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ext-SDL/docs/README-cmake.md
Ryan C. Gordon 16535b7ee2
examples: Add CMake glue to optionally build examples, as we do for the tests. 
In fact, most of the CMake code was stolen from the test directory.
2024-07-23 00:58:57 -04:00

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# CMake
[www.cmake.org](https://www.cmake.org/)
The CMake build system is supported on the following platforms:
* FreeBSD
* Linux
* Microsoft Visual C
* MinGW and Msys
* macOS, iOS, tvOS, and visionOS with support for XCode
* Android
* Emscripten
* NetBSD
* Haiku
* Nintendo 3DS
* PlayStation 2
* PlayStation Portable
* PlayStation Vita
* QNX 7.x/8.x
* RiscOS
## Building SDL
Assuming the source tree of SDL is located at `~/sdl`,
this will configure and build SDL in the `~/build` directory:
```sh
cmake -S ~/sdl -B ~/build
cmake --build ~/build
```
Installation can be done using:
```sh
cmake --install ~/build --prefix /usr/local # '--install' requires CMake 3.15, or newer
```
This will install SDL to /usr/local.
### Building SDL tests
You can build the SDL test programs by adding `-DSDL_TESTS=ON` to the first cmake command above:
```sh
cmake -S ~/sdl -B ~/build -DSDL_TEST_LIBRARY=ON -DSDL_TESTS=ON
```
and then building normally. In this example, the test programs will be built and can be run from `~/build/tests/`.
### Building SDL examples
You can build the SDL example programs by adding `-DSDL_EXAMPLES=ON` to the first cmake command above:
```sh
cmake -S ~/sdl -B ~/build -DSDL_EXAMPLES=ON
```
and then building normally. In this example, the example programs will be built and can be run from `~/build/examples/`.
## Including SDL in your project
SDL can be included in your project in 2 major ways:
- using a system SDL library, provided by your (*nix) distribution or a package manager
- using a vendored SDL library: this is SDL copied or symlinked in a subfolder.
The following CMake script supports both, depending on the value of `MYGAME_VENDORED`.
```cmake
cmake_minimum_required(VERSION 3.5)
project(mygame)
# Create an option to switch between a system sdl library and a vendored SDL library
option(MYGAME_VENDORED "Use vendored libraries" OFF)
if(MYGAME_VENDORED)
# This assumes you have added SDL as a submodule in vendored/SDL
add_subdirectory(vendored/SDL EXCLUDE_FROM_ALL)
else()
# 1. Look for a SDL3 package,
# 2. look for the SDL3-shared component, and
# 3. fail if the shared component cannot be found.
find_package(SDL3 REQUIRED CONFIG REQUIRED COMPONENTS SDL3-shared)
endif()
# Create your game executable target as usual
add_executable(mygame WIN32 mygame.c)
# Link to the actual SDL3 library.
target_link_libraries(mygame PRIVATE SDL3::SDL3)
```
### A system SDL library
For CMake to find SDL, it must be installed in [a default location CMake is looking for](https://cmake.org/cmake/help/latest/command/find_package.html#config-mode-search-procedure).
The following components are available, to be used as an argument of `find_package`.
| Component name | Description |
|----------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| SDL3-shared | The SDL3 shared library, available through the `SDL3::SDL3-shared` target |
| SDL3-static | The SDL3 static library, available through the `SDL3::SDL3-static` target |
| SDL3_test | The SDL3_test static library, available through the `SDL3::SDL3_test` target |
| SDL3 | The SDL3 library, available through the `SDL3::SDL3` target. This is an alias of `SDL3::SDL3-shared` or `SDL3::SDL3-static`. This component is always available. |
| Headers | The SDL3 headers, available through the `SDL3::Headers` target. This component is always available. |
SDL's CMake support guarantees a `SDL3::SDL3` target.
Neither `SDL3::SDL3-shared` nor `SDL3::SDL3-static` are guaranteed to exist.
### Using a vendored SDL
This only requires a copy of SDL in a subdirectory + `add_subdirectory`.
Alternatively, use [FetchContent](https://cmake.org/cmake/help/latest/module/FetchContent.html).
Depending on the configuration, the same targets as a system SDL package are available.
## CMake configuration options
### Build optimized library
By default, CMake provides 4 build types: `Debug`, `Release`, `RelWithDebInfo` and `MinSizeRel`.
The main difference(s) between these are the optimization options and the generation of debug info.
