Re: [fltk.general] fltk/test/sudoku - more keyboard support - Forums

Hi Mark, please don't top-post here, see
https://en.wikipedia.org/wiki/Posting_style#Top-posting

On 6/1/21 10:36 AM 'Mark' via fltk.general wrote:

I trie adding these methods:

```

int Sudoku::handle(int event) {
    if (event == FL_KEYBOARD) {
    // ...
    }
    return Fl_Widget::handle(event);
}
```

The result is that the _only_ keyboard events that are recognized are Home, End, PageUp, PageDown: none of the normal arrow key and numbers etc., nor the menus work anymore!

You're pretty close, but ...

Point 1: you must call Fl_[Double_]Window::handle(event) rather than Fl_Widget::handle(event). Your handle() method short-circuited all the "magic" of Fl_Group's event delivery. You should [almost] always use the handle() method of the direct parent (base) class. In this case I'd *guess* that using Fl_Group::handle(event) would work as well. I assume that most of your problems are caused by this fault.

Also my `find_focus_cell()` function never works; it always leaves the values at `-1`. This turns out not to be a surprise because FL_SHORTCUT only happens if Fl::focus() returns nullptr. However, to avoid this I use FL_KEYBOARD. But it still doesn't work.

Point 2: what you really need is the FL_SHORTCUT event. FL_KEYBOARD events are sent directly to the Fl::focus() widget which is in the sudoko program always a cell. If the focus widget doesn't use the event (returns 0) it is converted to FL_SHORTCUT and sent to (a lot of!) other widgets. At some point it will arrive at the Sudoku class which is why I suggested to add a handle() method to the Sudoku class.

That all said, I used your code with minimal changes (and I also added take_focus() statements) and it works as I expect:

int Sudoku::handle(int event) {
  if (event == FL_SHORTCUT) {     // needs FL_SHORTCUT
    int j, k;
    if (Fl::event_key(FL_Home)) {
      find_focus_cell(&j, &k);
      printf("home %d %d\n", j, k);
      grid_cells_[j][0]->take_focus();  // ADDED
      return 1;
    } else if (Fl::event_key(FL_End)) {
      find_focus_cell(&j, &k);
      printf("end %d %d\n", j, k);
      grid_cells_[j][8]->take_focus();  // ADDED
      return 1;
    } else if (Fl::event_key(FL_Page_Down)) {
      find_focus_cell(&j, &k);
      printf("pg down %d %d\n", j, k);
      grid_cells_[8][k]->take_focus();  // ADDED
      return 1;
    } else if (Fl::event_key(FL_Page_Up)) {
      find_focus_cell(&j, &k);
      printf("pg up %d %d\n", j, k);
      grid_cells_[0][k]->take_focus();  // ADDED
      return 1;
    }
  }
  return Fl_Double_Window::handle(event); // needs Fl_[Double_]Window::
}

So clearly I have a long way to go understanding how FLTK event-handling works!

It's not a simple model but if you read the docs (maybe not only once!) you'll get a feeling how it works step by step. Although in some cases it may be surprising and looking at the FLTK code and the comments may be helpful.

Besides reading the docs I suggest to take a look at test/handle_events.cxx which shows a way to print events in a better readable form. You can also modify it to find out what you need to know in practice.

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