Wrong value for ui->textEdit->document()->isModified()

silviubogan

I have created a new Qt Widgets Application project with a MainWindow class and a MainWindow.ui file. In MainWindow.ui I've added a QTextEdit widget with its objectName set to textEdit. MainWindow.cpp has the following content:

@#include "MainWindow.h"
#include "ui_MainWindow.h"

#include <QDebug>

MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);

connect(ui->textEdit->document(), &QTextDocument::modificationChanged,
        this, &MainWindow::on_textEditDocumentModificationChanged);

qDebug() << "before clear():" <<
            ui->textEdit->document()->isModified(); // false

qDebug() << "ui->textEdit->clear():";
ui->textEdit->clear();

qDebug() << "after clear():" <<
            ui->textEdit->document()->isModified() << // false
            "  [Why here it's false?]";

}

MainWindow::~MainWindow()
{
delete ui;
}

void MainWindow::on_textEditDocumentModificationChanged(bool modified)
{
qDebug() << " on_textEditDocumentModificationChanged:" <<
modified << ui->textEdit->document()->isModified(); // true true
}@

The on_textEditDocumentModificationChanged slot is called with a 'true' parameter and inside that slot @ui->textEdit->document()->isModified()@ has the value 'true', because calling the clear() method changes the modified status of the document to true, but when the execution returns to the MainWindow constructor, ui->textEdit->document()->isModified() has the value 'false'. I am interested if anyone can reproduce this issue and if there is a solution to this problem.

sierdzio

I suspect the textEdit is empty before you call clear(), right? In that case I would consider that to be expected behaviour.

silviubogan

Yes but in on_textEditDocumentModificationChanged slot the line @qDebug() << " on_textEditDocumentModificationChanged:" <<
modified << ui->textEdit->document()->isModified(); // true true@ prints "true true".

sierdzio

I would think that it does change the status while checking for changes (when clearing). I understand this might be strange at times, but to me it still looks like a valid behaviour ;)

What happens if you set some text in your textEdit before clearing?

silviubogan

I set some text in the textEdit before clearing and it's the same situation with the same output text.

sierdzio

OK, now it finally seems a bit weird to me :-) Sorry it took so long.

But, when you set the text, does it still show as isModified == false before the clearing?

Quoting from the documentation:
[quote]This property holds whether the document has been modified by the user.[/quote]

I suspect that is the key here: it will return true when modified by the user, but not when being modified programatically. In that light, I think the fact that the state changes briefly when clear() is called is a bug, please report it.

silviubogan

In the end I added just below this line:

@ui->textEdit->clear();@

the following line:

@ui->textEdit->document()->setModified(true);@

This simulates the expected behavior.

I think that, when I have enough time for this, I will report this bug.

Thank you for your messages!