CLOSES #1590, CLOSES #1592, CLOSES #1625, CLOSES #1657, CLOSES #1698, CLOSES #1699, CLOSES #1700, CLOSES #1843, CLOSES #1875, CLOSES #1898, CLOSES #1902, CLOSES #1905, CLOSES #1906, CLOSES #1907, CLOSES #1908, CLOSES #1909, CLOSES #1912, CLOSES #1915, CLOSES #1917, CLOSES #1919, CLOSES #1920, CLOSES #1921, CLOSES #1922, CLOSES #1923, CLOSES #1924, CLOSES #1925, CLOSES #1926, CLOSES #1927

src/core/RefreshRate.lua

@@ -0,0 +1,116 @@
+local RefreshRate = {}
+
+local DECLS = {
+  "typedef struct SDL_Window SDL_Window;",
+  "SDL_Window *SDL_GL_GetCurrentWindow(void);",
+  "typedef struct { uint32_t format; int w; int h; int refresh_rate;" ..
+    " void *driverdata; } SDL_DisplayMode;",
+  "int SDL_GetWindowDisplayIndex(SDL_Window *window);",
+  "int SDL_GetCurrentDisplayMode(int displayIndex, SDL_DisplayMode *mode);",
+}
+
+local ffiState = nil
+
+local function sdlFfi()
+  if ffiState ~= nil then return ffiState or nil end
+  if not (love and love.window) then return nil end
+  local okFfi, ffi = pcall(require, "ffi")
+  if not okFfi then ffiState = false return nil end
+  for _, decl in ipairs(DECLS) do pcall(ffi.cdef, decl) end
+  local ok = pcall(ffi.new, "SDL_DisplayMode")
+  ffiState = ok and ffi or false
+  return ffiState or nil
+end
+
+local function sdlHz()
+  local ffi = sdlFfi()
+  if not ffi then return nil end
+  local ok, hz = pcall(function()
+    local index = 0
+    local window = ffi.C.SDL_GL_GetCurrentWindow()
+    if window ~= nil then
+      local got = ffi.C.SDL_GetWindowDisplayIndex(window)
+      if got >= 0 then index = got end
+    end
+    local mode = ffi.new("SDL_DisplayMode")
+    if ffi.C.SDL_GetCurrentDisplayMode(index, mode) ~= 0 then return nil end
+    return tonumber(mode.refresh_rate)
+  end)
+  if not ok or not hz or hz <= 0 then return nil end
+  return hz
+end
+
+local SAMPLES = 31
+local ring, cursor, filled = {}, 0, 0
+local measured = nil
+
+local function quantize(hz)
+  if not hz or hz <= 0 then return nil end
+  local whole = math.floor(hz + 0.5)
+  local nearest = math.floor(whole / 60 + 0.5) * 60
+  if nearest > 0 and math.abs(whole - nearest) <= 1 then return nearest end
+  return whole
+end
+
+local function median(values)
+  local sorted = {}
+  for i = 1, #values do sorted[i] = values[i] end
+  table.sort(sorted)
+  local mid = sorted[math.floor(#sorted / 2) + 1]
+  local lo = sorted[math.floor(#sorted * 0.25) + 1]
+  local hi = sorted[math.floor(#sorted * 0.75) + 1]
+  if not mid or mid <= 0 or (hi - lo) > mid * 0.1 then return nil end
+  return mid
+end
+
+function RefreshRate.sample(dt)
+  if type(dt) ~= "number" or dt <= 0 or dt > 0.2 then return false end
+  cursor = cursor % SAMPLES + 1
+  ring[cursor] = dt
+  filled = math.min(filled + 1, SAMPLES)
+  if filled < SAMPLES or cursor ~= SAMPLES then return false end
+  local period = median(ring)
+  if not period then return false end
+  local hz = quantize(1 / period)
+  if not hz or measured == hz then return false end
+  measured = hz
+  return true
+end
+
+local queried, queriedAt = nil, nil
+
+local function now()
+  if love and love.timer and love.timer.getTime then return love.timer.getTime() end
+  return nil
+end
+
+function RefreshRate.hz()
+  local time = now()
+  if queried == nil or not time or not queriedAt or time - queriedAt > 1 then
+    queried = sdlHz() or false
+    queriedAt = time or 0
+  end
+  local hz = quantize(queried or measured)
+  if not hz or hz <= 20 or hz >= 1000 then return nil end
+  return hz
+end
+
+function RefreshRate.period()
+  local hz = RefreshRate.hz()
+  return hz and 1 / hz or nil
+end
+
+function RefreshRate.mismatch()
+  local hz = RefreshRate.hz()
+  if not hz then return nil end
+  local nearest = math.floor(hz / 60 + 0.5) * 60
+  if math.abs(hz - nearest) <= 1 then return nil end
+  return hz
+end
+
+function RefreshRate.reset()
+  ffiState, queried, queriedAt, measured = nil, nil, nil, nil
+  ring, cursor, filled = {}, 0, 0
+end
+
+return RefreshRate