Clarify which thread is the main thread

include/SDL3/SDL_main.h

@@ -167,12 +167,10 @@
         */
         #define SDL_MAIN_NEEDED
 
-    #elif defined(SDL_PLATFORM_IOS)
-        /* On iOS SDL provides a main function that creates an application delegate
-           and starts the iOS application run loop.
+    #elif defined(SDL_PLATFORM_IOS) || defined(SDL_PLATFORM_TVOS)
+        /* On iOS and tvOS SDL provides a main function that creates an application delegate and starts the application run loop.
 
-           To use it, just #include SDL_main.h in the source file that contains your
-           main() function.
+           To use it, just #include <SDL3/SDL_main.h> in the source file that contains your main() function.
 
            See src/video/uikit/SDL_uikitappdelegate.m for more details.
          */
@@ -230,6 +228,15 @@
         */
         #define SDL_MAIN_AVAILABLE
 
+    #else
+        /*
+          This platform SDL provides a main function that sets up the main
+          thread and calls your main function.
+
+          If you provide this yourself, you may define SDL_MAIN_HANDLED
+        */
+        #define SDL_MAIN_AVAILABLE
+
     #endif
 #endif /* SDL_MAIN_HANDLED */
 

src/SDL.c

@@ -189,6 +189,8 @@ static bool SDL_MainIsReady = false;
 static bool SDL_MainIsReady = true;
 #endif
 static SDL_ThreadID SDL_MainThreadID = 0;
+static SDL_ThreadID SDL_EventsThreadID = 0;
+static SDL_ThreadID SDL_VideoThreadID = 0;
 static bool SDL_bInMainQuit = false;
 static Uint8 SDL_SubsystemRefCount[32];
 
@@ -266,21 +268,28 @@ void SDL_SetMainReady(void)
 
 bool SDL_IsMainThread(void)
 {
-    if (SDL_MainThreadID == 0) {
-        // Not initialized yet?
-        return true;
+    if (SDL_VideoThreadID) {
+        return (SDL_GetCurrentThreadID() == SDL_VideoThreadID);
     }
-    if (SDL_MainThreadID == SDL_GetCurrentThreadID()) {
-        return true;
+    if (SDL_EventsThreadID) {
+        return (SDL_GetCurrentThreadID() == SDL_EventsThreadID);
     }
-    return false;
+    if (SDL_MainThreadID) {
+        return (SDL_GetCurrentThreadID() == SDL_MainThreadID);
+    }
+    return true;
 }
 
 // Initialize all the subsystems that require initialization before threads start
 void SDL_InitMainThread(void)
 {
     static bool done_info = false;
 
+    // If we haven't done it by now, mark this as the main thread
+    if (SDL_MainThreadID == 0) {
+        SDL_MainThreadID = SDL_GetCurrentThreadID();
+    }
+
     SDL_InitTLSData();
     SDL_InitEnvironment();
     SDL_InitTicks();
@@ -335,6 +344,11 @@ bool SDL_InitSubSystem(SDL_InitFlags flags)
     if (flags & SDL_INIT_EVENTS) {
         if (SDL_ShouldInitSubsystem(SDL_INIT_EVENTS)) {
             SDL_IncrementSubsystemRefCount(SDL_INIT_EVENTS);
+
+            // Note which thread initialized events
+            // This is the thread which should be pumping events
+            SDL_EventsThreadID = SDL_GetCurrentThreadID();
+
             if (!SDL_InitEvents()) {
                 SDL_DecrementSubsystemRefCount(SDL_INIT_EVENTS);
                 goto quit_and_error;
@@ -354,12 +368,16 @@ bool SDL_InitSubSystem(SDL_InitFlags flags)
                 goto quit_and_error;
             }
 
+            SDL_IncrementSubsystemRefCount(SDL_INIT_VIDEO);
+
             // We initialize video on the main thread
             // On Apple platforms this is a requirement.
             // On other platforms, this is the definition.
-            SDL_MainThreadID = SDL_GetCurrentThreadID();
+            SDL_VideoThreadID = SDL_GetCurrentThreadID();
+#ifdef SDL_PLATFORM_APPLE
+            SDL_assert(SDL_VideoThreadID == SDL_MainThreadID);
+#endif
 
-            SDL_IncrementSubsystemRefCount(SDL_INIT_VIDEO);
             if (!SDL_VideoInit(NULL)) {
                 SDL_DecrementSubsystemRefCount(SDL_INIT_VIDEO);
                 SDL_PushError();
@@ -609,6 +627,7 @@ void SDL_QuitSubSystem(SDL_InitFlags flags)
         if (SDL_ShouldQuitSubsystem(SDL_INIT_VIDEO)) {
             SDL_QuitRender();
             SDL_VideoQuit();
+            SDL_VideoThreadID = 0;
             // video implies events
             SDL_QuitSubSystem(SDL_INIT_EVENTS);
         }
@@ -619,6 +638,7 @@ void SDL_QuitSubSystem(SDL_InitFlags flags)
     if (flags & SDL_INIT_EVENTS) {
         if (SDL_ShouldQuitSubsystem(SDL_INIT_EVENTS)) {
             SDL_QuitEvents();
+            SDL_EventsThreadID = 0;
         }
         SDL_DecrementSubsystemRefCount(SDL_INIT_EVENTS);
     }

src/SDL_internal.h

@@ -265,6 +265,7 @@ extern "C" {
 #include "SDL_utils_c.h"
 #include "SDL_hashtable.h"
 
