Function button_panel_reserve 

pub unsafe extern "C" fn button_panel_reserve(
    button_panel: *mut ButtonPanel,
    reserve_x: usize,
    reserve_y: usize,
)

Reserve space for adding items.

One does not simply use button_panel_add_item() without this function. It should be allocated space for it first.

Arguments

• button_panel - ButtonPanel instance
• reserve_x - number of columns in button_panel
• reserve_y - number of rows in button_panel