#90 flashing GUI indicator lights

graphics/flasher.lua

@@ -0,0 +1,82 @@
+--
+-- Indicator Light Flasher
+--
+
+local tcd = require("scada-common.tcallbackdsp")
+
+local flasher = {}
+
+-- note: no additional call needs to be made in a main loop as this class automatically uses the TCD to operate
+
+---@alias PERIOD integer
+local PERIOD = {
+    BLINK_250_MS = 1,
+    BLINK_500_MS = 2,
+    BLINK_1000_MS = 3
+}
+
+flasher.PERIOD = PERIOD
+
+local active = false
+local registry = { {}, {}, {} } -- one registry table per period
+local callback_counter = 0
+
+-- start the flasher task
+function flasher.init()
+    active = true
+    registry = { {}, {}, {} }
+    flasher.callback_250ms()
+end
+
+-- clear all blinking indicators and stop the flasher task
+function flasher.clear()
+    active = false
+    registry = { {}, {}, {} }
+end
+
+-- register a function to be called on the selected blink period
+--
+-- times are not strictly enforced, but all with a given period will be set at the same time
+---@param f function function to call each period
+---@param period PERIOD time period option (1, 2, or 3)
+function flasher.start(f, period)
+    if type(registry[period]) == "table" then
+        table.insert(registry[period], f)
+    end
+end
+
+-- stop a function from being called at the blink period
+---@param f function function callback registered
+function flasher.stop(f)
+    for i = 1, #registry do
+        for j = 1, #registry[i] do
+            if registry[i][j] == f then
+                registry[i][j] = nil
+                break
+            end
+        end
+    end
+end
+
+-- blink registered indicators
+--
+-- this assumes it is called every 250ms, it does no checking of time on its own
+function flasher.callback_250ms()
+    if active then
+        for _, f in pairs(registry[PERIOD.BLINK_250_MS]) do f() end
+
+        if callback_counter % 2 == 0 then
+            for _, f in pairs(registry[PERIOD.BLINK_500_MS]) do f() end
+        end
+
+        if callback_counter % 4 == 0 then
+            for _, f in pairs(registry[PERIOD.BLINK_1000_MS]) do f() end
+        end
+
+        callback_counter = callback_counter + 1
+
+        tcd.dispatch(0.25, flasher.callback_250ms)
+    end
+end
+
+return flasher