Porting addons to Classic

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Addons for Retail will in most cases work on Classic with removal of any non-Classic API. For Vanilla there is a bit more work involved however.

Globe

Globe can tell you which API functions/events in an addon have been removed in Classic, if the TOC is set to the Retail version and with Globe: check-classic

For example: https://www.townlong-yak.com/globe/#h:2a8385bff94e98a6bad8f5f09b45a148-reads

## Interface: 100206
## Globe: check-classic

API

There is a list of Classic-specific API and a complete list of Classic API.

• Texture:SetTexture() can no longer set color textures in Patch 7.0.3, use Texture:SetColorTexture(r, g, b [, a]) instead.
• PlaySound() only accepts SoundKitIDs in Patch 7.0.3

old: PlaySound("igMainMenuOptionCheckBoxOn")
new: PlaySound(SOUNDKIT.IG_MAINMENU_OPTION_CHECKBOX_ON)

• PlaySoundFile() only accepts FileDataIDs for game sounds in Patch 8.2.0

old: PlaySoundFile("Sound/Spells/LevelUp.ogg")
new: PlaySoundFile(569593)

Maps

Maps were reworked in Patch 8.0.1 and the stateful API was changed to be stateless.

• WorldMapAreaIDs were replaced with UiMapIDs.
• It's no longer needed to call SetMapToCurrentZone() and GetCurrentMapAreaID() to get the current zone UI map, instead use C_Map.GetBestMapForUnit("player")

Combat Log

The combat log was reworked in Patch 2.4.0

• The event payload is returned from CombatLogGetCurrentEventInfo() since Patch 8.0.1
• See COMBAT_LOG_EVENT for details.

Frame Scripts

Most Vanilla addons still define their frames in XML, since CreateFrame() was only added in Patch 1.10

• Parameters like this, event and argN are no longer globals for the script handler. This was changed in Patch 4.0.1
• The this parameter was unique to WoW frame scripts. It can generally be replaced with self even though they are separate concepts.
• arg1, arg2, arg3, etc were replaced with the ... vararg for OnEvent(self, event, ...)

Quick fix

There are multiple ways to handle frame scripts in XML. For simplicity's sake we will only describe a quick fix in blue text.

• Lua

function SomeAddon_OnLoad(self)
	frame:RegisterEvent("ADDON_LOADED")
end

function SomeAddon_OnEvent(self, event, addon)
	print(self, event, addon)
end

• XML

<Frame name="SomeAddon">
	<Scripts>
		<OnLoad>
			SomeAddon_OnLoad(self)
		</OnLoad>
		<OnEvent>
			SomeAddon_OnEvent(self, event, ...)
		</OnEvent>
	</Scripts>
</Frame>

Lua only

It's also possible to create a frame and handle the scripts in Lua without use of XML, depending on how simple the addon is.

function f:OnEvent(event, addon)
	print(self, event, addon)
end

local f = CreateFrame("Frame")
f:RegisterEvent("ADDON_LOADED")
f:SetScript("OnEvent", f.OnEvent)