From b0c4b664f2775808c43af4e310ee9e8920960216 Mon Sep 17 00:00:00 2001
From: slederer <dev@insignificance.de>
Date: Sun, 2 Feb 2025 01:13:49 +0100
Subject: [PATCH] tridoraemu: update framebuffer image on palette change

---
 tridoraemu/framebuffer.go | 22 ++++++++++++++++++++++
 tridoraemu/tridoraemu.go  |  1 +
 2 files changed, 23 insertions(+)

diff --git a/tridoraemu/framebuffer.go b/tridoraemu/framebuffer.go
index 4586287..189100a 100644
--- a/tridoraemu/framebuffer.go
+++ b/tridoraemu/framebuffer.go
@@ -32,6 +32,7 @@ type Framebuffer struct {
 	paletteSlot word
 	vmem [VmemWords]word
 	readCount int
+        paletteChanged bool
 }
 
 func (f *Framebuffer) initialize() {
@@ -104,6 +105,26 @@ func (f *Framebuffer) readPalette() word {
 	return word(0)
 }
 
+func (f *Framebuffer) startFrame() {
+	// when the palette changes, we
+	// need to redraw every pixel
+	// to get the new colors
+	if f.paletteChanged {
+		oldRAddr := f.readAddr
+		oldWAddr := f.writeAddr
+		f.readAddr = 0
+		f.writeAddr = 0
+
+		for i := 0; i < VmemWords; i++ {
+			f.writeVmem(f.readVmem())
+		}
+
+		f.readAddr = oldRAddr
+		f.writeAddr = oldWAddr
+		f.paletteChanged = false
+	}
+}
+
 func (f *Framebuffer) writePalette(value word) {
 	// 4 bits per color channel
 	r := uint8((value & 0b111100000000) >> 8)
@@ -116,6 +137,7 @@ func (f *Framebuffer) writePalette(value word) {
 	b = b << 4
 
 	f.palette[f.paletteSlot] = color.RGBA{r,g,b,0}
+	f.paletteChanged = true
 }
 
 func (f *Framebuffer) readCtl() word {
diff --git a/tridoraemu/tridoraemu.go b/tridoraemu/tridoraemu.go
index 875c3c0..88804b4 100644
--- a/tridoraemu/tridoraemu.go
+++ b/tridoraemu/tridoraemu.go
@@ -43,6 +43,7 @@ type Game struct{
 func (g *Game) Update() error {
 	startTime := time.Now()
 
+	framebuffer.startFrame()
 	for i := 0; i < g.stepsPerFrame; i++ {
 		err := cpu.step()
 		if err != nil {