manage cpu widget better

widget/cpu/init.lua

@@ -1,9 +1,11 @@
+local gstring = require("gears.string")
 local gtimer = require("gears.timer")
 local icons = require("theme.icons")
 local mat_icon = require("widget.material.icon")
 local read_async = require("util.file.read_async")
 local wibox = require("wibox")
 local dpi = require("beautiful").xresources.apply_dpi
+local bind = require("util.bind")
 
 -- All special characters escaped in a string: %%, %^, %$, ...
 local patternchars = table.concat({ "[", ("%^$().[]*+-?"):gsub("(.)", "%%%1"), "]" })
@@ -22,36 +24,52 @@ end
 ---How often to update the widget in seconds (default: 15).
 ---@field timeout integer?
 
----@return integer cpu_idle_time
----@return integer cpu_total
+---@class proc_stat_info
+---@field user integer?
+---@field nice integer?
+---@field system integer?
+---@field idle integer?
+---@field iowait integer?
+---@field irq integer?
+---@field softirq integer?
+---@field steal integer?
+
+---@param content string
+---@return proc_stat_info
 local function parse_proc_stat(content)
   local rem = content:match("^cpu%s+([^\n]*)")
-  if not rem then return 0, 0 end
-  local user, nice, system, idle, iowait, irq, softirq, steal, guest, guest_nice
-  -- find values, even if not exist
-  user, rem = rem:match("(%d+)(.*)")
-  nice, rem = rem:match("(%d+)(.*)")
-  system, rem = rem:match("(%d+)(.*)")
-  idle, rem = rem:match("(%d+)(.*)")
-  iowait, rem = rem:match("(%d+)(.*)")
-  irq, rem = rem:match("(%d+)(.*)")
-  softirq, rem = rem:match("(%d+)(.*)")
-  steal, rem = rem:match("(%d+)(.*)")
-  guest, rem = rem:match("(%d+)(.*)")
-  guest_nice, rem = rem:match("(%d+)(.*)")
+  local ret = {} ---@type proc_stat_info
+  if not rem then return ret end
+  local vals = gstring.split(rem, " ")
+  for i, name in ipairs({ "user", "nice", "system", "idle", "iowait", "irq", "softirq", "steal" }) do
+    ret[name] = tonumber(vals[i]) -- Generate ret from the list of header names
+  end
+  return ret
+end
 
-  local cpu_total = user + nice + system + idle + iowait + irq + softirq + steal + guest + guest_nice
-  -- return user, nice, system, idle, iowait, irq, softirq, steal, guest, guest_nice, cpu_total
-  return idle, cpu_total
+---@param proc_info proc_stat_info
+---@return { total: integer, idle: integer }
+local function get_cpu_time(proc_info)
+  local user, nice, system, idle, iowait, irq, softirq, steal =
+    proc_info.user or 0,
+    proc_info.nice or 0,
+    proc_info.system or 0,
+    proc_info.idle or 0,
+    proc_info.iowait or 0,
+    proc_info.irq or 0,
+    proc_info.softirq or 0,
+    proc_info.steal or 0
+  local total_idle = idle + iowait
+  local total_nonidle = user + nice + system + irq + softirq + steal
+  local total = total_idle + total_nonidle
+  return { total = total, idle = total_idle }
 end
 
 ---Create a new CPU usage widget
 ---@param args CPUWidgetConfig?
 ---@return table
 function CPU(args)
   args = args or {}
-  local cpu_total_prev = 0
-  local idle_prev = 0
 
   local format = string.format(
     "%s%%.%df%s",
@@ -64,35 +82,31 @@ function CPU(args)
     widget = wibox.widget.textbox,
     text = string.format(format, 0),
   })
+  local prev = { total = 0, idle = 0 }
 
-  local file_callback = function(content, _)
-    if not content then return end
-    local idle, cpu_total = parse_proc_stat(content)
+  ---@param content string
+  local file_callback = function(content, _err, _path)
+    --- See: http://stackoverflow.com/questions/23367857/accurate-calculation-of-cpu-usage-given-in-percentage-in-linux
+    if not content or content == "" then return end
+    local proc_info = parse_proc_stat(content)
+    local time = get_cpu_time(proc_info)
 
-    -- Get the delta between two reads
-    local diff_cpu = cpu_total - cpu_total_prev
-    -- Get the idle time delta
-    local diff_idle = idle - idle_prev
-    -- Calc time spent working
-    local cpu_used = diff_cpu - diff_idle
-    -- Calc percentage
-    local cpu_usage = 100 * cpu_used / diff_cpu
+    local cpu_usage = ((time.total - prev.total) - (time.idle - prev.idle)) / (time.total - prev.total) * 100
+    cpu_usage = cpu_usage ~= cpu_usage and -1 or cpu_usage -- NaN is -1
+    cpu_usage = cpu_usage == math.huge and -1 or cpu_usage -- Inf is -1
+    cpu_usage = cpu_usage == -math.huge and -1 or cpu_usage -- -Inf is -1
 
     -- Round to percentage
     text_box:set_text(string.format(format, cpu_usage))
-
-    cpu_total_prev = cpu_total
-    idle_prev = idle
+    prev = time
     collectgarbage("collect")
   end
 
   gtimer.new({
     autostart = true,
     call_now = true,
     timeout = args.timeout or 15,
-    callback = function()
-      read_async("/proc/stat", file_callback)
-    end,
+    callback = bind.with_args(read_async, "/proc/stat", file_callback),
   })
 
   local cpu_meter = wibox.widget({