I have a QML file which contains a layout of QML items and now I want one of those items to be a QGLWidget. i.e. I want to render to a specific QML item.
Is anyone aware of how to do this?
The simplest way I suppose it to provide QML a new custom component implemented in C++. I couldn't find anything ready.
You could subclass the QDeclarativeItem and implement your OpenGL code in the paint function after using the QPainter::beginNative() function. After that you can "export" your new custom item to QML this way. This is quite simple and should work, but you'll have to setup the viewport of you QDeclarativeView to be a QGLWidget, something like this:
QDeclarativeView view;
// This is needed because OpenGL viewport doesn't support partial updates.
view.setViewportUpdateMode(QGraphicsView::FullViewportUpdateMode);
view.setViewport(new QGLWidget);
or you'll have to use the opengl graphics system for the entire application.
Another way is using QML/3D.
This thread will give you some other information.
Related
I'm working on a Qt application and I need to create windows dynamically. Each window consists of QObject-based c++ backend and qml-based interface. Each window needs to be connected to the bunch of signals emitted by core classes.
Current solution is to derive window from QQuickView, connect signals to it and load qml using setSource(). Is it a right way or there is a better way?
Is it better to use one QQmlEngine for all windows (and use this engine as parent for every window) or create new engine for each new window?
For this I would expose a c++ model to the QML code.
Since this model would be dynamic (elements can be added or removed), I'd use a QAbstractItemModel derived model that can inform the views that some elements are added/removed. Using something else like a QList<QObject*> would mean that you'd have to tell the view that the entire model should be reloaded after each change.
Instead of implementing the model from scratch, you could use a class like QQmlObjectListModel from Qt QML Tricks, it exposes a QList-like API from c++ but is a QAbstractItemModel exposing the QObject properties as roles under the scene.
Another solution that you could use if you don't want to use QObjects is benlau's QSyncable (I've actually used this in a similar situation to yours, where I expose my screens in a model and instantiate a Window displaying a taskbar for each).
Then, I'd use a QQmlApplicationEngine and expose the model to it with setContextProperty. A QQuickView is already a window, so I don't think you want to use that, better to manage your windows manually in the QML code.
Then in your QML code, use an Instantiator as your root object, set your model, and use Window as its delegate :
Instantiator {
model: yourModel
Window {
/* ... */
}
}
Yes, you are right. We have QListView already, it is prefect when we are trying to display simple list with Model/View.
But, QListView has lots of problem when we need to display complex list with rich text and widgets. Just think about a timeline-listview for Facebook or Twitter.
Sure, we can implement our own delegate for rich text or images, but ListView can print static item only. So, there isn't a way to show clickable hyperlink (you can calculate position of the mouse and hyperlink, but it is a really drity work) or load asynchronous images.
Well, QListWidget seems our solution. We can put widgets into it. But. we will lost our Model/View/Delegate architecture, that is terrible!
Now, my solution is writing my listview in QML. Other widget are still native Qt widget. (I don't like a non-native pure QML user interface.)
QML is really flexiable when doing that kind of work. Then export my model, finally put a viewer into my QMainWindow. But coding in two programming languages and trying to communicate with other native widget is really difficult.
So, is there a way to use Qt's Model/View architecture with QListWidget? Or I have to implement them by myself?
QListWidget does use Qt's MVC, as it derives from QListView and...
QListWidget uses an internal model to manage each QListWidgetItem in
the list.
Just use QListWidget::model () const to access the model.
I am trying to implement a custom OpenGL scene (wrapped in a QGLWidget), but still use QT controls (such as slide bars and buttons). I tried to make my main widget a QGLWidget, which has QWidgets as children. The child widgets seem to work (when I click a pulldown menu, its options appear), but the widget fails to draw (I see a white square). I changed the base class of my children widgets from QWidget to QGLWidget, and now QPainter calls work, but QT GUI stuff is still not displaying...
