From 3233cfc244057d62c28074d30a7eae2ab2172eda Mon Sep 17 00:00:00 2001
From: Will Angenent <will.angenent@five.ai>
Date: Sat, 26 May 2018 22:27:29 +0100
Subject: [PATCH] Added page switching in text, gr and hgr

---
 mmu/io.go      | 40 ++++++++++++++++++++++++++++------------
 mmu/mmu.go     | 24 +++++++++++++++++++++++-
 video/video.go | 14 ++++++++++++++
 3 files changed, 65 insertions(+), 13 deletions(-)

diff --git a/mmu/io.go b/mmu/io.go
index a136156..1c6fa26 100644
--- a/mmu/io.go
+++ b/mmu/io.go
@@ -160,15 +160,16 @@ func readWrite(address uint16, isRead bool) bool {
 		SetFakeAltZP(true)
 		return true
 	case CLR80VID:
-		// 80 column card hasn't been implemented yet
+		SetCol80(false)
+		return true
+	case SET80VID:
+		SetCol80(true)
 		return true
 	case TXTPAGE1:
-		// 80 column card hasn't been implemented yet
-		SetFakePage2(false)
+		SetPage2(false)
 		return true
 	case TXTPAGE2:
-		// 80 column card hasn't been implemented yet
-		SetFakePage2(true)
+		SetPage2(true)
 		return true
 	case CLRTEXT:
 		VideoState.TextMode = false
@@ -188,6 +189,16 @@ func readWrite(address uint16, isRead bool) bool {
 	case SETHIRES:
 		VideoState.HiresMode = true
 		return true
+	case CLR80COL:
+		if !isRead {
+			SetStore80(false)
+			return true
+		} else {
+			return false
+		}
+	case SET80COL:
+		SetStore80(true)
+		return true
 	case STATEREG:
 		// Ignore not implemented memory management reg
 		return true
@@ -294,6 +305,13 @@ func ReadIO(address uint16) uint8 {
 		// using 80-column display mode not implemented
 		return 0x0d
 
+	case RDPAGE2:
+		if Page2 {
+			return 0x8d
+		} else {
+			return 0x0d
+		}
+
 	// 4-bit annunciator inputs
 	case SETAN0, CLRAN0, SETAN1, CLRAN1, SETAN2, CLRAN2, SETAN3, CLRAN3:
 		// Annunciators not implemented
@@ -303,11 +321,11 @@ func ReadIO(address uint16) uint8 {
 	case CLSAPPLE:
 		// Closed apple key not implemented
 	case RD80COL:
-		// RD80COL not implemented
-		return 0x0d
-	case RDPAGE2:
-		// RDPAGE2 not implemented
-		return 0x0d
+		if Store80 {
+			return 0x8d
+		} else {
+			return 0x0d
+		}
 	case RDALTCH:
 		// RDALTCH not implemented
 		return 0x0d
@@ -341,8 +359,6 @@ func WriteIO(address uint16, value uint8) {
 	case CLR80COL:
 		// CLR80COL not implemented
 		return
-	case SET80COL:
-		// SET80COL not implemented
 	case CLRC3ROM:
 		// CLRC3ROM not implemented
 	case SETC3ROM:
diff --git a/mmu/mmu.go b/mmu/mmu.go
index 703f895..8cdbbd9 100644
--- a/mmu/mmu.go
+++ b/mmu/mmu.go
@@ -29,6 +29,9 @@ var (
 	FakeAuxMemoryWrite   bool // Aux memory isn't implemented
 	FakeAltZP            bool // Aux memory isn't implemented
 	FakePage2            bool // Aux memory isn't implemented
+	Col80                bool // 80 Column card is on (not implemented)
+	Store80              bool // 80 Column card is on (not implemented)
+	Page2                bool // Main memory Page2 is selected
 )
 
 func ApplyMemoryConfiguration() {
@@ -165,7 +168,24 @@ func SetFakeAltZP(value bool) {
 	ApplyMemoryConfiguration()
 }
 
-func SetFakePage2(value bool) {
+func SetCol80(value bool) {
+	Col80 = value
+	// No changes are needed when this is toggled
+}
+
+func SetPage2(value bool) {
+	// If the 80 column card is enabled, then this toggles aux memory
+	// Otherwise, page1/page2 is toggled in the main memory
+	if Col80 {
+		FakePage2 = value
+		ApplyMemoryConfiguration()
+	} else {
+		Page2 = value
+	}
+}
+
+func SetStore80(value bool) {
+	Store80 = value
 	FakePage2 = value
 	ApplyMemoryConfiguration()
 }
@@ -177,6 +197,8 @@ func InitRAM() {
 	FakeAuxMemoryWrite = false // Aux memory isn't implemented
 	FakeAltZP = false          // Aux memory isn't implemented
 	FakePage2 = false          // Aux memory isn't implemented
+	Col80 = false              // Aux memory isn't implemented
+	Page2 = false
 	ApplyMemoryConfiguration()
 }
 
diff --git a/video/video.go b/video/video.go
index 7b5f2a2..c8b1f85 100644
--- a/video/video.go
+++ b/video/video.go
@@ -120,6 +120,11 @@ func drawLores(screen *ebiten.Image, x int, y int, value uint8) error {
 func drawTextBlock(screen *ebiten.Image, start int, end int) error {
 	for y := start; y < end; y++ {
 		base := 128*(y%8) + 40*(y/8)
+
+		if mmu.Page2 {
+			base += 0x400
+		}
+
 		for x := 0; x < 40; x++ {
 			offset := textVideoMemory + base + x
 			value := mmu.ReadPageTable[offset>>8][offset&0xff]
@@ -136,6 +141,11 @@ func drawTextBlock(screen *ebiten.Image, start int, end int) error {
 func drawLoresBlock(screen *ebiten.Image, start int, end int) error {
 	for y := start; y < end; y++ {
 		base := 128*(y%8) + 40*(y/8)
+
+		if mmu.Page2 {
+			base += 0x400
+		}
+
 		for x := 0; x < 40; x++ {
 			offset := textVideoMemory + base + x
 			value := mmu.ReadPageTable[offset>>8][offset&0xff]
@@ -182,6 +192,10 @@ func drawHiresScreen(screen *ebiten.Image) error {
 		// Woz is a genius
 		yOffset := 0x2000 - (0x3d8)*(y>>6) + 0x80*(y>>3) + 0x400*(y&0x7)
 
+		if mmu.Page2 {
+			yOffset += 0x2000
+		}
+
 		for x := 0; x < 40; x++ {
 			offset := yOffset + x
 			value := mmu.ReadPageTable[offset>>8][offset&0xff]