From 261fa4d78af0629de38ab8863bf8d3080aea3951 Mon Sep 17 00:00:00 2001
From: Kevin Hamacher <kevin.hamacher@ruhr-uni-bochum.de>
Date: Tue, 18 Feb 2020 14:35:11 +0100
Subject: [PATCH] GBC: Fix vram selection

---
 src/display.rs | 22 ++++++++++++++--------
 1 file changed, 14 insertions(+), 8 deletions(-)

diff --git a/src/display.rs b/src/display.rs
index a589085..2d94b86 100644
--- a/src/display.rs
+++ b/src/display.rs
@@ -64,6 +64,9 @@ const MONOCHROME_PALETTE: &'static [[u8; 3]; 4] = &[
 struct CgbPalette([u8; 8]);
 impl CgbPalette {
     fn get_color(&self, n: usize) -> sdl2::pixels::Color {
+        if n == 0 {
+            return sdl2::pixels::Color::RGB(255, 255, 255);
+        }
         let v = ((self.0[2 * n + 1] as u16) << 8) | (self.0[2 * n] as u16);
         let r = (v & 0b1_1111) as u8;
         let g = ((v >> 5) & 0b1_1111) as u8;
@@ -333,7 +336,7 @@ impl Display {
     pub fn write_byte(&mut self, addr: u16, val: u8) {
         match addr {
             0x8000..=0x9FFF => {
-                if self.vram_bank == 0 {
+                if (self.vram_bank & 1) == 0 {
                     self.vram0[(addr - 0x8000) as usize] = val
                 } else {
                     self.vram1[(addr - 0x8000) as usize] = val
@@ -392,7 +395,7 @@ impl Display {
     pub fn read_byte(&self, addr: u16) -> u8 {
         match addr {
             0x8000..=0x9FFF => {
-                if self.vram_bank == 0 {
+                if (self.vram_bank & 1) == 0 {
                     self.vram0[(addr - 0x8000) as usize]
                 } else {
                     self.vram1[(addr - 0x8000) as usize]
@@ -431,6 +434,8 @@ impl Display {
         let vram_offset: usize =
             background_map + ((tile_index_y as usize) * 32) + tile_index_x as usize;
             */
+        // Background attributes are only in this memory range.
+        assert!(vram_offset >= 0x1800 && vram_offset < 0x2000, format!("offset: {:04X}", vram_offset));
 
         BgMapAttributes(self.vram1[vram_offset])
     }
@@ -669,6 +674,11 @@ impl Display {
         }
     }
 
+    pub fn dump_vram(&self) {
+        std::fs::File::create("vram0.dat").unwrap().write_all(&self.vram0);
+        std::fs::File::create("vram1.dat").unwrap().write_all(&self.vram1);
+    }
+
     #[inline]
     fn renderscan(&mut self) {
         // Points to the background map offset to use.
@@ -738,13 +748,9 @@ impl Display {
                 let tile_id = self.vram0[vram_offset];
 
                 // GBC stuff
-                let bg_attribs = self.get_background_attribute(vram_offset);
                 // Get BG map attributes
-                let vram = if bg_attribs.vram_bank_number() == 0 {
-                    &*self.vram0
-                } else {
-                    &*self.vram1
-                };
+                let bg_attribs = self.get_background_attribute(vram_offset);
+                let vram = [&*self.vram0, &*self.vram1][bg_attribs.vram_bank_number()];
 
                 // TODO: Priority
                 let tile_offset_y = if bg_attribs.vertical_flip() {