I was able to find the problem. The reason is that for these Trackpad taps, MacOS generates two consecutive events. File main.c of the SDL+OpenGL2 demo has this loop, whose purpose I guess is to combine consecutive events and thus be more efficient and improve performance:

while (SDL_PollEvent(&evt)) {
            if (evt.type == SDL_QUIT) goto cleanup;
            nk_sdl_handle_event(&evt);
        }

However, some events should never be combined. I've modified the loop as follows, and now all Trackpad taps are handled correctly, and no events are lost:

while (SDL_PollEvent(&evt)) {
            if (evt.type == SDL_QUIT) goto cleanup;
            nk_sdl_handle_event(&evt);
            if((evt.type==SDL_MOUSEBUTTONUP)||(evt.type==SDL_MOUSEBUTTONDOWN)||(evt.type==SDL_KEYUP)||(evt.type==SDL_KEYDOWN)) break;
        }

As you can see, I also included key up and key down events as not-combinable. I didn't have a problem with key up/down events, but my mind says is not a good idea to try to combine them.

In fact, I believe the only ones suitable for combining are motion events. And maybe this loop should be removed and never try to combine any event.

I'm leaving this issue open, because I believe the source code in the repository should be ready to work fine on MacBooks, so I think a good solution should be found.

This issue might be the same (or not) described at vurtun/nuklear#407
(I'm mentioning that issue from here, because it described the same situation and in Macs, so future users that are affected and read that issue in the old repository, can take a look at the solution I found)

Before discussing this further, would you have time to try the StickyMouseButtons input mode also as suggested in the old thread you found?

Thanks!

StickyMouseButtons is GLFW-specific. I'm experiencing this in SDL. And, even then, if it worked would be a workaround, not a fix, because the problem is not in the external library used, but in the Nuklear demos: they make the assumption that two consecutive mouse events with zero time between them can be combined together and managed like if it was a single event. In the case of motion events, maybe it can be true, but in the case of mouse clicks (and key clicks) it's a wrong assumption, and it's the reason by Trackpad tapping is missing events.

Note that the bug is not in Nuklear, but in the examples. If you implement your application loop taking care of never combining events related to clicks, then it will work perfectly with Apple Trackpads.

StickyMouseButtons is GLFW-specific. I'm experiencing this in SDL.

Oh, my bad. Thanks for clarification!

We definitely want to have demos working cross-platform as much as we can. The examples/demos are still just a showcase what can be done and are not a comprehensive solution.

That being said I am eager to accept PRs which combines only events can be combined. IIRC the reason for combining events was to save power and computational resources if the events come in higher frequency than the desired frame rate.

For non-nuklear.h PRs we are not that strict so do not be afraid of it 😉 - see https://github.com/Immediate-Mode-UI/Nuklear#reviewers-guide .