CODEWITHSUNDEEP
qtcross-platform
user1973386
user1973386

Reputation: 1135

How to draw over everything on the screen using Qt?

The basic idea is: I would like to draw over everything on the screen.

One way I can imagine this is creating a transparent full-screen window without window controls (minimise, maximise, etc.) or borders. Then drawing into that window which is transparent. The problem I can think of is that I will be unable to control windows which are behind our transparent window.

How could I do something similar to this, without the mentioned problem? I would also like it to work on multiple operating systems if possible.

Edit: The user will not be drawing with the mouse or other means on the screen, but will be able to continue use his desktop like normal, without that my program interferes in any way (other than the drawing on the screen). My program will only display something on the screen, which the user will be unable to interact with (at least that's the plan).

Upvotes: 1

Views: 1917

Answers (2)

Kuba hasn't forgotten Monica
Kuba hasn't forgotten Monica

Reputation: 98425

Qt 5 implements it:

QWidget w;
w.setWindowFlags(Qt::WindowTransparentForInput);

Qt 4 didn't support this functionality yet - see QTBUG-13559. The bug report had a hint on what needed to be done for Windows.

Upvotes: 2

TheDarkKnight
TheDarkKnight

Reputation: 27611

The method you describe is the one to use; a transparent full-screen window.

If you're using the left mouse button to draw, you'll need a mechanism of switching modes to be able to select items through the window and send events to the operating system.

Upvotes: 1

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