Drawing points in vertex array is offset?

[Robbis_1]

Hello, I'm running SFML 2.1 with revision (https://github.com/SFML/SFML/tree/56c2eb8cea5253e079bbf10aad80503512b87dd9) which is only 3 months old.

Take a look at this code:

int main()
{
        sf::RenderWindow window(sf::VideoMode(80, 60), "SFML window");
        window.setFramerateLimit(30);

        sf::VertexArray points;
        points.setPrimitiveType(sf::Points);
        points.append(sf::Vertex(sf::Vector2f(0, 0), sf::Color(255, 0, 0, 255)));
        points.append(sf::Vertex(sf::Vector2f(1, 1), sf::Color(255, 0, 0, 255)));
        points.append(sf::Vertex(sf::Vector2f(2, 2), sf::Color(255, 0, 0, 255)));

        sf::VertexArray lines;
        lines.setPrimitiveType(sf::Lines);
        lines.append(sf::Vertex(sf::Vector2f(0, 0), sf::Color(0, 255, 0, 127)));
        lines.append(sf::Vertex(sf::Vector2f(5, 5), sf::Color(0, 255, 0, 127)));

        while (window.isOpen())
        {
                window.clear();
                window.draw(points);
                window.draw(lines);
                window.display();
        }

        return 0;
}

This is currently producing this as a result (zoomed in):


Shouldn't it be something more like this?

[zsbzsb]

Seems to be another issue of how OpenGL tries to handle pixels. Make sure your view position is a whole number and it matches the window 1:1 (same size and not zoomed).   

[Robbis_1]

Considering that is the only code it should be whole numbers and no zoom.

EDIT: To clarify, the zoom is by taking a picture of the application that is running the code above and then scaling it in a separate program.

[eXpl0it3r]

Pixel perfect drawing is not the strongest feature of OpenGL unfortunately. Since you didn't put it in perspective, is the green pixel at 0,0 or is the red pixel at 0,0? Because sometimes OpenGL will select the middle path and thus the drawing can be one pixel off.
Maybe a screenshot of the window would be good enough.

[Robbis_1]

I'm not sure what you mean that I didn't put in perspective. The two images are taken directly from the window running the code I posted.

[eXpl0it3r]

Yes of course, but we don't know whether the top most pixel of your posted image is actually at position 0,0.
If the line gets drawn at the pixel position (0,1), (1,2), (2,3), (3,4), (4,5) then it can kind of make sense and the red pixels would be at the right position.

What happens if you draw the line as following:

    sf::VertexArray lines;
    lines.setPrimitiveType(sf::Lines);
    lines.append(sf::Vertex(sf::Vector2f(0.5f, 0.5f), sf::Color(0, 255, 0, 127)));
    lines.append(sf::Vertex(sf::Vector2f(4.5f, 4.5f), sf::Color(0, 255, 0, 127)));

[Robbis_1]

But isn't the top left pixel of the screen always 0, 0?

Your code produces the same result as the first image.

[eXpl0it3r]

But isn't the top left pixel of the screen always 0, 0?

Yes (unless you change the view), but that is exactly the point. You did not say whether the image you posted are from 0,0 or not. It might have been drawn on the bottom right of the window and we'd never know, since you didn't say.

[Robbis_1]

Right, sorry. I assumed it was obvious that my pictures are taken from running the example code. 
So the top left in my images is at 0, 0.