
+class LinuxTray {
+ public:
+  LinuxTray(::SDL_Window* app_window, const std::string& tooltip,
+            int language_index, uint32_t exit_event_type);
+  ~LinuxTray();
+
+  bool MinimizeToTray();
+  void RemoveTrayIcon();
+  void ProcessEvents();
+
+ private:
+  std::unique_ptr<LinuxTrayImpl> impl_;
+};
+
+}  // namespace crossdesk
+
+#endif  // defined(__linux__) && !defined(__APPLE__)
+
+#endif  // _LINUX_TRAY_H_

src/gui/windows/main_settings_window.cpp

@@ -356,10 +356,6 @@ int Render::SettingWindow() {
       ImGui::Separator();
 
       {
-#if !defined(_WIN32) && !defined(__APPLE__)
-        ImGui::BeginDisabled();
-        ImGui::PushStyleColor(ImGuiCol_Text, ImVec4(0.5f, 0.5f, 0.5f, 1.0f));
-#endif
         settings_items_offset += settings_items_padding;
         ImGui::SetCursorPosY(settings_items_offset);
         ImGui::AlignTextToFramePadding();
@@ -375,10 +371,6 @@ int Render::SettingWindow() {
 
         ImGui::Checkbox("##enable_minimize_to_tray_",
                         &enable_minimize_to_tray_);
-#if !defined(_WIN32) && !defined(__APPLE__)
-        ImGui::PopStyleColor();
-        ImGui::EndDisabled();
-#endif
       }
 
       ImGui::Separator();
@@ -626,14 +618,12 @@ int Render::SettingWindow() {
         }
         enable_daemon_last_ = enable_daemon_;
 
-#if defined(_WIN32) || defined(__APPLE__)
         if (enable_minimize_to_tray_) {
           config_center_->SetMinimizeToTray(true);
         } else {
           config_center_->SetMinimizeToTray(false);
         }
         enable_minimize_to_tray_last_ = enable_minimize_to_tray_;
-#endif
 
         // File transfer save path
         config_center_->SetFileTransferSavePath(file_transfer_save_path_buf_);