To configure SDL as an optimized `Release` library, configure SDL with:
```sh
cmake ~/SDL -DCMAKE_BUILD_TYPE=Release
```
To build it, run:
```sh
cmake --build . --config Release
```
### Shared or static
By default, only a dynamic (=shared) SDL library is built and installed.
The options `-DSDL_SHARED=` and `-DSDL_STATIC=` accept boolean values to change this.
Exceptions exist:
- some platforms don't support dynamic libraries, so only `-DSDL_STATIC=ON` makes sense.
- a static Apple framework is not supported
### Pass custom compile options to the compiler
- Use [`CMAKE_<LANG>_FLAGS`](https://cmake.org/cmake/help/latest/variable/CMAKE_LANG_FLAGS.html) to pass extra
flags to the compiler.
- Use [`CMAKE_EXE_LINKER_FLAGS`](https://cmake.org/cmake/help/latest/variable/CMAKE_EXE_LINKER_FLAGS.html) to pass extra option to the linker for executables.
- Use [`CMAKE_SHARED_LINKER_FLAGS`](https://cmake.org/cmake/help/latest/variable/CMAKE_SHARED_LINKER_FLAGS.html) to pass extra options to the linker for shared libraries.
#### Examples
- build a SDL library optimized for (more) modern x64 microprocessor architectures.
With gcc or clang:
```sh
cmake ~/sdl -DCMAKE_C_FLAGS="-march=x86-64-v3" -DCMAKE_CXX_FLAGS="-march=x86-64-v3"
```
With Visual C:
```sh
cmake .. -DCMAKE_C_FLAGS="/ARCH:AVX2" -DCMAKE_CXX_FLAGS="/ARCH:AVX2"
```
### Apple
CMake documentation for cross building for Apple:
[link](https://cmake.org/cmake/help/latest/manual/cmake-toolchains.7.html#cross-compiling-for-ios-tvos-visionos-or-watchos)
#### iOS/tvOS/visionOS
CMake 3.14+ natively includes support for iOS, tvOS and watchOS. visionOS requires CMake 3.28+.
SDL binaries may be built using Xcode or Make, possibly among other build-systems.
When using a compatible version of CMake, it should be possible to:
- build SDL dylibs, both static and dynamic dylibs
- build SDL frameworks, only shared
- build SDL test apps
#### Frameworks
Configure with `-DSDL_FRAMEWORK=ON` to build a SDL framework instead of a dylib shared library.
Only shared frameworks are supported, no static ones.
#### Platforms
Use `-DCMAKE_PLATFORM_NAME=<value>` to configure the platform. CMake can target only one platform at a time.
| Apple platform | `CMAKE_SYSTEM_NAME` value |
|-----------------|---------------------------|
| macOS (MacOS X) | `Darwin` |
| iOS | `iOS` |
| tvOS | `tvOS` |
| visionOS | `visionOS` |
| watchOS | `watchOS` |
#### Universal binaries
A universal binaries, can be built by configuring CMake with
`-DCMAKE_OSX_ARCHITECTURES=<semicolon-separated list of CPU architectures>`.
For example `-DCMAKE_OSX_ARCHITECTURES="arm64;x86_64"` will build binaries that run on both Intel cpus and Apple silicon.
SDL supports following Apple architectures:
| Platform | `CMAKE_OSX_ARCHITECTURES` value |
|----------------------------|---------------------------------|
| 64-bit ARM (Apple Silicon) | `arm64` |
| x86_64 | `x86_64` |
| 32-bit ARM | `armv7s` |
CMake documentation: [link](https://cmake.org/cmake/help/latest/variable/CMAKE_OSX_ARCHITECTURES.html)
#### Simulators and/or non-default maxOS platform SDK
Use `-DCMAKE_OSX_SYSROOT=<value>` to configure a different platform SDK.
The value can be either the name of the SDK, or a full path to the sdk (e.g. `/full/path/to/iPhoneOS.sdk`).
| SDK | `CMAKE_OSX_SYSROOT` value |
|----------------------|---------------------------|
| iphone | `iphoneos` |
| iphonesimulator | `iphonesimulator` |
| appleTV | `appletvos` |
| appleTV simulator | `appletvsimulator` |
| visionOS | `xr` |
| visionOS simulator | `xrsimulator` |
| watchOS | `watchos` |
| watchOS simulator | `watchsimulator` |
Append with a version number to target a specific SDK revision: e.g. `iphoneos12.4`, `appletvos12.4`.
