Hide cursor in fullscreen mode using Qt 4.8?

There is a program named unclutter that hides the mouse pointer. Here's an ArchLinux package:

https://www.archlinux.org/packages/community/i686/unclutter/

I currently use it on an embedded system for hiding the mouse cursor on a touchscreen.

I want to hide the cursor on fullscreen ...

You could set the cursor to be the blank cursor:

widget->setCursor(Qt::BlankCursor);

Also, as the docs state:

Some underlying window implementations will reset the cursor if it leaves a widget even if the mouse is grabbed. If you want to have a cursor set for all widgets, even when outside the window, consider QApplication::setOverrideCursor().

So you can call:

QApplication::setOverrideCursor(Qt::BlankCursor);