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Simplified SDL_main.h migration notes 

Thanks for the feedback!
https://github.com/exult/exult/issues/379#issuecomment-1701066992
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Sam Lantinga 2023-08-31 09:29:59 -07:00
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docs/README-migration.md
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@ -4,6 +4,8 @@ This guide provides useful information for migrating applications from SDL 2.0 t
Details on API changes are organized by SDL 2.0 header below.
The file with your main() function should include <SDL3/SDL_main.h>, as that is no longer included in SDL.h.
Many functions and symbols have been renamed. We have provided a handy Python script [rename_symbols.py](https://github.com/libsdl-org/SDL/blob/main/build-scripts/rename_symbols.py) to rename SDL2 functions to their SDL3 counterparts:
```sh
rename_symbols.py --all-symbols source_code_path
@ -11,14 +13,11 @@ rename_symbols.py --all-symbols source_code_path
It's also possible to apply a semantic patch to migrate more easily to SDL3: [SDL_migration.cocci](https://github.com/libsdl-org/SDL/blob/main/build-scripts/SDL_migration.cocci)
SDL headers should now be included as `#include <SDL3/SDL.h>`. Typically that's the only header you'll need in your application unless you are using OpenGL or Vulkan functionality. We have provided a handy Python script [rename_headers.py](https://github.com/libsdl-org/SDL/blob/main/build-scripts/rename_headers.py) to rename SDL2 headers to their SDL3 counterparts:
```sh
rename_headers.py source_code_path
```
The file with your main() function should also include <SDL3/SDL_main.h>, see below in the SDL_main.h section.
CMake users should use this snippet to include SDL support in their project:
```
find_package(SDL3 REQUIRED CONFIG REQUIRED COMPONENTS SDL3)
@ -39,10 +38,7 @@ LDFLAGS += $(shell pkg-config sdl3 --libs)
The SDL3test library has been renamed SDL3_test.
There is no SDLmain library anymore, it's now header-only, see below in the SDL_main.h section.
begin_code.h and close_code.h in the public headers have been renamed to SDL_begin_code.h and SDL_close_code.h. These aren't meant to be included directly by applications, but if your application did, please update your `#include` lines.
The SDLmain library has been removed, it's been entirely replaced by SDL_main.h.
The vi format comments have been removed from source code. Vim users can use the [editorconfig plugin](https://github.com/editorconfig/editorconfig-vim) to automatically set tab spacing for the SDL coding style.
@ -699,27 +695,6 @@ Instead SDL_main.h is now a header-only library **and not included by SDL.h anym
Using it is really simple: Just `#include <SDL3/SDL_main.h>` in the source file with your standard
`int main(int argc, char* argv[])` function.
The rest happens automatically: If your target platform needs the SDL_main functionality,
your main function will be renamed to SDL_main (with a macro, just like in SDL2),
and the real main-function will be implemented by inline code from SDL_main.h - and if your target
platform doesn't need it, nothing happens.
Like in SDL2, if you want to handle the platform-specific main yourself instead of using the SDL_main magic,
you can `#define SDL_MAIN_HANDLED` before `#include <SDL3/SDL_main.h>` - don't forget to call SDL_SetMainReady()
If you need SDL_main.h in another source file (that doesn't implement main()), you also need to
`#define SDL_MAIN_HANDLED` there, to avoid that multiple main functions are generated by SDL_main.h
There is currently one platform where this approach doesn't always work: WinRT.
It requires WinMain to be implemented in a C++ source file that's compiled with `/ZW`. If your main
is implemented in plain C, or you can't use `/ZW` on that file, you can add another .cpp
source file that just contains `#include <SDL3/SDL_main.h>` and compile that with `/ZW` - but keep
in mind that the source file with your standard main also needs that include!
See [README-winrt.md](./README-winrt.md) for more details.
Furthermore, the different SDL_*RunApp() functions (SDL_WinRtRunApp, SDL_GDKRunApp, SDL_UIKitRunApp)
have been unified into just `int SDL_RunApp(int argc, char* argv[], void * reserved)` (which is also
used by additional platforms that didn't have a SDL_RunApp-like function before).
## SDL_metal.h
SDL_Metal_GetDrawableSize() has been removed. SDL_GetWindowSizeInPixels() can be used in its place.