feat(display): Add revert display config on disconnect option (#3613)

src/config.cpp

@@ -504,6 +504,7 @@ namespace config {
       {},  // manual_refresh_rate
       video_t::dd_t::hdr_option_e::automatic,  // hdr_option
       3s,  // config_revert_delay
+      {},  // config_revert_on_disconnect
       {},  // mode_remapping
       {}  // wa
     },  // display_device
@@ -1132,6 +1133,7 @@ namespace config {
         video.dd.config_revert_delay = std::chrono::milliseconds {value};
       }
     }
+    bool_f(vars, "dd_config_revert_on_disconnect", video.dd.config_revert_on_disconnect);
     generic_f(vars, "dd_mode_remapping", video.dd.mode_remapping, dd::mode_remapping_from_view);
     bool_f(vars, "dd_wa_hdr_toggle", video.dd.wa.hdr_toggle);
 

src/config.h

@@ -132,6 +132,7 @@ namespace config {
       std::string manual_refresh_rate;  ///< Manual refresh rate in case `refresh_rate_option == refresh_rate_option_e::manual`.
       hdr_option_e hdr_option;
       std::chrono::milliseconds config_revert_delay;  ///< Time to wait until settings are reverted (after stream ends/app exists).
+      bool config_revert_on_disconnect;  ///< Specify whether to revert display configuration on client disconnect.
       mode_remapping_t mode_remapping;
       workarounds_t wa;
     } dd;

src/stream.cpp

@@ -1882,11 +1882,17 @@ namespace stream {
 
       // If this is the last session, invoke the platform callbacks
       if (--running_sessions == 0) {
+        bool revert_display_config {config::video.dd.config_revert_on_disconnect};
         if (proc::proc.running()) {
 #if defined SUNSHINE_TRAY && SUNSHINE_TRAY >= 1
           system_tray::update_tray_pausing(proc::proc.get_last_run_app_name());
 #endif
         } else {
+          // We have no app running and also no clients anymore.
+          revert_display_config = true;
+        }
+
+        if (revert_display_config) {
           display_device::revert_configuration();
         }