This lets apps optionally have a handful of callbacks for their entry points instead of a single main function. If used, the actual main/SDL_main/whatever entry point will be implemented in the single-header library SDL_main.h and the app will implement four separate functions:
First:
int SDL_AppInit(int argc, char **argv);
This will be called once before anything else. argc/argv work like they always do. If this returns 0, the app runs. If it returns < 0, the app calls SDL_AppQuit and terminates with an exit code that reports an error to the platform. If it returns > 0, the app calls SDL_AppQuit and terminates with an exit code that reports success to the platform. This function should not go into an infinite mainloop; it should do any one-time startup it requires and then return.
Then:
int SDL_AppIterate(void);
This is called over and over, possibly at the refresh rate of the display or some other metric that the platform dictates. This is where the heart of your app runs. It should return as quickly as reasonably possible, but it's not a "run one memcpy and that's all the time you have" sort of thing. The app should do any game updates, and render a frame of video. If it returns < 0, SDL will call SDL_AppQuit and terminate the process with an exit code that reports an error to the platform. If it returns > 0, the app calls SDL_AppQuit and terminates with an exit code that reports success to the platform. If it returns 0, then SDL_AppIterate will be called again at some regular frequency. The platform may choose to run this more or less (perhaps less in the background, etc), or it might just call this function in a loop as fast as possible. You do not check the event queue in this function (SDL_AppEvent exists for that).
Next:
int SDL_AppEvent(const SDL_Event *event);
This will be called once for each event pushed into the SDL queue. This may be called from any thread, and possibly in parallel to SDL_AppIterate. The fields in event do not need to be free'd (as you would normally need to do for SDL_EVENT_DROP_FILE, etc), and your app should not call SDL_PollEvent, SDL_PumpEvent, etc, as SDL will manage this for you. Return values are the same as from SDL_AppIterate(), so you can terminate in response to SDL_EVENT_QUIT, etc.
Finally:
void SDL_AppQuit(void);
This is called once before terminating the app--assuming the app isn't being forcibly killed or crashed--as a last chance to clean up. After this returns, SDL will call SDL_Quit so the app doesn't have to (but it's safe for the app to call it, too). Process termination proceeds as if the app returned normally from main(), so atexit handles will run, if your platform supports that.
The app does not implement SDL_main if using this. To turn this on, define SDL_MAIN_USE_CALLBACKS before including SDL_main.h. Defines like SDL_MAIN_HANDLED and SDL_MAIN_NOIMPL are also respected for callbacks, if the app wants to do some sort of magic main implementation thing.
In theory, on most platforms these can be implemented in the app itself, but this saves some #ifdefs in the app and lets everyone struggle less against some platforms, and might be more efficient in the long run, too.
On some platforms, it's possible this is the only reasonable way to go, but we haven't actually hit one that 100% requires it yet (but we will, if we want to write a RetroArch backend, for example).
Using the callback entry points works on every platform, because on platforms that don't require them, we can fake them with a simple loop in an internal implementation of the usual SDL_main.
The primary way we expect people to write SDL apps is with SDL_main, and this is not intended to replace it. If the app chooses to use this, it just removes some platform-specific details they might have to otherwise manage, and maybe removes a barrier to entry on some future platform.
Fixes#6785.
Reference PR #8247.
makes the SDL_main code shorter
Also added a generic SDL_RunApp() implementation for platforms that
don't really need it.
Some platforms (that use SDL_main but haven't been ported yet) are
still missing, but are added in the following commits.
and move the #undef main and #define main SDL_main to the start/end of
SDL_main_impl.h instead of repeating it in every platform implementation
Thanks to SDL_N3DSRunApp we don't need the #include <3ds.h> in
SDL_main_impl.h - that caused conflicts with testthread.c, because both
have (different) ThreadFunc typedefs.
As the implementation requires C++, the user will have to include
SDL_main.h in a C++ source file (that needs to be compiled with /ZW).
