adds GDK suspend/resume basic handling (#6596)

(cherry picked from commit f6144dfe03fc5e76e0e22242b67891fd97053787)

include/SDL_main.h

@@ -254,6 +254,12 @@ extern DECLSPEC int SDLCALL SDL_UIKitRunApp(int argc, char *argv[], SDL_main_fun
  */
 extern DECLSPEC int SDLCALL SDL_GDKRunApp(SDL_main_func mainFunction, void *reserved);
 
+/**
+ * Callback from the application to let the suspend continue.
+ *
+ */
+extern DECLSPEC void SDLCALL SDL_GDKSuspendComplete(void);
+
 #endif /* __GDK__ */
 
 #ifdef __cplusplus

src/core/gdk/SDL_gdk.cpp

@@ -20,16 +20,24 @@
 */
 #include "../../SDL_internal.h"
 
+extern "C" {
 #include "SDL_system.h"
 #include "../windows/SDL_windows.h"
 #include "SDL_messagebox.h"
 #include "SDL_main.h"
+#include "SDL_events.h"
+#include "../../events/SDL_events_c.h"
+}
 #include <XGameRuntime.h>
 #include <xsapi-c/services_c.h>
 #include <shellapi.h> /* CommandLineToArgvW() */
+#include <appnotify.h>
 
 static XTaskQueueHandle GDK_GlobalTaskQueue;
 
+PAPPSTATE_REGISTRATION hPLM = {};
+HANDLE plmSuspendComplete = nullptr;
+
 extern "C" DECLSPEC int
 SDL_GDKGetTaskQueue(XTaskQueueHandle * outTaskQueue)
 {
@@ -144,9 +152,40 @@ SDL_GDKRunApp(SDL_main_func mainFunction, void *reserved)
 
         SDL_SetMainReady();
 
+        /* Register suspend/resume handling */
+        plmSuspendComplete = CreateEventEx(nullptr, nullptr, 0, EVENT_MODIFY_STATE | SYNCHRONIZE);
+        if (!plmSuspendComplete ) {
+            SDL_SetError("[GDK] Unable to create plmSuspendComplete event");
+            return -1;
+        }
+        auto rascn = [](BOOLEAN quiesced, PVOID context)
+        {
+            SDL_LogDebug(SDL_LOG_CATEGORY_APPLICATION, "[GDK] in RegisterAppStateChangeNotification handler");
+            if (quiesced) {
+                ResetEvent(plmSuspendComplete);
+                SDL_SendAppEvent(SDL_APP_DIDENTERBACKGROUND);
+
+                // To defer suspension, we must wait to exit this callback.
+                // IMPORTANT: The app must call SDL_GDKSuspendComplete() to release this lock.
+                (void)WaitForSingleObject(plmSuspendComplete, INFINITE);
+
+                SDL_LogDebug(SDL_LOG_CATEGORY_APPLICATION, "[GDK] in RegisterAppStateChangeNotification handler: plmSuspendComplete event signaled.");
+            } else {
+                SDL_SendAppEvent(SDL_APP_WILLENTERFOREGROUND);
+            }
+        };
+        if (RegisterAppStateChangeNotification(rascn, NULL, &hPLM)) {
+            SDL_SetError("[GDK] Unable to call RegisterAppStateChangeNotification");
+            return -1;
+        }
+
         /* Run the application main() code */
         result = mainFunction(argc, argv);
 
+        /* Unregister suspend/resume handling */
+        UnregisterAppStateChangeNotification(hPLM);
+        CloseHandle(plmSuspendComplete);
+
         /* !!! FIXME: This follows the docs exactly, but for some reason still leaks handles on exit? */
         /* Terminate the task queue and dispatch any pending tasks */
         XTaskQueueTerminate(taskQueue, false, nullptr, nullptr);
@@ -173,3 +212,10 @@ SDL_GDKRunApp(SDL_main_func mainFunction, void *reserved)
 
     return result;
 }
+
+extern "C" DECLSPEC void
+SDL_GDKSuspendComplete() {
+    if (plmSuspendComplete) {
+        SetEvent(plmSuspendComplete);
+    }
+}

src/dynapi/SDL_dynapi_overrides.h

@@ -877,6 +877,7 @@
 #define SDL_utf8strnlen SDL_utf8strnlen_REAL
 #define SDL_GDKGetTaskQueue SDL_GDKGetTaskQueue_REAL
 #define SDL_GDKRunApp SDL_GDKRunApp_REAL
+#define SDL_GDKSuspendComplete SDL_GDKSuspendComplete_REAL
 #define SDL_GetOriginalMemoryFunctions SDL_GetOriginalMemoryFunctions_REAL
 #define SDL_ResetKeyboard SDL_ResetKeyboard_REAL
 #define SDL_GetDefaultAudioInfo SDL_GetDefaultAudioInfo_REAL

src/dynapi/SDL_dynapi_procs.h

@@ -955,6 +955,7 @@ SDL_DYNAPI_PROC(size_t,SDL_utf8strnlen,(const char *a, size_t b),(a,b),return)
 #if defined(__GDK__)
 SDL_DYNAPI_PROC(int,SDL_GDKGetTaskQueue,(XTaskQueueHandle *a),(a),return)
 SDL_DYNAPI_PROC(int,SDL_GDKRunApp,(SDL_main_func a, void *b),(a,b),return)
+SDL_DYNAPI_PROC(void,SDL_GDKSuspendComplete,(void),(),return)
 #endif
 SDL_DYNAPI_PROC(void,SDL_GetOriginalMemoryFunctions,(SDL_malloc_func *a, SDL_calloc_func *b, SDL_realloc_func *c, SDL_free_func *d),(a,b,c,d),)
 SDL_DYNAPI_PROC(void,SDL_ResetKeyboard,(void),(),)