How to include ft2build.h in SDL2 CMake project

Question

I want to compile a CMake project using SDL2 and SDL_ttf library.

I copied "SDL_ttf.c" & "SDL_ttf.h" into my src folder. (EDIT: removed it, see comments)

I also added this to my CMakeLists.txt: include_directories(${SDL2_TTF_INCLUDE_DIR})

freetype2 is also installed

but i get the error after calling make

src/SDL_ttf.c:28:10: fatal error: ft2build.h: No such file or directory
28 | #include <ft2build.h>

How do i properly install SDL_ttf to my system? (https://github.com/libsdl-org/SDL_ttf/blob/main/CMakeLists.txt)

EDIT:

my CMakeLists.txt:

cmake_minimum_required(VERSION 3.7)
set(CMAKE_CXX_STANDARD 17)
set(CMAKE_CXX_STANDARD_REQUIRED ON)

add_definitions(-std=c++17)

set(CXX_FLAGS "-Wall")
set(CMAKE_CXX_FLAGS, "${CXX_FLAGS}")

project(SDL2Test)

set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} "${CMAKE_SOURCE_DIR}/cmake/")

find_package(SDL2 REQUIRED)
find_package(SDL2_ttf REQUIRED)
include_directories(${SDL2_INCLUDE_DIRS} src)
include_directories(${SDL2_TTF_INCLUDE_DIR})

add_executable(Zokoban src/main.cpp src/game.cpp src/controller.cpp src/renderer.cpp src/hero.cpp src/level.cpp)
string(STRIP ${SDL2_LIBRARIES} SDL2_LIBRARIES)
target_link_libraries(Zokoban ${SDL2_LIBRARIES} ${SDL2_TTF_INCLUDE_DIR})

EDIT2:

after sudo make install (SDL_ttf source) and removing the SDL-source files from my repo:

[ 57%] Building CXX object CMakeFiles/Zokoban.dir/src/renderer.cpp.o
/07_Capstone/Zokoban/src/renderer.cpp:9:10: fatal error: SDL_ttf.h: No such file or directory
    9 | #include <SDL_ttf.h>

EDIT3

On another machine (debian11) i couldn't even compile the SDL_ttf - source

19:46 $ 
✔ ~/ThirdParty/SDL_ttf/build [main|✚ 3…1] 
19:46 $ make
/bin/bash ./libtool  --tag=CC   --mode=compile gcc -DPACKAGE_NAME=\"SDL2_ttf\" -DPACKAGE_TARNAME=\"SDL2_ttf\" -DPACKAGE_VERSION=\"2.21.0\" -DPACKAGE_STRING=\"SDL2_ttf\ 2.21.0\" -DPACKAGE_BUGREPORT=\"https://github.com/libsdl-org/SDL_ttf/issues\" -DPACKAGE_URL=\"\" -DSTDC_HEADERS=1 -DHAVE_SYS_TYPES_H=1 -DHAVE_SYS_STAT_H=1 -DHAVE_STDLIB_H=1 -DHAVE_STRING_H=1 -DHAVE_MEMORY_H=1 -DHAVE_STRINGS_H=1 -DHAVE_INTTYPES_H=1 -DHAVE_STDINT_H=1 -DHAVE_UNISTD_H=1 -DHAVE_DLFCN_H=1 -DLT_OBJDIR=\".libs/\" -DSDL_BUILD_MAJOR_VERSION=2 -DSDL_BUILD_MINOR_VERSION=21 -DSDL_BUILD_MICRO_VERSION=0 -DPACKAGE=\"SDL2_ttf\" -DVERSION=\"2.21.0\" -DTTF_USE_HARFBUZZ=1 -DHAVE_CXX11=1 -DALIGNOF_STRUCT_CHAR__=1 -I. -I..   -I../external/freetype/include -DFT2_BUILD_LIBRARY -DFT_PUBLIC_FUNCTION_ATTRIBUTE= -I../external/harfbuzz -I../external/harfbuzz/src -DHAVE_CONFIG_H -DFT_CONFIG_OPTION_USE_HARFBUZZ   -g -O2 -D_REENTRANT -I/usr/include/SDL2 -Wall -fvisibility=hidden  -DHAVE_OPENGL -MT libSDL2_ttf_la-SDL_ttf.lo -MD -MP -MF .deps/libSDL2_ttf_la-SDL_ttf.Tpo -c -o libSDL2_ttf_la-SDL_ttf.lo `test -f 'SDL_ttf.c' || echo '../'`SDL_ttf.c
libtool: compile:  gcc -DPACKAGE_NAME=\"SDL2_ttf\" -DPACKAGE_TARNAME=\"SDL2_ttf\" -DPACKAGE_VERSION=\"2.21.0\" "-DPACKAGE_STRING=\"SDL2_ttf 2.21.0\"" -DPACKAGE_BUGREPORT=\"https://github.com/libsdl-org/SDL_ttf/issues\" -DPACKAGE_URL=\"\" -DSTDC_HEADERS=1 -DHAVE_SYS_TYPES_H=1 -DHAVE_SYS_STAT_H=1 -DHAVE_STDLIB_H=1 -DHAVE_STRING_H=1 -DHAVE_MEMORY_H=1 -DHAVE_STRINGS_H=1 -DHAVE_INTTYPES_H=1 -DHAVE_STDINT_H=1 -DHAVE_UNISTD_H=1 -DHAVE_DLFCN_H=1 -DLT_OBJDIR=\".libs/\" -DSDL_BUILD_MAJOR_VERSION=2 -DSDL_BUILD_MINOR_VERSION=21 -DSDL_BUILD_MICRO_VERSION=0 -DPACKAGE=\"SDL2_ttf\" -DVERSION=\"2.21.0\" -DTTF_USE_HARFBUZZ=1 -DHAVE_CXX11=1 -DALIGNOF_STRUCT_CHAR__=1 -I. -I.. -I../external/freetype/include -DFT2_BUILD_LIBRARY -DFT_PUBLIC_FUNCTION_ATTRIBUTE= -I../external/harfbuzz -I../external/harfbuzz/src -DHAVE_CONFIG_H -DFT_CONFIG_OPTION_USE_HARFBUZZ -g -O2 -D_REENTRANT -I/usr/include/SDL2 -Wall -fvisibility=hidden -DHAVE_OPENGL -MT libSDL2_ttf_la-SDL_ttf.lo -MD -MP -MF .deps/libSDL2_ttf_la-SDL_ttf.Tpo -c ../SDL_ttf.c  -fPIC -DPIC -o .libs/libSDL2_ttf_la-SDL_ttf.o
../SDL_ttf.c:28:10: fatal error: ft2build.h: No such file or directory
   28 | #include <ft2build.h>
      |          ^~~~~~~~~~~~
compilation terminated.
make: *** [Makefile:1539: libSDL2_ttf_la-SDL_ttf.lo] Error 1

