From c40e1f929d16cfa88e4a1476c87823f5652f8251 Mon Sep 17 00:00:00 2001
From: Connor Olding <cloningdonor@gmail.com>
Date: Fri, 8 Jun 2018 13:48:59 +0200
Subject: [PATCH] fix skipped inputs on lag frames

---
 _NOTICE  |  1 -
 main.lua | 25 ++++++++++++++++---------
 2 files changed, 16 insertions(+), 10 deletions(-)

diff --git a/_NOTICE b/_NOTICE
index d038164..eada196 100644
--- a/_NOTICE
+++ b/_NOTICE
@@ -5,7 +5,6 @@ however, feel free to copy any snippets of code you find useful.
 TODOs: (that i can remember right now)
 - normalize and/or embed sprite type inputs
 - settle on a network architecture
-- fix lag-frames skipped-inputs bug
 - detect frames when Mario is in a controllable state
 - compute how many input neurons the network needs instead of hardcoding
 - rewrite positions to be relative to Mario
diff --git a/main.lua b/main.lua
index a64a837..04f739e 100644
--- a/main.lua
+++ b/main.lua
@@ -20,6 +20,7 @@ local mom2max -- running element-wise maximum of mom2.
 
 local trial_frames = 0
 local total_frames = 0
+local lagless_count = 0
 
 local force_start = false
 local force_start_old = false
@@ -563,6 +564,13 @@ local function prepare_reset()
     reset = true
 end
 
+local function draw_framecount(x, y, frames)
+    local tf0 = frames % 1000
+    local tf1 = (frames % 1000000 - tf0) / 1000
+    local tf2 = (frames - tf0 - tf1) / 1000000
+    gui.text(x, y, ("%03i,%03i,%03i"):format(tf2,tf1,tf0), '#FFFFFF', '#0000003F')
+end
+
 local function doit(dummy)
     local ingame_paused = game.get_state() == "paused"
 
@@ -581,10 +589,7 @@ local function doit(dummy)
         end
     end
 
-    local tf0 = total_frames % 1000
-    local tf1 = (total_frames % 1000000 - tf0) / 1000
-    local tf2 = (total_frames - tf0 - tf1) / 1000000
-    gui.text(12, 212, ("%03i,%03i,%03i"):format(tf2,tf1,tf0), '#FFFFFF', '#0000003F')
+    draw_framecount(12, 215, total_frames)
 
     screen_scroll_delta = screen_scroll_delta + game.R(0x775)
 
@@ -723,7 +728,10 @@ while true do
         state_old = game.get_state()
     end
 
-    if reset then do_reset() end
+    if reset then
+        do_reset()
+        lagless_count = 0
+    end
 
     if not cfg.enable_network then
         -- infinite time cheat. super handy for testing.
@@ -739,13 +747,12 @@ while true do
         game.W(0x75A, 1)
     end
 
-    -- FIXME: if the game lags then we might miss our frame to change inputs!
-    --        don't rely on emu.framecount.
-    local doot = jp == nil or emu.framecount() % cfg.frameskip == 0
+    local doot = jp == nil or lagless_count % cfg.frameskip == 0
     doit(not doot)
 
     -- jp might still be nil if we're not ingame or we're not playing.
     if jp ~= nil then joypad.write(1, jp) end
 
-    game.advance()
+    game.advance() -- remember, this skips lag frames.
+    lagless_count = lagless_count + 1
 end