SDL3/MigrationGuide: There were nothing before my proposal

Live page is here: https://wiki.libsdl.org/SDL3/MigrationGuide

SDL3/MigrationGuide.md

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+
+# Firstly let's start by the compilation 
+
+## cmake:
+
+```
+
+find_package(SDL3 QUIET)
+if(NOT SDL3_FOUND)
+        include(FetchContent)
+        FetchContent_Declare(
+                SDL
+                GIT_REPOSITORY https://github.com/libsdl-org/SDL.git
+                GIT_TAG main
+        #        GIT_SHALLOW TRUE
+        #        GIT_PROGRESS TRUE
+        )
+        FetchContent_MakeAvailable(SDL)
+endif()
+
+[...]
+
+target_link_libraries(${PROJECT_NAME} SDL3::SDL3)
+
+```
+The major things that change in a cmake is the linked library that change from "SDL2::SDL2" to "SDL3::SDL3"
+
+# Now let's continue with your code
+
+When compiling the error handling you can fall on some depreciation, the compilation will throw error like this:
+
+Compilation/Sdl/Main.cpp:36:13: error: use of undeclared identifier 'SDL_FillRect_renamed_SDL_FillSurfaceRect'
+            SDL_FillRect( screenSurface, NULL, SDL_MapRGB( screenSurface->format, 0xFF, 0xFF, 0xFF ) );
+
+looking closer we can read 'SDL_FillRect_renamed_SDL_FillSurfaceRect' meaning that old name SDL_FillRect turns into SDL_FillSurfaceRect 
+
+## Includes
+
+- `#include <SDL2/SDL.h>` turns into <SDL3/SDL.h>
+
+## Sources (let's give the basics change to run a default app)
+
+- `SDL_Window *SDL_CreateWindow(const char *title, int x, int y, int w, int h, Uint32 flags)` turns into `SDL_Window *SDL_CreateWindow(const char *title, int w, int h, SDL_WindowFlags flags)`
+- `int SDL_FillRect(SDL_Surface *dst, const SDL_Rect *rect, Uint32 color)` turns into `int SDL_FillSurfaceRect(SDL_Surface *dst, const SDL_Rect *rect, Uint32 color)`
+- `SDL_EventType::SDL_QUIT` turns into SDL_EventType::SDL_EVENT_QUIT`
+
+# Now let's open A window with SDL3
+
+##Source code
+
+CMakeList.txt
+```
+cmake_minimum_required(VERSION 3.24)
+project(app)
+
+set(CMAKE_CXX_STANDARD 17)
+
+#set(SDL_VERSION "2.30.2")
+
+find_package(SDL3 QUIET)
+if(NOT SDL3_FOUND)
+        include(FetchContent)
+        FetchContent_Declare(
+                SDL
+                GIT_REPOSITORY https://github.com/libsdl-org/SDL.git
+                GIT_TAG main
+        #        GIT_SHALLOW TRUE
+        #        GIT_PROGRESS TRUE
+        )
+        FetchContent_MakeAvailable(SDL)
+endif()
+
+set(SOURCE_FILES Main.cpp)
+
+add_executable(${PROJECT_NAME} ${SOURCE_FILES})
+target_link_libraries(${PROJECT_NAME} SDL3::SDL3)
+#target_compile_options(${PROJECT_NAME} -Wall)
+```
+
+Main.cpp
+```
+//Using SDL and standard IO
+#include <SDL3/SDL.h>
+#include <stdio.h>
+
+//Screen dimension constants
+const int SCREEN_WIDTH = 640;
+const int SCREEN_HEIGHT = 480;
+
+int main( int argc, char* args[] )
+{
+    //The window we'll be rendering to
+    SDL_Window* window = NULL;
+    
+    //The surface contained by the window
+    SDL_Surface* screenSurface = NULL;
+
+    //Initialize SDL
+    if( SDL_Init( SDL_INIT_VIDEO ) < 0 )
+    {
+        printf( "SDL could not initialize! SDL_Error: %s\n", SDL_GetError() );
+    }
+    else
+    {
+        //Create window
+        window = SDL_CreateWindow( "SDL Tutorial", /*SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED,*/ SCREEN_WIDTH, SCREEN_HEIGHT, SDL_WINDOW_MAXIMIZED);
+        if( window == NULL )
+        {
+            printf( "Window could not be created! SDL_Error: %s\n", SDL_GetError() );
+        }
+         else
+        {
+            //Get window surface
+            screenSurface = SDL_GetWindowSurface( window );
+
+            //Fill the surface white
+            SDL_FillSurfaceRect( screenSurface, NULL, SDL_MapRGB( screenSurface->format, 0xFF, 0xFF, 0xFF ) );
+            
+            //Update the surface
+            SDL_UpdateWindowSurface( window );
+
+            //Hack to get window to stay up
+            SDL_Event e; 
+            bool quit = false;
+            while(quit == false){
+                while( SDL_PollEvent( &e ) ){
+                    if( e.type == SDL_EVENT_QUIT ) {
+                        quit = true;
+                    }
+                }
+            }
+        }
+    }
+    //Destroy window
+    SDL_DestroyWindow( window );
+
+    //Quit SDL subsystems
+    SDL_Quit();
+
+    return 0;
+}
+```
+
+## Compilation
+
+- create a folder build/ in your project folder to keep your work clean
+- move in (using`cd` for unix based)
+- `cmake ..` (to call the cmake in the parent directory)
+- `cmake --build .` (then build your application)
+- `./app` (run your application)