// cargo run --example a_first_real_example

use tcl::*;
use tk::*;
use tk::cmd::*;

fn main() -> TkResult<()> {
    let tk = make_tk!()?;
    let root = tk.root();
    root.set_wm_title( "Feet to Meters" )?;

    let c = root.add_ttk_frame( "c" -padding(( 3,3,12,12 )))?
        .grid( -column(0) -row(0) -sticky("nwes") )?;

    root.grid_columnconfigure( 0, -weight(1) )?;
    root.grid_rowconfigure( 0, -weight(1) )?;

    let feet = c.add_ttk_entry( "feet" -width(7) -textvariable("feet") )?
        .grid( -column(2) -row(1) -sticky("we") )?;

    c.add_ttk_label( "meters" -textvariable("meters") )?
        .grid( -column(2) -row(2) -sticky("we") )?;

    c.add_ttk_button( "calc" -text("Calculate") -command("calculate") )?
        .grid( -column(3) -row(3) -sticky("w") )?;

    c.add_ttk_label( "flbl" -text("feet") )?
        .grid( -column(3) -row(1) -sticky("w") )?;

    c.add_ttk_label( "islbl" -text("is equivalent to") )?
        .grid( -column(1) -row(2) -sticky("e") )?;

    c.add_ttk_label( "mlbl" -text("meters") )?
        .grid( -column(3) -row(2) -sticky("w") )?;

    c.winfo_children()?
        .iter()
        .try_for_each( |child| child.grid_configure( -padx(5) -pady(5) ))?;

    feet.focus()?;

    #[proc]
    fn calculate() -> TkResult<()> {
        let interp = tcl_interp!();
        let feet = interp.get_double("feet");
        match feet {
            Ok( feet ) => {
                let meters = f64::floor( feet * 0.3048 * 10000.0 ) / 10000.0;
                interp.set_double( "meters", meters )
            },
            Err( _ ) => interp.set( "meters", "" ),
        };
        Ok(())
    }

    // it's safe because `fn calculate()` is tagged with `#[proc]`.
    unsafe{ tk.def_proc( "calculate", calculate ); }

    root.bind_more( event::key_press( TkKey::Return ), "calculate" )?;

    Ok( main_loop() )
}