stats: fix ingame timer not working correctly

Fixes #1420.

Also, refactors the stat calculation for simpler usage.

The timer would become inaccurate when opening the inventory due to the
internal stats timer not being reset on launch. As a result, the
previous value was meaningless, leading to incorrect elapsed time
calculations on the opening frame.

src/game/phase/phase_demo.c

@@ -249,7 +249,6 @@ static GAMEFLOW_COMMAND Phase_Demo_Run(int32_t nframes)
         Sound_ResetAmbient();
         Effect_RunActiveFlipEffect();
         Sound_UpdateEffects();
-        g_GameInfo.current[g_CurrentLevel].stats.timer++;
         Overlay_BarHealthTimerTick();
 
         // Discard demo input; check for debounced real keypresses

src/game/phase/phase_game.c

@@ -1,5 +1,6 @@
 #include "game/phase/phase_game.h"
 
+#include "game/stats.h"
 #include "game/camera.h"
 #include "game/effects.h"
 #include "game/game.h"
@@ -33,6 +34,7 @@ static void Phase_Game_Draw(void);
 static void Phase_Game_Start(void *arg)
 {
     Interpolation_Remember();
+    Stats_StartTimer();
     if (Phase_Get() != PHASE_PAUSE) {
         Output_FadeReset();
     }
@@ -45,6 +47,7 @@ static void Phase_Game_End(void)
 static GAMEFLOW_COMMAND Phase_Game_Control(int32_t nframes)
 {
     Interpolation_Remember();
+    Stats_UpdateTimer();
     CLAMPG(nframes, MAX_FRAMES);
 
     for (int32_t i = 0; i < nframes; i++) {
@@ -123,7 +126,6 @@ static GAMEFLOW_COMMAND Phase_Game_Control(int32_t nframes)
             Sound_ResetAmbient();
             Effect_RunActiveFlipEffect();
             Sound_UpdateEffects();
-            g_GameInfo.current[g_CurrentLevel].stats.timer++;
             Overlay_BarHealthTimerTick();
         }
     }

src/game/phase/phase_inventory.c

@@ -5,6 +5,7 @@
 #include "game/console.h"
 #include "game/game.h"
 #include "game/gameflow.h"
+#include "game/stats.h"
 #include "game/input.h"
 #include "game/interpolation.h"
 #include "game/inventory.h"
@@ -571,6 +572,9 @@ static bool Inv_CheckDemoTimer(const IMOTION_INFO *const motion)
 static void Phase_Inventory_Start(void *arg)
 {
     Interpolation_Remember();
+    if (g_Config.enable_timer_in_inventory) {
+        Stats_StartTimer();
+    }
 
     INV_MODE inv_mode = (INV_MODE)arg;
 
@@ -696,11 +700,6 @@ static GAMEFLOW_COMMAND Phase_Inventory_ControlFrame(void)
         && ((ring->type == RT_MAIN && g_InvKeysObjects)
             || (ring->type == RT_OPTION && g_InvMainObjects));
 
-    if (g_Config.enable_timer_in_inventory) {
-        const double ticks = Clock_GetElapsedLogicalFrames(&m_StatsTimer);
-        g_GameInfo.current[g_CurrentLevel].stats.timer += round(ticks);
-    }
-
     if (ring->rotating) {
         return (GAMEFLOW_COMMAND) {
             .command = GF_PHASE_CONTINUE,
@@ -1091,12 +1090,17 @@ static GAMEFLOW_COMMAND Phase_Inventory_ControlFrame(void)
 static GAMEFLOW_COMMAND Phase_Inventory_Control(int32_t nframes)
 {
     Interpolation_Remember();
+    if (g_Config.enable_timer_in_inventory) {
+        Stats_UpdateTimer();
+    }
+
     for (int32_t i = 0; i < nframes; i++) {
         GAMEFLOW_COMMAND result = Phase_Inventory_ControlFrame();
         if (result.command != GF_PHASE_CONTINUE) {
             return result;
         }
     }
+
     return (GAMEFLOW_COMMAND) {
         .command = GF_PHASE_CONTINUE,
         .param = 0,

src/game/stats.c

@@ -1,6 +1,7 @@
 #include "game/stats.h"
 
 #include "game/carrier.h"
+#include "game/clock.h"
 #include "game/gamebuf.h"
 #include "game/gameflow.h"
 #include "game/items.h"
@@ -25,6 +26,11 @@ static uint32_t m_SecretRoom = 0;
 static bool m_KillableItems[MAX_ITEMS] = { 0 };
 static bool m_IfKillable[O_NUMBER_OF] = { 0 };
 
+static struct {
+    double start_counter;
+    int32_t start_timer;
+} m_StatsTimer = { 0 };
+
 int16_t m_PickupObjs[] = { O_PICKUP_ITEM1,   O_PICKUP_ITEM2,  O_KEY_ITEM1,
                            O_KEY_ITEM2,      O_KEY_ITEM3,     O_KEY_ITEM4,
                            O_PUZZLE_ITEM1,   O_PUZZLE_ITEM2,  O_PUZZLE_ITEM3,
@@ -282,3 +288,20 @@ bool Stats_CheckAllSecretsCollected(GAMEFLOW_LEVEL_TYPE level_type)
     Stats_ComputeTotal(level_type, &total_stats);
     return total_stats.player_secret_count >= total_stats.total_secret_count;
 }
+
+void Stats_StartTimer(void)
+{
+    m_StatsTimer.start_counter = Clock_GetHighPrecisionCounter();
+    m_StatsTimer.start_timer = g_GameInfo.current[g_CurrentLevel].stats.timer;
+}
+
+void Stats_UpdateTimer(void)
+{
+    const double elapsed =
+        (Clock_GetHighPrecisionCounter() - m_StatsTimer.start_counter)
+        * LOGIC_FPS / 1000.0;
+    g_GameInfo.current[g_CurrentLevel].stats.timer =
+        m_StatsTimer.start_timer + elapsed;
+}
+
+void Stats_StopTimer(void);

src/game/stats.h

@@ -24,3 +24,7 @@ int32_t Stats_GetKillables(void);
 int32_t Stats_GetSecrets(void);
 void Stats_ComputeTotal(GAMEFLOW_LEVEL_TYPE level_type, TOTAL_STATS *stats);
 bool Stats_CheckAllSecretsCollected(GAMEFLOW_LEVEL_TYPE level_type);
+
+void Stats_StartTimer(void);
+void Stats_UpdateTimer(void);
+void Stats_StopTimer(void);