Draw a line of certain length in Pine Script - pivot

Question

I'm trying to develop a Pivot Points indicator on Trading View v4.0 and an issue I'm facing is that the pivot lines are drawn only up to the current bar. The behavior I want is that I want the line to extend for the duration of the period. For example, the weekly pivot line should extend from Monday to Sunday even if today is Monday.
Below is the code I'm using as well as the result:
// Function outputs 1 when it's the first bar of the D/W/M/Y
is_newbar(res) =>
ch = 0
if(res == 'Y')
t = year(time('D'))
ch := change(t) != 0 ? 1 : 0
else
t = time(res)
ch := change(t) != 0 ? 1 : 0
ch
bars_since_week = 0
bars_since_week := is_newbar(pp_res_week) ? 0 : bars_since_week[1] + 1
vpp_p_week = line.new(bar_index[min(bars_since_week, 300)], PP_week, bar_index, PP_week, color=color.black, width = 2, style = line.style_solid, extend = extend.none)
vs1_p_week = line.new(bar_index[min(bars_since_week, 300)], S1_week, bar_index, S1_week, color=color.black, width = 2, style = line.style_solid, extend = extend.none)
vs2_p_week = line.new(bar_index[min(bars_since_week, 300)], S2_week, bar_index, S2_week, color=color.black, width = 2, style = line.style_solid, extend = extend.none)
vs3_p_week = line.new(bar_index[min(bars_since_week, 300)], S3_week, bar_index, S3_week, color=color.black, width = 2, style = line.style_solid, extend = extend.none)
vr1_p_week = line.new(bar_index[min(bars_since_week, 300)], R1_week, bar_index, R1_week, color=color.black, width = 2, style = line.style_solid, extend = extend.none)
vr2_p_week = line.new(bar_index[min(bars_since_week, 300)], R2_week, bar_index, R2_week, color=color.black, width = 2, style = line.style_solid, extend = extend.none)
vr3_p_week = line.new(bar_index[min(bars_since_week, 300)], R3_week, bar_index, R3_week, color=color.black, width = 2, style = line.style_solid, extend = extend.none)
Also, below is the behavior I would expect - notice the longer lines:

Answer 1

It's not a simple matter, at least not the way it's done here ) There is perhaps a better way, but haven't figured out any:
You'll need to work with xloc = xloc.bar_time to be able to draw a line in the future when you need to.
Use the f_avgDilationOf() from the PineCoders MTF Selection Framework to know the average number of chart bars in the dilation of the higher TF (on a 24/7 market, this would be 7 on a daily chart if HTF=1W).
Figure out if current chart bars (current being the one the script is executing on) are included in the last dilation of the HTF. We need this info because when that is true, we will project the line in the future.
//#version=4
study("Periodic lines", "", true)
htf = input("W", type = input.resolution)
// Returns the average number of current chart bars in the given target HTF resolution (this reflects the dataset's history).
f_avgDilationOf(_res) =>
// _res: resolution of any TF (in "timeframe.period" string format).
b = barssince(change(time(_res)))
cumTotal = cum(b == 0 ? b[1] + 1 : 0)
cumCount = cum(b == 0 ? 1 : 0)
cumTotal / cumCount
// Period change detection.
pChange(res) =>
change(time(res == 'Y' ? 'D' : res))
// Get some previous value from last HTF period.
pHi = security(syminfo.tickerid, htf, high[1], lookahead = barmerge.lookahead_on)
// Verify if current charts bars are part of the last dilation of HTF.
lastPBar = security(syminfo.tickerid, htf, barstate.islast, lookahead = barmerge.lookahead_on)
// Get avg no of chart bars in one dilation of HTF.
dilation = round(f_avgDilationOf(htf))
timeDelta = time - time[1]
var line pHiLine = na
// Holds bar index where a new line is created.
var pHiBar = 0
if pChange(htf)
// Extend old line for the last bar before creating a new one.
line.set_xy2(pHiLine, time, pHi[1])
// Save bar index on transition.
pHiBar := bar_index
// Create new line.
pHiLine := line.new(time, pHi, time + timeDelta, pHi, xloc.bar_time, color = color.black, width = 2)
// Make type of the 2 `if` blocks the same.
float(na)
else
// We are not on a transition; prolong line until next transition.
line.set_xy2(pHiLine, time, pHi)
float(na)
// If we are in the last bars of the HTF resolution's dilation, project line into the future with remaining bars in average no of bars in dilation.
if lastPBar
line.set_xy2(pHiLine, time + (timeDelta * (dilation - (bar_index - pHiBar))), pHi)
Caveat: Haven't forward-tested this, so unsure how it'll perform in those conditions.