Log issues

Cobra91151

Thanks. Now it works but the same as it was without static, when I use Log::writeToLog("Some data"); to write to QTextBrowser in for example Test window and close it, then open Log window to check data, QTextBrowser is empty.

To open Log I use:

Log *appLog = new Log(this);
appLog->show();

Chris Hennes

How/where are you allocating the QTextBrowser?

Cobra91151

@Chris-Hennes

I have initialized textBrowser = new QTextBrowser(); in constructor and in function below because constructor is not called when I call Log::writeToLog("Some data") in Test.cpp and app crashes.

void Log::writeToLog(QString logMessage)
{
    textBrowser = new QTextBrowser();
    textBrowser->append(logMessage);
}

But the result is the same (QTextBrowser is empty), I think because of two initialization.

Chris Hennes

Definitely do not make a new QTextBrowser every time you call writeToLog, that defeats the purpose of making it static. You need to instantiate it one time in any given program run. Start by initializing it to null (or Q_NULLPTR), then in writeToLog check to see if it exists already. If it does not, then allocate it and set its parameters as appropriate, so something like:

QTextBrowser *Log::textBrowser = null;

...

void Log::writeToLog(QString logMessage)
{
    if (!textBrowser) {
        textBrowser = new QTextBrowser;
        textBrowser->installEventFilter(this);
        connect(textBrowser, &QTextBrowser::textChanged, this, &Log::checkLogTextBrowser);
    }
    textBrowser->append(logMessage);
}

Chris Hennes

(Note that my example code won't actually work as written because writeToLog is static, so you don't have a "this" pointer... those two lines will need to be in your constructor, along with appropriate checks to create textBrowser there if needed.)

Cobra91151

@Chris-Hennes

Thanks for code example. It now works. One more question, since Log::writeToLog(QString logMessage) is a static function I can't use this, I get error: log.cpp:116: error: C2355: 'this': can only be referenced inside non-static member functions or non-static data member initializers. So I need to get the instance of the Log class. Any ideas?

Chris Hennes

Yes, remove those two lines from the if statement in writeToLog, but keep them in an identical if statement in your constructor.

Cobra91151

@Chris-Hennes

I have added also check in constructor, because it crashes when open Log without adding anything to it.

   if (!textBrowser) {
        textBrowser = new QTextBrowser();
        textBrowser->installEventFilter(this);
        connect(textBrowser, &QTextBrowser::textChanged, this, &Log::checkLogTextBrowser);
    } else {
        textBrowser->installEventFilter(this);
        connect(textBrowser, &QTextBrowser::textChanged, this, &Log::checkLogTextBrowser);
    }

Also I have notices that connect(textBrowser, &QTextBrowser::textChanged, this, &Log::checkLogTextBrowser); is not working. I have some buttons which is disabled and when new log data is added, those buttons should be enabled, but it still disabled.

void Log::checkLogTextBrowser()
{
     if (textBrowser->document()->isEmpty()) {
         saveLog->setEnabled(false);
         saveLogAs->setEnabled(false);
         openLog->setEnabled(false);
         clearLog->setEnabled(false);
         deleteLog->setEnabled(false);
         sendLog->setEnabled(false);
     } else {
         saveLog->setEnabled(true);
         saveLogAs->setEnabled(true);
         openLog->setEnabled(false);
         clearLog->setEnabled(true);
         deleteLog->setEnabled(false);
         sendLog->setEnabled(false);
     }
}

I can use some trigger as bool checkButtonsState to check when log is added and then set it true to enable buttons? But why connect is not working?

Chris Hennes

Make sure to call checkLogTextBrowser() directly in your constructor as well, to handle anything that was logged before you opened it.

Cobra91151

@Chris-Hennes

Now everything works. Thank you.