It's ok to keep the standard main() implementation in plain C and use
an otherwise empty C++ source file for the SDL_main implementation part,
if both source files #include <SDL3/SDL_main.h>
Including SDL_main.h in a C source file will print a message at
compilation (when building for WinRT or possibly other not yet implemented
platforms that require C++ for main), to remind the user of also
including it in a .cpp source file. This message/warning can be disabled
with #define SDL_MAIN_NOIMPL before including SDL_main.h in the C file.
When including it in a .cpp file, there will be a compiler error with
helpful message if it's not compiled with /ZW
For this I renamend _SDL_MAIN_NOIMPL to SDL_MAIN_NOIMPL, because now it's
not for internal use only anymore, but also useful for users (that want
their main() function in a different file than the SDL_main implementation)
Add a project for the testdraw2.c test to the WinRT solution to at least
get some minimal testing on WinRT.
I won't add all tests because it's a lot of manual clicking per test,
but this should be better than nothing :)
Also adjusted iOS demo's includes to <SDL3/..> and explicit SDL_main.h
untested, I don't have Xcode (or a Mac, for that matter)
The xcode projects (for both Xcode-iOS/ and Xcode/) will probably
have to be adjusted for the SDL_main changes to work, but now at least
the iOS demo source should work as is :)
(remaining platforms will follow)
SDL_main.h is *not* included by SDL.h anymore, users are supposed to
include it directly now, usually only in the file they implement main() in.
If they need the header elsewhere or don't want SDL_main to implement
main() (but only call SDL_SetMainReady() or whatever), they
can #define SDL_MAIN_HANDLED first, same as before.
For SDL-internal usage, I added _SDL_MAIN_NOIMPL, which *also* skips the
implementation and `#define main SDL_main`, but still defines
SDL_MAIN_AVAILABLE and SDL_MAIN_NEEDED in SDL_main.h, as before.
To make the implementaion in the header shorter and avoid including windows.h,
I moved most of the Win32 SDL_main code into SDL3.dll via SDL_Win32RunApp(),
so the header-only part is just the different main functions calling
SDL_Win32RunApp(SDL_main, NULL)
Note that I changed changed the return value and type of OutOfMemory()
to return -1 instead of FALSE, so main() (or WinMain() or whatever)
returns -1 instead of 0 in case of an out-of-memory error
Compared to original Win32 SDL_main, I tweaked the part of the
implementation in SDL_main_impl.h a bit to avoid linker warnings
and conflicts with stuff from windows.h:
- replaced windows.h with own define of WINAPI
and typedef-ing HINSTANCE and LPSTR.
This prevents conflicts between all the generically-named #defines and
types in windows.h and user code (like DrawState in some SDL tests)
- only using one of main() or wmain() gets rid of a MSVC linker error
("warning LNK4067: ambiguous entry point")
If this still causes problems, we might try getting rid of wmain(),
seemed to me like MSVC can use regular main() in UNICODE mode as well
- simplified the UNICODE logic for that - while this is not exactly
equivalent to the old, it should make sense and Works For Me
I ran this script in the include directory:
```sh
sed -i '' -e 's,#include "\(SDL.*\)",#include <SDL3/\1>,' *.h
```
I ran this script in the src directory:
```sh
for i in ../include/SDL3/SDL*.h
do hdr=$(basename $i)
if [ x"$(echo $hdr | egrep 'SDL_main|SDL_name|SDL_test|SDL_syswm|SDL_opengl|SDL_egl|SDL_vulkan')" != x ]; then
find . -type f -exec sed -i '' -e 's,#include "\('$hdr'\)",#include <SDL3/\1>,' {} \;
else
find . -type f -exec sed -i '' -e '/#include "'$hdr'"/d' {} \;
fi
done
```
Fixes https://github.com/libsdl-org/SDL/issues/6575
Ryan C. Gordon
luzpaz
Anonymous Maarten
Sylvain
SDL Wiki Bot
Sam Lantinga
Daniel Gibson