Fl_Button callback does not get called

Question

I'm coding some custom widgets in FLTK, one is a single digit spinner for touch screen which is a value with one arrow above and another below.

class Spinner: public Fl_Group
{
private:
    ::std::unique_ptr<Fl_Button> button_up_;
    ::std::unique_ptr<Fl_Button> button_down_;
    ::std::unique_ptr<Fl_Output> value_;
public:
    static unsigned int const WIDTH = 36;
    static unsigned int const HEIGHT = 100;
...
};

Spinner::Spinner(int x, int y, size_t val)
        :Fl_Group(x, y, WIDTH, HEIGHT)
        ,button_up_(new Fl_Button(x + 2, y + 1, 32, 17))
        ,button_down_(new Fl_Button(x + 2, y + 82, 32, 17))
        ,value_(new Fl_Output(x + 2, y + 18, 32, 64))
{
    char v[] = {'0', 0};
    if (val > 9) val = 9;
    v[0] = val + '0';
    button_up_->callback(reinterpret_cast<Fl_Callback*>(&Spinner::upcbk), this);
    button_down_->callback(reinterpret_cast<Fl_Callback*>(&Spinner::downcbk), this);
    button_up_->image(up_arrow);
    button_down_->image(down_arrow);
    button_up_->color(FL_BLACK);
    button_down_->color(FL_BLACK);
    button_up_->box(FL_FLAT_BOX);
    button_down_->box(FL_FLAT_BOX);
    value_->box(FL_BORDER_BOX);
    value_->color(FL_BLACK);
    value_->labelcolor(FL_RED);
    value_->selection_color (FL_RED);
    value_->textsize(46);
    value_->textcolor(FL_RED);
    value_->value(v);
    value_->redraw();
    end();
}

void Spinner::upcbk(Fl_Widget*, Spinner* spnr)
{
    cout << "Spinner::upcbk()" << endl;
    spnr->increment();
}

void Spinner::downcbk(Fl_Widget*, Spinner* spnr)
{
    cout << "Spinner::downcbk()" << endl;
    spnr->decrement();
}

When I instantiate one Spinner object in the window it works ok and each callback gets called when its corresponding arrow is clicked.

The other custom widget is a Spinner agregation:

class UintSpinner: public Fl_Group
{
private:
    uint16_t value_;
    uint16_t const max_;
    uint16_t const min_;
    uint16_t const order_;
    char fmt_[6];
    ::std::vector< ::std::unique_ptr <Spinner> > spinners_;
...
};

UintSpinner::UintSpinner(int x, int y, uint16_t minval, uint16_t maxval
                        ,uint16_t val)
        :Fl_Group(x, y, Spinner::WIDTH * static_cast<uint16_t>(log10(max_)) + 1, Spinner::HEIGHT)
        ,value_(val < minval ? minval : (val > maxval ? maxval : val))
        ,max_(maxval)
        ,min_(minval)
        ,order_(static_cast<uint16_t>(log10(max_)) + 1)
{
    strncpy(fmt_, "%00hu", 6);
    fmt_[2] = static_cast<char>(order_) + '0';
    char buffer[6];
    snprintf(buffer, 6, fmt_, val);
    for (ssize_t i = order_ - 1; i >= 0; i--) {
        spinners_.emplace_back(new Spinner(x + i * Spinner::WIDTH, y, buffer[i] - '0'));
        spinners_.back()->callback(&UintSpinner::spinner_cb, this);
    }
}

void UintSpinner::spinner_cb(Fl_Widget* cb, void* p)
{
    cout << "UintSpinner::spinner_cb()" << endl;
    reinterpret_cast<UintSpinner*>(p)->spinnercb();
}

In this case If I istantiate an object of UintSpinner class with max value of 244 it correctly renders three individual spinners but neither Spinner::upcbk nor Spinner::downcbk get called when I hit one of the arrows.

I tried to use stack variables for Fl_Button and Fl_Output inside the Spinner class and the behavior is the same. I also tried to create a vector of Spinners instead of a vector of pointers but it does not compile because the Fl_Group seems not moveable.

Am I doing something wrong? Why using the exactly the same code in Spinner class their internal members callbacks works when using that instance directly and not when using the instance inside another custom widget?

Best regards and thank you for your help.

Answer 1

Ok, I found the solution.

In the UintSpinner constructor, when calling the base Fl_Group constructor, I pass a width parameter with an undefined value (a copy-paste error). According to Erco's FLTK Cheat Page -> Fl_Group Event vs. Draw Clipping when the children of a Fl_Group expands outside its bounding box, by default the render is not clipped but its mouse events are. So changing the constructor to:

UintSpinner::UintSpinner(int x, int y, uint16_t minval, uint16_t maxval
                        ,uint16_t val)
        :Fl_Group(x, y, Spinner::WIDTH * static_cast<uint16_t>(log10(maxval) + 1), Spinner::HEIGHT)
        ,value_(val < minval ? minval : (val > maxval ? maxval : val))
        ,max_(maxval)
        ,min_(minval)
        ,order_(static_cast<uint16_t>(log10(max_)) + 1)
{
...

solve the issue.