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Basic question regarding callbacks [message #27015]

Mon, 21 June 2010 13:47

281264
Messages: 270
Registered: June 2010
Location: Spain

Experienced Member

I am completely new in Ultimate++, so one thousand apologizes if I ask very basic questions.

My question is regarding functioning of callbacks. As reference let�s take the example 7 Menu contained in the GUI Tutorial, which I am copying here for convenience:

#include <CtrlLib/CtrlLib.h>
using namespace Upp;
struct MyAppWindow : TopWindow {

MenuBar menu;

void Exit() {
if(PromptOKCancel("Exit MyApp?"))
Break();
}

void SubMenu(Bar& bar) {
bar.Add("Exit", THISBACK(Exit));
}

void MainMenu(Bar& bar) {
bar.Add("Menu", THISBACK(SubMenu));
}

typedef MyAppWindow CLASSNAME;

MyAppWindow() {
Title("My application with menu").Sizeable();
AddFrame(menu);
menu.Set(THISBACK(MainMenu));
}

};

GUI_APP_MAIN
{
MyAppWindow app;
app.Run();
}

Question 1: What is really happening when menu.Set(THISBACK(MainMenu)); is executed?.

Question 2: I guess that menu.Set is the method void Set(Callback1<Bar&> menu) described in the Menu Class help; if that is ok, the expected argument is a Callback1, which subsequently ask for TWO arguments [as indicated in template <class Object, class M, class P, class T> Callback callback1(Object *object, void (M::*method)(P), T arg)]. Why are we passing only the methid MainMenu and not both the ManiMenua and the expected argument menu?.

Question 3: How is MainMenu executed from menu.Set(THISBACK(MainMenu)) if we do not pass the argument bar?.

Question 4: I tried to debug the code and added some breakpoints (for example in manu.Set(..). But the debugger do not work and enters in an infinite loop; what is happening?

Sorry again for my clumsiness and my lack of knowledge of C++.

Best wishes and many thanks.

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