fix(switch): stop pad cursor flicker from SDL mouse drift

Disable mouse-yield on NX where stick/touch moves the system pointer between sparse axis events, clamp pad dt, pixel-snap the overlay, and soften FlexLove GC so the launcher cursor stays steady.

Co-authored-by: Cursor <cursoragent@cursor.com>

src/import/LauncherView.lua

@@ -109,6 +109,15 @@ function LauncherView.applyNxPerfGuards(imp)
   FlexLove._Performance.enabled = false
   local mp = FlexLove._Performance._memoryProfiler
   if mp then mp.enabled = false end
+  -- Immediate-mode rebuilds allocate a full tree every frame; the default
+  -- auto GC steps hitch the pad cursor on Switch. Less frequent steps, higher
+  -- threshold — desktop keeps FlexLove defaults.
+  if FlexLove._gcConfig then
+    FlexLove._gcConfig.strategy = "periodic"
+    FlexLove._gcConfig.interval = 90
+    FlexLove._gcConfig.stepSize = 40
+    FlexLove._gcConfig.memoryThreshold = 180
+  end
   return true
 end
 
@@ -1734,7 +1743,12 @@ end
 
 local function drawPadCursor(imp)
   if not imp._padCursorActive then return end
+  -- Pixel-snap on NX: subpixel polygon edges shimmer on the 720p Switch
+  -- framebuffer when the stick advances by fractional pixels each frame.
   local x, y = imp._padCursor.x, imp._padCursor.y
+  if imp.isNX then
+    x, y = math.floor(x + 0.5), math.floor(y + 0.5)
+  end
   love.graphics.push("all")
   love.graphics.origin()
   love.graphics.setLineWidth(1)

src/import/RomImporter.lua

@@ -1984,24 +1984,24 @@ end
 function RomImporter:_updatePadCursor(dt)
   if self.isNX then
     self:_ensureNxPointerBridge()
+    -- Cap dt so a hitch in the FlexLove immediate-mode frame does not fling
+    -- the cursor; desktop keeps raw dt (setPosition path already smooth there).
+    if dt > 1 / 30 then dt = 1 / 30 end
   end
 
   -- Real mouse motion yields the pad cursor so desktop users keep a normal
-  -- pointer after bumping a stick once. On NX the bridged getPosition returns
-  -- pad coords while active, so yield must sample the *real* mouse or an A
-  -- press after idle falsely drops the cursor (pad vs last real position).
-  local mx, my
-  if self.isNX and self._nxRealGetPosition then
-    mx, my = self._nxRealGetPosition()
-  else
-    mx, my = love.mouse.getPosition()
-  end
-  if self._lastMouseX and self._padCursorActive then
-    if math.abs(mx - self._lastMouseX) > 3 or math.abs(my - self._lastMouseY) > 3 then
-      self._padCursorActive = false
+  -- pointer after bumping a stick once. On NX this must stay off: love-nx /
+  -- SDL often drifts the system mouse with the stick (or touch), and axis
+  -- events are not every frame, so yield+reactivate flickers the overlay.
+  if not self.isNX then
+    local mx, my = love.mouse.getPosition()
+    if self._lastMouseX and self._padCursorActive then
+      if math.abs(mx - self._lastMouseX) > 3 or math.abs(my - self._lastMouseY) > 3 then
+        self._padCursorActive = false
+      end
     end
+    self._lastMouseX, self._lastMouseY = mx, my
   end
-  self._lastMouseX, self._lastMouseY = mx, my
 
   local ax = self._padAxis.leftx or 0
   local ay = self._padAxis.lefty or 0
@@ -2025,8 +2025,7 @@ function RomImporter:_updatePadCursor(dt)
     self._padCursor.x = math.max(ox, math.min(ox + w, nx))
     self._padCursor.y = math.max(oy, math.min(oy + h, ny))
     -- Desktop: FlexLove polls the real mouse, so warp it with the pad pointer.
-    -- NX: the getPosition bridge already returns pad coords — skip setPosition
-    -- and leave _lastMouse* on the real pointer baseline (yield above).
+    -- NX: the getPosition bridge already returns pad coords — skip setPosition.
     if not self.isNX and love.mouse.setPosition then
       pcall(love.mouse.setPosition, self._padCursor.x, self._padCursor.y)
       self._lastMouseX, self._lastMouseY = self._padCursor.x, self._padCursor.y