Fake lineCapMode() for line(), when noSmooth() is activated in Codea.

LineCaps.lua

local _line = line

local function lineCap(d)
    for x = 1, d do
        y = math.sqrt(d*d - x*x)
        rect(0, 0, x, y)
    end
end

function line(x1, y1, x2, y2, capMode)
    local p1, p2 = vec2(x1, y1), vec2(x2, y2)
    
    pushStyle()
    pushMatrix()
    rectMode(CENTER)
    
    if capMode then
        noSmooth()
        
        local angle = math.deg(vec2(0, 1):angleBetween(p2 - p1))
        local size  = strokeWidth()
        
        if capMode == ROUND then -- default condition when smooth()!
            pushMatrix()
                translate(p1.x, p1.y)
                rotate(angle)
                lineCap(size)
            popMatrix()
                translate(p2.x, p2.y)
                rotate(angle)
                lineCap(size)
            popMatrix()
        elseif capMode == PROJECT then
            pushMatrix()
                translate(p1.x, p1.y)
                rotate(angle)
                rect(0, 0, size)
            popMatrix()
                translate(p2.x, p2.y)
                rotate(angle)
                rect(0, 0, size)
            popMatrix()
        elseif capMode == SQUARE then
            --pass condition because this is default line() behaviour when noSmooth()!
        end
    end
    
    _line(p1.x, p1.y, p2.x, p2.y)
    
    popMatrix()
    popStyle()
end

Main.lua

function setup()
    smooth()
end

function draw()
    background(45)
    
    stroke(255, 0, 0)
    strokeWidth(30)
    line(30, 30, 300, 200, ROUND)
    
    stroke(255, 90, 0)
    strokeWidth(20)
    line(30, 30, 300, 200, PROJECT)
    
    stroke(255, 120, 20)
    strokeWidth(10)
    line(30, 30, 300, 200, SQUARE)
    
    stroke(0)
    strokeWidth(10)
    line(30, 120, 300, 150, ROUND) -- uses default line() with is now affected by smooth() from setup()
    
    stroke(0)
    strokeWidth(10)
    line(30, 100, 300, 130) -- uses default line() with is now affected by smooth() from setup()
end