fixed sum stuff

libs/windows.lua

@@ -7,6 +7,60 @@ local function add(t, v)
         end
     end
 end
+local function normalize_color(c)
+  if type(c) ~= "number" then error("bad color", 2) end
+  if c < 1 then error("bad color", 2) end
+
+  -- If c is already a power of two, this keeps it.
+  -- If it's a mask, this picks the highest power-of-two <= c.
+  local p = 1
+  while p * 2 <= c do p = p * 2 end
+  return p
+end
+
+-- Returns: bestColor, bestCount, totalCells, countsTable
+-- countsTable maps colorBit -> count
+local function most_common_bg(win, opts)
+    opts = opts or {}
+
+    local w, h
+    if win.getSize then
+        w, h = win.getSize()
+    else
+        w, h = win.w, win.h
+    end
+
+    local ignore = opts.ignore
+    if ignore ~= nil then ignore = normalize_color(ignore) end
+
+    local counts = {}
+    local total = 0
+
+    for x = 1, w do
+        local col = win.buffer and win.buffer[x]
+        for y = 1, h do
+            local cell = col and col[y]
+            local bc = cell and cell.bc or win.bgColor or colors.black
+            bc = normalize_color(bc)
+
+            if not ignore or bc ~= ignore then
+                counts[bc] = (counts[bc] or 0) + 1
+                total = total + 1
+            end
+        end
+    end
+
+    local fallback = normalize_color(opts.fallback or win.bgColor or colors.black)
+    local best, bestN = fallback, -1
+
+    for c, n in pairs(counts) do
+        if n > bestN or (n == bestN and c == fallback) then
+            best, bestN = c, n
+        end
+    end
+
+    return best, bestN, total, counts
+end
 
 -- hex <-> color bit lookups (Lua 5.1 safe)
 local HEX = "0123456789abcdef"
@@ -64,6 +118,11 @@ function lib.create(name, w, h, x, y)
         closing = false,
         _palette = {}, -- optional local palette store
     }
+    
+    function t.getMostCommonBackgroundColor(opts)
+        local c, n, total, counts = most_common_bg(t, opts)
+        return c, color_to_hex[c], n, total, counts
+    end
 
     local function init_col(xi)
         local w = t.w