Application with multiple windows in Qt - c++

Question

What is a good way to create application with multiple windows in Qt? Something like GIMP. I have already read this answer and it is not what I need.
I have two windows, one with controls and one with OpenGL inside. Right now I have something like this:
int main()
{
// some code
MainWindow mw;
mw.show();
GLWindow gw;
gw.show();
// ...
}
I don't like this for two reasons. First reason is when I start my application, window with OpenGL will be on top (because it is last to call show()) but MainWindow will be buried somewhere under all opened windows. What I need is both windows in front of everything (like GIMP), preferably with focus on MainWindow (I guess I can bring them to front, so that is minor issue). Second reason I don't like this is that my application will be closed completely only when I close both windows.
So I was thinking of having a reference to GLWindow inside MainWindow, and creating it from MainWindow.
Would that be a good way to create application with several windows?
EDIT: GLWindow inherits from QOpenGLWindow.

Answer 1

You are doing right, but with the following simple tricks, you can resolve both issues that cause you do not like your right method:
To activate both windows, just do as follows:
MainWindow mw;
mw.show();
mw.activateWindow();
GLWindow gw;
gw.show();
gw.activateWindow();
To resolve the quit problem, you have to override the closeEvent in both windows. To do that, add the following code into the header file of your both windows:
protected:
void closeEvent(QCloseEvent *event) override;
and in the implementation of the closeEvent, just write qApp->quit();. This way once you close either window, your application will terminate completely.
MainWindow.cpp
void MainWindow::closeEvent(QCloseEvent *event)
{
qApp->quit();
}
and
GLWindow.cpp
void GLWindow::closeEvent(QCloseEvent *event)
{
qApp->quit();
}

Answer 2

I'm not sure I completely understand the situation but, typically, you can make the 'secondary' widgets child dialogs of the QMainWindow. Given your example code that would be something like...
int main ()
{
// some code
MainWindow mw;
mw.show();
/*
* Secondary windows should be created with the QMainWindow mw
* as their parent.
*/
GLWindow gw(&mw);
/*
* Set the Qt::Dlaog window flag to `encourage' the QMainWindow
* and its children to behave as a group.
*/
gw.setWindowFlags(gw.windowFlags() | Qt::Dialog);
gw.show();
// ...
}
Now all widgets behave as a group (possibly subject to the window manager being used) and closing the QMainWindow will, by default, close the application.