How to draw a line between two points ?

[Elfayer]

Hi,
I've found in the documentation this part of code :

sf::VertexArray lines(sf::LinesStrip, 2);
 lines[0].position = sf::Vector2f(10, 0);
 lines[1].position = sf::Vector2f(20, 0);

 window.draw(lines);

(cf. :  http://www.sfml-dev.org/documentation/2.0/classsf_1_1VertexArray.php )

Which is drawing a line !
But, how can I change the color of this line ?

And is there another easier way to draw lines ? (I mean is it the good way to do it ?)

Thanks in advance !

[Laurent]

A VertexArray is an array of Vertex.

If you just want to draw a single line, use a static array of vertex (sf::Vertex[]) rather than a sf::VertexArray, which uses dynamic memory allocation.

This is the best way if you want lines with no thickness. If you want thickness, you must draw a rotated rectangle instead (sf::RectangleShape).

[Haze]

But, how can I change the color of this line ?

Each vertex has a position and a color property.

sf::Vertex line[2];
line[0].position = sf::Vector2f(10, 0);
line[0].color  = sf::Color::Red;
line[1].position = sf::Vector2f(20, 0);
line[1].color = sf::Color::Red;
 

If the two vertices of the line have a different color, you'll obtain a gradient from color 1 to color 2.

[Laurent]

When we link to the documentation rather than giving the answer directly, why does someone always come and ruin it?

[Haze]

Oh, sorry about that!
I assumed you've only addressed the fact the OP used a vector for just 2 vertices.

[Bondrusiek]

Hi, I created a function which use Bresenham's line algorithm and help drawing a line between two points:

int drawLine(sf::RenderWindow &window, sf::Vector2i point1, sf::Vector2i point2, int lineWidth, sf::Color lineColor)
{
    int x0 = point1.x;
    int y0 = point1.y;
    int x1 = point2.x;
    int y1 = point2.y;
    int dx = abs(x1 - x0);
    int sx, sy;
    if (x0 < x1) {
        sx = 1;
    }
    else {
        sx = -1;
    }

    int dy = -abs(y1 - y0);
    if (y0 < y1) {
        sy = 1;
    }
    else {
        sy = -1;
    }

    int err = dx + dy;

    while (true) {
        sf::RectangleShape rect(sf::Vector2f(lineWidth, lineWidth));
        rect.setFillColor(lineColor);
        rect.setPosition(x0, y0);
        window.draw(rect);
        if (x0 == x1 && y0 == y1) {
            break;
        }
        int e2 = 2 * err;

        if (e2 >= dy) {
            err += dy;
            x0 += sx;
        }

        if (e2 <= dx) {
            err += dx;
            y0 += sy;
        }
    }
}