+
 /* SDL_ExitProcess is not declared in any public header, although
    it is shared between some parts of SDL, because we don't want
    anything calling it without an extremely good reason. */

src/events/SDL_events.c

@@ -1494,6 +1494,9 @@ void SDL_PumpEventMaintenance(void)
 // Run the system dependent event loops
 static void SDL_PumpEventsInternal(bool push_sentinel)
 {
+    // This should only be called on the main thread, check in debug builds
+    SDL_assert(SDL_IsMainThread());
+
     // Free any temporary memory from old events
     SDL_FreeTemporaryMemory();
 

src/main/SDL_main_callbacks.c

@@ -147,13 +147,19 @@ void SDL_QuitMainCallbacks(SDL_AppResult result)
     SDL_Quit();
 }
 
-void SDL_CheckDefaultArgcArgv(int *argc, char ***argv)
+static void SDL_CheckDefaultArgcArgv(int *argc, char ***argv)
 {
-    if (!argv)
-    {
+    if (!*argv) {
         static char dummyargv0[] = { 'S', 'D', 'L', '_', 'a', 'p', 'p', '\0' };
         static char *argvdummy[2] = { dummyargv0, NULL };
         *argc = 1;
         *argv = argvdummy;
     }
 }
+
+int SDL_CallMainFunction(int argc, char *argv[], SDL_main_func mainFunction)
+{
+    SDL_CheckDefaultArgcArgv(&argc, &argv);
+    SDL_SetMainReady();
+    return mainFunction(argc, argv);
+}

src/main/SDL_main_callbacks.h

@@ -27,10 +27,7 @@ SDL_AppResult SDL_InitMainCallbacks(int argc, char *argv[], SDL_AppInit_func app
 SDL_AppResult SDL_IterateMainCallbacks(bool pump_events);
 void SDL_QuitMainCallbacks(SDL_AppResult result);
 
-// (not a callback thing, but convenient to stick this in here.)
-// If *_argv is NULL, update *_argc and *_argv to point at a static array of { "SDL_app", NULL }.
-void SDL_CheckDefaultArgcArgv(int *_argc, char ***_argv);
+// Check args and call the main function
+extern int SDL_CallMainFunction(int argc, char *argv[], SDL_main_func mainFunction);
 
 #endif // SDL_main_callbacks_h_
-
-

src/main/SDL_runapp.c

@@ -21,15 +21,20 @@
 #include "SDL_internal.h"
 #include "SDL_main_callbacks.h"
 
-/* Most platforms that use/need SDL_main have their own SDL_RunApp() implementation.
- * If not, you can special case it here by appending || defined(__YOUR_PLATFORM__) */
-#if ( !defined(SDL_MAIN_NEEDED) && !defined(SDL_MAIN_AVAILABLE) ) || defined(SDL_PLATFORM_ANDROID)
+// Add your platform here if you define a custom SDL_RunApp() implementation
+#if !defined(SDL_PLATFORM_WIN32) && \
+    !defined(SDL_PLATFORM_GDK) && \
+    !defined(SDL_PLATFORM_IOS) && \
+    !defined(SDL_PLATFORM_TVOS) && \
+    !defined(SDL_PLATFORM_EMSCRIPTEN) && \
+    !defined(SDL_PLATFORM_PSP) && \
+    !defined(SDL_PLATFORM_PS2) && \
+    !defined(SDL_PLATFORM_3DS)
 
 int SDL_RunApp(int argc, char *argv[], SDL_main_func mainFunction, void * reserved)
 {
     (void)reserved;
-    SDL_CheckDefaultArgcArgv(&argc, &argv);
-    return mainFunction(argc, argv);
+    return SDL_CallMainFunction(argc, argv, mainFunction);
 }
 
 #endif

src/main/emscripten/SDL_sysmain_runapp.c

@@ -37,8 +37,6 @@ int SDL_RunApp(int argc, char *argv[], SDL_main_func mainFunction, void * reserv
 {
     (void)reserved;
 
-    SDL_CheckDefaultArgcArgv(&argc, &argv);
-
     // Move any URL params that start with "SDL_" over to environment
     //  variables, so the hint system can pick them up, etc, much like a user
     //  can set them from a shell prompt on a desktop machine. Ignore all
@@ -59,7 +57,7 @@ int SDL_RunApp(int argc, char *argv[], SDL_main_func mainFunction, void * reserv
         }
     }, SDL_setenv_unsafe);
 
-    return mainFunction(argc, argv);
+    return SDL_CallMainFunction(argc, argv, mainFunction);
 }
 
