C++ and SDL with Clickable. A little help please.

Wendigo

I'm interested in this too. SDL seems to be the only way to get GPU acceleration on Ubuntu Touch currently. A step by step tutorial on how to set up an SDL project would be awesome.

lduboeuf

I remember a great app witch uses SDL2 , but seems not using clickable wrapper

https://github.com/pseuudonym404/tuxracer-touch

Craig

Thanks to all for your input and suggestions so far. I ran searches online for "CMakeLists.txt SDL tutorial", and read many tutorials. This is what I have so far that seems to almost work:

sudo apt install libsdl2-dev
clickable create
I chose option [7] main-cpp - C++/QML App (built using CMake with a main.cpp)
I replaced the main.cpp file in my project directory with a very small 512 byte SDL test program. It just produces a blank screen for 5 seconds and then quits. I compiled and tested it with the Code::Blocks IDE and it works fine there.
I added these lines to my CMakeLists.txt file in my project directory and finally I got it to link up with the SDL library:
add_executable(${PROJECT_NAME} main.cpp)
find_package(SDL2 REQUIRED)
include_directories(${SDL2_INCLUDE_DIRS})
set(SDL2_LIBRARIES "-lSDL2")
target_link_libraries(${PROJECT_NAME} ${SDL2_LIBRARIES})
I run clickable from my project directory and it compiles the program just fine and sends it to my Ubuntu Touch tablet where I see the logo.svg flash on the screen for only 1 second. Finally, no error messages not being able to link up with SDL. However, I don't get the expected blank screen for 5 seconds. The logo.svg shows on the screen along with my project name for only 1 second, but it seems to quit before running the program which should show a blank screen for 5 seconds. On my tablet I now have the logo.svg icon displayed as one of my apps. When I click on it the icon shows along with the app name for about 1 second and then closes.

Does anyone know what I need to tweak to get SDL to run on UT through clickable? Then, like Wendigo said, we will have a working SDL recipe for UT/clickable for other app developers.

Craig

Here's the source of the main.cpp:

#include <SDL.h>

int main(int argc, char *argv[])
{
SDL_Init(SDL_INIT_VIDEO);

SDL_Window *window = SDL_CreateWindow( "SDL2Test", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, 640, 480, 0 );

SDL_SetWindowFullscreen( window, SDL_TRUE );

SDL_Renderer *renderer = SDL_CreateRenderer(window, -1, SDL_RENDERER_SOFTWARE);
SDL_SetRenderDrawColor(renderer, 255, 0, 0, SDL_ALPHA_OPAQUE);
SDL_RenderClear(renderer);
SDL_RenderPresent(renderer);

SDL_Delay(5000);

SDL_DestroyWindow(window);
SDL_Quit();

return 0;
}

lduboeuf

@Craig any news regarding your port of SDL game ?

zubozrout

Some of you may find these demos usable:
https://gitlab.com/zub2/SDLDemo
https://gitlab.com/zub2/MirGLESDemo

However with the Mir upgrade things should become a bit easier as regular Wayland-compiled SDL stuff should start working there. That is if I understand it correctly.

bhdouglass

@Craig I just came across this thread and tried out what you mentioned. You'll need to bundle sdl2 with your app to be able to use it (Ubuntu Touch doesn't have it preinstalled). But it looks like @zubozrout 's demo might be a good place to start for that.

lduboeuf

@zubozrout thanks for sharing, it works nicely. I've compiled sdl2 also in a project that only requires audio, i will post the source link here whenever i will publish it

lduboeuf

for reference, it helps understand about clickable and dependencies : https://docs.ubports.com/en/latest/appdev/guides/dependencies.html

Craig

@lduboeuf
Thank you for your response. I ran "clickable create" and entered this option:
[7] main-cpp - C++/QML App (built using CMake with a main.cpp)
My project name is "mytest". I ran "clickable" and my USB connected tablet running Ubuntu Touch shows the app with "Hello World!". Good!

Next, I changed the main.cpp file so that is has the SDL test C++ code that you see in this posting. Also, I tried to make changes to the clickable.json file so the dependencies can be met, like so:

{
"template": "cmake",
"dir": "build/app",
"libraries": {
"SDL2": {
"template": "cmake"
}
},
"dependencies_target": [
"libsdl2-dev"
]
}

I saw clickable downloading the SDL2 files for armhf architecture. Looked good. But I get these error messages:

[ 90%] Linking CXX executable mytest
CMakeFiles/mytest.dir/main.cpp.o: In function main': main.cpp:(.text+0xc): undefined reference to SDL_Init'
main.cpp:(.text+0x2e): undefined reference to `SDL_CreateWindow'
etc...

What should I adjust to get this test SDL test program working? Thanks!

lduboeuf

@Craig have you looked at @zubozrout example for SDL2 ?

mymike

https://gitlab.com/zub2/SDLDemo

I managed to build this fine (getting some warnings btw) but the app won't start. I get

Command 'echo "sleep 1s && ubuntu-app-launch zub.sdldemo_SDLDemo_0.2" | ssh phablet@ubuntu-phablet' returned non-zero exit status 255.

And I can neither grab any log (neither with clickable logs nor with Logviewer) as the log file doesn't exist.

lduboeuf

@mymike not sure but i had that also, try replacing in apparmor file 1.3 with 16.04

mymike

@lduboeuf thanks https://gitlab.com/mymike00/SDLDemo this works for me!

bhdouglass

@mymike what do you think about turning your demo into a template for clickable? It could be really great way to get more people creating/porting SDL apps.

mymike

@bhdouglass of course! but I don't know how that app work, neither how to make a clickable template. I'll may have a look at it when I'll find some time, but if someone else wants to do it before me, no problem, just do it!

lduboeuf

@mymike yes maybe @zubozrout ? who did the hard work with SDL2 template

lduboeuf

@lduboeuf just for sharing, published a sample app that using only SDL2 audio https://github.com/lduboeuf/sfxr-qt. I've used template from @zubozrout SDL2 and it works fine.
On my device, sounds are not good quality ( some noises ) , not sure if it is hardware pb or something in-between ( on Desktop it plays fine ).

zubozrout

Just FYI, the credit is not mine but goes to my brother - his nick is zub, mine is not :). Unfortunately I lack the deeper knowledge necessary for such things. All I did was that I upgraded it to work with clickable (already on the original repo) and to run on 16.04 (apparently the apparmor framework update is still not there, but whatever).

Regarding the SDL2 clickable template it doesn't sound as a bad idea though. However I really can't spend the time on it now :(. And the second thing is that SDL is no longer supporting Mir and new stuff may require newer SDL. So the question is whether this is useful. With Unity 8 and Mir upgrades (now on Edge) Wayland-enabled stuff should start working. So it would probably be better to start from scratch and take a look at how to compile SDL apps with Wayland. And I suspect that will be much more documented and a more streamlined experience.

Sadly Mir didn't turned out the way I was hoping it would ... it is a nicely written code on par with the latest standards as that's how Canonical rolls but that's probably not what the general Linux community wants :(.

jonius

@mymike and others: Creating a clickable template is as simple as providing a git repository with an app that showcases the use case. If someone would like to provide some (it looks like you guys already have something running), simply reply on the feature request: https://gitlab.com/clickable/clickable/issues/122