需要帮助来解释C ++中的功能

Question

I am doing simple version of pacman for c++. When I look up for some example in the internet, I found some code which I dont really understand. Please help me to explain it, grateful for that.

void GoToXY(int column, int line)
{
// Create a COORD structure and fill in its members.
// This specifies the new position of the cursor that we will set.
COORD coord;
coord.X = column;
coord.Y = line;

// Obtain a handle to the console screen buffer.
// (You're just using the standard console, so you can use STD_OUTPUT_HANDLE
// in conjunction with the GetStdHandle() to retrieve the handle.)
// Note that because it is a standard handle, we don't need to close it.
HANDLE hConsole = GetStdHandle(STD_OUTPUT_HANDLE);

// Finally, call the SetConsoleCursorPosition function.
if (!SetConsoleCursorPosition(hConsole, coord))
{
    // Uh-oh! The function call failed, so you need to handle the error.
    // You can call GetLastError() to get a more specific error code.
    // ...
}
}

My questions are: What does this line do? : HANDLE hConsole = GetStdHandle(STD_OUTPUT_HANDLE); Why we have an empty if? And what is the point of an empty if statement?

Answer 1

The line you ask about gives you a file handler for the standard output. It is likely that below it is used to print something to the console, or may be to draw the actual Pacman game there.

Here's some documentation on it, that might be helpful:

https://msdn.microsoft.com/en-us/library/windows/desktop/ms682075(v=vs.85).aspx

With regard to your second question, empty if is usually pointless. In your particular case the author of the example just points out, that GetStdHandle can fail (which is highly unlikely in reality), and that you might want to handle it in some way (may be print some error message and gracefully exit), but he himself doesn't fill it in.

Now as you develop your game on top of that example you might either choose to ignore that error (in which case you might as well just remove that entire if block), or handle it in some way (in which case you would fill in the body of that if statement)

Answer 2

HANDLE hConsole = GetStdHandle(STD_OUTPUT_HANDLE); GetStdHandle(STD_OUTPUT_HANDLE) retrieves a HANDLE to the standard output (Which is usually the active console) see here

A HANDLE is pointer to anything. You can see here

Answer to your second and third question is, it is not necessary here to write an empty if statement. Control will go to the if statement, if the SetConsoleCursorPosition() function doesn't work correctly. So, you can handle your error in the if, and if u don't want to handle the error, leave the if statement empty.