Compose pointer to property of object

[McLion]

@mrjj
Thanks.
I'll try to implement your idea .. and get back with the result ( or more questions ;-)

[McLion]

@mrjj
I got stock at some other place.
What's the best way to create the webGUI's (qWebView) at run-time, only as needed?
I mean, I always need one at least, but only sometimes more than one and was thinking of not using up the memory by preparing a defined number of copies.
Any hint's, if possible at all?
Thanks.

[mrjj]

hi
its always possible to NEW widgets on demand.
How you will do it, mostly depends tón the GUI.
How user will do it.

At any time you can do
QWebView *view = new QWebView(parent);
view->load(QUrl("http://qt-project.org"));
view->show();

[McLion]

@mrjj
Here's what I'm doing:

  QWebView *webGUI = new QWebView(this);
  webGUI->setObjectName(QString::fromUtf8("webGUI"));
  webGUI->setGeometry(QRect(280, 190, 150, 120));
  webGUI->setAcceptDrops(false);
  webGUI->setStyleSheet(QString::fromUtf8("background-color: rgba(127, 127, 127, 0);"));
  webGUI->setUrl(QUrl("about:blank"));
  webGUI->setRenderHints(QPainter::SmoothPixmapTransform|QPainter::TextAntialiasing);
  webGUI->page()->mainFrame()->setScrollBarPolicy( Qt::Vertical, Qt::ScrollBarAlwaysOff );
  webGUI->page()->mainFrame()->setScrollBarPolicy( Qt::Horizontal, Qt::ScrollBarAlwaysOff );
  webGUI->setGeometry(0, 0, SCREEN_SIZE_X, SCREEN_SIZE_Y);

This is in a separate function and does not yet have the code to make it create webGUI[01] .. webGUI[n]. I thought of trying with one first.
I currently call this from the main constructor.

Before, the concept used only one webGUI that I created in the Designer - everything worked as supposed.

I'm accessing these webGUI's from various places in my code.

[mrjj]

hi
If you make this into a fine function that returns a QWebView *, you
can easy make more than one.

I do wonder how the parent QWebView(this); << the "this" can
show mutiple QWebView ?
will you use a tab control or a stackedwidetget to allow user to flip between the
WEbViews or ill the be in same page and just take a smaller share of it ?
as in share the page/parent ?

[McLion]

'This' might be one of my problems.
While in Designer I had a centralWidget as parent for all my elements.
The webGUI's are dynamically loaded with content from a local server and are shown/hidden as needed. They also are placed and sized as needed at run-time and cover all of the screen or or only parts, may overlap with transparency ...
There is at least one, but should now be extendable on request.

Am I correct that I will need to create webView01 from the constructor at startup and make it available in *.h. Otherwise all the references to it are not satisfied.

All references/calls to any webGui need to make use pof the QList, right.

As you may surely have noted, I never implemented such a logic/functionality before.
Thanks a lot for your help and guidance!

[mrjj]

@McLion said:

• 'This' might be one of my problems.
  Well "this" is just the parent. if no parent are giving, it will become a window.
  So often this will be mainwindow. There nothing wrong having mutiple
  WebViews in same parent but u might need to arrange them to not overlap.
  (use move or setGeometry) Since it sounds you will arrange them manually and not use a layout or tabs or something like that.

• Am I correct that I will need to create webView01 from the constructor at startup and make it available in *.h. Otherwise all the references to it are not satisfied.
  Well you dont need that.
  You can have list
  QList< QWebView *> Webs;
  QWebView *webGUI = new QWebView(this);
  ...
  Webs.append(webGUI); // keep in list

Then at any time
QWebView *w = Webs[0]; // take from list
or Webs[1] , 2,3,4 etc.

So you dont need a named variable to access it.

Also, handling signals. You a can use same slot for all webviews.
the sender() function will tell you which webview
QWebView * wv= qobject_cast<QWebView *>(sender());
if (wv) ...
inside the slot for a signal to know which of the webviews that send the signal.
Not sure you will need it, so just a note :)

[McLion]

Getting forward :-)
The hint with the sender in the signal was great too. As if you would know before, I really stumbled over this - thanks!

I came across an issue with the list though.
There are no absolute positions in the list. Saying if 3 entries are made (0,1,2) and the second list (1) is cancelled for instance because it's not needed anymore, former entry 2 becomes entry 1.
QList seems to always fill from the 0 up and there are no absolute positions.

I either did not get all of QList or I may need to switch to some other solution - unfortunately- because it otherwise works a treat.

[mrjj]

hi
Im not sure what wrong with QList since its dynamic and
we cant have invalid pointers around ?
else use a map
http://doc.qt.io/qt-5/qmap.html
QMap<int,QWebView * > map;
QWebView *webGUI = new QWebView(this);
...
map[1] =webGUI ;
map[2] =nextwebGUI ;
...
QWebView *w=map[2]; // it will stay "2"

They wont change position as 1,2 is a key
like map["onekey"] =webGUI ;
but we use int as no need for string.
so even if we remove map[1] then
map[2] is still there.

So maybe it works better for you ?

[McLion]

Tried quickly ... and the Map is exactly what I need.
Thanks a million! .... I'll be back ;-)

[mrjj]

@McLion
super
notice if you reuse the key
map[1] =webGUI ;
map[1] =nextwebGUI ;
It will replace the web *.

[McLion]

Thanks for the heads-up.
I'll do some testing and experiment.

[McLion]

So far, everything related to this threads question and the QMap as solution seems to work.

I stumbled over something else while relacing the QwebView from the Designer by my 'on-demand' created one:
I can not load an url, it crashes with sig11.

I get the following connect error on bootup:

QMetaObject::connectSlotsByName: No matching signal for on_webGUI_loadFinished(bool)

which I dont understand and may be the cause.
I have connected:

connect(webGUI, SIGNAL(loadFinished(bool)), this, SLOT(on_webGUI_loadFinished(bool)));

and in *.h as private slot:

void on_webGUI_loadFinished(bool arg1);

This worked before, with the QWebView from the Designer.
Any idea? Thanks.

[mrjj]

@McLion said:

no matching signal for on_webGUI_loadFinished(bool)

Hi
this warning comes as you name slot on_XXX
This will trigger Qt auto connect feature so when you use
a concrete connect you should rename it so it dont
start with on__
(right click it- refactor->rename)

also please do
qDebug() << "loadfin:" << connect(webGUI, SIGNAL(loadFinixxxx

to see if it returns true; ( as in , it can connect)

[McLion]

I wasn't aware that using on_ in the name will trigger any functionality!
Refactoring solved this problem - Thanks !

However, the signal 11 crash when trying to load an url seems to have some other cause .... I'm searching ;-)

[jsulm]

You're most probably dereferencing a null pointer. Signal 11 means SIGSEGV (segmentation error).

[McLion]

@jsulm
Yes - Thanks . Problem loacted, but not yet solved:

void QTGUI_MainWindow::populateJavaScriptWindowObject()
{
  QWebView * webGUI = qobject_cast<QWebView *>(sender());
  webGUI->page()->mainFrame()->addToJavaScriptWindowObject("NativeBridge", this);
}

The sender is the JS and not the QWebView and so I do not get the pointer to the QWebView that I need. Instead, the pointer is 0x0 and then - of course - the addToJ... crashes.

Any idea how I get the pointer to the QWebView from which the JS is sending?
Thanks

[jsulm]

What is JS?

[McLion]

@jsulm
JavaScript (in/from QWebKit ... more precise page()->mainFrame().

[McLion]

I posted this as a separate question in the WebKit group.