Show pfUI's dropdowns and menus with ClassicAPI's menu system

pfUIDropdownTemplate (a DropdownButton) replaces CreateDropDownButton in
the config GUI, addon profiles, the trigger editor and the icon picker
filter. The equipment set gear menu and the tracking menu open
MenuUtil context menus. pfUIMenuStyleMixin draws pfUI's backdrop behind
them, and the skin module makes it the default style and draws the
checkboxes and radios as pfUI boxes.

modules/skin.lua

@@ -35,6 +35,62 @@ pfUI:RegisterModule("skin", function ()
     CreateBackdropShadow(_G["DropDownList"..i.."Backdrop"])
   end
 
+  -- ClassicAPI menus that don't name a style of their own take pfUI's
+  function MenuVariants.GetDefaultMenuMixin() return pfUIMenuStyleMixin end
+  function MenuVariants.GetDefaultContextMenuMixin() return pfUIMenuStyleMixin end
+
+  -- ClassicAPI menus draw their checkboxes and radios with these. Both get a
+  -- pfUI box: a checked box holds a check, a selected radio a filled square.
+  local function CreateSelectionBox(frame, text)
+    local _, border = GetBorderSize()
+
+    local box = frame:AttachTexture()
+    frame.leftTexture1 = box
+    box:SetDrawLayer("BORDER")
+    box:SetPoint("LEFT")
+    box:SetSize(12, 12)
+    box:SetColorTexture(GetStringColorObject(C.appearance.border.color):GetRGBA())
+
+    local inside = frame:AttachTexture()
+    inside:SetDrawLayer("ARTWORK")
+    inside:SetPoint("TOPLEFT", box, "TOPLEFT", border, -border)
+    inside:SetPoint("BOTTOMRIGHT", box, "BOTTOMRIGHT", -border, border)
+    local r, g, b = GetStringColorObject(C.appearance.border.background):GetRGB()
+    inside:SetColorTexture(r, g, b, 1)
+
+    local fontString = frame:AttachFontString()
+    frame.fontString = fontString
+    fontString:SetPoint("LEFT", box, "RIGHT", 6, 0)
+    fontString:SetHeight(20)
+    fontString:SetTextToFit(text)
+
+    return box
+  end
+
+  function MenuVariants.CreateCheckbox(text, frame, isSelected, data)
+    local box = CreateSelectionBox(frame, text)
+    if isSelected(data) then
+      local check = frame:AttachTexture()
+      check:SetDrawLayer("OVERLAY")
+      check:SetPoint("CENTER", box)
+      check:SetSize(16, 16)
+      check:SetTexture("Interface\\Buttons\\UI-CheckBox-Check")
+    end
+    return box
+  end
+
+  function MenuVariants.CreateRadio(text, frame, isSelected, data)
+    local box = CreateSelectionBox(frame, text)
+    if isSelected(data) then
+      local dot = frame:AttachTexture()
+      dot:SetDrawLayer("OVERLAY")
+      dot:SetPoint("TOPLEFT", box, "TOPLEFT", 3, -3)
+      dot:SetPoint("BOTTOMRIGHT", box, "BOTTOMRIGHT", -3, 3)
+      dot:SetColorTexture(.2, 1, .8, 1)
+    end
+    return box
+  end
+
   if C.global.errors_limit == "1" then
     UIErrorsFrame:SetHeight(25)
   end