This method clears all widget items and redraws the widget.
#include "Leadwerks.h"
using namespace Leadwerks;
int main(int argc, const char* argv[])
{
    //Get the displays
    auto displays = GetDisplays();
    //Create a window
    auto window = CreateWindow("Leadwerks", 0, 0, 800, 600, displays[0]);
    //Create User Interface
    auto ui = CreateInterface(window);
    auto sz = ui->root->GetSize();
    //Create filter input
    auto button = CreateButton("Clear Items", 20, 20, sz.x - 40, 30, ui->root);
    //Create list box
    auto listbox = CreateListBox(20, 55, sz.x - 40, sz.y - 75, ui->root);
    listbox->AddItem("Item 1", true);
    listbox->AddItem("Item 2");
    listbox->AddItem("Item 3");
    listbox->AddItem("Item 4");
    listbox->AddItem("Item 5");
    listbox->AddItem("Item 6");
    while (true)
    {
        const Event ev = WaitEvent();
        switch (ev.id)
        {
        case EVENT_WIDGETACTION:
            if (ev.source == button)
            {
                listbox->ClearItems();
            }
            break;
        case EVENT_WINDOWCLOSE:
            return 0;
            break;
        }
    }
    return 0;
}