DrawFilledBox

function drawFilledBox(startX, startY, endX, endY, nColour)
    if type(startX) ~= "number" or type(startX) ~= "number" or
       type(endX) ~= "number" or type(endY) ~= "number" or
       (nColour ~= nil and type(nColour) ~= "number") then
        error("Expected startX, startY, endX, endY, colour", 2)
    end

    startX = math.floor(startX)
    startY = math.floor(startY)
    endX = math.floor(endX)
    endY = math.floor(endY)

    if nColour then
        term.setBackgroundColor(nColour)
    end
    if startX == endX and startY == endY then
        drawPixelInternal(startX, startY)
        return
    end

    local minX = math.min(startX, endX)
    if minX == startX then
        minY = startY
        maxX = endX
        maxY = endY
    else
        minY = endY
        maxX = startX
        maxY = startY
    end

    for x = minX, maxX do
        for y = minY, maxY do
            drawPixelInternal(x, y)
        end
    end
end