Reduce noise by wram bank switching

src/display/mod.rs

@@ -334,31 +334,6 @@ impl Display {
         }
     }
 
-    fn get_background_attribute(
-        &self,
-        //tile_index_x: usize,
-        //tile_index_y: usize,
-        vram_offset: usize,
-    ) -> BgMapAttributes {
-        /*
-        let background_map = if self.control & CTRL_BG_TILE_MAP_SELECT != 0 {
-            0x1C00
-        } else {
-            0x1800
-        };
-
-        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])
-    }
-
     pub fn tick(&mut self, ticks: u16) {
         self.status &= 0xFC;
         if self.control & CTRL_LCD_DISPLAY_ENABLE == 0 {
@@ -474,7 +449,6 @@ impl Display {
 
                 // Calculate correct coords
                 let x: u8 = sprite.x.wrapping_sub(8);
-                // Flip sprite, TODO: What does this do in WIDE mode?
                 let y: u8 = sprite.y.wrapping_sub(16);
                 let render_y = self.curline;
 
@@ -482,13 +456,14 @@ impl Display {
                 let wide_mode = self.control & CTRL_BG_SPRITE_SIZE > 0;
                 let actual_h = if wide_mode { 16 } else { 8 };
 
-                if sprite.is_y_flipped() {
-                    eprintln!("Sorry, no y flip support yet, rendering as-is");
-                }
-
                 if y.wrapping_add(actual_h) > render_y && y <= render_y {
                     num_rendered += 1;
-                    let tile_offset_y: usize = render_y as usize - y as usize;
+                    let tile_offset_y = if sprite.is_y_flipped() {
+                        render_y as usize - (y as usize) ^ (actual_h as usize - 1)
+                    } else {
+                        render_y as usize - y as usize
+                    };
+
                     let tile_base_addr: usize = sprite.tile as usize * 16;
 
                     let tile_addr = tile_base_addr + tile_offset_y * 2;
@@ -516,6 +491,10 @@ impl Display {
                             }
                         }
 
+                        if pixel_origin == PixelOrigin::BackgroundPriority {
+                            continue;
+                        }
+
                         let x_maybe_flipped: u8 = if sprite.is_x_flipped() { x_o ^ 7 } else { x_o };
                         b1 = (tile_line_1 & 1 << (7 - x_o)) > 0;
                         b2 = (tile_line_2 & 1 << (7 - x_o)) > 0;
@@ -621,10 +600,9 @@ impl Display {
 
                 // GBC stuff
                 // Get BG map attributes
-                let bg_attribs = self.get_background_attribute(vram_offset);
+                let bg_attribs = BgMapAttributes(self.vram1[vram_offset]);
                 let vram = [&*self.vram0, &*self.vram1][bg_attribs.vram_bank_number()];
 
-                // TODO: Priority
                 let tile_offset_y = if bg_attribs.vertical_flip() {
                     7 ^ tile_offset_y
                 } else {
@@ -656,7 +634,11 @@ impl Display {
                 let c = ((b2 as u8) * 2 + b1 as u8) as usize;
                 // let color = self.background_palette.get_color(c);
                 let color = self.background_palette_cgb[bg_attribs.palette_number()].get_color(c);
-                self.set_pixel(render_x, render_y, color, PixelOrigin::Background(c));
+                if bg_attribs.has_priority() && (self.control & 1) == 1 {
+                    self.set_pixel(render_x, render_y, color, PixelOrigin::BackgroundPriority);
+                } else {
+                    self.set_pixel(render_x, render_y, color, PixelOrigin::Background(c));
+                }
             }
         }
 
@@ -687,11 +669,7 @@ impl Display {
 
                         // Obtain tile ID in this area
                         let tile_id = self.vram0[vram_offset];
-
-                        let bg_attribs = self.get_background_attribute(
-                            //tile_index_x as usize, tile_index_y as usize
-                            vram_offset,
-                        );
+                        let bg_attribs = BgMapAttributes(self.vram1[vram_offset]);
 
                         // Get BG map attributes
                         let vram = if bg_attribs.vram_bank_number() == 0 {
@@ -700,13 +678,12 @@ impl Display {
                             &*self.vram1
                         };
 
-                        // TODO: Priority
-                        let tile_offset_x = if bg_attribs.vertical_flip() {
+                        let tile_offset_x = if bg_attribs.horizontal_flip() {
                             7 ^ tile_offset_x
                         } else {
                             tile_offset_x
                         };
-                        let tile_offset_y = if bg_attribs.horizontal_flip() {
+                        let tile_offset_y = if bg_attribs.vertical_flip() {
                             7 ^ tile_offset_y
                         } else {
                             tile_offset_y

src/display/structs.rs

@@ -11,18 +11,23 @@ impl BgMapAttributes {
     }
 
     pub fn horizontal_flip(&self) -> bool {
-        (self.0 >> 5) != 0
+        ((self.0 >> 5) & 1) == 1
     }
 
     pub fn vertical_flip(&self) -> bool {
-        (self.0 >> 6) != 0
+        ((self.0 >> 6) & 1) == 1
+    }
+
+    pub fn has_priority(&self) -> bool {
+        (self.0 >> 7) != 0
     }
 }
 
-#[derive(Debug, Copy, Clone)]
+#[derive(Copy, Clone, Debug, PartialEq)]
 pub enum PixelOrigin {
     Empty,
     Background(usize),
+    BackgroundPriority,
     Window,
     Sprite,
 }
@@ -36,10 +41,10 @@ pub struct Sprite {
 
 impl Sprite {
     pub fn load(buf: &[u8]) -> Self {
-        assert!(buf.len() > 4);
+        assert!(buf.len() >= 4);
         Self {
-            x: buf[0],
-            y: buf[1],
+            x: buf[1],
+            y: buf[0],
             tile: buf[2],
             flags: buf[3],
         }

src/interconnect.rs

@@ -368,9 +368,8 @@ impl Interconnect {
             }
             0xFF70 => {
                 if self.wram_bank != val {
-                    println!("Switching wram bank to {:02X}", val);
                     if val > 7 {
-                        panic!("R u sure this is correct?");
+                        panic!("Trying to switch to wram bank {} which is non-existing", val);
                     }
                     if val == 0 {
                         self.wram_bank = 1;