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.
The following objects now have properties that can be user modified:
* SDL_AudioStream
* SDL_Gamepad
* SDL_Joystick
* SDL_RWops
* SDL_Renderer
* SDL_Sensor
* SDL_Surface
* SDL_Texture
* SDL_Window
Also switched the D3D11 and D3D12 renderers to use real NV12 textures for NV12 data.
The combination of these two changes allows us to implement 0-copy video decode and playback for D3D11 in testffmpeg without any access to the renderer internals.
You can see it in action in testaudio by mousing over a logical device; it
will show a visualizer for the current PCM (whatever is currently being
recorded on a capture device, or whatever is being mixed for output on
playback devices).
Fixes#8122.
This is meant to offer a simplified API for people that are either migrating
directly from SDL2 with minimal effort or just want to make noise without
any of the fancy new API features.
Users of this API can just deal with a single SDL_AudioStream as their only
object/handle into the audio subsystem.
They are still allowed to open multiple devices (or open the same device
multiple times), but cannot change stream bindings on logical devices opened
through this function.
Destroying the single audio stream will also close the logical device behind
the scenes.
The current status is stored in the SDL_rwops 'status' field to be able to determine whether a 0 return value is caused by end of file, an error, or a non-blocking source not being ready.
The functions to read sized datatypes now return SDL_bool so you can detect read errors.
Fixes https://github.com/libsdl-org/SDL/issues/6729
Add SDL_ShowWindowSystemMenu() to display the system-level menu for windows. Typically, this is done by right-clicking on the system provided window decorations, however, if an application is rendering its own client-side decorations, there is currently no way to display it. This menu is provided by the system and can provide privileged desktop functionality such as moving or pinning a window to a specific workspace or display, setting the always-on-top property, or taking screenshots. In many cases, there are no APIs which allow applications to perform these actions manually.
Implemented for Wayland via functionality provided by the xdg_toplevel protocol, Win32 via the undocumented message 0x313 (typically called WM_POPUPSYSTEMMENU), and X11 via the "_GTK_SHOW_WINDOW_MENU" atom (supported in GNOME and KDE).
This rips up the entire SDL audio subsystem! While we still feed the audio device from a separate thread, the audio callback into the app is now gone a totally optional alternative.
Now the app will bind an SDL_AudioStream to a given device and feed data to it. As many streams as one likes can be bound to a device; SDL will mix them all into a single buffer and feed the device from there.
So not only does this function as a basic mixer, it also means that multiple device opens are handled seamlessly (so if you want to open the device for your game, but you also link to a library that provides VoIP and it wants to open the device separately, you don't have to worry about stepping on each other, or that the OS will fail to allow multiple opens of the same device, etc).
Merged from pull request #7704.
Fixes#7379.
Reference Issue #6889.
Reference Issue #6632.
Now you open an audio device and attach streams, as planned, but each
open generates a new logical device. Each logical device has its own
streams that are managed as a group, but all streams on all logical
devices are mixed into a single buffer for a single OS-level open of
the physical device.
This allows multiple opens of a device that won't interfere with each
other and also clean up just what the opener assigned to their logical
device, so all their streams will go away on close but other opens will
continue to mix as they were.
More or less, this makes things work as expected at the app level, but
also gives them the power to group audio streams, and (once added) pause
them all at once, etc.
Also renamed most cases of SDL_GAMEPAD_TYPE_UNKNOWN to SDL_GAMEPAD_TYPE_STANDARD, and SDL_GetGamepadType() will return SDL_GAMEPAD_TYPE_UNKNOWN only if the gamepad is invalid.
Also renamed SDL_GetDisplayOrientation() SDL_GetDisplayCurrentOrientation()
The natural orientation of the primary display is the frame of reference for accelerometer and gyro sensor readings.
