QWebEngineView no longer render html files with no .html extension

Ghis64 · 18 Nov 2020, 14:53

Hi,
Last week my company upgraded the Qt version to Qt5.15.1 and now I have several issues with my code.
One of them is that the QWebEngineView::load no longer render the html code set in the file: the html code is displayed instead of its rendering.
After 2 days of investigation I realized that if I add .html at the end of my file name it works!
It was working with any file name with Qt5.9.
Is it a regression or is it a new requirement?

Here is a simple example that illustrate this issue:
int main(int argc, char *argv[])
{
QApplication a(argc, argv);

QDialog* dialog = new QDialog (nullptr);

QVBoxLayout* vertLayout = new QVBoxLayout (dialog);
QDialogButtonBox* buttonBox = new QDialogButtonBox (QDialogButtonBox::Close, dialog);

QWebEngineSettings::globalSettings ()->setAttribute (QWebEngineSettings::AutoLoadImages, true);
QWebEngineSettings::globalSettings ()->setAttribute (QWebEngineSettings::PluginsEnabled, true);
QWebEngineSettings::globalSettings ()->setAttribute (QWebEngineSettings::JavascriptEnabled, true);

QWebEngineView* web_view_ = new QWebEngineView (dialog);
web_view_->setMinimumHeight (500);
web_view_->setMinimumWidth (700);
vertLayout->addWidget (web_view_);
vertLayout->addWidget (buttonBox);
dialog->connect (buttonBox, SIGNAL (rejected ()), dialog, SLOT (reject ()));
dialog->resize (QSize (1200, 800));

QString file_name = "C:/Users/XXX/AppData/Local/Temp/report.txt";  // if here I use report.html it works!!
web_view_->load (QUrl::fromLocalFile (file_name));

dialog->show();
return a.exec();

}

and here is the contents of the report.txt file:

<html>
<body><h1>Training Set Construction Summary</h1>
Survey: TEXAS3D@vm -pau-pns-2 
Domain: Time Migrated 
 
Seismic Attributes : 
-Amplitude 
 
Filter out constant value traces : yes 
 
Extraction Geometry 
-Top Surface : CHANNELROOF UPGRADE RandD TEXAS3D Picking Interpretation - Offset Above : 0 ms 
 
-Bottom Surface : CHANNELROOF UPGRADE RandD TEXAS3D Picking Interpretation - Offset Below : 20 ms 
 
</body>
</html>

jsulm · 18 Nov 2020, 14:59

@Ghis64 You can use https://doc.qt.io/qt-5/qwebengineview.html#setHtml instead of load()

JonB · G Ghis64 18 Nov 2020, 14:49

@Ghis64 said in QWebEngineView no longer render html files with no .html extension:

One of them is that the QWebEngineView::load no longer render the html code set in the file:

It was working with any file name with Qt4.9.

How was that, given that Qt 4 did not have QWebEngine... anything? Must have been miraculous....

JonB · 18 Nov 2020, 15:03

@jsulm said in QWebEngineView no longer render html files with no .html extension:

@Ghis64 You can use https://doc.qt.io/qt-5/qwebengineview.html#setHtml instead of load()

HI @jsulm. Nonetheless, this does seem to be a "gotcha"! Is it intentional? (Might help if the docs for load() said so?) Does this .htm vs .html behaviour apply to Linux, or is it a Windows-thing only?

Whoops, I mis-read OP's situation, explained later on below.

Ghis64 · 18 Nov 2020, 15:04

@jsulm setHtml has a limit of 2 MB and it fails with some of our files that display plots with a lot of data.

jsulm · 18 Nov 2020, 15:41

@JonB Sure, it could be documented (and should). I think it simply behaves like any web-broweser: if you enter an URL to a *.txt file the browser will not parse its content, but simply show the text even if it contains valid HTML.

jsulm · 18 Nov 2020, 15:14

@Ghis64 Is there a reason why you name HTML files like text files?

Ghis64 · 18 Nov 2020, 15:16

@jsulm In fact in my application code I don't use the .txt extension (I have done like this only in my example). In the application we had this code :
QTemporaryFile* tf = new QTemporaryFile (dialog);
if (!tf->open ()) {
return 0;
}

tf->write (html_text.toLatin1 ());
tf->close ();
QString file_name = tf->fileName ();
web_view_->load (QUrl::fromLocalFile (file_name));

I have replaced it by:

QTemporaryFile* tf_html = new QTemporaryFile ("XXXXXX.html", dialog);
if (!tf_html->open ()) {
    return 0;
}

tf_html->write (html_text.toLatin1 ());
tf_html->close ();
QString file_name_html = tf_html->fileName ();
web_view_->load (QUrl::fromLocalFile (file_name_html));

jsulm · 18 Nov 2020, 15:24

@Ghis64 said in QWebEngineView no longer render html files with no .html extension:

I have replaced it by:

Does it work now?

Ghis64 · J jsulm 18 Nov 2020, 15:16

@jsulm Yes :) But I would have saved a lot of time if it was indicated in the documentation...

JonB · J jsulm 18 Nov 2020, 15:03

@jsulm said in QWebEngineView no longer render html files with no .html extension:

@JonB Sure, it could be documented (and should). I think it simply behaves like any web-broweser: if you enter an URL to a *.txt file the browser will not parse its content, but simply show the text even if it contains valid HTML.

Sorry, I seem to have quite mis-read what the OP said/meant! I had understood him to be saying he used to use .htm and now found he needs to use .html. Hence my question about Linux vs Windows. But I now see he says nothing of the kind...

@Ghis64
Now that I understand you had always used .txt. Then it's not a documentation/behaviour issue. Browsers should always open .txt files as text, only .htm or .html should be opened as HTML.