QWebView for running D3 javascript is slow after reloading HTML.

[CLang]

I am using a QWebView to display plots using javascript and D3. There is a combobox to select different datasets. Each time a new dataset is selected, some calculations are done, then the javascript is reinitialized with the new data and set as an html string. Then the QWebview is reset using QWebView::setHtml().

If I change the combobox value a few times, the plots load exponentially slower each time until it eventually freezes. Sometimes it will eventually load and sometimes not.

(I'm not sure the javascript is relevant - it is not my area of expertise so I haven't taken the time to understand it yet. I'm hoping the problem can be resolved with Qt code)

From the QWebView documentation: "The html is loaded immediately; external objects are loaded asynchronously."

My guess is that the javascript continues to execute in the background and it doesn't stop when the html is updated and reloaded. Is there a way to stop this?

The code for initializing and updating are as follows:

dataView::dataView(QWidget* parent) : QWidget(parent)
{
  init();
}

void dataview::updatePlot()
{
  //Get new value and do some calculations

  // Update html string with new data
  std::string htmlString = "[new javascript]";

  webView->setHtml(QString::fromLocal8bit(htmlString.c_str()));
}

void dataView::init()
{
   webView = new QWebView();
  // Need path to exe as this is where the local copies of the js files are.
  QUrl path = webView->url();
  path.setUrl(QCoreApplication::applicationDirPath());
  m_jsPath = path.toString().toStdString();  

  // Initialise the html string
  htmlText=""

  webSetting = webView->settings();

   // Maybe doing nothing-----------------------
   webSetting->setObjectCacheCapacities(0, 0, 0);
   webSetting->setMaximumPagesInCache(1);    
   //--------------------------------------------

  QPointer<QVBoxLayout> mainLayout = new QVBoxLayout();
  mainLayout->addWidget(webView);
  setLayout(mainLayout);
}

Hopefully I have included all the relative information code.

[CLang]

The issue seems to be in Qt5.5 - I compiled with 5.3 and the issue is gone.

[Konstantin Tokarev]

Which version of QtWebKit are you using?
Does problem reproduce if you remove cache settings?

[CLang]

This post is deleted!

[CLang]

@Konstantin-Tokarev

I am using Qt 5.5

I am unsure how to remove the cache settings but I will try that right now.

Edit: It appears that

webSetting->setObjectCacheCapacities(0, 0, 0);

should disable cache, so I have tried this.

[Konstantin Tokarev]

Yep, try without this line

[CLang]

@Konstantin-Tokarev

I have tried it with all combinations of the following settings (one, other one, both, none)

webSetting->setObjectCacheCapacities(0, 0, 0);
webSetting->setMaximumPagesInCache(1);

I am going to try another Qt version and see if that has an effect.

[Konstantin Tokarev]

You should use qtwebkit from 5.212 branch, version coming with Qt 5.5 is obsolete

[CLang]

@Konstantin-Tokarev said in QWebView for running D3 javascript is slow after reloading HTML.:

5.212

Thanks for the advice. Is 5.212 > 5.10?

And why such a weird version number? Should I download form git or is the qt installer going to have it?

[Konstantin Tokarev]

@CLang For use with Qt 5.10, get binaries from http://download.qt.io/snapshots/ci/qtwebkit/5.212/latest/qtwebkit/

And why such a weird version number?

It isn't tied to particular Qt version, instead respective WebKitGTK's branch name is used as a basis

[CLang]

@Konstantin-Tokarev

Thanks for all your help.

Does this mean I could download the source, compile it with cmake and msvc2013_64 and use it with qt5.5?

[Konstantin Tokarev]

No, MSVC 2013 is not supported. You need MSVC >= 2015 or MinGW >= 4.9

[CLang]

@Konstantin-Tokarev I actually downgraded to 5.3 and the issue has resolved.

What's the best way to resolve this post? Reply to the initial post with the solution and change to 'solved'?

[CLang]

The issue seems to be in Qt5.5 - I compiled with 5.3 and the issue is gone.