CLOSES #1603

src/core/ScreenPosition.lua

@@ -0,0 +1,66 @@
+local ScreenPosition = {}
+
+ScreenPosition.MODES = { "center", "upper", "top" }
+ScreenPosition.DEFAULT = "center"
+ScreenPosition.mode = ScreenPosition.DEFAULT
+
+local LABELS = { center = "CENTER", upper = "UPPER", top = "TOP" }
+
+function ScreenPosition.normalize(v)
+  if LABELS[v] then return v end
+  return ScreenPosition.DEFAULT
+end
+
+function ScreenPosition.label(v)
+  return LABELS[ScreenPosition.normalize(v)]
+end
+
+function ScreenPosition.cycle(v, dir)
+  v = ScreenPosition.normalize(v)
+  local modes = ScreenPosition.MODES
+  local cur = 1
+  for i, mode in ipairs(modes) do
+    if mode == v then cur = i break end
+  end
+  return modes[(cur - 1 + (dir or 1)) % #modes + 1]
+end
+
+function ScreenPosition.setMode(v)
+  ScreenPosition.mode = ScreenPosition.normalize(v)
+end
+
+function ScreenPosition.applyOptions(opts)
+  ScreenPosition.setMode(opts and opts.screenPos)
+end
+
+function ScreenPosition.safeTop()
+  local ok, SafeArea = pcall(require, "src.core.SafeArea")
+  if not ok then return 0 end
+  local okr, _, y = pcall(SafeArea.rect)
+  if not okr then return 0 end
+  return math.max(0, tonumber(y) or 0)
+end
+
+function ScreenPosition.skinActive(w, h)
+  local ok, TouchSkin = pcall(require, "src.core.TouchSkin")
+  if not ok or type(TouchSkin.viewport) ~= "function" then return false end
+  local okv, x = pcall(TouchSkin.viewport, w, h)
+  return okv and x ~= nil
+end
+
+function ScreenPosition.lift(viewH, contentH, safeTop)
+  if ScreenPosition.mode == "center" then return 0 end
+  viewH = tonumber(viewH) or 0
+  contentH = tonumber(contentH) or 0
+  local slack = viewH - contentH
+  if slack <= 0 then return 0 end
+  local centered = math.floor(slack / 2)
+  local target = ScreenPosition.mode == "top" and 0 or math.floor(slack / 4)
+  safeTop = math.floor(tonumber(safeTop) or 0)
+  if safeTop > 0 and target < safeTop then
+    target = math.min(safeTop, centered)
+  end
+  return centered - target
+end
+
+return ScreenPosition