[fltk.coredev] Fl_Scroll x/yposition and scroll_to confusion - Forums

Fl_Scroll scroll (10,10,200,200);

Fl_Box b1 ( 10, 10,50,50,"b1"); // relative (x,y) = (0,0)

Fl_Box b2 ( 60, 60,50,50,"b2"); // relative (x,y) = (50,50)

Fl_Box b3 ( 60,110,50,50,"b3"); // relative (x,y) = (50,100)

a modified example from the docs:

```

#include <FL/Fl.H>

#include <FL/Fl_Scroll.H>

#include <FL/Fl_Button.H>

#include <FL/Fl_Window.H>

void btn_cb(Fl_Widget *w, void *data) {

auto s = (Fl_Scroll*)data;

s->scroll_to(0, 0);

}

int main() {

Fl_Window win(400, 300);

Fl_Scroll s(0, 0, 400, 300);

Fl_Button b1(10, 10, 30, 30, "B1");

Fl_Button b2(60, 60, 30, 30, "B2");

Fl_Button b3(60, 110, 30, 30, "B3");

s.end();

win.end();

win.show();

b3.callback(btn_cb, &s);

return Fl::run();

}

```

This makes the relative position of b1 (following the docs) be (10, 10), but using s.scroll_to(0, 0), actually appears to scroll to 10, 10, making the the first button appear at position 0, 0 of the window. To get the initial appearance, one would need to s.scroll_to(-10, -10).
I could be misunderstanding the docs, or is the position of the topleft-most widget the reference for the Fl_Scroll?