AceGUI-3.0: ColorPicker: Fix alpha handling on Classic Era

Fixes WoWHead Ticket #655
Closes GitHub #11

.luacheckrc

@@ -94,6 +94,8 @@ read_globals = {
 	"OpacitySliderFrame",
 	"SELECTED_CHAT_FRAME",
 	"UIParent",
+	"WOW_PROJECT_ID",
+	"WOW_PROJECT_MAINLINE",
 
 	-- Custom Globals
 	"GAME_LOCALE",

AceGUI-3.0/widgets/AceGUIWidget-ColorPicker.lua

@@ -1,7 +1,7 @@
 --[[-----------------------------------------------------------------------------
 ColorPicker Widget
 -------------------------------------------------------------------------------]]
-local Type, Version = "ColorPicker", 27
+local Type, Version = "ColorPicker", 28
 local AceGUI = LibStub and LibStub("AceGUI-3.0", true)
 if not AceGUI or (AceGUI:GetWidgetVersion(Type) or 0) >= Version then return end
 
@@ -11,10 +11,17 @@ local pairs = pairs
 -- WoW APIs
 local CreateFrame, UIParent = CreateFrame, UIParent
 
+-- Unfortunately we have no way to realistically detect if a client uses inverted alpha
+-- as no API will tell you. Wrath uses the old colorpicker, era uses the new one, both are inverted
+local INVERTED_ALPHA = (WOW_PROJECT_ID ~= WOW_PROJECT_MAINLINE)
+
 --[[-----------------------------------------------------------------------------
 Support functions
 -------------------------------------------------------------------------------]]
 local function ColorCallback(self, r, g, b, a, isAlpha)
+	if INVERTED_ALPHA then
+		a = 1 - a
+	end
 	if not self.HasAlpha then
 		a = 1
 	end
@@ -56,7 +63,10 @@ local function ColorSwatch_OnClick(frame)
 		ColorPickerFrame:EnableMouse(true) -- Make sure the background isn't click-through
 
 		if ColorPickerFrame.SetupColorPickerAndShow then -- 10.2.5 color picker overhaul
-			local r2, g2, b2, a2 = self.r, self.g, self.b, self.a
+			local r2, g2, b2, a2 = self.r, self.g, self.b, (self.a or 1)
+			if INVERTED_ALPHA then
+				a2 = 1 - a2
+			end
 
 			local info = {
 				swatchFunc = function()
@@ -71,7 +81,7 @@ local function ColorSwatch_OnClick(frame)
 					local a = ColorPickerFrame:GetColorAlpha()
 					ColorCallback(self, r, g, b, a, true)
 				end,
-				opacity = (a2 or 1),
+				opacity = a2,
 
 				cancelFunc = function()
 					ColorCallback(self, r2, g2, b2, a2, true)
@@ -86,20 +96,20 @@ local function ColorSwatch_OnClick(frame)
 		else
 			ColorPickerFrame.func = function()
 				local r, g, b = ColorPickerFrame:GetColorRGB()
-				local a = 1 - OpacitySliderFrame:GetValue()
+				local a = OpacitySliderFrame:GetValue()
 				ColorCallback(self, r, g, b, a)
 			end
 
 			ColorPickerFrame.hasOpacity = self.HasAlpha
 			ColorPickerFrame.opacityFunc = function()
 				local r, g, b = ColorPickerFrame:GetColorRGB()
-				local a = 1 - OpacitySliderFrame:GetValue()
+				local a = OpacitySliderFrame:GetValue()
 				ColorCallback(self, r, g, b, a, true)
 			end
 
-			local r, g, b, a = self.r, self.g, self.b, self.a
+			local r, g, b, a = self.r, self.g, self.b, 1 - (self.a or 1)
 			if self.HasAlpha then
-				ColorPickerFrame.opacity = 1 - (a or 0)
+				ColorPickerFrame.opacity = a
 			end
 			ColorPickerFrame:SetColorRGB(r, g, b)