C++娜娜 如何从全局列表框*指针访问列表框内的索引 0 上的按钮?

我有一个listbox，在第一列它包含一个带有button的text字段。

我有一个nanalistBox的全局指针：

listbox*                listBox = nullptr;

我从这里检索到这个class：

#include <nana/gui.hpp>
#include <nana/gui/widgets/label.hpp>
#include <nana/gui/widgets/button.hpp>
#include <nana/gui/widgets/listbox.hpp>
#include <nana/gui/widgets/textbox.hpp>
#include <nana/gui/wvl.hpp> 
#include <nana/system/platform.hpp>
#include <iostream>
#include <string.h>
#include <stdio.h>
#include <iostream>
#include <fstream>
#include <vector>
#include <thread>
#include <Windows.h>
using namespace nana;
//Creates a textbox and button
//textbox shows the value of the sub item
//button is used to delete the item.
class inline_widget : public listbox::inline_notifier_interface
{
private:
//Creates inline widget
//listbox calls this method to create the widget
//The position and size of widget can be ignored in this process
virtual void create(window wd) override
{
//Create listbox
txt_.create(wd);
txt_.events().click([this]
{
//Select the item when clicks the textbox
indicator_->selected(pos_);
});
txt_.events().mouse_move([this]
{
//Highlight the item when hovers the textbox
indicator_->hovered(pos_);
});
txt_.events().key_char([this](const arg_keyboard& arg)
{
if (arg.key == keyboard::enter)
{
//Modify the item when enter is pressed
arg.ignore = true;
indicator_->modify(pos_, txt_.caption());
}
});
//Or modify the item when typing
txt_.events().text_changed([this]()
{
indicator_->modify(pos_, txt_.caption());
});
//Create button
btn_.create(wd);
btn_.caption("Start");
btn_.enabled(false);
btn_.events().click([this]
{
//Delete the item when button is clicked
auto & lsbox = dynamic_cast<listbox&>(indicator_->host());
//buttonPressed(btn_, pos_.item);
});
btn_.events().mouse_move([this]
{
//Highlight the item when hovers the button
indicator_->hovered(pos_);
});
}
//Activates the inline widget, bound to a certain item of the listbox
//The inline_indicator is an object to operate the listbox item,
//pos is an index object refers to the item of listbox
virtual void activate(inline_indicator& ind, index_type pos)
{
indicator_ = &ind;
pos_ = pos;
}
void notify_status(status_type status, bool status_on) override
{
//Sets focus for the textbox when the item is selected
if ((status_type::selecting == status) && status_on)
txt_.focus();
}
//Sets the inline widget size
//dimension represents the max size can be set
//The coordinate of inline widget is a logical coordinate to the sub item of listbox
void resize(const size& dimension) override
{
auto sz = dimension;
sz.width -= 50;
txt_.size(sz);
rectangle r(sz.width + 5, 0, 45, sz.height);
btn_.move(r);
}
//Sets the value of inline widget with the value of the sub item
virtual void set(const value_type& value)
{
//Avoid emitting text_changed to set caption again, otherwise it
//causes infinite recursion.
if (txt_.caption() != value)
txt_.caption(value);
}
//Determines whether to draw the value of sub item
//e.g, when the inline widgets covers the whole background of the sub item,
//it should return false to avoid listbox useless drawing
bool whether_to_draw() const override
{
return false;
}
private:
inline_indicator * indicator_{ nullptr };
index_type pos_;
textbox txt_;
button btn_;
};

这是我的thread：

void theThread()
{
while (1)
{
//How can I access a button on index 0 from my listbox?
button* mybutton = listBox.at(0). ... ? -->HOW CAN I DO THIS?
mybutton->caption("I did it!!");
Sleep(1000);
}
}

而我的main()功能：

void main()
{
using namespace nana;
form fm(nana::API::make_center(750, 500), appear::decorate<appear::taskbar>());

listbox lsbox(fm, rectangle{ 10, 50, 700, 200 });
listBox = &lsbox;
//Create columns
lsbox.append_header("Col1");
lsbox.append_header("Col2");
lsbox.append_header("Col3");
lsbox.append_header("Col4");
lsbox.append_header("Col5");
lsbox.at(0).append({ "text1", "text2", "text3", "text4", "text5" });
lsbox.at(0).append({ "text1", "text2", "text3", "text4", "text5" });
lsbox.at(0).append({ "text1", "text2", "text3", "text4", "text5" });
lsbox.column_at(0).width(200);
lsbox.at(0).inline_factory(0, pat::make_factory<inline_widget>());
fm.show();

std::thread myThread(theThread);
exec();
myThread.join();
}

问题：

如何从全局listbox*指针访问listbox内的索引0上的button？