.. although ft2build.h is obviously installed:

ls /usr/include/freetype2/
freetype  ft2build.h

EDIT4:

I downloaded from https://github.com/libsdl-org/SDL_ttf/releases "SDL2_ttf-2.20.0.tar.gz". And could configure, make and sudo make install SDL_ttf.

... but make my project is still not possible

18:03 $ make
[ 14%] Building CXX object CMakeFiles/Zokoban.dir/src/main.cpp.o
[ 28%] Building CXX object CMakeFiles/Zokoban.dir/src/game.cpp.o
[ 42%] Building CXX object CMakeFiles/Zokoban.dir/src/controller.cpp.o
[ 57%] Building CXX object CMakeFiles/Zokoban.dir/src/renderer.cpp.o
/home/Zokoban/src/renderer.cpp:9:10: fatal error: SDL_ttf.h: No such file or directory
    9 | #include <SDL_ttf.h>
      |          ^~~~~~~~~~~

When i tried it with the released sourcecode i get still the error.

~/learning/ThirdParty/SDL_ttf-release-2.20.0/build$ make
depbase=`echo showfont.o | sed 's|[^/]*$|.deps/&|;s|\.o$||'`;\
gcc -DPACKAGE_NAME=\"SDL2_ttf\" -DPACKAGE_TARNAME=\"SDL2_ttf\" -DPACKAGE_VERSION=\"2.20.0\" -DPACKAGE_STRING=\"SDL2_ttf\ 2.20.0\" -DPACKAGE_BUGREPORT=\"https://github.com/libsdl-org/SDL_ttf/issues\" -DPACKAGE_URL=\"\" -DHAVE_STDIO_H=1 -DHAVE_STDLIB_H=1 -DHAVE_STRING_H=1 -DHAVE_INTTYPES_H=1 -DHAVE_STDINT_H=1 -DHAVE_STRINGS_H=1 -DHAVE_SYS_STAT_H=1 -DHAVE_SYS_TYPES_H=1 -DHAVE_UNISTD_H=1 -DSTDC_HEADERS=1 -DHAVE_DLFCN_H=1 -DLT_OBJDIR=\".libs/\" -DSDL_BUILD_MAJOR_VERSION=2 -DSDL_BUILD_MINOR_VERSION=20 -DSDL_BUILD_MICRO_VERSION=0 -DPACKAGE=\"SDL2_ttf\" -DVERSION=\"2.20.0\" -DTTF_USE_HARFBUZZ=1 -DHAVE_CXX11=1 -DALIGNOF_STRUCT_CHAR__=1 -I. -I..     -g -O2 -D_REENTRANT -I/usr/include/SDL2 -Wall -fvisibility=hidden  -DHAVE_OPENGL -MT showfont.o -MD -MP -MF $depbase.Tpo -c -o showfont.o ../showfont.c &&\
mv -f $depbase.Tpo $depbase.Po
/bin/bash ./libtool  --tag=CC   --mode=compile gcc -DPACKAGE_NAME=\"SDL2_ttf\" -DPACKAGE_TARNAME=\"SDL2_ttf\" -DPACKAGE_VERSION=\"2.20.0\" -DPACKAGE_STRING=\"SDL2_ttf\ 2.20.0\" -DPACKAGE_BUGREPORT=\"https://github.com/libsdl-org/SDL_ttf/issues\" -DPACKAGE_URL=\"\" -DHAVE_STDIO_H=1 -DHAVE_STDLIB_H=1 -DHAVE_STRING_H=1 -DHAVE_INTTYPES_H=1 -DHAVE_STDINT_H=1 -DHAVE_STRINGS_H=1 -DHAVE_SYS_STAT_H=1 -DHAVE_SYS_TYPES_H=1 -DHAVE_UNISTD_H=1 -DSTDC_HEADERS=1 -DHAVE_DLFCN_H=1 -DLT_OBJDIR=\".libs/\" -DSDL_BUILD_MAJOR_VERSION=2 -DSDL_BUILD_MINOR_VERSION=20 -DSDL_BUILD_MICRO_VERSION=0 -DPACKAGE=\"SDL2_ttf\" -DVERSION=\"2.20.0\" -DTTF_USE_HARFBUZZ=1 -DHAVE_CXX11=1 -DALIGNOF_STRUCT_CHAR__=1 -I. -I..   -I../external/freetype/include -DFT2_BUILD_LIBRARY -DFT_PUBLIC_FUNCTION_ATTRIBUTE= -I../external/harfbuzz -I../external/harfbuzz/src -DHAVE_CONFIG_H -DFT_CONFIG_OPTION_USE_HARFBUZZ   -g -O2 -D_REENTRANT -I/usr/include/SDL2 -Wall -fvisibility=hidden  -DHAVE_OPENGL -MT libSDL2_ttf_la-SDL_ttf.lo -MD -MP -MF .deps/libSDL2_ttf_la-SDL_ttf.Tpo -c -o libSDL2_ttf_la-SDL_ttf.lo `test -f 'SDL_ttf.c' || echo '../'`SDL_ttf.c
libtool: compile:  gcc -DPACKAGE_NAME=\"SDL2_ttf\" -DPACKAGE_TARNAME=\"SDL2_ttf\" -DPACKAGE_VERSION=\"2.20.0\" "-DPACKAGE_STRING=\"SDL2_ttf 2.20.0\"" -DPACKAGE_BUGREPORT=\"https://github.com/libsdl-org/SDL_ttf/issues\" -DPACKAGE_URL=\"\" -DHAVE_STDIO_H=1 -DHAVE_STDLIB_H=1 -DHAVE_STRING_H=1 -DHAVE_INTTYPES_H=1 -DHAVE_STDINT_H=1 -DHAVE_STRINGS_H=1 -DHAVE_SYS_STAT_H=1 -DHAVE_SYS_TYPES_H=1 -DHAVE_UNISTD_H=1 -DSTDC_HEADERS=1 -DHAVE_DLFCN_H=1 -DLT_OBJDIR=\".libs/\" -DSDL_BUILD_MAJOR_VERSION=2 -DSDL_BUILD_MINOR_VERSION=20 -DSDL_BUILD_MICRO_VERSION=0 -DPACKAGE=\"SDL2_ttf\" -DVERSION=\"2.20.0\" -DTTF_USE_HARFBUZZ=1 -DHAVE_CXX11=1 -DALIGNOF_STRUCT_CHAR__=1 -I. -I.. -I../external/freetype/include -DFT2_BUILD_LIBRARY -DFT_PUBLIC_FUNCTION_ATTRIBUTE= -I../external/harfbuzz -I../external/harfbuzz/src -DHAVE_CONFIG_H -DFT_CONFIG_OPTION_USE_HARFBUZZ -g -O2 -D_REENTRANT -I/usr/include/SDL2 -Wall -fvisibility=hidden -DHAVE_OPENGL -MT libSDL2_ttf_la-SDL_ttf.lo -MD -MP -MF .deps/libSDL2_ttf_la-SDL_ttf.Tpo -c ../SDL_ttf.c  -fPIC -DPIC -o .libs/libSDL2_ttf_la-SDL_ttf.o
../SDL_ttf.c:28:10: fatal error: ft2build.h: No such file or directory
   28 | #include <ft2build.h>
      |          ^~~~~~~~~~~~
compilation terminated.
make: *** [Makefile:1536: libSDL2_ttf_la-SDL_ttf.lo] Error 1

My ideas run out :(