Using zoom and second mouse click over phone.

[saboTec]

Hello, i am using a implot and zooming and "right" click are very usefull for my case, however i did not find how can i use the 2 finger on phones or "second" click. Is there any option for it?
Thanks a lot.

[saboTec]

This workaround helped. i can use the finger ids to make the zoom and other options.

    // Event handling and GUI rendering
    runnerParams.callbacks.AnyBackendEventCallback = [&](void *pEvent) -> bool {
        const auto event = static_cast<SDL_Event*>(pEvent);
        
        ImGuiIO& io = ImGui::GetIO();
        static ImPlotFlags plotFlags = ImPlotFlags_None;
        return HandleTouchForPlotTools(*event, io, plotFlags);
    };
    
    runnerParams.callbacks.BeforeImGuiRender = [&]() {
        
        // Declare and initialize plotFlags
        
        SDL_Event event;
        while (SDL_PollEvent(&event)) {
            // Handle SDL events (e.g., mouse, touch, keyboard)
            if (event.type == SDL_QUIT) {
                exit(0); // Terminate application when the user closes the app
            }
            // Additional event handling (e.g., custom touch support) can go here
        }
    };
    

[pthom]

Hello,

I'm interested. Would you mind giving me more info about HandleTouchForPlotTools, as I could not find info about it online.

Thanks!

[saboTec]

Hello, it is just own method to work with the implot simulating mouse. But it is still buggy, like when i open the implot popup with flags then the event one finger just stays on the whole time.
When i do it i will give an update.
Thanks

bool HandleTouchForPlotTools(SDL_Event& event, ImGuiIO& io, ImPlotFlags& plotFlags) {
    static bool twoFingerTouch = false;
    static float initialDistance = 0.0f;
    static float initialMouseWheel = 0.0f;
    static std::map<SDL_FingerID, ImVec2> pressedFingers;
    static auto clickCount = 0;

    if (event.type == SDL_MULTIGESTURE) {
        if (event.mgesture.numFingers == 2) {
            // Two-finger touch detected
            twoFingerTouch = true;

            if (initialDistance == 0.0f) {
                initialDistance = event.mgesture.dDist; // Initialize zoom distance
                initialMouseWheel = io.MouseWheel;
            } else {
                // Handle zoom in/out
                float delta = event.mgesture.dDist; // - initialDistance;
                io.MouseWheel = initialMouseWheel + delta * 0.03f;
                
                std::cout << "Delta: " << delta << ", wheel: " << io.MouseWheel << std::endl;
            }
        }
    }

    if (event.type == SDL_FINGERDOWN) {
        const auto fingerId = event.tfinger.fingerId;
        if(pressedFingers.find(fingerId) == pressedFingers.end()) {
            pressedFingers[fingerId] = ImVec2(event.tfinger.x, event.tfinger.y);
            std::cout << "Added finger " << fingerId << std::endl;
            if(pressedFingers.size() == 3) {
                io.MouseDown[1] = true;
            }
        }
    } else if (event.type == SDL_FINGERUP) {
        const auto fingerId = event.tfinger.fingerId;
        if(pressedFingers.find(fingerId) != pressedFingers.end()) {
            if(pressedFingers.size() == 3) {
                io.MouseDown[1] = false;
            }
            
            pressedFingers.erase(fingerId);
            std::cout << "Removed finger " << fingerId << std::endl;
        }
    }
    
    std::cout << "Number of pressed fingers: " << pressedFingers.size() << ", event " << event.type << std::endl;

    if(pressedFingers.size() == 2) {
        return true;
    }

    return false;
}

[pthom]

Hum, interesting :-)

This could serve as a later inspiration for a possible patch to ImGui_ImplSDL2_ProcessEvent inside imgui itself.

[saboTec]

That sounds good :)
It would be great if implot would built this option for phones like it already has for a mouse.

[pthom]

If you do it in ImGui_ImplSDL2_ProcessEvent, you will have it everywhere (including ImPlot an all ImGui based libraries).

[saboTec]

I did it there and works great. Now the finger is not stucked on the popup of the implot.
Thanks a lot.

[pthom]

Could you share the diff or the patch you did in imgui_impl_sdl2.cpp ?

[saboTec]

I did not do much, just copied the one method to it, and from the main.cpp i remove the event code and works great.
When i have more time i will try to do it "cleaner"

bool ImGui_ImplSDL2_ProcessEvent(const SDL_Event* event)
{
    ImGui_ImplSDL2_Data* bd = ImGui_ImplSDL2_GetBackendData();
    IM_ASSERT(bd != nullptr && "Context or backend not initialized! Did you call ImGui_ImplSDL2_Init()?");
    ImGuiIO& io = ImGui::GetIO();

    // Static variables for multi-touch handling
    static bool twoFingerTouch = false;
    static float initialDistance = 0.0f;
    static float initialMouseWheel = 0.0f;
    static std::map<SDL_FingerID, ImVec2> pressedFingers;

    switch (event->type)
    {
        case SDL_FINGERDOWN:
        {
            const auto fingerId = event->tfinger.fingerId;
            if (pressedFingers.find(fingerId) == pressedFingers.end())
            {
                pressedFingers[fingerId] = ImVec2(event->tfinger.x, event->tfinger.y);
                if (pressedFingers.size() == 3)
                {
                    io.MouseDown[1] = true; // Simulate right-click on three fingers
                }
            }
            return true;
        }
        case SDL_FINGERUP:
        {
            const auto fingerId = event->tfinger.fingerId;
            if (pressedFingers.find(fingerId) != pressedFingers.end())
            {
                if (pressedFingers.size() == 3)
                {
                    io.MouseDown[1] = false; // Release right-click on three fingers
                }
                pressedFingers.erase(fingerId);
            }
            return true;
        }
        case SDL_MULTIGESTURE:
        {
            if (event->mgesture.numFingers == 2)
            {
                // Two-finger gesture handling
                twoFingerTouch = true;

                if (initialDistance == 0.0f)
                {
                    initialDistance = event->mgesture.dDist; // Initialize zoom distance
                    initialMouseWheel = io.MouseWheel;
                }
                else
                {
                    // Handle zoom in/out
                    float delta = event->mgesture.dDist;
                    io.MouseWheel = initialMouseWheel + delta * 0.03f;
                }
            }
            return true;
        }

rest of the code is the same from the line case SDL_MOUSEMOTION: