chat: use parent to determine docked state

Remove every texture of the chat frame and only restore background
for chat frames that are not docked to the left or the right side.

modules/chat.lua

@@ -334,17 +334,6 @@ pfUI:RegisterModule("chat", "vanilla:tbc", function ()
         frame.pfCombatLog = nil
       end
 
-      for _, tex in pairs(CHAT_FRAME_TEXTURES) do
-        local texture = _G["ChatFrame"..i..tex]
-        texture.oldTexture = texture.oldTexture or texture:GetTexture()
-
-        if i == 3 or frame.isDocked then
-          texture:SetTexture()
-          texture:Hide()
-        else
-          texture:SetTexture(texture.oldTexture)
-        end
-      end
 
       if not frame.pfStartMoving then
         frame.pfStartMoving = frame.StartMoving
@@ -408,6 +397,24 @@ pfUI:RegisterModule("chat", "vanilla:tbc", function ()
         v:SetHeight(C.global.font_size+default_border*2)
       end
 
+      -- remove background on docked frames
+      for _, tex in pairs(CHAT_FRAME_TEXTURES) do
+        local texture = _G["ChatFrame"..i..tex]
+        if tex == "Background" then
+          texture.oldTexture = texture.oldTexture or texture:GetTexture()
+          if frame:GetParent() == pfUI.chat.left or frame:GetParent() == pfUI.chat.right then
+            texture:SetTexture()
+            texture:Hide()
+          else
+            texture:SetTexture(texture.oldTexture)
+            texture:Show()
+          end
+        else
+          texture:SetTexture()
+          texture:Hide()
+        end
+      end
+
       _G["ChatFrame" .. i .. "ResizeBottom"]:Hide()
       _G["ChatFrame" .. i .. "TabText"]:SetJustifyV("CENTER")
       _G["ChatFrame" .. i .. "TabText"]:SetHeight(C.global.font_size+default_border*2)