From:	"Steven S. Falls" <broadview AT earthlink DOT net>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: Function Pointer Problem
Date:	Tue, 22 Dec 1998 12:04:29 -0800
References:	<367F672B DOT E7A3F4CA AT earthlink DOT net> <367f982c DOT 23433981 AT news DOT snafu DOT de>
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To:	djgpp AT delorie DOT com
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What if a function requires a "normal" fuction pointer  but I need to give it
a function from a class. fo ex.
#include <dos.h>
#include "fgraphwa.h"  //My windowing GUI library for DJGPP avalible soon
when I get these //bugs finished

class HelloClass {
   private:
      MSGHANDLE Hello_Message,Exit_Message;
      WINHANDLE Hello_Window;
      BTNHANDLE Hello_Button;
      void Hello_Button_Action_Proc(void);
      void Hello_Button_Static_Proc(void);
      void Hello_Proc(void);
   public:
      HelloClass(void);
};
void HelloClass::Hello_Button_Action_Proc(void) {
   exit(0);
}
void HelloClass::Hello_Button_Static_Proc(void) {
   type_btnnode *ThisBtn;
   ThisBtn=Api_Interface.info_button(Hello_Button);
   if(ThisBtn->PressDown) {
      Graphix.Draw_Filled_Box(20,25,70,35,22); //Draws Button Background
Based On The Current Window Cordinats
      Graphix.Draw_VLine(20,25,35,25);  //Draws Button Backgraound
      Graphix.Draw_HLine(20,35,71,25); //Draws Button Background
      Graphix.Draw_VLine(71,25,35,20); //Draws Button Background
      Graphix.Draw_HLine(20,25,71,20);  //Draws Button Background

Api_Interface.display_message(Api_Interface.info_message(Exit_Message));
//Displayes Exit Message
   }else{
      Graphix.Draw_Filled_Box(20,25,70,35,25); //Draws Button Background
Based On The Current Window Cordinats
      Graphix.Draw_VLine(20,25,35,22);  //Draws Button Backgraound
      Graphix.Draw_HLine(20,35,71,22); //Draws Button Background
      Graphix.Draw_VLine(71,25,35,28); //Draws Button Background
      Graphix.Draw_HLine(20,25,71,28);  //Draws Button Background

Api_Interface.display_message(Api_Interface.info_message(Exit_Message));
//Displayes Exit Message
   }
}
void HelloClass::Hello_Proc(void) {
   Graphix.Set_Drawing_Window(Api_Interface.info_window(Hello_Window));
//Set Graphics Drawing To This Window
   Graphix.Clear_Window(); //Clears Window
   Api_Interface.display_message(Api_Interface.info_message(Hello_Message));
//Displayes Hello World Message
   Api_Interface.display_buttons(Hello_Button,Hello_Window); //Tests If
Button Has Been Clicked And If It Has It Runs The Action
   Graphix.Copy_Window(Api_Interface.info_window(Hello_Window)); //Copys
Window to the Ram Page
   Graphix.Set_Drawing_Screen();  //Sets Graphics Drawing to the Ram Page
}
HelloClass::HelloClass(void) {
   Hello_Window=Api_Interface.new_window(260,175,110,50,(void (*)
())Hello_Proc); //Make New Window
   Hello_Button=Api_Interface.new_button(20,25,50,10,15,(void (*)
())Hello_Button_Action_Proc,(void (*) ())Hello_Button_Static_Proc);//Make New
Button
   Hello_Message=Api_Interface.new_message(10,5,"Hello World",109,49); //Make
New Message
   Exit_Message=Api_Interface.new_message(30,27,"Exit",70,35); //Make New
Message
}
void main(void) {
   Api_Interface.load_gui_font("default.fnt");  //Load Font
   HelloClass HelloWorld;
   for(int a=0;a<2;a++) {  //Make An Endless Loop
      a=0;
      Graphix.Clear_Ram_Page();
      Api_Interface.display_windows(); //Display All windows
      Io_Interface.Display_Mouse_Pointer();
      Graphix.Copy_Ram_Page();         //Copy Ram Page To The Screen
   }
}

   Thnaks
            Ardy

Horst Kraemer wrote:

> On Tue, 22 Dec 1998 01:32:27 -0800, "Steven S. Falls"
> <broadview AT earthlink DOT net> wrote:
>
> > Hi I am trying to get a fuction pointer point to another part of a
> > class. It compiles but it does not run properly. Any ideas why? and how
> > to solve the problem?
>
> [...snipped...]
>
> Pointers to non-static member functions of a class have nothing to do
> with "normal" pointers to functions.
>
> They have to evoked with a special syntax .* or ->* including the
> object through which they are called.
>
> Example
>
> #include <iostream>
>
> struct X {
>   void (X::*fp)();  // declares a pointer to a non-static member
>                     // function of X
>   void f(void) { cout << "hello" << endl; }
>   X()          { fp = &X::f; (this->*fp)(); }
> };
>
> int main()
> {
>   X x;
>   return 0;
> }
>
> Regards
> Horst

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