Classic Era regression: SetBackdropColor() / SetBackdropBorderColor() throws “table index is nil” if called before first frame render, due to uninitialized backdropInfo inside BackdropTemplate

[Halfdays-firemaw]

It seems since recent Classic Era client updates (mid-2025, 1.15.x+), many addons that use BackdropTemplate or call SetBackdropColor / SetBackdropBorderColor during early loading have started throwing the following error:

Message: Interface/AddOns//Main.lua line XXX:
table index is nil

It originates in Blizzard’s C-side implementation of BackdropTemplate, which stores its internal color/border data in a table called frame.backdropInfo.

In older builds:

• SetBackdropColor() and SetBackdropBorderColor() were safe to call any time after CreateFrame() — even if the frame was hidden.

In current Classic Era builds:

• backdropInfo isn’t created until the frame is actually rendered once on screen.
• If any Lua code calls SetBackdropColor or SetBackdropBorderColor before that moment (for example, during ADDON_LOADED or PLAYER_LOGIN), the engine throws a C-level “table index is nil” before control even returns to Lua.
• Wrapping the call in pcall() or using seterrorhandler() does not catch it, because it’s raised inside the client’s C-code, not Lua.

When it triggers

• On cold login (especially when the affected frame is hidden, off-screen, or parented to UIParent before it’s drawn).
• Not usually on /reload, because by then the frame has already been rendered once.
• It’s intermittent and depends on addon load order, frame visibility, and UI scale.

Impact

• The error is harmless but noisy.
• It doesn’t break functionality — it only fires once on login.
• Many addons that tint or recolor hidden frames (chat boxes, panels, config windows, etc.) are affected.

Known workarounds I’ve read up on

There doesn’t seem to be a full Lua-side fix but these methods reduce or hide the issue sometimes:

1. Delay backdrop coloring until after PLAYER_ENTERING_WORLD and after the frame is visible.
2. Use Container:HookScript("OnShow", function() ...color... end) instead of calling it immediately.
3. Replace backdrops with plain textures (frame:CreateTexture() + SetColorTexture) instead of SetBackdropColor.

Unfortunately in my case none of these are working

Blizzard would need to restore a safe lazy initialization of backdropInfo or suppress the thrown error until the table is allocated, as it was in previous Classic clients (and possibly in retail Dragonflight?)