Some claim that a QGLWidget can not have QWidgets as children... I am not sure about that and I'm not willing to give up. By the way, I am using Visualization Library to draw the OpenGL scene, but it is just an OpenGL wrapper...
Any clues where the problem might be? Also, key events stop being processed for some reason when I add subwidgets to the GQLWidget.
Update:
I tried various combinations of widgets and layouts. It seems that the QGLWidget just gets drawn on top of anything. I even tried with raise() to arrange Z-depth of the widgets, to no avail. Is overlayGL() the only way to draw on top of an OpenGL widget?
Update 2
After months of trying, I figured out it is something related to QT. Whenever a QGLWidget is drawn on top of another QGLWidget, the first's background() function is not called. So a button is there and can be clicked, but it's not drawn. My workaround was to draw everything myself using QPainter - that works. What I found curious is, one has to use QPainter::startNativePainting() in order to draw with it. One would expect that they would overload start() in QPainter to call startNativePainting() whenever a QGLWidget is the painting device...
Another (maybe useful) fact is that QPainter calls CHANGE the Opengl context. So if you have another tool in cooperation with QPainter (in my case Visualization Library), chances are that one of them will crash (in my case VL which checks if the context state has been cleared before each frame).
There is a labs example of rendering Qt widgets using opengl it's a little old and I haven't tried it with the improved qglwidget in 4.8
There is also an issue with drawing over the top of a fullscreen QGLwidget - it was supposedly a bug in NVidia's openGL driver. It doesn't seem to have been resolved
https://bugreports.qt-project.org/browse/QTBUG-7556
If I were you I would use the QGLWidget as a viewport for a QGraphicsScene, then you can draw your widgets using a QGraphicsProxyWidget. That way you get a proper OpenGL viewport with the ability to put widgets in and manipulate them easily.
Did u try to call update() explicitly? I find that sometimes QGLWidget update the display stuff kind of slow.
This is an old question, but I recently had quite a bit of trouble with this, and this is what helped me -
Use QML/QT Quick. QML is a javascript-like language that allows you to layout your widget elements on a window and do basic processing on events like mouse clicks. There are a few other cool features, but the one that is most relevant to this question is that you can import qt widgets from C++ code.
So you can make a custom QGLWidget, import it into the QML window, and set the size/position/stick widgets on top of it in whatever you want, very easily. QT's Scenegraph example does a great job explaining this. Scenegraph's code is also included as an example in at least Qt Creator 3.2.1 Open Source (that's the version I have anyway)
I am writing a simple file browser app with Nokia Qt4.7 on Symbian^3 platform. I can display the directory/file list in the listview widget using QFileSystemModel. But I want to customize the list view item. And I am using QItemDelegate to do the trick overriding sizHint and paint functions. I want to display a checkbox in the end of every item (ListMode) or in the right down corder of the icon(IconMode). How can I do it?
Thanks.
I'd suggest you to reimplement QItemDelegate::paint function and use QStylePainter and use QStylePainter::drawControl to render checkbox element. Depending on the mode you can vary your painting.
You can also do this using QML . Styling rows is much easier in QML.
To be more specific your Model will still be c++ . Only the list can be in QML.
I'm learning Qt independently, and this may seem like an easy question (because it is). I primarily come from a Swing background, so the concepts are very similar.
My question:
I am using Qt Designer to create a QTreeView item in the UI Designer. How do I do something as simple as setting the model of the TreeView?
Usually I would do something like:
QTreeView *tree = new QTreeView();
tree->setModel( &myModel);
I don't even know how to get a reference to the QTreeView object that the UI Designer created. Any direction will be appreciated!
Depending on your version of Qt, your main window will either include as a member or privately inherit a class with all of your designer widgets. So, within MainWindow, e.g. either my_widget->show(); or ui->my_widget->show(); to show the widget, respectively.
In your case, my_tree_view->setModel(my_model);