WebKit crashes when fast zooming in/out in Google Maps (Qt 5.2, Windows 7)

outdoor_guy

Hi

Qt is 5.2.0, with MinGW 4.8, downloaded from Qt website as precompiled)
System is Windows7, 64bit

I'm writing an application which should include Google Maps. However, I got constantly crashes which looks like that Google Maps is not fast enough for providing Data.
I could reproduce the problem with the debugger and got the following printout:
@
QPainter::begin: Paint device returned engine == 0, type: 2
ASSERTION FAILED: m_ptr
..\WTF/wtf/OwnPtr.h(72) : WTF::OwnPtr<T>::ValueType* WTF::OwnPtr<T>::operator->() const [with T = WebCore::ImageBuffer; WTF::OwnPtr<T>::PtrType = WebCore::ImageBuffer*; WTF::OwnPtr<T>::ValueType = WebCore::ImageBuffer]
@

The stack shows the following (all in file Qt\5.2.0\minw48_32\bin\QtWebKitd.dll)
@

0 WTFCrash C:\Qt\5.2.0\mingw48_32\bin\Qt5WebKitd.dll 0x189a9be5
1 WebCore::BitmapTextureImageBuffer::updateContents(WebCore::TextureMapper*, WebCore::GraphicsLayer*, WebCore::IntRect const&, WebCore::IntPoint const&, WebCore::BitmapTexture::UpdateContentsFlag) C:\Qt\5.2.0\mingw48_32\bin\Qt5WebKitd.dll 0x181857de
2 WebCore::TextureMapperTile::updateContents(WebCore::TextureMapper*, WebCore::GraphicsLayer*, WebCore::IntRect const&, WebCore::BitmapTexture::UpdateContentsFlag) C:\Qt\5.2.0\mingw48_32\bin\Qt5WebKitd.dll 0x1817f7fa
3 _fu2170___ZTVN10__cxxabiv120__si_class_type_infoE C:\Qt\5.2.0\mingw48_32\bin\Qt5WebKitd.dll 0x1a8d1f08
4 ?? 0x38b1a308
@

The constructor which calles the WebView looks as follow:
@
MapView::MapView(CGPX_File *gpxFile,QWidget *parent) :
QWebView(parent)
{

m_GPXFile = gpxFile;
QDir dir;
QString path = dir.absolutePath();
QString htmlfile = "file:///"+path+"/map_html/map.html";
qDebug()<<"HTML: "+htmlfile;

this->load(QUrl(htmlfile));

}
@

map.html is as follows:

(I had to remove the < before script, otherwise the lines were not visible in the preview
@
<html>
<head>
<meta name="viewport" content="initial-scale=1.0, user-scalable=yes" />
script type="text/javascript" src="http://maps.google.com/maps/api/js?v=3.1&sensor=true"> /script>
script type="text/javascript">
var map;
var Parkimage;
var CurPosImage;
var flightPath;

var markersArray = [];
var parkingArray = [];
var positionArray = [];
var CurPositionArray = [];

var trackArray = [];

var currentMarker;
function initialize()
{

var latlng = new google.maps.LatLng(48.397,9.644);
var myOptions =
{
    zoom:8,
    center:latlng,
    mapTypeId:google.maps.MapTypeId.ROADMAP,
    draggable: true
 };
    map = new google.maps.Map(document.getElementById("map_canvas"),myOptions);
    Parkimage = 'parkplatz.jpg';
    CurPosImage = 'Flag.png';
    google.maps.event.addListener(map, 'click', function(event) {
      placePosition(event.latLng);
    });
    flightPath = new google.maps.Polyline({
       strokeColor: '#FF0000',
       strokeOpacity: 1.0,
       strokeWeight: 3
     });

     flightPath.setMap(map);

}

[removed]
</head>
<body >
<div id="map_canvas" ></div>
<input id="MyPosition" type="hidden">
</body>
</html>

@

Checking the Internet for that problem, I found the following:

http://developer.nokia.com/community/wiki/QPainter::begin:Paint_device_returned_engine_==0(Known_Issue)

However, I have no idea how to set this with QWebView.

krekeltronics

Hi there, we've got the same issue with Qt 5.x up to 5.3.2 now. Were you able to resolve? Otherwise perhaps we can help one another.

Cheers!

brcontainer

Try RELEASE mode, DEBUG mode causes crashs

krekeltronics

I narrowed it down to the use of Ground Overlays (https://developers.google.com/maps/documentation/javascript/groundoverlays). I am rendering a custom image, writing it to local storage, and passing a file URL to the map. It works just fine, but when zooming in or out quickly, the issue occurs. Generally, the app runs out of memory, which seems to suggest a memory leak in the Ground Overlay implementation.

As far as I have seen, removing the ground overlay during zooming (upon "zoom_changed" event) has eliminated the issue, but it's awkward for the overlay to disappear, then reappear once the map is idle again ("idle" event). So I'm looking for another workaround.

outdoor_guy

[quote author="krekeltronics" date="1413569611"]Hi there, we've got the same issue with Qt 5.x up to 5.3.2 now. Were you able to resolve? Otherwise perhaps we can help one another.

Cheers![/quote]

Sorry, I didn't made much more with this. This was only a hobby project to write my own GPX-Viewer, so I was not able (and also willing :-) ) to do a lot of investigation there. Maybe I will port it to Linux and see what will happen there, but I work on this only from time to time, so this could mean that it will be a long time until I work on it again.
From my work side (the one I get paid for), I do nothing with Windows

krekeltronics

I am looking into porting our implementation to use the new QtWebEngine, but haven't yet figured out how to get the JavaScript to talk to the C++. It used to use addToJavaScriptWindowObject on the frame, but I think it would use QtWebChannel now.

krekeltronics

I am still finding this consistently with Windows 7/8 and Mac OS X 10.9/10.10.x and Qt 5.4rc, both release and debug. I'm not sure I have any choice any more short of migrating away from Qt (that would be bad) or trying Qt WebEngine (and finding a way for the JS and C++ functions to talk to each other).

krekeltronics

I am still finding this consistently with Windows 7/8 and Mac OS X 10.9/10.10.x and Qt 5.4rc, both release and debug. I'm not sure I have any choice any more short of migrating away from Qt (that would be bad) or trying Qt WebEngine (and finding a way for the JS and C++ functions to talk to each other).

SGaist

Hi,

Did you already saw the "porting guide":http://qt-project.org/wiki/QtWebEnginePortingFromQtWebKit ?

Hope it helps

SGaist

Hi,

Did you already saw the "porting guide":http://qt-project.org/wiki/QtWebEnginePortingFromQtWebKit ?

Hope it helps

krekeltronics

Thanks, that guide was useful in my initial port, but without addToJavaScriptWindowObject I need to find a different way to be able to call C++ from the JS side (sockets, I am guessing).

krekeltronics

Thanks, that guide was useful in my initial port, but without addToJavaScriptWindowObject I need to find a different way to be able to call C++ from the JS side (sockets, I am guessing).