mods: add OS-independent game viewport composition

src/ui/gen2/BattleTransition.lua

@@ -28,6 +28,7 @@
 -- covered by tests; the state at the bottom is the only part that draws.
 
 local GbcPalette = require("src.render.GbcPalette")
+local GameViewport = require("src.render.GameViewport")
 local Palettes = require("src.world.gen2.Palettes")
 local Runtime = require("src.mods.Runtime")
 local SpriteAnims = require("src.ui.gen2.SpriteAnims")
@@ -509,7 +510,7 @@ function BattleTransition:blackAt(col, row)
 end
 
 function BattleTransition:draw()
-  local w, h = love.graphics.getDimensions()
+  local w, h = GameViewport.dimensions()
   self:drawWidescreen(w, h)
 end
 

src/ui/kit/Layout.lua

@@ -17,6 +17,7 @@
 local Kit = require("src.ui.kit.Kit")
 local Theme = require("src.ui.kit.Theme")
 local SafeArea = require("src.core.SafeArea")
+local GameViewport = require("src.render.GameViewport")
 
 local Layout = {}
 
@@ -41,7 +42,7 @@ local lastW, lastH, lastOx, lastOy, lastSw, lastSh, lastMax
 function Layout.metrics(maxAppW)
   local W, H = 0, 0
   if love and love.graphics and love.graphics.getDimensions then
-    W, H = love.graphics.getDimensions()
+    W, H = GameViewport.dimensions()
   end
   local ox, oy, sw, sh = SafeArea.rect()
   local s = Kit.layout(sw, sh)