Mirror timers: bars fill from duration objects, drop the OnUpdate

A breath, fatigue or feign death bar fills from a duration object that
spans the bar at the timer's rate, and a text binding writes the m:ss
countdown. MirrorTimer_Show and MIRROR_TIMER_PAUSE resync it from
GetMirrorTimerProgress; a paused bar holds its value.

modules/mirrortimers.lua

@@ -3,20 +3,53 @@ pfUI:RegisterModule("mirrortimers", function ()
   local fontsize = tonumber(C.global.font_size)
   local height = fontsize * 1.3
 
+  -- The value of a mirror timer moves by `scale` per second: breath drains at
+  -- -1, and refills faster than that. A running bar fills from a duration
+  -- object that spans the whole bar at that rate, and its text binding shows
+  -- the value as m:ss. A paused bar holds its value.
+  local function Sync(frame)
+    local value = GetMirrorTimerProgress(frame.timer) / 1000
+    local max, scale = frame.maxvalue, frame.scale
+    local label = frame.label:GetText() or ""
+
+    if frame.paused or scale == 0 then
+      frame.statusbar:SetMinMaxValues(0, max)
+      frame.statusbar:SetValue(value)
+      frame.binding:Disable()
+      frame.text:SetFormattedText("%s (%d:%02d)", label, value / 60, value % 60)
+      return
+    end
+
+    -- the shown value is the seconds of the duration times the rate
+    local rate = math.abs(scale)
+    local property
+    if scale < 0 then
+      frame.duration:SetTimeFromEnd(GetTime() + value / rate, max / rate)
+      frame.statusbar:SetTimerDuration(frame.duration, Enum.StatusBarInterpolation.Immediate, Enum.StatusBarTimerDirection.RemainingTime)
+      property = Enum.DurationTextBindingProperty.RemainingDuration
+    else
+      frame.duration:SetTimeFromEnd(GetTime() + (max - value) / rate, max / rate)
+      frame.statusbar:SetTimerDuration(frame.duration, Enum.StatusBarInterpolation.Immediate, Enum.StatusBarTimerDirection.ElapsedTime)
+      property = Enum.DurationTextBindingProperty.ElapsedDuration
+    end
+
+    local Down = Enum.NumericRuleFormatRounding.Down
+    frame.clock:SetBreakpoints({
+      { threshold = 0, format = "%d:%02d", components = {
+        { div = 60 / rate, step = 1, rounding = Down },
+        { div = 1 / rate, mod = 60, step = 1, rounding = Down },
+      } },
+    })
+    frame.binding:SetTextFormat(label .. " ({})", { { property = property, formatter = frame.clock } })
+    frame.binding:Enable()
+  end
+
   for i = 1, MIRRORTIMER_NUMTIMERS do
     local frame = _G["MirrorTimer"..i]
     frame:GetRegions():Hide()
     frame:SetWidth(200)
     frame:SetHeight(height)
-    frame:SetScript("OnUpdate", function()
-      if this.paused or not this.timer then return end
-      MirrorTimerFrame_OnUpdate(this, arg1)
-
-      local text = this.label:GetText()
-      if text and this.value then
-        this.text:SetText(format("%s (%d:%02d)", text, this.value/60, this.value - math.floor(this.value/60)*60))
-      end
-    end)
+    frame:SetScript("OnUpdate", nil)
 
     frame:ClearAllPoints()
     frame:SetPoint("TOP", UIParent, "TOP", 0, -120-(i-1)*(height + 10))
@@ -38,5 +71,34 @@ pfUI:RegisterModule("mirrortimers", function ()
     frame.text = frame:CreateFontString(nil, "OVERLAY")
     frame.text:SetFont(font, fontsize, "OUTLINE")
     frame.text:SetPoint("CENTER", frame.statusbar, "CENTER", 0, 0)
+
+    frame.duration = C_DurationUtil.CreateDuration()
+    frame.clock = C_StringUtil.CreateNumericRuleFormatter()
+    frame.binding = C_DurationUtil.CreateDurationTextBinding()
+    frame.binding:SetFontString(frame.text)
+    frame.binding:SetDuration(frame.duration)
+
+    -- the stock handler has already set the pause state
+    frame:HookScript("OnEvent", function()
+      if event == "MIRROR_TIMER_PAUSE" and this:IsShown() and arg1 == this.timer then
+        Sync(this)
+      end
+    end)
+
+    frame:HookScript("OnHide", function()
+      this.binding:Disable()
+    end)
   end
+
+  -- the stock function picks the bar and sets its timer, scale and pause state
+  hooksecurefunc("MirrorTimer_Show", function(timer, _, maxvalue)
+    for i = 1, MIRRORTIMER_NUMTIMERS do
+      local frame = _G["MirrorTimer"..i]
+      if frame:IsShown() and frame.timer == timer then
+        frame.maxvalue = maxvalue / 1000
+        Sync(frame)
+        return
+      end
+    end
+  end)
 end)