按住滚动条会在Windows中暂停命令提示符

Question

I have a program where I record data through an ADC system from National Instruments (NI).

The device buffers information for some time, and then the program collects the buffer data at some point. If the program collects data larger than the buffer, then the buffer would have to free without my program receiving the data, which will cause the NI library to throw an exception saying that requested data isn't available anymore, since it was lost.

Since my program is a command-prompt program, if the user clicks and holds the scrollbar, the program pauses, which could get this problem to happen.

How can I get over this problem without increasing the buffer size? Can I disable this holding thing in Windows?

Thanks.

Answer 1

Only the thread that is attempting to output to the console is blocked. Make this a separate thread, and your problem goes away.

Of course, you'll need to buffer up your output, and do something sensible if the buffer overflows.

For reference, here's the simple code I used to test this, you will note that the counter continues to increase even when the scroll bar is held down:

#include <Windows.h>
#include <stdio.h>

volatile int n = 0;

DWORD WINAPI my_thread(LPVOID parameter)
{
    for (;;)
    {
        n = n + 1;
        Sleep(800);
    }
}

int main(int argc, char ** argv)
{
    if (!CreateThread(NULL, 0, my_thread, NULL, 0, NULL))
    {
        printf("Error %u from CreateThread\n", GetLastError());
        return 0;
    }
    for (;;)
    {
        printf("Hello!  We're at %u\n", n);
        Sleep(1000);
    }
    return 0;
}

Answer 2

Whilst there may be ways to bypass each individual problem you can possibly conceive with the output [including for example running it over a network on a sometimes slow output link, or some such], I think the correct thing to do is to disconnect your output from your collecting of data. It shouldn't be hard to do this by adding a separate thread that collects the data, and having the main thread display to the command prompt window. That way, not matter which variation of "output is blocked" Windows throws at you, it will work - at least until you run out of RAM, but tat that point it's YOUR program's decision to do something [eg throw away some data or some such].

This is generally how the problem "I need to collect something, and I also need to allow users to view the data, but I don't want the two to interfere with each other" is solved.

Answer 3

First use the GetConsoleWindow winapi function and get the HWND of your console. now i suggest two ways to do this,

Method I Subclass the window by creating your own WindowProcedure. ( get help from here ) Now that you have subclassed it, you can intercept the WM_VSCROLL and WM_HSCROLL messages and do your own remedy to your code.

Method II Change the size of the window using some function like SetWindowPos so that the scroll bars are not needed. or Change the size of the console screen buffer so that the scroll bars are not needed.

Method I has lot of control over the application, but its a little bit complex than the method II which is very simple. If you want to forbid the user from resizing the console window, just remove the WS_THICKFRAME from the WindowStyle of the console window.