From 67c12236e6521c854f384fd013efb7619c1d7e17 Mon Sep 17 00:00:00 2001
From: Campbell Barton <campbell@blender.org>
Date: Thu, 8 Feb 2024 08:53:34 +1100
Subject: [PATCH] GHOST/WIN32: remove start time offset from getMilliSeconds

This isn't necessary and has been removed from macOS & X11,
Wayland never did this.

Besides removing the offset GetTickCount() has been replaced by
GetTickCount64 to prevent 32bit rollover when high resolution timers
aren't supported.

Ref !117618
---
 intern/ghost/intern/GHOST_SystemWin32.cc | 29 ++++++------------------
 intern/ghost/intern/GHOST_SystemWin32.hh | 11 ---------
 2 files changed, 7 insertions(+), 33 deletions(-)

diff --git a/intern/ghost/intern/GHOST_SystemWin32.cc b/intern/ghost/intern/GHOST_SystemWin32.cc
index 226a144585a..36f36e14f0d 100644
--- a/intern/ghost/intern/GHOST_SystemWin32.cc
+++ b/intern/ghost/intern/GHOST_SystemWin32.cc
@@ -135,8 +135,7 @@ static void initRawInput()
 
 typedef BOOL(API *GHOST_WIN32_EnableNonClientDpiScaling)(HWND);
 
-GHOST_SystemWin32::GHOST_SystemWin32()
-    : m_hasPerformanceCounter(false), m_freq(0), m_start(0), m_lfstart(0)
+GHOST_SystemWin32::GHOST_SystemWin32() : m_hasPerformanceCounter(false), m_freq(0)
 {
   m_displayManager = new GHOST_DisplayManagerWin32();
   GHOST_ASSERT(m_displayManager, "GHOST_SystemWin32::GHOST_SystemWin32(): m_displayManager==0\n");
@@ -178,22 +177,17 @@ GHOST_SystemWin32::~GHOST_SystemWin32()
 uint64_t GHOST_SystemWin32::performanceCounterToMillis(__int64 perf_ticks) const
 {
   /* Calculate the time passed since system initialization. */
-  __int64 delta = (perf_ticks - m_start) * 1000;
+  __int64 delta = perf_ticks * 1000;
 
   uint64_t t = uint64_t(delta / m_freq);
   return t;
 }
 
-uint64_t GHOST_SystemWin32::tickCountToMillis(__int64 ticks) const
-{
-  return ticks - m_lfstart;
-}
-
 uint64_t GHOST_SystemWin32::getMilliSeconds() const
 {
   /* Hardware does not support high resolution timers. We will use GetTickCount instead then. */
   if (!m_hasPerformanceCounter) {
-    return tickCountToMillis(::GetTickCount());
+    return ::GetTickCount64();
   }
 
   /* Retrieve current count */
@@ -204,10 +198,9 @@ uint64_t GHOST_SystemWin32::getMilliSeconds() const
 }
 
 /**
- * Returns the number of milliseconds since the start of the Blender process to the time of the
- * last message, using the high frequency timer if available. This should be used instead of
- * getMilliSeconds when you need the time a message was delivered versus collected, so for all
- * event creation that are in response to receiving a Windows message.
+ * Returns the message time, compatible with the time value from #getMilliSeconds.
+ * This should be used instead of #getMilliSeconds when you need the time a message was delivered
+ * versus collected, so for all event creation that are in response to receiving a Windows message.
  */
 static uint64_t getMessageTime(GHOST_SystemWin32 *system)
 {
@@ -219,7 +212,7 @@ static uint64_t getMessageTime(GHOST_SystemWin32 *system)
     t_delta -= int64_t(UINT32_MAX) + 1;
   }
 
-  /* Return message time as 64-bit milliseconds since Blender start. */
+  /* Return message time as 64-bit milliseconds with the delta applied. */
   return system->getMilliSeconds() + t_delta;
 }
 
@@ -575,16 +568,8 @@ GHOST_TSuccess GHOST_SystemWin32::init()
   SetProcessDPIAware();
   initRawInput();
 
-  m_lfstart = ::GetTickCount();
   /* Determine whether this system has a high frequency performance counter. */
   m_hasPerformanceCounter = ::QueryPerformanceFrequency((LARGE_INTEGER *)&m_freq) == TRUE;
-  if (m_hasPerformanceCounter) {
-    GHOST_PRINT("GHOST_SystemWin32::init: High Frequency Performance Timer available\n");
-    ::QueryPerformanceCounter((LARGE_INTEGER *)&m_start);
-  }
-  else {
-    GHOST_PRINT("GHOST_SystemWin32::init: High Frequency Performance Timer not available\n");
-  }
 
   if (success) {
     WNDCLASSW wc = {0};
diff --git a/intern/ghost/intern/GHOST_SystemWin32.hh b/intern/ghost/intern/GHOST_SystemWin32.hh
index e61709f1788..5d6f7a752c3 100644
--- a/intern/ghost/intern/GHOST_SystemWin32.hh
+++ b/intern/ghost/intern/GHOST_SystemWin32.hh
@@ -60,13 +60,6 @@ class GHOST_SystemWin32 : public GHOST_System {
    */
   uint64_t performanceCounterToMillis(__int64 perf_ticks) const;
 
-  /**
-   * This method converts system ticks into milliseconds since the start of the
-   * Blender process.
-   * \return The number of milliseconds since the start of the Blender process.
-   */
-  uint64_t tickCountToMillis(__int64 ticks) const;
-
   /**
    * Returns the system time.
    * Returns the number of milliseconds since the start of the Blender process.
@@ -476,10 +469,6 @@ class GHOST_SystemWin32 : public GHOST_System {
   bool m_hasPerformanceCounter;
   /** High frequency timer variable. */
   __int64 m_freq;
-  /** High frequency timer variable. */
-  __int64 m_start;
-  /** Low frequency timer variable. */
-  __int64 m_lfstart;
   /** AltGr on current keyboard layout. */
   bool m_hasAltGr;
   /** Language identifier. */