Activate window - c++

Question

i have a QMainWindow. It has this parameters:
this->setWindowFlags(Qt::Tool);
this->setFocusPolicy(Qt::StrongFocus);
this->setAttribute(Qt::WA_QuitOnClose,true);
After showEvent calles my window is shown but unactivated.
I tried to overload show function:
...
QMainWindow::showEvent(event);
this->activateWindow();
...
But it doesn't help me.
EDIT:
When i commented line
this->setWindowFlags(Qt::Tool);
everything worked fine, but i need in tool-flag.
Any ideas?
EDIT:
OS: Linux
Programming language: c++
Qt version: 4.5.1

Answer 1

The Windows Manager Decides
Before I start: As pointed out by elcuco and Javier, focus policy and other aspects of the windows layout (e.g. the title bar) belongs to a substantial extend to the respective windows manager, and Qt might have limited control. To see this, just look at a user interface that has a "focus follows mouse" policy. In these cases, the windows manager might ignore Qt's focus request. For this reasons, the Qt documentation calls many of the respective flags "hints". Consequently, some of the suggested solutions might or might not work for you.
QApplication::setActiveWindow()
This not withstanding, e.tadeu's solution to use QApplication::setActiveWindow() works for me for both Windows and Ubuntu with Gnome. I tested it with the following code. Apologies that it is Python using PyQt (I use questions like these to learn a bit about PyQt). It should be fairly easy for you to read it and translate it into C++.
import sys
from PyQt4 import QtGui
from PyQt4 import QtCore
class MainWindow(QtGui.QMainWindow):
def __init__(self, parent=None):
QtGui.QMainWindow.__init__(self)
# main window
self.setGeometry(300, 300, 250, 150)
self.setWindowTitle('Test')
# text editor
self.textEdit = QtGui.QTextEdit()
self.setCentralWidget(self.textEdit)
def closeEvent(self, event):
QtGui.QApplication.instance().quit()
#main
app = QtGui.QApplication(sys.argv)
testWindow = MainWindow()
testWindow.setWindowFlags(QtCore.Qt.Tool)
testWindow.show()
app.setActiveWindow(testWindow)
app.exec_()
Note that you have to add some handling of the close event of the testWindow, because the app does not exit automatically if you close a Qt::Tool window.
The grabKeyboard() Hack
If this does not work for you, the following hack might. I assume that you have a window in your application that is active. You can then use grabKeyboard() to redirect the input. The Qt::Tool window doesn't get the focus, but receives the input. The following main code demonstrates it (the other code remains unchanged).
#main
app = QtGui.QApplication(sys.argv)
testWindow = MainWindow()
testWindow.setWindowFlags(QtCore.Qt.Tool)
testWindow2 = MainWindow() # second window which is active
testWindow2.show()
testWindow.show()
testWindow.textEdit.grabKeyboard()
app.exec_()
Basically, while the window testWindow2 is the active one, all text entered shows up in testWindow.textEdit. It is not nice, I know...
Creating Your Own Window
You gain the most flexibility (and create the most work for yourself) by rolling out your own window layout. The idea is described in the following FAQ.
Other "Solutions"
You could directly call the respective window manager's API function to get the desired result (clearly against the very reason for using Qt in the first place). You could also hack the Qt source code. For example, on Windows, Qt uses the ShowWindow() function with a SW_SHOWNOACTIVATE flag, to show a window with style WS_EX_TOOLWINDOW if you set the Qt::Tool flag. You could easily replace the SW_SHOWNOACTIVATE with whatever you want. Linux should be the same. Clearly also not recommended.

Answer 2

Try to use QApplication::setActiveWindow()

Answer 3

The original apple Human Interface Guidelines(*) said that toolbox windows were "always on top but never activated". It also advises against using text boxes on them, precisely because the lack of activation-state feedback.
Check how other 'toolbox heavy' apps behave. I faintly recall that at least GIMP and InkScape seem very different in this aspect.
As elcuco said, the window manager can do whatever it wants with Qt's flags. Also, it sure would be different under KDE, Gnome, fluxbox, whatever.
(*):great document! somewhat outdated; but tool windows were already used and considered

Answer 4

Which operating system? Which Qt4?
On Linux you are doomed, the window manager can ignore what you are telling him. Keep it under consideration.

Answer 5

Does the same thing happen if you just make it a regular QWidget instead of a QMainWindow?
Also, perhaps you might be better trying to achieve whatever effect you need Qt::Tool for by other means if that's possible?

Answer 6

Regarding Qt::Tool WindowFlags To quote Qt documentation
Indicates that the widget is a tool
window. A tool window is often a small
window with a smaller than usual title
bar and decoration, typically used for
collections of tool buttons. It there
is a parent, the tool window will
always be kept on top of it. If there
isn't a parent, you may consider using
Qt::WindowStaysOnTopHint as well. If
the window system supports it, a tool
window can be decorated with a
somewhat lighter frame. It can also be
combined with Qt::FramelessWindowHint
It seems the flags is a problem and using Qt::WindowStaysOnTopHint should solve your problem.

Answer 7

Just call show() after setWindowFlags().