Introduce a way to add a 100% external custom platform

CMakeLists.txt

@@ -1,4 +1,13 @@
 cmake_minimum_required(VERSION 3.0)
+
+# Directory for easier includes
+# Anywhere you see include(...) you can check <root>/cmake for that file
+set(CMAKE_MODULE_PATH ${CMAKE_CURRENT_SOURCE_DIR}/cmake)
+
+include(CustomPlatform)
+
+custom_platform_include_if_exists("raylibPlatformCustomProjectConfig")
+
 project(raylib)
 
 # Avoid excessive expansion of variables in conditionals. In particular, if
@@ -18,9 +27,6 @@ cmake_policy(SET CMP0054 NEW)
 # See https://cmake.org/cmake/help/latest/policy/CMP0063.html
 cmake_policy(SET CMP0063 NEW)
 
-# Directory for easier includes
-# Anywhere you see include(...) you can check <root>/cmake for that file
-set(CMAKE_MODULE_PATH ${CMAKE_CURRENT_SOURCE_DIR}/cmake)
 
 # RAYLIB_IS_MAIN determines whether the project is being used from root
 # or if it is added as a dependency (through add_subdirectory for example).

CMakeOptions.txt

@@ -2,7 +2,7 @@
 include(CMakeDependentOption)
 include(EnumOption)
 
-enum_option(PLATFORM "Desktop;Web;Android;Raspberry Pi;DRM" "Platform to build for.")
+enum_option(PLATFORM "Desktop;Web;Android;Raspberry Pi;DRM;Custom" "Platform to build for.")
 
 enum_option(OPENGL_VERSION "OFF;4.3;3.3;2.1;1.1;ES 2.0;ES 3.0" "Force a specific OpenGL Version?")
 

cmake/BuildOptions.cmake

@@ -11,7 +11,7 @@ endif()
 # This helps support the case where emsdk toolchain file is used
 # either by setting it with -DCMAKE_TOOLCHAIN_FILE=<path_to_emsdk>/upstream/emscripten/cmake/Modules/Platform/Emscripten.cmake
 # or by using "emcmake cmake -B build -S ." as described in https://emscripten.org/docs/compiling/Building-Projects.html
-if(EMSCRIPTEN)
+if(EMSCRIPTEN AND NOT ${PLATFORM} MATCHES "Custom")
     SET(PLATFORM Web CACHE STRING "Forcing PLATFORM_WEB because EMSCRIPTEN was detected")
 endif()
 

cmake/CustomPlatform.cmake

@@ -0,0 +1,9 @@
+macro(custom_platform_include_if_exists file)
+  if("${PLATFORM}" MATCHES "Custom")
+    if (EXISTS "${PLATFORM_CUSTOM_ROOT_DIR}/cmake/${file}.cmake")
+      include("${PLATFORM_CUSTOM_ROOT_DIR}/cmake/${file}.cmake")
+    else ()
+      message(STATUS "No file ${PLATFORM_CUSTOM_ROOT_DIR}/cmake/${file}.cmake detected... skipped")
+    endif ()
+  endif()
+endmacro()

cmake/LibraryConfigurations.cmake

@@ -91,6 +91,8 @@ elseif ("${PLATFORM}" MATCHES "DRM")
     endif ()
     set(LIBS_PRIVATE ${GLESV2} ${EGL} ${DRM} ${GBM} atomic pthread m dl)
 
+elseif ("${PLATFORM}" MATCHES "Custom")
+  set(PLATFORM_CPP "PLATFORM_CUSTOM")
 endif ()
 
 if (NOT ${OPENGL_VERSION} MATCHES "OFF")

external/README.md

@@ -0,0 +1,26 @@
+For the sake of this PR, this folder was added to demonstrate what a custom platform look like as well
+as how to use a custom platform
+
+* `custom_platforms/custom_platform_1`: clone of the web platform
+* `custom_platforms/custom_platform_2`: clone of the desktop platform
+
+
+* `examples/example_for_custom_platform_1`: example using the custom_platform_1
+
+  How to build (use emscripten since it is a web platform: make sure you use the proper locations)
+    ```text
+    mkdir build
+    cd build
+    cmake -DCMAKE_TOOLCHAIN_FILE=/usr/local/emsdk/upstream/emscripten/cmake/Modules/Platform/Emscripten.cmake -DEMSDK=/usr/local/emsdk -DPLATFORM=Custom -DCMAKE_BUILD_TYPE=Debug ..
+    cmake --build . --target example_for_custom_platform_1
+    ```
+
+* `examples/example_for_custom_platform_2`: example using the custom_platform_2
+
+  How to build:
+    ```text
+    mkdir build
+    cd build
+    cmake -DPLATFORM=Custom -DCMAKE_BUILD_TYPE=Debug ..
+    cmake --build . --target example_for_custom_platform_2
+    ```

external/custom_platforms/custom_platform_1/cmake/raylibPlatformCustomLibraryConfig.cmake

@@ -0,0 +1,5 @@
+message(STATUS "From raylibPlatformCustomLibraryConfig (Custom platform 1 (Web)")
+
+set(GRAPHICS "GRAPHICS_API_OPENGL_ES2")
+set(CMAKE_LD_FLAGS "${CMAKE_LD_FLAGS} -s USE_GLFW=3 -s ASSERTIONS=1 --profiling")
+set(CMAKE_STATIC_LIBRARY_SUFFIX ".a")

external/custom_platforms/custom_platform_1/cmake/raylibPlatformCustomTargetConfig.cmake

@@ -0,0 +1,3 @@
+message(STATUS "From raylibPlatformCustomTargetConfig (Custom platform 1 (Web)")
+
+target_link_options(raylib PRIVATE "-sUSE_GLFW=3")