From f0b2369c9d6f59799865056f8d67a145a395ed9c Mon Sep 17 00:00:00 2001
From: Alex Janka <alex@alexjanka.com>
Date: Mon, 6 Feb 2023 19:17:52 +1100
Subject: [PATCH] object rendering + usermode ram

---
 src/main.rs          | 11 +++++-
 src/processor/gpu.rs | 89 +++++++++++++++++++++++++++++++++++++++++++-
 src/processor/mod.rs |  2 +
 3 files changed, 99 insertions(+), 3 deletions(-)

diff --git a/src/main.rs b/src/main.rs
index b7f3d4f..3b0bb0e 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -78,6 +78,7 @@ pub struct Memory {
     ime: bool,
     ime_scheduled: u8,
     io: [u8; 76],
+    user_mode: bool,
 }
 
 impl Memory {
@@ -95,6 +96,7 @@ impl Memory {
             ime: false,
             ime_scheduled: 0x0,
             io: [0xFF; 76],
+            user_mode: false,
         }
     }
 
@@ -171,7 +173,14 @@ impl Memory {
             0xFEA0..0xFF00 => {
                 // println!("empty space write: {:#X} to addr {:#X}", data, address);
             }
-            0xFF00..0xFF4C => {
+            0xFF04 => {
+                if self.user_mode {
+                    self.io[0xFF04 - 0xFF00] = 0;
+                } else {
+                    self.io[0xFF04 - 0xFF00] = data;
+                }
+            }
+            0xFF00..0xFF04 | 0xFF05..0xFF4C => {
                 // verbose_print!("writing to addr {:#X}\r", address);
                 stdout().flush().unwrap();
 
diff --git a/src/processor/gpu.rs b/src/processor/gpu.rs
index ba81f03..a527a41 100644
--- a/src/processor/gpu.rs
+++ b/src/processor/gpu.rs
@@ -14,6 +14,7 @@ enum DrawMode {
     Mode3,
 }
 
+#[derive(Debug)]
 enum TilemapArea {
     T9800,
     T9C00,
@@ -28,6 +29,7 @@ impl TilemapArea {
     }
 }
 
+#[derive(Debug)]
 enum TiledataArea {
     D8000,
     D9000,
@@ -42,12 +44,22 @@ impl TiledataArea {
     }
 }
 
+#[derive(Debug)]
 enum ObjSize {
     S8x8,
     S8x16,
 }
 
-#[allow(dead_code)]
+impl ObjSize {
+    fn get_height(&self) -> u8 {
+        match self {
+            ObjSize::S8x8 => 8,
+            ObjSize::S8x16 => 16,
+        }
+    }
+}
+
+#[derive(Debug)]
 struct LCDC {
     enable: bool,
     window_tilemap: TilemapArea,
@@ -91,6 +103,20 @@ struct Palette {
     three: Colour,
 }
 
+struct ObjectFlags {
+    behind_bg_and_window: bool,
+    y_flip: bool,
+    x_flip: bool,
+    palette: Palette,
+}
+
+struct Object {
+    x: u8,
+    y: u8,
+    tile_index: u8,
+    flags: ObjectFlags,
+}
+
 const TILE_WINDOW_EDGE_LENGTH: usize = 16 * 8;
 const TILE_WINDOW_EDGE_LENGTH_SCALED: usize = TILE_WINDOW_EDGE_LENGTH * FACTOR;
 
@@ -227,6 +253,7 @@ impl CPU {
             self.render_window();
             self.memory.set(0xFF0F, set_bit(self.memory.get(0xFF0F), 0));
         }
+        // println!("lcdc: {:#?}", lcdc);
     }
 
     fn exit_vblank(&mut self) {
@@ -297,7 +324,65 @@ impl CPU {
         }
     }
 
-    fn render_scanline_obj(&mut self, _scanline: u8, _lcdc: &LCDC) {}
+    fn render_scanline_obj(&mut self, scanline: u8, lcdc: &LCDC) {
+        let objs = self.parse_oam(scanline, &lcdc.obj_size);
+        for object in objs {
+            println!("rendering object");
+            self.render_object(scanline, object, &lcdc.obj_size);
+        }
+    }
+
+    fn parse_oam(&mut self, scanline: u8, obj_size: &ObjSize) -> Vec<Object> {
+        let mut objs = vec![];
+        for i in (0xFE00..0xFE9F).step_by(4) {
+            let y_pos = self.memory.get(i).wrapping_sub(16);
+            if y_pos <= scanline && (y_pos + obj_size.get_height()) > scanline {
+                // sprite is on line
+                let x_pos = self.memory.get(i + 1);
+                let tile_index = self.memory.get(i + 2);
+                let flags = self.memory.get(i + 3);
+                let palette_addr = if get_bit(flags, 4) { 0xFF49 } else { 0xFF48 };
+                objs.push(Object {
+                    x: x_pos,
+                    y: y_pos,
+                    tile_index,
+                    flags: ObjectFlags {
+                        behind_bg_and_window: get_bit(flags, 7),
+                        y_flip: get_bit(flags, 6),
+                        x_flip: get_bit(flags, 5),
+                        palette: byte_to_palette(self.memory.get(palette_addr)),
+                    },
+                });
+                if objs.len() >= 10 {
+                    break;
+                }
+            }
+        }
+        objs
+    }
+
+    fn render_object(&mut self, scanline: u8, object: Object, obj_size: &ObjSize) {
+        let mut object_row = scanline - object.y;
+        if object.flags.y_flip {
+            object_row = obj_size.get_height() - object_row;
+        }
+        let tile_row = object_row % 8;
+        let tile_addr = TiledataArea::D8000
+            .get_addr(object.tile_index + if object_row >= 8 { 1 } else { 0 })
+            + (tile_row as u16 * 2);
+        let lsbs = self.memory.get(tile_addr);
+        let msbs = self.memory.get(tile_addr + 1);
+        for px_x in 0..8 {
+            let x_addr = if object.flags.x_flip { px_x } else { 7 - px_x };
+            let lsb = get_bit(lsbs, x_addr);
+            let msb = get_bit(msbs, x_addr);
+            let colour = bits_to_mapped_colour(lsb, msb, object.flags.palette);
+            let x_coord = (object.x as usize * 8) + (px_x as usize);
+            if x_coord < WIDTH {
+                self.gpu.buffer[(scanline as usize * WIDTH) + x_coord] = colour.to_rgb();
+            }
+        }
+    }
 
     fn render_tiles(
         &mut self,
diff --git a/src/processor/mod.rs b/src/processor/mod.rs
index 6bff17f..eed661c 100644
--- a/src/processor/mod.rs
+++ b/src/processor/mod.rs
@@ -66,7 +66,9 @@ impl CPU {
             opcode,
             self.last_instruction_addr
         );
+        self.memory.user_mode = true;
         let cycles = self.run_opcode(opcode);
+        self.memory.user_mode = false;
         self.increment_timers(cycles);
 
         let interrupt_cycles = self.handle_interrupts();