Writing a new component with asynchronous needs

[kjhermans]

Hi,

I am - amongst others - using NappGUI to write a new GUI component, based on a View, that tracks and displays the contents of a log file. The displaying I've got working now - it's the tracking that I have a question about. Say I want to keep the code strictly to within the component and I wanted to get a callback every second or so, so I can see if the log file has grown and when it has, call 'update' on the component - how would I go about it? I could just spawn a thread, but I'm not sure that GUI component code is reentrant.

I found this: #101 but that doesn't seem to quite do what I want.

[frang75]

Hi @kjhermans. Sorry for the delay in answering, I've been away for a few days. What you're describing is a specific case of a synchronous application. In that case, you should use osmain_sync() and implement the i_update method.

https://nappgui.com/en/osapp/osapp.html#h2

typedef struct _app_t App;
struct _app_t
{
    Window *window;
    View *your_sync_view;
    real64_t last_callback;
};

static App* i_create(void)
{
    App *app = heap_new(App);
    // Init program data, GUI and Event handlers
    app->window = ...
    return app;
}

static void i_update(App *app, const real64_t prtime, const real64_t ctime)
{
    real64_t frame = ctime - app->last_callback;
    if (frame > 1)
    {
        // Will update your view every second
        update_your_view(app->your_sync_view, frame);   
    }

   app->last_callback = ctime;
    
}

static void i_destroy(App *app)
{
    // Destroy program data
    window_destroy(&(*app)->window);
    heap_delete(app, App);
}

// 25 fps callback
osmain_sync(0.04, i_create, i_destroy, i_update, "", App);

[kjhermans]

Ok. But then I'm solving this outside the component. Making the approach non modular: I need a 'main-like' function to pick up some of the functionality that I seek as an independent GUI component. I can see that it works, but design-wise it's a little bit (?) ugly to have to say: "you can create this component (say, the display of a clock) but if you really want it to work you have to do some coding around it". I just want to be able to say:

Clock* clock = clock_create();
layout_add_clock(layout, clock, 1, 1);

And have it work. As a running clock.

[frang75]

I disagree. If your component is synchronous, it will NEVER be independent. It will need to run in a synchronous application that sends clock pulses periodically (which is what the i_update() function does). For example, in a video game, the entire scene is updated within a single method update_game(). Player, enemies, NPCs, camera, etc. Additionally, any changes you make to widgets (text, dimensions, images, etc) must be re-rendered when the i_update() function completes. Your component must store its internal state and provide a function mycomponent_update(View *view, const real32_t frame), which must be called by the main runloop when necessary. Having independent clocks for each of the synchronous elements opens the door to collapse. However, you can choose the design pattern you prefer for your application.