CMake documentation: [link](https://cmake.org/cmake/help/latest/variable/CMAKE_OSX_SYSROOT.html)
#### Examples
- for macOS, building a dylib and/or static library for x86_64 and arm64:
```bash
cmake ~/sdl -DCMAKE_SYSTEM_NAME=Darwin -DCMAKE_OSX_ARCHITECTURES="x86_64;arm64"
- for macOS, building an universal framework for x86_64 and arm64:
```bash
cmake ~/sdl -DSDL_FRAMEWORK=ON -DCMAKE_SYSTEM_NAME=Darwin -DCMAKE_OSX_ARCHITECTURES="x86_64;arm64"
- for iOS-Simulator, using the latest, installed SDK:
```bash
cmake ~/sdl -DCMAKE_SYSTEM_NAME=iOS -DCMAKE_OSX_SYSROOT=iphonesimulator -DCMAKE_OSX_ARCHITECTURES=x86_64
```
- for iOS-Device, using the latest, installed SDK, 64-bit only
```bash
cmake ~/sdl -DCMAKE_SYSTEM_NAME=iOS -DCMAKE_OSX_SYSROOT=iphoneos -DCMAKE_OSX_ARCHITECTURES=arm64
```
- for iOS-Device, using the latest, installed SDK, mixed 32/64 bit
```cmake
cmake ~/sdl -DCMAKE_SYSTEM_NAME=iOS -DCMAKE_OSX_SYSROOT=iphoneos -DCMAKE_OSX_ARCHITECTURES="arm64;armv7s"
```
- for iOS-Device, using a specific SDK revision (iOS 12.4, in this example):
```cmake
cmake ~/sdl -DCMAKE_SYSTEM_NAME=iOS -DCMAKE_OSX_SYSROOT=iphoneos12.4 -DCMAKE_OSX_ARCHITECTURES=arm64
```
- for iOS-Simulator, using the latest, installed SDK, and building SDL test apps (as .app bundles):
```cmake
cmake ~/sdl -DSDL_TESTS=1 -DCMAKE_SYSTEM_NAME=iOS -DCMAKE_OSX_SYSROOT=iphonesimulator -DCMAKE_OSX_ARCHITECTURES=x86_64
```
- for tvOS-Simulator, using the latest, installed SDK:
```cmake
cmake ~/sdl -DCMAKE_SYSTEM_NAME=tvOS -DCMAKE_OSX_SYSROOT=appletvsimulator -DCMAKE_OSX_ARCHITECTURES=x86_64
```
- for tvOS-Device, using the latest, installed SDK:
```cmake
cmake ~/sdl -DCMAKE_SYSTEM_NAME=tvOS -DCMAKE_OSX_SYSROOT=appletvos -DCMAKE_OSX_ARCHITECTURES=arm64`
```
- for QNX/aarch64, using the latest, installed SDK:
```cmake
cmake ~/sdl -DCMAKE_TOOLCHAIN_FILE=~/sdl/build-scripts/cmake-toolchain-qnx-aarch64le.cmake -DSDL_X11=0
```
## SDL-specific CMake options
SDL can be customized through (platform-specific) CMake options.
The following table shows generic options that are available for most platforms.
At the end of SDL CMake configuration, a table shows all CMake options along with its detected value.
| CMake option | Valid values | Description |
|-------------------------------|--------------|-----------------------------------------------------------------------------------------------------|
| `-DSDL_SHARED=` | `ON`/`OFF` | Build SDL shared library (not all platforms support this) (`libSDL3.so`/`libSDL3.dylib`/`SDL3.dll`) |
| `-DSDL_STATIC=` | `ON`/`OFF` | Build SDL static library (`libSDL3.a`/`SDL3-static.lib`) |
| `-DSDL_TEST_LIBRARY=` | `ON`/`OFF` | Build SDL test library (`libSDL3_test.a`/`SDL3_test.lib`) |
| `-DSDL_TESTS=` | `ON`/`OFF` | Build SDL test programs (**requires `-DSDL_TEST_LIBRARY=ON`**) |
| `-DSDL_DISABLE_INSTALL=` | `ON`/`OFF` | Don't create a SDL install target |
| `-DSDL_DISABLE_INSTALL_DOCS=` | `ON`/`OFF` | Don't install the SDL documentation |
| `-DSDL_INSTALL_TESTS=` | `ON`/`OFF` | Install the SDL test programs |
## CMake FAQ
### How do I copy a SDL3 dynamic library to another location?
Use [CMake generator expressions](https://cmake.org/cmake/help/latest/manual/cmake-generator-expressions.7.html#target-dependent-expressions).
Generator expressions support multiple configurations, and are evaluated during build system generation time.
On Windows, the following example this copies `SDL3.dll` to the directory where `mygame.exe` is built.
On Unix systems, `$<TARGET_FILE:...>` will refer to the dynamic library (or framework).
```cmake
if(WIN32)
add_custom_command(
TARGET mygame POST_BUILD
COMMAND "${CMAKE_COMMAND}" -E copy $<TARGET_FILE:SDL3::SDL3-shared> $<TARGET_FILE_DIR:mygame>
VERBATIM
)
endif()
```
### Linking against a static SDL library fails due to relocation errors
On unix platforms, all code that ends up in shared libraries needs to be built as relocatable (=position independent) code.
However, by default CMake builds static libraries as non-relocatable.
Configuring SDL with `-DCMAKE_POSITION_INDEPENDENT_CODE=ON` will result in a static `libSDL3.a` library
which you can link against to create a shared library.
## Help, it doesn't work!
Below, a SDL3 CMake project can be found that builds 99.9% of time (assuming you have internet connectivity).
When you have a problem with building or using SDL, please modify it until it reproduces your issue.
```cmake
cmake_minimum_required(VERSION 3.16)
project(sdl_issue)
# !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
# !!!!!! !!!!!!
# !!!!!! This CMake script is not using "CMake best practices". !!!!!!
# !!!!!! Don't use it in your project. !!!!!!
# !!!!!! !!!!!!
# !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
# 1. Try system SDL3 package first
find_package(SDL3 QUIET)
if(SDL3_FOUND)
message(STATUS "Using SDL3 via find_package")
endif()
# 2. Try using a vendored SDL library
if(NOT SDL3_FOUND AND EXISTS "${CMAKE_CURRENT_LIST_DIR}/SDL/CMakeLists.txt")
add_subdirectory(SDL EXCLUDE_FROM_ALL)
message(STATUS "Using SDL3 via add_subdirectory")
set(SDL3_FOUND TRUE)
endif()
# 3. Download SDL, and use that.
if(NOT SDL3_FOUND)
include(FetchContent)
set(SDL_SHARED TRUE CACHE BOOL "Build a SDL shared library (if available)")
set(SDL_STATIC TRUE CACHE BOOL "Build a SDL static library (if available)")
FetchContent_Declare(
SDL
GIT_REPOSITORY https://github.com/libsdl-org/SDL.git
GIT_TAG main # Replace this with a particular git tag or git hash
GIT_SHALLOW TRUE
GIT_PROGRESS TRUE
)
message(STATUS "Using SDL3 via FetchContent")
FetchContent_MakeAvailable(SDL)
set_property(DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}/_deps/sdl-src" PROPERTY EXCLUDE_FROM_ALL TRUE)
endif()
file(WRITE main.c [===========================================[
/**
* Modify this source such that it reproduces your problem.
*/
/* START of source modifications */
#include <SDL3/SDL.h>
/*
* SDL3/SDL_main.h is explicitly not included such that a terminal window would appear on Windows.
*/
int main(int argc, char *argv[]) {
(void)argc;
(void)argv;
if (SDL_Init(SDL_INIT_VIDEO) < 0) {
SDL_Log("SDL_Init failed (%s)", SDL_GetError());
return 1;
}
SDL_Window *window = NULL;
SDL_Renderer *renderer = NULL;
if (SDL_CreateWindowAndRenderer("SDL issue", 640, 480, 0, &window, &renderer) < 0) {
SDL_Log("SDL_CreateWindowAndRenderer failed (%s)", SDL_GetError());
SDL_Quit();
return 1;
}
while (1) {
int finished = 0;
SDL_Event event;
while (SDL_PollEvent(&event)) {
if (event.type == SDL_EVENT_QUIT) {
finished = 1;
break;
}
}
if (finished) {
break;
}
SDL_SetRenderDrawColor(renderer, 80, 80, 80, SDL_ALPHA_OPAQUE);
SDL_RenderClear(renderer);
SDL_RenderPresent(renderer);
}
SDL_DestroyRenderer(renderer);
SDL_DestroyWindow(window);
SDL_Quit();
return 0;
}
/* END of source modifications */
]===========================================])
add_executable(sdl_issue main.c)
target_link_libraries(sdl_issue PRIVATE SDL3::SDL3)
# target_link_libraries(sdl_issue PRIVATE SDL3::SDL3-shared)
# target_link_libraries(sdl_issue PRIVATE SDL3::SDL3-static)
```
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