From ae233fe1fcfe00412fbc8ecf1a188eff03adace5 Mon Sep 17 00:00:00 2001
From: tomcw <tomcw@users.noreply.github.com>
Date: Tue, 8 Jul 2014 20:58:48 +0100
Subject: [PATCH] Remove redundant 'BOOL behind' which was always zero. -
 allowed some simplification to VideoSetMode() Tidy up ContinueExecution(),
 removing unused 'BOOL pageflipping'. Refactor VideoCheckPage() to make it
 more readable.

---
 source/Applewin.cpp | 23 +++++---------------
 source/Applewin.h   |  1 -
 source/Video.cpp    | 52 +++++++++++++++++++++++++--------------------
 3 files changed, 34 insertions(+), 42 deletions(-)

diff --git a/source/Applewin.cpp b/source/Applewin.cpp
index 34dcb502..ccceefea 100644
--- a/source/Applewin.cpp
+++ b/source/Applewin.cpp
@@ -44,7 +44,6 @@ TCHAR *g_pAppTitle = TITLE_APPLE_2E_ENHANCED;
 
 eApple2Type	g_Apple2Type = A2TYPE_APPLE2EENHANCED;
 
-BOOL      behind            = 0;			// Redundant
 DWORD     cumulativecycles  = 0;			// Wraps after ~1hr 9mins
 DWORD     cyclenum          = 0;			// Used by SpkrToggle() for non-wave sound
 DWORD     emulmsec          = 0;
@@ -163,8 +162,6 @@ void SetPriorityNormal(void)
 
 void ContinueExecution(void)
 {
-	static BOOL pageflipping    = 0; //?
-
 	const double fUsecPerSec        = 1.e6;
 #if 1
 	const UINT nExecutionPeriodUsec = 1000;		// 1.0ms
@@ -241,22 +238,16 @@ void ContinueExecution(void)
 		emulmsec_frac %= CLKS_PER_MS;
 	}
 
-	//
-	// DETERMINE WHETHER THE SCREEN WAS UPDATED, THE DISK WAS SPINNING,
-	// OR THE KEYBOARD I/O PORTS WERE BEING EXCESSIVELY QUERIED THIS CLOCKTICK
-	VideoCheckPage(0);
-	BOOL screenupdated = VideoHasRefreshed();
-	BOOL systemidle    = 0;	//(KeybGetNumQueries() > (clockgran << 2));	//  && (!ranfinegrain);	// TO DO
-
-	if (screenupdated)
-		pageflipping = 3;
-
 	//
 
 	if (g_dwCyclesThisFrame >= dwClksPerFrame)
 	{
 		g_dwCyclesThisFrame -= dwClksPerFrame;
 
+		// DETERMINE WHETHER THE SCREEN WAS UPDATED THIS CLOCKTICK
+		VideoCheckPage(0);								// force=0
+		const BOOL screenupdated = VideoHasRefreshed();	// Only called from here. Clears & returns 'hasrefreshed' flag.
+
 		if (g_nAppMode != MODE_LOGO)
 		{
 			VideoUpdateFlash();
@@ -276,20 +267,16 @@ void ContinueExecution(void)
 				static DWORD lasttime = 0;
 				DWORD currtime = GetTickCount();
 				if ((!g_bFullSpeed) ||
-					(currtime-lasttime >= (DWORD)((g_bGraphicsMode || !systemidle) ? 100 : 25)))
+					(currtime-lasttime >= (DWORD)(g_bGraphicsMode ? 100 : 25)))
 				{
 					VideoRefreshScreen();
 					lasttime = currtime;
 				}
-				screenupdated = 1;
 			}
 
 			lastupdates[1] = lastupdates[0];
 			lastupdates[0] = anyupdates;
 			anyupdates     = 0;
-
-			if (pageflipping)
-				pageflipping--;
 		}
 
 		MB_EndOfVideoFrame();
diff --git a/source/Applewin.h b/source/Applewin.h
index af17cebc..1c113d27 100644
--- a/source/Applewin.h
+++ b/source/Applewin.h
@@ -10,7 +10,6 @@ extern TCHAR     *g_pAppTitle;
 
 extern eApple2Type g_Apple2Type;
 
-extern BOOL       behind;
 extern DWORD      cumulativecycles;
 extern DWORD      cyclenum;
 extern DWORD      emulmsec;
diff --git a/source/Video.cpp b/source/Video.cpp
index bedf9cec..1f35fb89 100644
--- a/source/Video.cpp
+++ b/source/Video.cpp
@@ -3117,14 +3117,22 @@ BYTE VideoCheckMode (WORD, WORD address, BYTE, BYTE, ULONG uExecutedCycles)
 }
 
 //===========================================================================
-void VideoCheckPage (BOOL force) {
-  if ((g_bVideoDisplayPage2 != (SW_PAGE2 != 0)) &&
-      (force || (emulmsec-lastpageflip > 500))) {
-    g_bVideoDisplayPage2 = (SW_PAGE2 != 0);
-    VideoRefreshScreen();
-    hasrefreshed = 1;
-    lastpageflip = emulmsec;
-  }
+
+// Check if we should call VideoRefreshScreen() based on unexpected page
+// - Only called from a single place in main ContinueExecution() loop
+void VideoCheckPage(BOOL force)
+{
+	const bool bUnexpectedPage = (g_bVideoDisplayPage2 != (SW_PAGE2 != 0));
+	//_ASSERT(!bUnexpectedPage);					// [TC] Q: When does this happen? A: EG. When page-flipping && Scroll-Lock is pressed
+
+	if (bUnexpectedPage &&							// Unexpected page &&
+		(force || (emulmsec-lastpageflip > 500)))	// force || >500ms since last flip
+	{
+		g_bVideoDisplayPage2 = (SW_PAGE2 != 0);
+		VideoRefreshScreen();
+		hasrefreshed = 1;
+		lastpageflip = emulmsec;
+	}
 }
 
 //===========================================================================
@@ -3701,24 +3709,22 @@ BYTE VideoSetMode (WORD, WORD address, BYTE write, BYTE, ULONG uExecutedCycles)
 		else
 			oldpage2 = SW_PAGE2;
 	}
-	if (oldpage2 != SW_PAGE2) {
-		static DWORD lastrefresh = 0;
-		if ((g_bVideoDisplayPage2 && !SW_PAGE2) || (!behind)) {
-			g_bVideoDisplayPage2 = (SW_PAGE2 != 0);
-			if (!g_VideoForceFullRedraw) {
-				VideoRefreshScreen();
-				hasrefreshed = 1;
-				lastrefresh  = emulmsec;
-			}
-		}
-		else if ((!SW_PAGE2) && (!g_VideoForceFullRedraw) && (emulmsec-lastrefresh >= 20)) {
-		  g_bVideoDisplayPage2 = 0;
-		  VideoRefreshScreen();
-		  hasrefreshed = 1;
-		  lastrefresh  = emulmsec;
+
+	if (oldpage2 != SW_PAGE2)
+	{
+		g_bVideoDisplayPage2 = (SW_PAGE2 != 0);
+		if (!g_VideoForceFullRedraw)
+		{
+#if 1
+			VideoRefreshScreen();
+			hasrefreshed = 1;
+#else
+			g_VideoForceFullRedraw = 1;		// GH#129,GH204: Defer the redraw until the main ContinueExecution() loop (TODO: What effect does this have on other games?)
+#endif
 		}
 		lastpageflip = emulmsec;
 	}
+
 	return MemReadFloatingBus(uExecutedCycles);
 }