-- @titre Approches des lettres témoins
-- @title Sidebearings of the control letters
-- @categorie relire
-- @resume Les approches gauche et droite de H, O, n, o et du zéro dans chaque master, puis les glyphes dont une approche est très négative (souvent une erreur, sauf pour f, j et quelques italiques).
-- @summary Left and right sidebearings of H, O, n, o and zero in every master, then the glyphs with a strongly negative sidebearing (often a mistake, except for f, j and some italics).
-- Fontista · bibliothèque de scripts · https://fontista.thinkspark.dev/scripts.html

local CONTROL = { "H", "O", "n", "o", "zero" }
local NEGATIVE = 0.05 -- flag sidebearings below minus this share of the em (0.05 = -50 at 1000)

local en = lang == "en"

-- horizontal extent of the outline (curves sampled, components followed)
local function extent(name, master, depth)
  local l = layer(name, master)
  if not l or l.ink or (depth or 0) > 5 then return nil end
  local x0, x1 = nil, nil
  local function add(x) if not x0 or x < x0 then x0 = x end if not x1 or x > x1 then x1 = x end end
  for _, c in ipairs(l.contours) do
    local n, first = #c.nodes, nil
    for i = 1, n do if c.nodes[i].kind ~= "off" then first = i break end end
    if first then
      local prev, offs = c.nodes[first], {}
      add(prev.x)
      local last = c.closed and n or (n - first)
      for k = 1, last do
        local q = c.nodes[(first - 1 + k) % n + 1]
        if q.kind == "off" then offs[#offs + 1] = q
        else
          for i = 1, (#offs == 0 and 1 or 24) do
            local t = i / (#offs == 0 and 1 or 24)
            local u = 1 - t
            local x = q.x
            if #offs == 1 then x = u * u * prev.x + 2 * u * t * offs[1].x + t * t * q.x
            elseif #offs >= 2 then x = u ^ 3 * prev.x + 3 * u * u * t * offs[1].x + 3 * u * t * t * offs[#offs].x + t ^ 3 * q.x end
            add(x)
          end
          prev, offs = q, {}
        end
      end
    end
  end
  for _, comp in ipairs(components(name, master)) do
    local a, b = extent(comp.base, master, (depth or 0) + 1)
    if a then add(a + comp.dx) add(b + comp.dx) end
  end
  return x0, x1, l.width
end

for _, m in ipairs(font.masters) do
  print("— " .. m.name)
  for _, g in ipairs(CONTROL) do
    local a, b, w = extent(g, m.id)
    if a then print(string.format(en and "   %-6s left %5.0f   right %5.0f   width %5.0f" or "   %-6s gauche %5.0f   droite %5.0f   chasse %5.0f", g, a, w - b, w)) end
  end
  local odd = {}
  for _, g in ipairs(font.glyphs) do
    local a, b, w = extent(g, m.id)
    if a and (a < -NEGATIVE * font.upm or w - b < -NEGATIVE * font.upm) then
      odd[#odd + 1] = string.format("%s (%.0f / %.0f)", g, a, w - b)
    end
  end
  if #odd > 0 then
    print(string.format(en and "   strongly negative: %s" or "   très négatives : %s", table.concat(odd, ", ")))
  end
end