Implementing fullscreen mode - frameless window that hides the taskbar

Violet Giraffe

I'm trying to make a true fullscreen window (not just maximized one). Experimenting on Windows for now. According to this article a window should be able to hide the taskbar, i. e. have a higher z-order. But this code

setGeometry(qApp->desktop()->geometry());

only produces this result: http://i.imgur.com/XXPkqdz.jpg
and this message in the output:

QWindowsWindow::setGeometryDp: Unable to set geometry 1920x1080+0+0 on QWidgetWindow/'CMainWindowWindow'. Resulting geometry: 1916x1054+0+0 (frame: 8, 30, 8, 8, custom margin: 0, 0, 0, 0, minimum size: 568x323, maximum size: 16777215x16777215).

How can achieve what I want? The screenshot looks great, except that the taskbar is drawn over my window, and I need it to be the other way around.

NetZwerg

Try adding

QMainWindow::setWindowFlags(Qt::FramelessWindowHint);

Violet Giraffe

Finally got time to return to this task.
If I do as you suggested, the window just disappears both from screen and from the taskbar (no button, which is typical for frameless windows).

UPDATE: Turns out, a mere showFullScreen call does the trick. What got me confused previously when I tried was that there's a ~1 second delay between the window maximizing and the taskbar disappearing.
Now the only problem I have is how to restore the original size and position of the window. Guess I'm gonna have to use the saveGeometry / restoreGeometry methods.

? Offline

Hi, using the following function works for me:
void QWindow::setWindowState(Qt::WindowState state) with state Qt::WindowFullScreen.

Violet Giraffe

That has the same effect as showFullscreen. Perhaps, the implementation is the same. I find showFullscreen much more neat.

For restoring, I call QRect savedGeometry = geometry() before showFullscreen, and then when I need to get back to a regular window:

showNormal();
setGeometry(_nonFullscreenWindowGeometry);
raise();
activateWindow();

Not sure if raise and activateWindow are necessary, it's just a code snippet I see in many different Qt projects that's called when window state changes. Could be a fix for some very old Qt bug that's been fixed long ago, for all I know.

? Offline

@Violet-Giraffe Yes, it has the same effect. You said you want to restore the window's previous geometry: You can just read the current state with Qt::WindowState QWindow::windowState() const and restore it when you need to. This also automatically restores the previous geometry.

Violet Giraffe

@Wieland said:

This also automatically restores the previous geometry.

That's neat! setWindowState(windowState() & ~Qt::WindowFullScreen) works like charm (at least on Windows 7), no need for any additional member variables.
Thanks.

Chris Kawa

Also note there's a showNormal()method that does the same as tinkering with windows states.
There are basically 4 methods for setting the state: showNormal(), showMaximized(), showMinimized() and showFullScreen(). They might be more convenient than tracking the state flags, depending on your need.

Violet Giraffe

showNormal alone doesn't restore the original geometry, it just exits the full screen mode.

Chris Kawa

That's... weird. The implementation is basically the same, i.e.

void QWidget::showNormal()
{
   ensurePolished();
   setWindowState(windowState() & ~(Qt::WindowMinimized | Qt::WindowMaximized | Qt::WindowFullScreen));
   setVisible(true);
}

I wonder if that's some bug then?

Violet Giraffe

Re-checked and confirmed: showNormal works properly in conjunction with showFullScreen.