some refactoring, fixed bg_color

desktop/src/main.rs

@@ -131,11 +131,13 @@ fn main() {
 
         // render VRAM
 
+        let bg_color = emu.core.mem.vdp.bg_color();
+
         // clear screen
         for pixel in screenbuf.chunks_mut(4) {
-            pixel[0] = cram_rgb[0].0;
-            pixel[1] = cram_rgb[0].1;
-            pixel[2] = cram_rgb[0].2;
+            pixel[0] = bg_color.0;
+            pixel[1] = bg_color.1;
+            pixel[2] = bg_color.2;
         };
 
         for (i, duxels) in emu.core.mem.vdp.VRAM.chunks(32).enumerate() {

emu/src/lib.rs

@@ -34,7 +34,9 @@ impl Megadrive {
     pub fn frame(&mut self) {
         // https://segaretro.org/Sega_Mega_Drive/Technical_specifications#Graphics
 
-        self.core.mem.vdp.status &= !8; // clear vblank
+        self.core.mem.vdp.unset_status(vdp::VBLANK_MASK);
+
+        self.core.mem.vdp.unset_status(128);
 
         let screen_height = self.core.mem.vdp.screen_height();
         let mut hint_counter = self.core.mem.vdp.hint_counter();
@@ -51,16 +53,16 @@ impl Megadrive {
 
             }
 
-            self.core.mem.vdp.status |= 4;
+            self.core.mem.vdp.set_status(vdp::HBLANK_MASK);
             self.core.execute(636);
-            self.core.mem.vdp.status &= !4;
+            self.core.mem.vdp.unset_status(vdp::HBLANK_MASK);
 
             self.core.execute(104);
 
             // render
         }
 
-        self.core.mem.vdp.status |= 4;
+        self.core.mem.vdp.set_status(vdp::VBLANK_MASK);
 
         self.core.execute(588);
 
@@ -70,6 +72,7 @@ impl Megadrive {
 
         if self.core.mem.vdp.registers[1] & 0x20 > 0 {
             self.core.int_ctrl.request_interrupt(6);
+            self.core.mem.vdp.set_status(128);
         }
 
         self.core.execute(3420-788);

emu/src/vdp.rs

@@ -13,6 +13,9 @@ pub struct VDP {
     pub dma_pending: bool,
 }
 
+pub const VBLANK_MASK: u32 = 8;
+pub const HBLANK_MASK: u32 = 4;
+
 pub enum VDPType {
     VRAM, CRAM, VSRAM,
 }
@@ -28,6 +31,14 @@ impl From<u32> for VDPType {
     }
 }
 
+pub fn cram_to_rgb(color: u16) -> (u8, u8, u8) {
+    let red = color & 0xf;
+    let green = (color & 0xf0) >> 4;
+    let blue = (color & 0xf00) >> 8;
+    let dupe = |x| (x << 4) | x;
+    (dupe(red as u8), dupe(green as u8), dupe(blue as u8))
+}
+
 impl VDP {
     pub fn new() -> Self {
         Self {
@@ -45,19 +56,19 @@ impl VDP {
 
     pub fn cram_rgb(&self) -> [(u8, u8, u8); 64] {
         let mut rgb = [(0, 0, 0); 64];
-
-        let dupe = |x| (x << 4) | x;
-
         for (i, color) in self.CRAM.iter().enumerate() {
-            let red = color & 0xf;
-            let green = (color & 0xf0) >> 4;
-            let blue = (color & 0xf00) >> 8;
-            rgb[i] = (dupe(red as u8), dupe(green as u8), dupe(blue as u8));
+            rgb[i] = cram_to_rgb(*color);
         }
-
         rgb
     }
 
+    pub fn bg_color(&self) -> (u8, u8, u8) {
+        let vdp_bg = self.registers[7];
+        let index = vdp_bg & 0xF;
+        let line = (vdp_bg >> 4) & 3;
+        cram_to_rgb(self.CRAM[(index + (line * 0x10)) as usize])
+    }
+
     pub fn screen_width(&self) -> usize {
         if self.registers[12] & 0x01 > 0 { 320 } else { 256 }
     }
@@ -74,6 +85,14 @@ impl VDP {
         self.registers[0x13] as u32 | ((self.registers[0x14] as u32) << 8)
     }
 
+    pub fn set_status(&mut self, mask: u32) {
+        self.status |= mask;
+    }
+
+    pub fn unset_status(&mut self, mask: u32) {
+        self.status &= !mask;
+    }
+
     pub fn read(&self, mut address: u32) -> u32 {
         address &= 0x1F;
 
@@ -84,7 +103,6 @@ impl VDP {
         todo!("vdp read {:X}", address);
     }
 
-
     pub fn write(mem: &mut Mem, mut address: u32, value: u32) {
         address &= 0x1F;
         if address < 0x4 {