api: preparation to use perfect pixels on borders

Add some preparation to allow perfect sized borders on all backdrops.
There's no option set yet to avoid broken borders on other elements.
An option that is enabled by default will be added as soon as all modules
are prepared to use pfUI.border instead of reading the config on their own.

api/api.lua

@@ -799,15 +799,34 @@ end
 -- Returns a number that equals a real pixel on regular scaled frames.
 -- Respects the current UI-scale and calculates a real pixel based on
 -- the screen resolution and the 768px sized drawlayer.
-local ppixel
 function pfUI.api.GetPerfectPixel()
-  if ppixel then return ppixel end
+  if pfUI.pixel then return pfUI.pixel end
 
-  local scale = GetCVar("uiScale")
-  local resolution = GetCVar("gxResolution")
-  local _, _, screenwidth, screenheight = strfind(resolution, "(.+)x(.+)")
-  ppixel = 768 / screenheight / scale
-  return ppixel
+  if pfUI_config.appearance.border.pixelperfect == "1" then
+    local scale = GetCVar("uiScale")
+    local resolution = GetCVar("gxResolution")
+    local _, _, screenwidth, screenheight = strfind(resolution, "(.+)x(.+)")
+
+    pfUI.pixel = 768 / screenheight / scale
+  else
+    pfUI.pixel = 1
+  end
+
+  pfUI.border = tonumber(pfUI_config.appearance.border.default) * pfUI.pixel
+
+  pfUI.backdrop = {
+    bgFile = "Interface\\BUTTONS\\WHITE8X8", tile = false, tileSize = 0,
+    edgeFile = "Interface\\BUTTONS\\WHITE8X8", edgeSize = pfUI.pixel,
+    insets = {left = -pfUI.pixel, right = -pfUI.pixel, top = -pfUI.pixel, bottom = -pfUI.pixel},
+  }
+
+  pfUI.backdrop_thin = {
+    bgFile = "Interface\\BUTTONS\\WHITE8X8", tile = false, tileSize = 0,
+    edgeFile = "Interface\\BUTTONS\\WHITE8X8", edgeSize = pfUI.pixel,
+    insets = {left = 0, right = 0, top = 0, bottom = 0},
+  }
+
+  return pfUI.pixel
 end
 
 -- [ Create Backdrop ]
@@ -820,12 +839,11 @@ function pfUI.api.CreateBackdrop(f, inset, legacy, transp, backdropSetting)
   -- exit if now frame was given
   if not f then return end
 
-  -- use default inset if nothing is given
-  local border = inset
-  if not border then
-    border = tonumber(pfUI_config.appearance.border.default)
-  end
+  -- load raw and pixel perfect scaled border
+  local rawborder = inset or tonumber(pfUI_config.appearance.border.default)
+  local border = rawborder * GetPerfectPixel()
 
+  -- get the color settings
   local br, bg, bb, ba = pfUI.api.GetStringColor(pfUI_config.appearance.border.background)
   local er, eg, eb, ea = pfUI.api.GetStringColor(pfUI_config.appearance.border.color)
 
@@ -833,7 +851,7 @@ function pfUI.api.CreateBackdrop(f, inset, legacy, transp, backdropSetting)
 
   -- use legacy backdrop handling
   if legacy then
-    local backdrop = border == 1 and pfUI.backdrop_thin or pfUI.backdrop
+    local backdrop = rawborder == 1 and pfUI.backdrop_thin or pfUI.backdrop
     if backdropSetting then f:SetBackdrop(backdropSetting) end
     f:SetBackdrop(backdrop)
     f:SetBackdropColor(br, bg, bb, ba)