 #endif

src/main/gdk/SDL_sysmain_runapp.cpp

@@ -24,6 +24,7 @@ extern "C" {
 #include "../../core/gdk/SDL_gdk.h"
 #include "../../core/windows/SDL_windows.h"
 #include "../../events/SDL_events_c.h"
+#include "../SDL_main_callbacks.h"
 }
 #include <XGameRuntime.h>
 #include <xsapi-c/services_c.h>
@@ -65,14 +66,12 @@ int SDL_RunApp(int argc, char **argv, SDL_main_func mainFunction, void *reserved
             SDL_SetError("[GDK] Unable to get titleid. Will not call XblInitialize. Check MicrosoftGame.config!");
         }
 
-        SDL_SetMainReady();
-
         if (!GDK_RegisterChangeNotifications()) {
             return -1;
         }
 
         // Run the application main() code
-        result = mainFunction(argc, argv);
+        result = SDL_CallMainFunction(argc, argv, mainFunction);
 
         GDK_UnregisterChangeNotifications();
 

src/main/n3ds/SDL_sysmain_runapp.c

@@ -31,14 +31,11 @@ int SDL_RunApp(int argc, char *argv[], SDL_main_func mainFunction, void * reserv
 {
     int result;
 
-    SDL_CheckDefaultArgcArgv(&argc, &argv);
-
     // init
     osSetSpeedupEnable(true);
     romfsInit();
 
-    SDL_SetMainReady();
-    result = mainFunction(argc, argv);
+    result = SDL_CallMainFunction(argc, argv, mainFunction);
 
     // quit
     romfsExit();

src/main/ps2/SDL_sysmain_runapp.c

@@ -68,21 +68,17 @@ static void deinit_drivers(void)
 
 int SDL_RunApp(int argc, char *argv[], SDL_main_func mainFunction, void * reserved)
 {
-    int res;
+    int result;
     (void)reserved;
 
-    SDL_CheckDefaultArgcArgv(&argc, &argv);
-
     prepare_IOP();
     init_drivers();
 
-    SDL_SetMainReady();
-
-    res = mainFunction(argc, argv);
+    result = SDL_CallMainFunction(argc, argv, mainFunction);
 
     deinit_drivers();
 
-    return res;
+    return result;
 }
 
 #endif // SDL_PLATFORM_PS2

src/main/psp/SDL_sysmain_runapp.c

@@ -74,13 +74,9 @@ int SDL_RunApp(int argc, char *argv[], SDL_main_func mainFunction, void * reserv
 {
     (void)reserved;
 
-    SDL_CheckDefaultArgcArgv(&argc, &argv);
-
     sdl_psp_setup_callbacks();
 
-    SDL_SetMainReady();
-
-    return mainFunction(argc, argv);
+    return SDL_CallMainFunction(argc, argv, mainFunction);
 }
 
 #endif // SDL_PLATFORM_PSP

src/main/windows/SDL_sysmain_runapp.c

@@ -23,6 +23,7 @@
 #ifdef SDL_PLATFORM_WIN32
 
 #include "../../core/windows/SDL_windows.h"
+#include "../SDL_main_callbacks.h"
 
 /* Win32-specific SDL_RunApp(), which does most of the SDL_main work,
   based on SDL_windows_main.c, placed in the public domain by Sam Lantinga  4/13/98 */
@@ -37,8 +38,7 @@ int MINGW32_FORCEALIGN SDL_RunApp(int argc, char *argv[], SDL_main_func mainFunc
     if (args_error) {
         SDL_ShowSimpleMessageBox(SDL_MESSAGEBOX_ERROR, "Fatal Error", args_error, NULL);
     } else {
-        SDL_SetMainReady();
-        result = mainFunction(argc, argv);
+        result = SDL_CallMainFunction(argc, argv, mainFunction);
         if (heap_allocated) {
             HeapFree(GetProcessHeap(), 0, heap_allocated);
         }

src/video/uikit/SDL_uikitappdelegate.m

@@ -42,8 +42,6 @@
 
 int SDL_RunApp(int argc, char *argv[], SDL_main_func mainFunction, void *reserved)
 {
-    SDL_CheckDefaultArgcArgv(&argc, &argv);
-
     // store arguments
     forward_main = mainFunction;
     forward_argc = argc;
@@ -483,7 +481,7 @@ - (void)postFinishLaunch
     [self performSelector:@selector(hideLaunchScreen) withObject:nil afterDelay:0.0];
 
     SDL_SetiOSEventPump(true);
-    exit_status = forward_main(forward_argc, forward_argv);
+    exit_status = SDL_CallMainFunction(forward_argc, forward_argv, forward_main);
     SDL_SetiOSEventPump(false);
 
     if (launchWindow) {
@@ -553,7 +551,7 @@ - (void)postFinishLaunch
 
     // run the user's application, passing argc and argv
     SDL_SetiOSEventPump(true);
-    exit_status = forward_main(forward_argc, forward_argv);
+    exit_status = SDL_CallMainFunction(forward_argc, forward_argv, forward_main);
     SDL_SetiOSEventPump(false);
 
     if (launchWindow) {