GetCursorPos returns 0

[Crocopep]

Hey all,

Let me introduce myself. I'm Pepijn and I've programmed a few years in PHP. I'm trying to learn c++ now, but it's not very easy.

I wrote the following script so far, it has to display the cursors position in a dos window;

#include <iostream>
#include <windows.h>

using namespace std;

int main()
{    
     LPPOINT lpPoint;
     int x;
     int y; 
     if(!GetCursorPos(lpPoint))
     {
                               cout << "An error occurred: " << endl;
                               cout << GetLastError();
     }
     else
     {                              
        x = lpPoint->x;
        y = lpPoint->y;
        cout << x << endl;
        cout << y << endl;
     }
    cin.get();
    return 0;
}

The problem is that GetCursorPos returns 0, but GetLastError returns 0 either.
I hope you can help.

Best regards,
Pepijn

[Russco]

AN LPPOINT is a pointer to a POINT struct. However you have just a pointer and no POINT struct.

Change LPPOINT to POINT and call GetCursorPos with the address of that POINT struct

POINT point
GetCursorPos(&point)

[Crocopep]

x = point->x;
y = point->y;

I got the following errors now:
18: base operand of `->' has non-pointer type `POINT'
19: base operand of `->' has non-pointer type `POINT'

What does that mean?

Thankyou for you help

[Russco]

point.x not point->x

point is a struct. lppoint was a pointer.

You access a structs members with the dot operator

[BobS0327]

You're not allocating any memory for lpPoint.

lpPoint = (LPPOINT)GlobalAlloc(GPTR, sizeof(POINT));

[Crocopep]

Thx for you help!
The script is working now:

#include <iostream>
#include <windows.h>

using namespace std;

int main()
{
    POINT point;
    int x;
    int y;

    while(true) {
        if(!GetCursorPos(&point))
        {
            cout << "An error occurred: " << endl;
            cout << GetLastError();
        }
        else
        {
           x = point.x;
           y = point.y;
           cout << x << endl;
           cout << y << endl;
        }
        Sleep(100);
        system("cls");
    }
    return 0;
}

[GCDEF]

You're not allocating any memory for lpPoint.

lpPoint = (LPPOINT)GlobalAlloc(GPTR, sizeof(POINT));

    POINT Point;
     if(!GetCursorPos(&Point))

would be simpler in this case. If you really want to put it on the heap, new would be simpler than GlobalAlloc.

[hoxsiew]

You should get out of the habit of calling it a "script" too. You're a real programmer now. You're writing a "program".

[Paul McKenzie]

You're not allocating any memory for lpPoint.

lpPoint = (LPPOINT)GlobalAlloc(GPTR, sizeof(POINT));

Please read this link:

http://www.flounder.com/badprogram.h...%20reason%20to

Even though you used GlobalAlloc, the article still is valid with respect to allocating memory when you do not need to do it.

Regards,

Paul McKenzie

[BobS0327]

Please read this link:

http://www.flounder.com/badprogram.h...%20reason%20to

Even though you used GlobalAlloc, the article still is valid with respect to allocating memory when you do not need to do it.

Regards,

Paul McKenzie

Actually, Microsoft recommends using heap functions instead of global and local functions.

[Russco]

If you wanted to show how its done with a pointer then it would have been simpler to do :-

POINT point;
LPPOINT lppoint = &point;

What is the point in dynamically allocating a POINT struct in this single function program, when a simpler stack allocated object will suffice, especially when the OP said how new to C++ he was.