問題描述

有一個基于 Qt 和 ncurses 的應(yīng)用程序，在等待用戶輸入時每秒刷新屏幕的最佳方法是什么?(例如，顯示時鐘并獲取用戶輸入).

Having a Qt and ncurses based application, what is the best way to refresh the screen every second, while waiting for user input? (e.g. show the clock and get user input).

我需要在 CPU 使用率和應(yīng)用程序響應(yīng)能力之間取得最佳折衷.

I need the best compromise between CPU usage and application responsiveness.

更具體地說，如何獲取用戶輸入并仍然使用 QTimer 和信號槽機(jī)制?

To be more specific with the question, how to get user input and still use QTimer and the signal-slot mechanism?

使用下面的代碼時，定時器不起作用.

When using the code below, the timers doen't work.

nodelay(stdscr,true); while(1) { sleep(1); getch(); processInput(); }

推薦答案

1. 使用 QSocketNotifier 來通知 stdin 上可用的東西.

1. Use QSocketNotifier to be notified of things being available on stdin.

在循環(huán)中調(diào)用非阻塞 getch() 直到?jīng)]有更多輸入可用.這一點(diǎn)非常重要:只有當(dāng)新數(shù)據(jù)可用時，通知程序才會通知，但這并不意味著它會通知每個字符！如果您一次收到多個字符，您通常只會收到一個通知 - 因此您必須繼續(xù)發(fā)出非阻塞 getch() 直到它返回 ERR 意味著沒有更多數(shù)據(jù)目前可用.

Call nonblocking getch() in a loop until no more input is available. This is vitally important: the notifier will notify only when new data is available, but this doesn't mean that it notifies on every character! If you receive multiple characters at a time, you will usually get just one notification - thus you must keep issuing non-blocking getch() until it returns ERR meaning that no more data is available at the moment.

您還應(yīng)該讀取在連接套接字通知程序之前可用的所有數(shù)據(jù).

You should also read all of the data that became available in the time before the socket notifier became attached.

下面的代碼在接收到輸入時回顯，并且每秒額外輸出一個 *.這適用于 Linux 和 OS X，不能移植到 Windows.要退出，請按 Q.

The code below echoes the input as it receives it, and additionally outputs a * every second. This works on Linux and OS X, and is not portable to Windows. To quit, press Q.

在需要時將 ncurses 用于傳統(tǒng)文本模式用戶界面，同時將 Qt 用于其他所有方面(計時、網(wǎng)絡(luò)、具有基于文本的視圖的數(shù)據(jù)模型、XML、QObjects 等)是一種完全有效的方法.

Using ncurses for a legacy text-mode user interface, where desired, while leveraging Qt for everything else (timing, networking, data models with text-based views, XML, QObjects, etc.) is a perfectly valid approach.

// https://github.com/KubaO/stackoverflown/tree/master/questions/ncurses-20606318
#include <QtCore>
#include <ncurses.h>

class Worker : public QObject
{
   Q_OBJECT
   QSocketNotifier m_notifier{0, QSocketNotifier::Read, this};
   QBasicTimer m_timer;
   Q_SLOT void readyRead() {
      // It's OK to call this with no data available to be read.
      int c;
      while ((c = getch()) != ERR) {
         printw("%c", (char)(c <= 255 ? c : '?'));
         if (c == 'q' || c == 'Q') qApp->quit();
      }
   }
   void timerEvent(QTimerEvent * ev) {
      if (ev->timerId() != m_timer.timerId()) return;
      printw("*");
      refresh();
   }
public:
   Worker(QObject * parent = 0) : QObject(parent) {
      connect(&m_notifier, SIGNAL(activated(int)), SLOT(readyRead()));
      readyRead(); // data might be already available without notification
      m_timer.start(1000, this);
   }
};

int main(int argc, char *argv[])
{
   QCoreApplication a{argc, argv};
   Worker w;
   auto win = initscr();
   clear();
   cbreak(); // all input is available immediately
   noecho(); // no echo
   printw("Press <q> to quit
");
   keypad(win, true); // special keys are interpreted and returned as single int from getch()
   nodelay(win, true); // getch() is a non-blocking call
   auto rc = a.exec();
   endwin();
   return rc;
}

#include "main.moc"

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