How to draw to screen in c++?

Question

How would I draw something on the screen ? not the console window but the entire screen, preferably with the console minimised.

Also, would it show up on a printscreen ? What I want to do is create something like a layer on top of the screen that only me and my aplication are aware of yet still be able to use aplications as usual.

Here's an example: Let's say I want 2 yellow squares 5 by 5 pixels in size appearing in the center of the screen on top of all the other applications, unclickable and invisible to a printscreen.

[Edit]

I forgot to mention that I'm using Visual Studio 2010 on Windows XP.

More context about what you're trying to accomplish might be useful here. — Thanatos, Jun 05 '10 at 19:11
It sounds like you are making a bad troll preventing people from closing the application. :D — Jeroen, Jul 11 '13 at 18:21

OlimilOops · Accepted Answer · 2010-06-05T19:16:00.057

9

in windows you can use the GetDC-function. just a minimalistic example:

#include <Windows.h>
#include <iostream>

void drawRect(){
    HDC screenDC = ::GetDC(0);
    ::Rectangle(screenDC, 200, 200, 300, 300);
::ReleaseDC(0, screenDC);
}
int main(void){
    char c;
    std::cin >> c;
    if (c == 'd') drawRect();
    std::cin >> c;
    return 0;
}

but since Windows Vista it is very slow

edited Jun 05 '10 at 19:16

answered Jun 05 '10 at 18:58

OlimilOops

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Use Direct2D on Windows Vista. – Puppy Jun 05 '10 at 19:27
Yes, it works, but it shows up in the printscreen :P I wonder if there's a way to make it invisible to any screen capture. – Kesarion Jun 05 '10 at 19:48
Hey how do I change the colour? :D. – JSideris Mar 19 '13 at 07:51

score 4 · Answer 2 · edited Jul 22 '12 at 22:25

4

C++ has no notion of a "screen" and especially none of "graphics". The functionality needed is provided by your operating system. On many systems you will need a "Window" and draw on it. To do this portably, a library like Qt might help. A Windows solution was given by Oops. Maybe you want to use some OpenGL library, or Windows' DirectDraw/Direct3D from DirectX, in case you want to do some 3D stuff with your graphics.

edited Jul 22 '12 at 22:25

Ry-

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answered Jun 05 '10 at 19:20

johannes

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Another cross-platform graphics library: http://en.wikipedia.org/wiki/Simple_DirectMedia_Layer – ʇsәɹoɈ Jun 05 '10 at 19:30

score 2 · Answer 3 · answered Jun 05 '10 at 19:27

2

Windows offers GDI/+, WPF, and DirectX (including Direct2D on Vista+).

answered Jun 05 '10 at 19:27

Puppy

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score 1 · Answer 4 · answered Jun 05 '10 at 19:24

The (rather nice but not recently updated) graphics library anti-grain geometry has very simple bindings to display its demos on a variety of windowing systems, you could look at those for examples. But for anything much more involved you're probably talking about operating system specific libraries.

How to draw to screen in c++?

4 Answers4

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