Expose window margins to tool HUDs

docs/modding.md

@@ -164,10 +164,11 @@ for a tool to offer a fresh-session action before gameplay begins.
 Ephemeral tools can wrap `save.write(next, game)` and return `false` to veto a
 progress write before world state is captured or any bytes reach disk.
 
-`render.hud` receives `(next, game, viewport)` after visible states draw and
+`render.hud` receives `(next, game, viewport)` after the finished game frame is
-before the UI canvas is presented. `viewport.width` and `viewport.height` are
+composited and before touch controls draw. The window-space viewport contains
-the active UI dimensions, so status indicators can stay visible over normal
+`width`, `height`, `gameX`, `gameY`, `gameWidth`, `gameHeight`, `scale`, `dpiX`,
-and widescreen screens without pushing an updating game state.
+and `dpiY`, so a tool can use the letterbox margins without drawing over the
+playfield or pushing an updating game state.
 
 Developer mode also arms the mod loader's dev tripwire, which flags mods
 that reach outside their permission set.

src/core/Game.lua

@@ -255,14 +255,6 @@ function Game:draw()
   end
   Renderer:beginFrame(worldBelow)
   self.stack:draw()
-  -- Persistent tool status belongs above every game state but inside the
-  -- active UI canvas, so it composes with palette/render mods and survives
-  -- menus, battles, and transitions without becoming an updating state.
-  if ModRuntime.wantsHook("render.hud") then
-    local width, height = Renderer:uiSize()
-    ModRuntime.call("render.hud", function() end, self,
-      { width = width, height = height })
-  end
   -- SGB colorization: the topmost state that knows its palette owns the
   -- screen (overlays like text boxes inherit from what's beneath them);
   -- the overworld's world pass colors each visible map area separately
@@ -282,7 +274,13 @@ function Game:draw()
   if worldBelow and self.overworld.sgbWorldZones then
     worldZones = self.overworld:sgbWorldZones()
   end
-  Renderer:endFrame(zones, worldZones)
+  local viewport = Renderer:endFrame(zones, worldZones)
+  -- Persistent tool status is screen-space UI: draw it over the completed
+  -- render pipeline with exact playfield/margin geometry, but below mobile
+  -- controls. It never becomes an updating game state.
+  if ModRuntime.wantsHook("render.hud") then
+    ModRuntime.call("render.hud", function() end, self, viewport)
+  end
   -- on-screen mobile controls: pure screen-space, over the finished frame
   TouchControls:draw()
 end

src/render/Renderer.lua

@@ -706,6 +706,13 @@ function Renderer:endFrame(zones, worldZones)
   self.uprightActive = false
   self.worldOverride = nil
   PaletteFX.setPass(nil)
+  return {
+    width = ww, height = wh,
+    gameX = ox, gameY = oy,
+    gameWidth = vpw, gameHeight = vph,
+    scale = Sp,
+    dpiX = dpiX, dpiY = dpiY,
+  }
 end
 
 return Renderer

tests/engine/tool_mod_hooks.lua

@@ -86,9 +86,9 @@ do
   hooks:removeOwner("tool_fixture")
 end
 
--- A tool status indicator must draw after every visible game state but before
+-- A tool status indicator draws in window space after the renderer composites
--- the renderer presents that frame. This keeps the HUD visible over the
+-- the game. This gives it exact playfield/margin geometry and keeps it crisp
--- overworld, menus, battles, and compatible render pipelines.
+-- over compatible render pipelines without entering the game canvas.
 do
   local Renderer = require("src.render.Renderer")
   local TouchControls = require("src.core.TouchControls")
@@ -98,7 +98,15 @@ do
   local order = {}
   Renderer.setUISize = function() end
   Renderer.beginFrame = function() end
-  Renderer.endFrame = function() order[#order + 1] = "present" end
+  Renderer.endFrame = function()
+    order[#order + 1] = "present"
+    return {
+      width = 1024, height = 768,
+      gameX = 112, gameY = 24,
+      gameWidth = 800, gameHeight = 720,
+      scale = 5,
+    }
+  end
   TouchControls.draw = function() order[#order + 1] = "touch" end
 
   local fake = { overworld = {}, stack = { states = {} } }
@@ -108,15 +116,17 @@ do
 
   hooks:wrap("render.hud", function(nextFn, game, viewport)
     T.check(game == fake, "render.hud receives the live Game object")
-    T.eq(viewport.width, 160, "render.hud receives the UI width")
+    T.eq(viewport.width, 1024, "render.hud receives the window width")
-    T.eq(viewport.height, 144, "render.hud receives the UI height")
+    T.eq(viewport.height, 768, "render.hud receives the window height")
+    T.eq(viewport.gameX, 112, "render.hud receives the playfield origin")
+    T.eq(viewport.gameWidth, 800, "render.hud receives the playfield width")
     order[#order + 1] = "hud"
     return nextFn(game, viewport)
   end, 0, "tool_fixture")
 
   require("src.core.Game").draw(fake)
-  T.eq(table.concat(order, ","), "states,hud,present,touch",
+  T.eq(table.concat(order, ","), "states,present,hud,touch",
-    "render.hud draws over states before frame presentation")
+    "render.hud draws after frame composition and before touch controls")
   hooks:removeOwner("tool_fixture")
   Renderer.setUISize, Renderer.beginFrame, Renderer.endFrame,
     TouchControls.draw = savedSetUISize, savedBegin, savedEnd, savedTouch