From 9fcd4992410837c1f606edc94932ae27af88176d Mon Sep 17 00:00:00 2001
From: Ivan Izaguirre <ivanizag@gmail.com>
Date: Wed, 1 May 2019 16:54:53 +0200
Subject: [PATCH] Improved CRT sumulation. P1 phosphor green and vertical line
 separation.

---
 apple2/screen.go | 29 ++++++++++++++++++++++++++---
 apple2sdl/run.go |  3 ++-
 2 files changed, 28 insertions(+), 4 deletions(-)

diff --git a/apple2/screen.go b/apple2/screen.go
index 53fb968..e01c372 100644
--- a/apple2/screen.go
+++ b/apple2/screen.go
@@ -19,7 +19,8 @@ func Snapshot(a *Apple2) *image.RGBA {
 	}
 
 	if isTextMode {
-		return snapshotTextMode(a, pageIndex)
+		//return snapshotTextMode(a, pageIndex)
+		return linesSeparatedFilter(snapshotTextMode(a, pageIndex))
 	} else {
 		if isHiResMode {
 			//return snapshotHiResModeReferenceMono(a, pageIndex)
@@ -52,6 +53,22 @@ func saveSnapshot(a *Apple2) {
 	png.Encode(f, img)
 }
 
+func linesSeparatedFilter(in *image.RGBA) *image.RGBA {
+	b := in.Bounds()
+	size := image.Rect(0, 0, b.Dx(), 4*b.Dy())
+	out := image.NewRGBA(size)
+	for y := b.Min.Y; y < b.Max.Y; y++ {
+		for x := b.Min.X; x < b.Max.X; x++ {
+			c := in.At(x, y)
+			out.Set(x, 4*y, c)
+			out.Set(x, 4*y+1, c)
+			out.Set(x, 4*y+2, c)
+			out.Set(x, 4*y+3, color.Black)
+		}
+	}
+	return out
+}
+
 const (
 	charWidth         = 7
 	charHeight        = 8
@@ -86,6 +103,10 @@ func getTextChar(a *Apple2, col int, line int, page int) uint8 {
 func snapshotTextMode(a *Apple2, page int) *image.RGBA {
 	// TODO: Missing inverse and flash modes
 
+	// Color for typical Apple ][ period green phosphor monitors
+	// See: https://superuser.com/questions/361297/what-colour-is-the-dark-green-on-old-fashioned-green-screen-computer-displays
+	p1GreenPhosphorColor := color.RGBA{65, 255, 0, 255}
+
 	width := textColumns * charWidth
 	height := textLines * charHeight
 	size := image.Rect(0, 0, width, height)
@@ -99,9 +120,11 @@ func snapshotTextMode(a *Apple2, page int) *image.RGBA {
 			colInChar := x % charWidth
 			char := getTextChar(a, col, line, page)
 			pixel := a.cg.getPixel(char, rowInChar, colInChar)
-			colour := color.Black
+			var colour color.Color
 			if pixel {
-				colour = color.White
+				colour = p1GreenPhosphorColor
+			} else {
+				colour = color.Black
 			}
 			img.Set(x, y, colour)
 		}
diff --git a/apple2sdl/run.go b/apple2sdl/run.go
index cec4778..be2b841 100644
--- a/apple2sdl/run.go
+++ b/apple2sdl/run.go
@@ -44,7 +44,8 @@ func SDLRun(a *apple2.Apple2) {
 
 		img := apple2.Snapshot(a)
 		if img != nil {
-			surface, err := sdl.CreateRGBSurfaceFrom(unsafe.Pointer(&img.Pix[0]), 40*7, 24*8, 32, 40*7*4,
+			surface, err := sdl.CreateRGBSurfaceFrom(unsafe.Pointer(&img.Pix[0]),
+				int32(img.Bounds().Dx()), int32(img.Bounds().Dy()), 32, 40*7*4,
 				0x0000ff, 0x0000ff00, 0x00ff0000, 0xff000000)
 			// Valid for little endian. Should we reverse for big endian?
 			// 0xff000000, 0x00ff0000, 0x0000ff00, 0x000000ff)