maybe smoother mobile scroll on installed mods

src/import/LauncherView.lua

@@ -2142,16 +2142,20 @@ local function buildModsPanel(imp, x, y, w, availH, m)
     + math.floor(8 * m.s)
   local listTop = cy
 
-  -- One continuous list: every row is laid out, the region scroll moves
+  -- One continuous list: derive the rows that can touch the viewport before
-  -- through all of it, and only rows inside the region's viewport draw --
+  -- entering the loop. Drawing was already culled, but scanning every
-  -- so the per-frame cost stays bounded by the window, not the list.
+  -- installed row to discover that defeats the point on a large mod library.
   local view = imp._tabRegionRect
   local viewTop = view and view.y or listTop
   local viewBot = view and (view.y + view.h) or (listTop + availH)
-  for i = 1, #mods do
+  local stride = rowH + gap
+  local first = math.max(1,
+    math.ceil((viewTop - rowH - listTop) / stride) + 1)
+  local last = math.min(#mods,
+    math.floor((viewBot - listTop) / stride) + 1)
+  for i = first, last do
     local mod = mods[i]
     local ry = listTop + (i - 1) * (rowH + gap)
-    if ry + rowH >= viewTop and ry <= viewBot then
     local rowKey = rowKeyFor(imp, "mod-row-", mod.id)
     local isFullyDisabled = true
     if mod.enabledByVersion then
@@ -2261,7 +2265,6 @@ local function buildModsPanel(imp, x, y, w, availH, m)
         px, ly, PAL.detail)
     end
   end
-  end
 
   local contentH = #mods * rowH + (#mods - 1) * gap
   return (listTop + contentH + gap) - y

src/import/RomImporter.lua

@@ -4154,7 +4154,6 @@ function RomImporter:_refreshMods()
     end
     self.mods = kept
   end
-  self:_syncModUpdateInfo(false)
 end
 
 -- Point the MODS panel at one game (or nil for all of them) and relist, so
@@ -4168,15 +4167,12 @@ function RomImporter:_ensureMods()
   if not self.mods then self:_refreshMods() end
 end
 
--- Resolve cached (or freshly fetched) GitHub status for every mod that
+-- Resolve GitHub status for every installed mod that declares a github field.
--- declares a github field. force=true bypasses the 6h cache on every repo.
+-- This is deliberately opt-in: only the explicit "Check for updates" action
--- Results live on self.modUpdateInfo[id] = { status, latest, best, releases }.
+-- calls it. Opening, scrolling, toggling, or relisting the MODS tab must not
--- ASYNC (was synchronous).  This runs on every _refreshMods -- boot, and any
+-- create a burst of release work behind the list. force=true bypasses the 6h
--- toggle or install -- and used to make one blocking curl call per mod with a
+-- cache on every repo. Results live on self.modUpdateInfo[id] = {
--- github field, in a loop, on the render thread.  A handful of mods was a
+-- status, latest, best, releases } and resolve asynchronously across frames.
--- multi-second freeze of the whole launcher.  Now each mod gets a handle and
--- they resolve together across later frames; a mod whose cache is still fresh
--- resolves on the first pump with no network at all.
 function RomImporter:_syncModUpdateInfo(force)
   local ModUpdate = require("src.mods.ModUpdate")
   self.modUpdateInfo = self.modUpdateInfo or {}

tests/engine/launcher_scroll_test.lua

@@ -388,6 +388,35 @@ mdown = false
 LauncherView.update(gameImp, 0.016)
 love.mouse.isDown = nil
 
+-- Opening or relisting MODS is display work only. Release checks are an
+-- explicit action, otherwise each installed GitHub mod creates background
+-- work exactly when the player starts scrolling the panel.
+do
+  local savedMods = package.loaded["src.mods.LauncherMods"]
+  local savedSaveData = package.loaded["src.core.SaveData"]
+  local listCalls, updateCalls = 0, 0
+  package.loaded["src.mods.LauncherMods"] = {
+    list = function()
+      listCalls = listCalls + 1
+      return { { id = "test", github = "owner/repo" } }
+    end,
+  }
+  package.loaded["src.core.SaveData"] = {
+    loadOptions = function() return {} end,
+    isSafeMode = function() return false end,
+  }
+  local refreshImp = setmetatable({
+    modStraysChecked = true,
+    _syncModUpdateInfo = function() updateCalls = updateCalls + 1 end,
+  }, RomImporter)
+  refreshImp:_refreshMods()
+  eq(listCalls, 1, "relisting MODS still obtains its installed rows")
+  eq(updateCalls, 0,
+    "relisting MODS does not start release checks without the explicit button")
+  package.loaded["src.mods.LauncherMods"] = savedMods
+  package.loaded["src.core.SaveData"] = savedSaveData
+end
+
 local function read(path)
   local f = assert(io.open(path, "r"))
   local src = f:read("*a")