From 1c85827e94cec071215e758d6a39e4c7733031ef Mon Sep 17 00:00:00 2001
From: Theron Spiegl <tspiegl@gmail.com>
Date: Thu, 9 Jan 2020 19:49:31 -0600
Subject: [PATCH] fix graphical glitch, mapper idea

---
 src/main.rs          |  1 -
 src/memory_model.rs  | 34 ++++++++++++++++++++++++++++++++++
 src/ppu/rendering.rs | 15 ++++++++-------
 3 files changed, 42 insertions(+), 8 deletions(-)
 create mode 100644 src/memory_model.rs

diff --git a/src/main.rs b/src/main.rs
index bc072b7..d99c7f2 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -114,7 +114,6 @@ fn main() -> Result<(), String> {
 
             println!("samples per second: {}", sps);
             sps = 0;
-
         }
     }
     // PROFILER.lock().unwrap().stop().unwrap();
diff --git a/src/memory_model.rs b/src/memory_model.rs
new file mode 100644
index 0000000..ca54bd0
--- /dev/null
+++ b/src/memory_model.rs
@@ -0,0 +1,34 @@
+use std::rc::Rc;
+use std::cell::RefCell;
+
+fn main() {
+    let mapper = Rc::new(RefCell::new(Mmc1{a:32}));
+    
+    let ppu = Ppu{mapper: mapper.clone()};
+    let cpu = Cpu{mapper: mapper.clone()};
+    println!("{}", cpu.mapper.borrow_mut().doit());
+    println!("{}", ppu.mapper.borrow_mut().doit());
+}
+
+struct Mmc1 {
+    a: u8,
+}
+
+trait Mapper {
+    fn doit(&mut self) -> u8;
+}
+
+impl Mapper for Mmc1 {
+    fn doit(&mut self) -> u8 {
+        self.a += 1;
+        self.a
+    }
+}
+
+struct Ppu {
+    mapper: Rc<RefCell<dyn Mapper>>,
+}
+
+struct Cpu {
+    mapper: Rc<RefCell<dyn Mapper>>,
+}
diff --git a/src/ppu/rendering.rs b/src/ppu/rendering.rs
index 1774ba0..9824083 100644
--- a/src/ppu/rendering.rs
+++ b/src/ppu/rendering.rs
@@ -142,12 +142,6 @@ impl super::Ppu {
             let mut low_bit  = 0;
             let mut high_bit = 0;
             let mut secondary_index = 0;
-            // Every cycle, the 8 x-position counters for the sprites are decremented by one.
-            for i in 0..self.num_sprites {
-                if self.sprite_counters[i] > 0 {
-                    self.sprite_counters[i] -= 1;
-                }
-            }
             for i in 0..self.num_sprites {
                 // If the counter is zero, the sprite becomes "active", and the respective pair of shift registers for the sprite is shifted once every cycle.
                 // This output accompanies the data in the sprite's latch, to form a pixel.
@@ -169,6 +163,12 @@ impl super::Ppu {
                     self.sprite_pattern_table_srs[i].1 <<= 1;
                 }
             }
+            // Every cycle, the 8 x-position counters for the sprites are decremented by one.
+            for i in 0..self.num_sprites {
+                if self.sprite_counters[i] > 0 {
+                    self.sprite_counters[i] -= 1;
+                }
+            }
             ((high_bit << 1) | low_bit, secondary_index)
         } else {
             (0, 0)
@@ -193,6 +193,7 @@ impl super::Ppu {
             }
         }
         self.num_sprites = sprite_count;
+
     }
 
     pub fn fetch_sprites(&mut self) {
@@ -201,7 +202,7 @@ impl super::Ppu {
             let sprite_y_position = self.secondary_oam[(4*i)+0] as usize; // byte 0 of sprite, sprite's vertical position on screen
             let sprite_tile_index = self.secondary_oam[(4*i)+1] as usize; // byte 1 of sprite, sprite's location within pattern table
             let sprite_attributes = self.secondary_oam[(4*i)+2];          // byte 2 of sprite, sprite's palette, priority, and flip attributes
-            let sprite_x_position = self.secondary_oam[(4*i)+3] + 1;      // byte 3 of sprite, sprite's horizontal position on screen
+            let sprite_x_position = self.secondary_oam[(4*i)+3];          // byte 3 of sprite, sprite's horizontal position on screen
             // For 8x8 sprites, this is the tile number of this sprite within the pattern table selected in bit 3 of PPUCTRL ($2000).
             if self.sprite_size == 8 {
                 address = self.sprite_pattern_table_base;