Prevent clicking more than one (overlapping) button per frame

[keharriso]

This hopefully prevents a single click from activating multiple, overlapping buttons. This is a problem when you click in one place on one window that opens a new window with a button in the same place.

See below for the C code to reproduce the problem.

[keharriso]

I just want to give a high-level overview of the changes here:
I added a field clicked to struct nk_mouse. It's reset to 0 at the beginning of every frame and set to 1 when a button is clicked (in nk_button_behavior). If mouse.clicked is true, then nk_input_has_mouse_click_in_rect returns false.

These simple changes unfortunately mean that the struct nk_input parameters need to be non-const, propagating throughout all of the higher-level API.

[keharriso]

Here is the example code demonstrating the problem:

static int showB = 0;
if (nk_begin(ctx, "Window A", nk_rect(100, 100, 100, 100), NK_WINDOW_TITLE))
{
  nk_layout_row_dynamic(ctx, 50, 1);
  if (nk_button_label(ctx, "Button A")) {
    puts("Button A");
    showB = 1;
  }
}
nk_end(ctx);
if (showB) {
  if (nk_begin(ctx, "Window B", nk_rect(100, 100, 100, 100), NK_WINDOW_TITLE))
  {
    nk_layout_row_dynamic(ctx, 50, 1);
    if (nk_button_label(ctx, "Button B")) {
      puts("Button B");
      showB = 0;
    }
  }
  nk_end(ctx);
}

[keharriso]

Is anyone able to reproduce this problem? Do I need to bump the version myself before being accepted?

[revolucas]

Great find. A real shame all these fix-related pull requests aren't being implemented in some way. But probably the better way of implementing the fix would have been to add a new nk_flag to nk_widget_states enum, like NK_WIDGET_STATE_CLICKED. Then the only changes need to be made to function nk_button_behavior rather than changing all the const, which has consequences on version backwards compatibility.

Something like:

nk_button_behavior(nk_flags *state, struct nk_rect r,
	const struct nk_input *i, enum nk_button_behavior behavior)
{
	int ret = 0;
	nk_widget_state_reset(state);
	if (!i) return 0;
	if (nk_input_is_mouse_hovering_rect(i, r)) {
		*state = NK_WIDGET_STATE_HOVERED;
		if (nk_input_is_mouse_down(i, NK_BUTTON_LEFT))
			*state = NK_WIDGET_STATE_ACTIVE;
		if (nk_input_has_mouse_click_in_rect(i, NK_BUTTON_LEFT, r) && !(*state & NK_WIDGET_STATE_CLICKED)) {
			ret = (behavior != NK_BUTTON_DEFAULT) ?
				nk_input_is_mouse_down(i, NK_BUTTON_LEFT):
#ifdef NK_BUTTON_TRIGGER_ON_RELEASE
				nk_input_is_mouse_released(i, NK_BUTTON_LEFT);
#else
				nk_input_is_mouse_pressed(i, NK_BUTTON_LEFT);
#endif
		}
	}
	if (*state & NK_WIDGET_STATE_HOVER && !nk_input_is_mouse_prev_hovering_rect(i, r))
		*state |= NK_WIDGET_STATE_ENTERED;
	else if (nk_input_is_mouse_prev_hovering_rect(i, r))
		*state |= NK_WIDGET_STATE_LEFT;

	if (!ret)
		*state &= ~(nk_flags)NK_WIDGET_STATE_CLICKED;
	else
		*state |= NK_WIDGET_STATE_CLICKED;
	return ret;
}

[dumblob]

@revolucas I hope I can come back to Nuklear maintenance next year (currently it's kind of difficult for me - see #913 (comment) ).