Thread: Can I have some Sample Code? (OpenGL, glDrawPixels();)

Actually we didn't do anything much, just try with some of the code to create the seats. It's kinda confusing but i think i'll get it.

Bubba has gone very far out of his way to help you. Just keep that in mind (and recognize his effort).

I think the underlying structure of this is quite simple to understand. The class hiearchy is completely flat and only consists of two major classes. I chose this because:

1. A customer is not a seat. (essentially)
2. A seat is not a seat section.
3. A seat section is not an auditorium.

So:

1. A seat has a customer.
2. A seat section has seats
3. An auditorium is a collection of seat sections, with seats that have customers.

When you fix the pointer errors you should be ready to use it. Notice the constructor cannot fail. That is if you instantiate the class globally, it is guaranteed never to fail because the constructor does not allocate memory or perform any other action that could assert or throw an exception. This does necessitate the need for a Create() function which is similar to most people's init. I choose to use Create() even though technically the object was already created at instantiation. However the object has no use until you call Create() which really gets the ball rolling. Change it to Init() if you want and return a boolean value to indicate success or failure.

The only leak that might happen is in the destructor code for the CAuditorium. When a empty() is called on a vector it "should" iterate through the vector and call the destructor for each object in the vector. The destructor for CSeatSection then de-allocates the array and sets it to NULL. Use the debugger to ensure this is what is happening. Notice that upon creation of the object in Create() a temporary is used and then pushed to the vector.

Use the debugger to obtain the addresses of the pointer and the object in the vector.
Just because you pushed the object into the vector does not mean that temp does not point to that same object. If you delete temp, then you delete the object in the vector. The empty() function for the vector will call the destructor for the CSeatSection and thus the memory will be de-allocated that way.

Perhaps you should read a book on STL to understand what is taking place. There is no copy constructor for CSeatSection but it really needs one since it does allocate memory. The copy constructor should allocate another block of memory so that the object and a copy of the object do not point to the same memory. Without it, if the copy goes out of scope and it's memory is de-allocated, then the memory in the other object has been de-allocated since they both are using the same block of memory but the object has not gone out of scope. Future references and access to memory in this object will cause an exception and a nice message from Windows. A copy constructor which allocates another block of memory for copies of the object would alleviate this problem. Without it, both objects use the same block.

Since constructors cannot return values there isn't a really good way to test to see if the copy constructor failed or not unless you implement an exception class. Attempt to allocate the memory and throw an exception if it fails. This will cause the program to exit, but it's better than nothing. And it really should terminate since the object cannot be created.

The copy constructor for CSeatSection would take this form:

CSeatSection(const CSeatSection &section);

Well I don't think I can help you any more with this whole thing. If you cannot understand the code, data structure, or remove the errors from it perhaps you've bitten off more than you can chew at this time in your programming adventure.

I would suggest doing some research, learning more, and then attempt this again.

I will not post oodles of code just so you can go back to what you had. Your data structures and approach to this problem are lacking. It's a simple problem with a simple solution and yet you insist on using something else. Mine is not the only solution but what do you have to lose? Yours obviously isn't either.

Only a fool continues walking down a path even though he's been forewarned it's a dead end.

I just don't understand right here

Code:

bool GetSeatInfo(DWORD ID, int Row, int Col, CSeatSection *outSeat)
{
	if(ID<SeatSections.size())
	{
		bool failed=SeatSections[ID]->GetSeatInfo(Row,Col,outSeat);
		if(failed)
		{
			outSeat=NULL;
			return true;
		}else return false;
	}

	outSeat=NULL;
	return true;
}

It bugged me from last night till now. So you set the bool value equal to the SeatSections[ID] which will get information from GetSeatInfo(Row, Col, outSeat) from the CSeatSection class.

So it only gets data, not convert, but my errors said that it can't convert parameter 3 from 'class CSeatSection *' to 'struct Seat *'.

I know i kinda slow and not very bright but these kind of format kinda new to me. Please help me.

Here it is, error free..

Code:

#include <windows.h>											// Header File For Windows
#include <gl\gl.h>												// Header File For The OpenGL32 Library
#include <gl\glu.h>												// Header File For The GLu32 Library
#include <gl\glaux.h>											// Header File For The GLaux Library
#include "NeHeGL.h"												// Header File For NeHeGL
#include <vector>

using namespace std;
#pragma comment( lib, "opengl32.lib" )							// Search For OpenGL32.lib While Linking
#pragma comment( lib, "glu32.lib" )								// Search For GLu32.lib While Linking
#pragma comment( lib, "glaux.lib" )								// Search For GLaux.lib While Linking

struct Customer
{
  char Name[40];
  char Address[40];
  char Age[3];
  char TimeOfPurchase[5];
}; 


struct Seat
{
  //Customers for this seat
  Customer  DayCustomer;
  Customer  NightCustomer;
  int Row;
  int Column;
  float Price;
  Seat(void):Row(0),Column(0),Price(0.0f) {}
};

class CSeatSection
{
	Seat *m_pSeatArray;
	int m_iWidth, m_iHeight, m_iSize;

public:

	CSeatSection(void):m_pSeatArray(NULL), m_iWidth(0), m_iHeight(0){}


	virtual ~CSeatSection(void)
	{

		if(m_pSeatArray)
		{
			delete [] m_pSeatArray;
			m_pSeatArray = NULL;
		}
	}

		bool Create(int Width, int Height)
		{
			m_pSeatArray = new Seat[Width * Height];

			if(m_pSeatArray)
			{
				m_iWidth = Width;
				m_iHeight = Height;
				m_iSize = Width * Height;

				int row=0, col=0;

				for(int offset=0; offset < m_iSize; offset++)
				{
					m_pSeatArray[offset].Row = row;
					m_pSeatArray[offset].Column = col;
					col++;
					if(col > m_iWidth)
					{
						col = 0;
						row++;
					}
				}
				return false;
			}else return true;

			}

		bool GetSeatInfo(int row, int col, Seat *outSeat)
		{
			int offset=row*m_iWidth+col;
			if(offset<m_iSize)
			{
				outSeat=&m_pSeatArray[offset];
				return false;
			}
			outSeat = NULL;
			return true;
		}

		bool SetSeatInfo(int row, int col, Seat *inSeat)
		{
			int offset=row*m_iWidth+col;
			if(offset<m_iSize)
			{
				m_pSeatArray[offset]=*inSeat;
				return false;
			}
			return true;
		}
	
	
};


class CAuditorium
{
   std::vector<CSeatSection *> SeatSections;

   public:
     virtual ~CAuditorium(void)
     {
        SeatSections.empty();
     }

     DWORD CreateSeatSection(int Width,int Height)
     {
        CSeatSection *temp=new CSeatSection();
        temp->Create(Width,Height);
        SeatSections.push_back(temp);

        return SeatSections.size()-1;
     }

	bool GetSeatInfo(DWORD ID, int Row, int Col, Seat *outSeat)
	{
	if(ID<SeatSections.size())
	{
	  bool failed=SeatSections[ID]->GetSeatInfo(Row,Col,outSeat);
	  if(failed)
	 {
	    outSeat=NULL;
	    return true;
	  }else return false;
	 }

	 outSeat=NULL;
	 return true;
	}

     bool SetSeatInfo(DWORD ID,int Row,int Col, Seat *inSeat)
     {
       if (ID<SeatSections.size())
       {
         bool failed=SeatSections[ID]->SetSeatInfo(Row,Col,inSeat);
         if (failed) 
         {
            return true;
         } else return false;
       }
        return true;
      }
};

In true, object oriented, C++ programming

Funny how you can debug a program without fully understanding it...