some cairo code snippet in cinder

cairo_snippet.cpp

// draw window background
// before this ctx should be created first in every rendering frame, like this:
// cairo::Context ctx(cario::createWindowSurface())
void renderScene(cairo::Contect& ctx)
{
	// clear the context with our radial gradient
	cairo::GradientRadial radialGrad( getWindowCenter(), 0, getWindowCenter(), getWindowWidth() );
	radialGrad.addColorStop( 0, Color( 1, 1, 1 ) );
	radialGrad.addColorStop( 1, Color( 0.6, 0.6, 0.6 ) );
	ctx.setSource( radialGrad );
	ctx.paint();
}

void drawCircle(cinder::cairo::Context& ctx)
{
    ColorA color(CM_RGB, 0.0f, 0.0f, 0.0f, 0.65f);
    ctx.setSource(color);
    ctx.newPath();
    
    ctx.circle(location, 10);
    ctx.fill();

    ctx.closePath();
}

void drawTriangle(cinder::cairo::Context& ctx, cinder::Vec2f pos, float length)
{
    ColorA color(CM_RGB, 0.0f, 0.0f, 0.0f, 0.65f);
    ctx.setSource(color);
    ctx.newPath();

    {
    const float squareRoot3 = sqrt(3.0f);
    cinder::Vec2f b(pos.x - length / 2, pos.y + length / (2 * squareRoot3));
    cinder::Vec2f c(pos.x + length / 2, pos.y + length / (2 * squareRoot3));
    cinder::Vec2f a(pos.x, pos.y - length);
    
    ctx.line(a, b);
    ctx.line(b, c);
    ctx.line(c, a);
    }
    
    ctx.stroke();
    

    ctx.closePath();
}

void rotateContext()
{
    ctx.save();
    
    ctx.translate(location); // first, move context origin to location where you want to draw
    ctx.rotate(m_rotation); // rotate
    
    
    cinder::ColorA color(CM_RGB, m_isPushing ? 1.0f : 0.0f, 0.0f, 0.0f, 0.65f); // always draw at (0.0f, 0.0f)
    ctx.setSource(color);
    ctx.newPath();
    
    makeTrianglePathAtPos(Vec2f(0.0f, 0.0f), 30, ctx);
    ctx.stroke();
    
    ctx.closePath();
    
    ctx.restore();
}