SDL2 does not work

[zxslzx]

I tested under debian12, error occurred during startup, Segmentation fault.

[kisvegabor]

Please share your lv_conf.h and main.c. How did you compile the project?

[biglion1990]

[main] Building folder: /home/ubuntu/Desktop/lvgl/build
[build] Starting build
[proc] Executing command: /usr/bin/cmake --build /home/ubuntu/Desktop/lvgl/build --config Debug --target all -j 10 --
[build] [ 45%] Built target lvgl
[build] [ 52%] Built target lvgl_thorvg
[build] [ 69%] Built target lvgl_demos
[build] [ 99%] Built target lvgl_examples
[build] [100%] Linking CXX executable ../bin/lvglsim
[build] /usr/bin/ld: lib/liblvgl.a(lv_sdl_window.c.o): in function lv_sdl_window_create': [build] /home/ubuntu/Desktop/lvgl/lvgl/src/drivers/sdl/lv_sdl_window.c:86: undefined reference to SDL_Init'
[build] /usr/bin/ld: /home/ubuntu/Desktop/lvgl/lvgl/src/drivers/sdl/lv_sdl_window.c:87: undefined reference to SDL_StartTextInput' [build] /usr/bin/ld: /home/ubuntu/Desktop/lvgl/lvgl/src/drivers/sdl/lv_sdl_window.c:89: undefined reference to SDL_GetTicks'
[build] /usr/bin/ld: lib/liblvgl.a(lv_sdl_window.c.o): in function lv_sdl_window_set_resizeable': [build] /home/ubuntu/Desktop/lvgl/lvgl/src/drivers/sdl/lv_sdl_window.c:144: undefined reference to SDL_SetWindowResizable'
[build] /usr/bin/ld: lib/liblvgl.a(lv_sdl_window.c.o): in function lv_sdl_get_disp_from_win_id': [build] /home/ubuntu/Desktop/lvgl/lvgl/src/drivers/sdl/lv_sdl_window.c:168: undefined reference to SDL_GetWindowID'
[build] /usr/bin/ld: lib/liblvgl.a(lv_sdl_window.c.o): in function lv_sdl_window_set_title': [build] /home/ubuntu/Desktop/lvgl/lvgl/src/drivers/sdl/lv_sdl_window.c:179: undefined reference to SDL_SetWindowTitle'
[build] /usr/bin/ld: lib/liblvgl.a(lv_sdl_window.c.o): in function lv_sdl_quit': [build] /home/ubuntu/Desktop/lvgl/lvgl/src/drivers/sdl/lv_sdl_window.c:191: undefined reference to SDL_Quit'
[build] /usr/bin/ld: lib/liblvgl.a(lv_sdl_window.c.o): in function sdl_event_handler': [build] /home/ubuntu/Desktop/lvgl/lvgl/src/drivers/sdl/lv_sdl_window.c:303: undefined reference to SDL_Quit'
[build] /usr/bin/ld: /home/ubuntu/Desktop/lvgl/lvgl/src/drivers/sdl/lv_sdl_window.c:271: undefined reference to SDL_PollEvent' [build] /usr/bin/ld: lib/liblvgl.a(lv_sdl_window.c.o): in function window_create':
[build] /home/ubuntu/Desktop/lvgl/lvgl/src/drivers/sdl/lv_sdl_window.c:325: undefined reference to SDL_CreateWindow' [build] /usr/bin/ld: /home/ubuntu/Desktop/lvgl/lvgl/src/drivers/sdl/lv_sdl_window.c:329: undefined reference to SDL_CreateRenderer'
[build] /usr/bin/ld: /home/ubuntu/Desktop/lvgl/lvgl/src/drivers/sdl/lv_sdl_window.c:341: undefined reference to SDL_SetWindowSize' [build] /usr/bin/ld: lib/liblvgl.a(lv_sdl_window.c.o): in function window_update':
[build] /home/ubuntu/Desktop/lvgl/lvgl/src/drivers/sdl/lv_sdl_window.c:353: undefined reference to SDL_UpdateTexture' [build] /usr/bin/ld: /home/ubuntu/Desktop/lvgl/lvgl/src/drivers/sdl/lv_sdl_window.c:355: undefined reference to SDL_RenderClear'
[build] /usr/bin/ld: /home/ubuntu/Desktop/lvgl/lvgl/src/drivers/sdl/lv_sdl_window.c:358: undefined reference to SDL_RenderCopy' [build] /usr/bin/ld: /home/ubuntu/Desktop/lvgl/lvgl/src/drivers/sdl/lv_sdl_window.c:360: undefined reference to SDL_RenderPresent'
[build] /usr/bin/ld: lib/liblvgl.a(lv_sdl_window.c.o): in function texture_resize': [build] /home/ubuntu/Desktop/lvgl/lvgl/src/drivers/sdl/lv_sdl_window.c:382: undefined reference to SDL_DestroyTexture'
[build] /usr/bin/ld: /home/ubuntu/Desktop/lvgl/lvgl/src/drivers/sdl/lv_sdl_window.c:396: undefined reference to SDL_CreateTexture' [build] /usr/bin/ld: /home/ubuntu/Desktop/lvgl/lvgl/src/drivers/sdl/lv_sdl_window.c:398: undefined reference to SDL_SetTextureBlendMode'
[build] /usr/bin/ld: lib/liblvgl.a(lv_sdl_window.c.o): in function res_chg_event_cb': [build] /home/ubuntu/Desktop/lvgl/lvgl/src/drivers/sdl/lv_sdl_window.c:435: undefined reference to SDL_SetWindowSize'
[build] /usr/bin/ld: lib/liblvgl.a(lv_sdl_window.c.o): in function release_disp_cb': [build] /home/ubuntu/Desktop/lvgl/lvgl/src/drivers/sdl/lv_sdl_window.c:453: undefined reference to SDL_DestroyTexture'
[build] /usr/bin/ld: /home/ubuntu/Desktop/lvgl/lvgl/src/drivers/sdl/lv_sdl_window.c:455: undefined reference to SDL_DestroyRenderer' [build] /usr/bin/ld: /home/ubuntu/Desktop/lvgl/lvgl/src/drivers/sdl/lv_sdl_window.c:456: undefined reference to SDL_DestroyWindow'
[build] collect2: error: ld returned 1 exit status
[build] make[2]: *** [CMakeFiles/lvglsim.dir/build.make:104: ../bin/lvglsim] Error 1
[build] make[1]: *** [CMakeFiles/Makefile2:133: CMakeFiles/lvglsim.dir/all] Error 2
[build] make: *** [Makefile:130: all] Error 2
[proc] The command: /usr/bin/cmake --build /home/ubuntu/Desktop/lvgl/build --config Debug --target all -j 10 -- exited with code: 2
[driver] Build completed: 00:00:01.089
[build] Build finished with exit code 2

