Added MinGW Intro readme, touched up CMake and Visual Studio readmes. (#12485)

(cherry picked from commit 04b4577b58)

docs/INTRO-cmake.md

@@ -5,7 +5,12 @@ The easiest way to use SDL is to include it as a subproject in your project.
 
 We'll start by creating a simple project to build and run [hello.c](hello.c)
 
-Create the file CMakeLists.txt
+# Get a copy of the SDL source:
+```sh
+git clone https://github.com/libsdl-org/SDL.git vendored/SDL
+```
+
+# Create the file CMakeLists.txt
 ```cmake
 cmake_minimum_required(VERSION 3.16)
 project(hello)
@@ -25,24 +30,26 @@ add_executable(hello WIN32 hello.c)
 target_link_libraries(hello PRIVATE SDL3::SDL3)
 ```
 
-Build:
+# Configure and Build:
 ```sh
 cmake -S . -B build
 cmake --build build
 ```
 
-Run:
-- On Windows the executable is in the build Debug directory:
-```sh
-cd build/Debug
-./hello
-``` 
-- On other platforms the executable is in the build directory:
+# Run:
+The executable should be in the `build` directory:
+
 ```sh
 cd build
 ./hello
 ```
 
+If there wasn't an executable there despite the above Build section running successfully, it's likely because you're following this guide using the Visual Studio toolchain, it should instead be in the `build/Debug` directory:
+```sh
+cd build/Debug
+./hello
+```
+
 A more complete example is available at:
 
 https://github.com/Ravbug/sdl3-sample

docs/INTRO-mingw.md

@@ -0,0 +1,95 @@
+# Introduction to SDL with MinGW
+
+Without getting deep into the history, MinGW is a long running project that aims to bring gcc to Windows. That said, there's many distributions, versions, and forks floating around. We recommend installing [MSYS2](https://www.msys2.org/), as it's the easiest way to get a modern toolchain with a package manager to help with dependency management. This would allow you to follow the MSYS2 section below. 
+
+Otherwise you'll want to follow the "Other Distributions" section below.
+
+We'll start by creating a simple project to build and run [hello.c](hello.c).
+
+# MSYS2
+
+Open the `MSYS2 UCRT64` prompt and then ensure you've installed the following packages. This will get you working toolchain, CMake, Ninja, and of course SDL3.
+
+```sh
+pacman -S mingw-w64-ucrt-x86_64-gcc mingw-w64-ucrt-x86_64-ninja mingw-w64-ucrt-x86_64-cmake mingw-w64-ucrt-x86_64-sdl3
+```
+
+## Create the file CMakeLists.txt
+```cmake
+project(sdl_test C CXX)
+cmake_minimum_required(VERSION 3.26)
+
+find_package(SDL3 REQUIRED)
+
+add_executable(sdl_test)
+
+target_sources(sdl_test
+PRIVATE
+    hello.c
+)
+
+target_link_libraries(sdl_test SDL3::SDL3)
+```
+
+## Configure and Build:
+```sh
+cmake -S . -B build
+cmake --build build
+```
+
+## Run:
+
+The executable is in the `build` directory:
+```sh
+cd build
+./hello
+```
+
+# Other Distributions
+
+Things can get quite complicated with other distributions of MinGW. If you can't follow [the cmake intro](INTRO-cmake.md), perhaps due to issues getting cmake to understand your toolchain, this section should work.
+
+## Acquire SDL
+
+Download the `SDL3-devel-<version>-mingw.zip` asset from [the latest release.](https://github.com/libsdl-org/SDL/releases/latest) Then extract it inside your project folder such that the output of `ls SDL3-<version>` looks like `INSTALL.md  LICENSE.txt  Makefile  README.md  cmake  i686-w64-mingw32  x86_64-w64-mingw32`.
+
+## Know your Target Architecture
+
+It is not uncommon for folks to not realize their distribution is targeting 32bit Windows despite things like the name of the toolchain, or the fact that they're running on a 64bit system. We'll ensure we know up front what we need:
+
+Create a file named `arch.c` with the following contents:
+```c
+#include <stddef.h>
+#include <stdio.h>
+int main() {
+    #if defined(__x86_64__) || defined(_M_X64) || defined(i386) || defined(__i386__) || defined(__i386) || defined(_M_IX86)
+        size_t ptr_size = sizeof(int*);
+        if (4 == ptr_size) puts("i686-w64-mingw32");
+        else if (8 == ptr_size) puts("x86_64-w64-mingw32");
+        else puts("Unknown Architecture");
+    #else
+        puts("Unknown Architecture");
+    #endif
+    return 0;
+}
+```
+
+Then run
+
+```sh
+gcc arch.c
+./a.exe
+```
+
+This should print out which library directory we'll need to use when compiling, keep this value in mind, you'll need to use it when compiling in the next section as `<arch>`. If you get "Unknown Architecture" please [report a bug](https://github.com/libsdl-org/SDL/issues).
+
+
+## Build and Run
+
+Now we should have everything needed to compile and run our program. You'll need to ensure to replace `<version>` with the version of the release of SDL3 you downloaded, as well as use the `<arch>` we learned in the previous section.
+
+```sh
+gcc hello.c -o hello.exe -I SDL3-<version>/<arch>/include -L SDL3-<version>/<arch>/lib -lSDL3 -mwindows 
+cp SDL3-<version>/<arch>/bin/SDL3.dll SDL3.dll
+./hello.exe
+```

docs/INTRO-visualstudio.md

@@ -5,10 +5,12 @@ The easiest way to use SDL is to include it as a subproject in your project.
 
 We'll start by creating a simple project to build and run [hello.c](hello.c)
 
+- Get a copy of the SDL source, you can clone the repo, or download the "Source Code" asset from [the latest release.](https://github.com/libsdl-org/SDL/releases/latest)
+  - If you've downloaded a release, make sure to extract the contents somewhere you can find it.
 - Create a new project in Visual Studio, using the C++ Empty Project template
 - Add hello.c to the Source Files
-- Right click the solution, select add an existing project, navigate to VisualC/SDL and add SDL.vcxproj
-- Select your main project and go to Project -> Add Reference and select SDL3
-- Select your main project and go to Project -> Properties, set the filter at the top to "All Configurations" and "All Platforms", select VC++ Directories and add the SDL include directory to "Include Directories"
+- Right click the solution, select add an existing project, navigate to `VisualC/SDL` from within the source you cloned or downloaded above and add SDL.vcxproj
+- Select your main project and go to Project -> Add -> Reference and select SDL3
+- Select your main project and go to Project -> Properties, set the filter at the top to "All Configurations" and "All Platforms", select C/C++ -> General and add the SDL include directory to "Additional Include Directories"
 - Build and run!