From 652cc4f2c94570ea35c2c686e6ce453c7813b31a Mon Sep 17 00:00:00 2001
From: Matthew Budd <mjbudd77@gmail.com>
Date: Tue, 6 Oct 2020 20:08:17 -0400
Subject: [PATCH] Added logic to protect against PPU and NT view windows from
 crash when being opened with no game loaded.

---
 src/drivers/Qt/NameTableViewer.cpp | 25 ++++++++++---------------
 src/drivers/Qt/ppuViewer.cpp       | 17 +++++++++++++----
 2 files changed, 23 insertions(+), 19 deletions(-)

diff --git a/src/drivers/Qt/NameTableViewer.cpp b/src/drivers/Qt/NameTableViewer.cpp
index aa70168f..485dbd85 100644
--- a/src/drivers/Qt/NameTableViewer.cpp
+++ b/src/drivers/Qt/NameTableViewer.cpp
@@ -572,15 +572,8 @@ static void DrawNameTable(int scanline, int ntnum, bool invalidateCache)
 
 				//obviously this whole scheme of nt cache doesnt work if an mmc5 game is playing tricks with the attribute table
 			}
-			//pbitmap += (8*3);
 		}
-		//pbitmap += 7*((NTWIDTH*3));
 	}
-
-	 //this copies the attribute tables to the cache if needed. but we arent using it now because 
-	//if(redrawtables){
-	//	memcpy(tablecache+0x3c0,table+0x3c0,0x40);
-	//}
 }
 //----------------------------------------------------
 void FCEUD_UpdateNTView(int scanline, bool drawall) 
@@ -594,12 +587,8 @@ void FCEUD_UpdateNTView(int scanline, bool drawall)
 		return;
 	}
 
-	//uint8 *pbitmap = ppuv_palette;
-	//if (!hNTView) return;
-	
 	ppu_getScroll(xpos,ypos);
 
-
 	if (NTViewSkip < NTViewRefresh)
 	{
 		NTViewSkip++;
@@ -618,13 +607,19 @@ void FCEUD_UpdateNTView(int scanline, bool drawall)
 		memcpy(palcache,PALRAM,32);
 		drawall = 1; //palette has changed, so redraw all
 	}
+
+	if ( vnapage[0] == NULL )
+	{
+		return;
+	}
 	 
 	ntmirroring = NT_NONE;
-	if(vnapage[0] == vnapage[1])ntmirroring = NT_HORIZONTAL;
-	if(vnapage[0] == vnapage[2])ntmirroring = NT_VERTICAL;
-	if((vnapage[0] != vnapage[1]) && (vnapage[0] != vnapage[2]))ntmirroring = NT_FOUR_SCREEN;
+	if (vnapage[0] == vnapage[1])ntmirroring = NT_HORIZONTAL;
+	if (vnapage[0] == vnapage[2])ntmirroring = NT_VERTICAL;
+	if ((vnapage[0] != vnapage[1]) && (vnapage[0] != vnapage[2]))ntmirroring = NT_FOUR_SCREEN;
 
-	if((vnapage[0] == vnapage[1]) && (vnapage[1] == vnapage[2]) && (vnapage[2] == vnapage[3])){ 
+	if ((vnapage[0] == vnapage[1]) && (vnapage[1] == vnapage[2]) && (vnapage[2] == vnapage[3]))
+	{ 
 		if(vnapage[0] == &NTARAM[0x000])ntmirroring = NT_SINGLE_SCREEN_TABLE_0;
 		if(vnapage[0] == &NTARAM[0x400])ntmirroring = NT_SINGLE_SCREEN_TABLE_1;
 		if(vnapage[0] == ExtraNTARAM)ntmirroring = NT_SINGLE_SCREEN_TABLE_2;
diff --git a/src/drivers/Qt/ppuViewer.cpp b/src/drivers/Qt/ppuViewer.cpp
index a48be32c..ba334f3d 100644
--- a/src/drivers/Qt/ppuViewer.cpp
+++ b/src/drivers/Qt/ppuViewer.cpp
@@ -510,19 +510,28 @@ void FCEUD_UpdatePPUView(int scanline, int refreshchr)
 
 	if (refreshchr)
 	{
+		int i10, x10;
 		for (i = 0, x=0x1000; i < 0x1000; i++, x++)
 		{
-			chrcache0[i] = VPage[i>>10][i];
-			chrcache1[i] = VPage[x>>10][x];
+			i10 = i>>10;
+			x10 = x>>10;
+
+			if ( VPage[i10] == NULL )
+			{
+				continue;
+			}
+			chrcache0[i] = VPage[i10][i];
+			chrcache1[i] = VPage[x10][x];
+
 			if (debug_loggingCD) 
 			{
 				if (cdloggerVideoDataSize)
 				{
 					int addr;
-					addr = &VPage[i >> 10][i] - CHRptr[0];
+					addr = &VPage[i10][i] - CHRptr[0];
 					if ((addr >= 0) && (addr < (int)cdloggerVideoDataSize))
 						logcache0[i] = cdloggervdata[addr];
-					addr = &VPage[x >> 10][x] - CHRptr[0];
+					addr = &VPage[x10][x] - CHRptr[0];
 					if ((addr >= 0) && (addr < (int)cdloggerVideoDataSize))
 						logcache1[i] = cdloggervdata[addr];
 				}