I tested under ubuntu20.04 , installed SDL2, error。

[kisvegabor]

Have you installed SDL like this:

sudo apt-get install libsdl2-dev 

[biglion1990]

I removed the if().... .elseif()... .endif. and it works!

cmake_minimum_required(VERSION 3.10)
project(lvgl)


#Uncomment if the program needs debugging
#set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -O0 -ggdb")

set(CMAKE_C_STANDARD 99) # LVGL officially supports C99 and above
set(CMAKE_CXX_STANDARD 17) #C17
set(CMAKE_CXX_STANDARD_REQUIRED ON)
set(EXECUTABLE_OUTPUT_PATH ${PROJECT_SOURCE_DIR}/bin)
add_subdirectory(lvgl)
target_include_directories(lvgl PUBLIC ${PROJECT_SOURCE_DIR})

find_package(PkgConfig REQUIRED)
pkg_check_modules(SDL2 REQUIRED sdl2)
pkg_check_modules(SDL2_image REQUIRED SDL2_image)

target_include_directories(lvgl PRIVATE ${SDL2_INCLUDE_DIRS})
target_include_directories(lvgl PRIVATE ${SDL2_IMAGE_INCLUDE_DIRS})
add_executable(lvglsim main.c mouse_cursor_icon.c)
target_link_libraries(lvglsim lvgl lvgl::examples lvgl::demos lvgl::thorvg ${SDL2_LIBRARIES} ${SDL2_IMAGE_LIBRARIES} m pthread)

add_custom_target (run COMMAND ${EXECUTABLE_OUTPUT_PATH}/lvglsim DEPENDS lvglsim)

[kisvegabor]

I've just tried it out and could reproduce the issue. You should call CMake like this: cmake -DLV_USE_SDL=1 ...

It's something that we really should document. There is also an LVGL issue to make CMake handling more unified. @etag4048 will work on it soon.

[shaleh]

I just ran into this...

What is interesting is the cmake logic claims to read lv_conf.h. Which has LV_USE_SDL 1 in my case. scripts/backend_conf.sh returns ON like it should. But the variable is not set for some reason. I can fix it by manually set(LV_USE_SDL ON).

[shaleh]

Sigh. Fun with paths and arguments....

If you follow the cmake guidance and do:

mkdir build
cd build
cmake .....

The supplied configuration does not work. This is because it is looking for scripts/backend_conf.sh in the build/ directory.
If instead you do:

# No cd, stay in the top of the git checkout.
cmake -B build
cmake --build build/

Everything works out.

The fix is to pass WORKING_DIRECTORY to execute_process

    execute_process(COMMAND "scripts/backend_conf.sh" ${BACKEND_NAME}
                    WORKING_DIRECTORY ${PROJECT_SOURCE_DIR}
                    OUTPUT_VARIABLE IS_BACKEND_ENABLED)

Now you do not have to repeat yourself and pass in -DLV_USE_SDL as @kisvegabor recommends above. The lv_conf.h is the source of truth.

[kisvegabor]

cc @etag4048

[stale]

This issue or pull request has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[AndreCostaaa]

Hi

I believe the issues mentioned here have been resolved:

lv_port_linux/CMakeLists.txt

Lines 9 to 10 in adbca69

	execute_process(WORKING_DIRECTORY ${PROJECT_SOURCE_DIR}
	COMMAND "scripts/backend_conf.sh" ${BACKEND_NAME} ${CONF_PATH} OUTPUT_VARIABLE IS_BACKEND_ENABLED)

Thank you @shaleh and @etag4048

Feel free to reopen this if you still encounter some issues