I'm new to QT. when I create a qwidget such as a qlabel, programmatically, it never shows in my main window or anywhere else. But when I create one using the IDE it works fine. What am I missing ?
By default, widgets are set to invisible, therefore, you need to call .show() to make a widget visible. For example,
QLabel *label = new QLabel("click");
label->show();
Using the debugger I noticed that my QLabel had the wrong parent. Setting the parent correctly cured all of my problems. The other answers to my question were relevant too.
Related
I created a GUI with Qt5 but I will like the objects to be always contained in the window. When I change the size of the window (with the mouse), the objects dont resize themselves and therefore are hidden by the window.
Basically, I will like my GUI to act like a Web Page for example.
I think I have to use the Layout properties to do that but I dont seem to find it in Qt (in the QBBoxLayout or QWidget ?). I will like to change this in Qt and not in my PyQt script if possible.
Have you set the layout of the window ?
Normally you should have a code similar to this one
dialog = QDialog()
verticalLayout = QVBoxLayout()
label1 = QLabel("first")
label2 = QLabel("second")
verticalLayout.addWidget(label1)
verticalLayout.addWidget(label2)
dialog.setLayout(verticalLayout)
if you are creating the gui writing the necessary the code yourself.
If you are creating the gui with the designer, probably you have not applied a layout to your window.
I have a Qt project where I'm using QGraphicsView framework, also I have popup windows on the scenes. (QDialogs)
When someone clicks on a certain button a popup window appears, and I'm invoking it with the .exec() method instead of .show() to make it the active one. Also I want to give it a visual effect like lightbox provides for html pages, so it would be obvious for the user too, that the background window won't communicate. Do you know any simple solution to make it work? or is it hard to implement in Qt?
EDIT: I don't know if it's obvious of not, but it's a desktop application, not a web application.
Just create QFrame over necessary area with customized background and transparency. For animation effect you may use QPropertyAnimation + QGraphicEffects and other stuff from qt animation framework.
Now I found another way to accomplish what I wanted. Like this:
QWidget* mytranswidget = new QWidget(mybgwidget);
mytranswidget->setStyleSheet( "background:transparent; background-color:rgba(0,0,0,95)");
mytranswidget->setWindowFlag(Qt::FramelessWindowHint);
mytranswidget->setGeometry(mybgwidget->rect());
mytranswidget->show();
I'm doing it at the beginning of my popup widget's constructor so it's being drawn before draw my popup, so it will be shown in the right order.
Can i have another window over main window in Qt , and how can i implement it? I have a plugin which must return another window. I created in plugin a QWidget and set it as centralWidget but my app crashes.Anyway this will not show two windows at same time . Could someone explain how to do that ?
Any new widget created without a parent will show up as a new window. Don't try to reset 'centralWidget' unless you don't actually want the old one anymore.
If all you want is a main window whose contents change, take a look at StackedWidget.
i'm quite new to Qt and i've a question.
I've got an application with multiple windows/QFrame. I'd like them to only exist within the mainwindow (it's also the parent gadget). When I move them, I want the to stay within the parent gadget.
Is is possible ?
If yes, how ?
I've been through the Qt doc and i've found nothing. I though maybe a simple option can do that. Or do I have to create a new Widget with customs mouse Event methods ?
Thx
If you want a Multiple Document Interface (MDI) GUI you can use the QMdiArea and QMdiSubWindow classes to implement this. Have a look at the detailed description section of QMdiArea for using it with a QMainWindow example, but it also works on any other widget as well.
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)