From 1690c52bac2a0ea927b8ed11058505374cf9f5ba Mon Sep 17 00:00:00 2001
From: Atreya Bain <atreyabain@gmail.com>
Date: Mon, 4 Mar 2024 09:40:33 +0530
Subject: [PATCH] [ref] Make framebuffer bool array and add missing
 implementation

---
 src/device/device.rs        | 58 ++++++++++++++++++++++---------------
 src/main.rs                 |  6 ++--
 src/sdl_graphics_adapter.rs |  9 +++---
 3 files changed, 43 insertions(+), 30 deletions(-)

diff --git a/src/device/device.rs b/src/device/device.rs
index a664d05..2cd22b3 100644
--- a/src/device/device.rs
+++ b/src/device/device.rs
@@ -13,7 +13,7 @@ pub struct Device {
     pub memory: Box<[u8; Self::DEVICE_MEMORY_SIZE]>,
     pub timer: Timer,
     pub stack: Vec<u16>,
-    pub frame_buffer: Arc<Mutex<Box<[u8;64*32]>>>
+    pub frame_buffer: Arc<Mutex<Box<[bool;64*32]>>>
 }
 
 impl Device {
@@ -21,7 +21,7 @@ impl Device {
     pub const FRAME_BUFFER_WIDTH: usize = 64;
     pub const FRAME_BUFFER_HEIGHT: usize = 32;
     pub const FRAME_BUFFER_SIZE: usize = Self::FRAME_BUFFER_WIDTH*Self::FRAME_BUFFER_HEIGHT;
-    pub fn new(timer: Timer, fb: Arc<Mutex<Box<[u8;64*32]>>>) -> Device {
+    pub fn new(timer: Timer, fb: Arc<Mutex<Box<[bool;Device::FRAME_BUFFER_SIZE]>>>) -> Device {
         let memory = vec![0u8; Self::DEVICE_MEMORY_SIZE].into_boxed_slice().try_into().unwrap();
         log::trace!("Successfully initiated device memory");
         Device {
@@ -66,7 +66,8 @@ impl Device {
 
 
     }
-    pub fn get_framebuffer_index(x:usize,y:usize)->usize{
+    /// convert the 2 indices into one
+    fn get_framebuffer_index(x:usize,y:usize)->usize{
         y*Self::FRAME_BUFFER_WIDTH + x
     }
     pub fn execute_instruction(&mut self, instruction: Instruction) {
@@ -79,7 +80,7 @@ impl Device {
             Instruction::ClearScreen => {
                 let mut frame_buffer = self.frame_buffer.lock().expect("Failed to grab framebuffer for drawing");
                 for pixel in frame_buffer.iter_mut(){
-                    *pixel = 0;
+                    *pixel = false;
                 }
                 log::trace!("ClearScreen")
             }
@@ -97,30 +98,41 @@ impl Device {
                 self.registers.i = value;
             }
             Instruction::Draw(regx,regy, n) => {
-                let mut frame_buffer = self.frame_buffer.lock().expect("Failed to grab framebuffer for drawing");
                 let x = self.registers.v[regx] as usize;
                 let y = self.registers.v[regy] as usize;
-
-                for i in 0..n as usize{
-                    let index = Self::get_framebuffer_index(x,y+i);
-                    let slice_from_memory = self.memory[self.registers.i as usize + i];
-
-                    for bit_index in (0..8).rev() {
-                        // if i'm going to the next line, stop
-                        if Self::get_framebuffer_index(0, y+1)==index {
-                            break;
-                        }
-                        let bit = (slice_from_memory & (1<<bit_index)) >> bit_index;
-
-                        let byte = bit * 0xff;
-                        frame_buffer[index+(7-bit_index)] = frame_buffer[index+(7-bit_index)] ^ (byte);
-                    }
-                }
-                // TODO fix carry bit
-                log::warn!("Draw call incomplete");
+                let toggle_state = self.draw_sprite_at_location(x, y, n);
+                self.set_flag_register(toggle_state);
             }
         };
     }
+    ///
+    /// Draw a sprite at location at (x,y) for n pixels long and 8 pixels wide.
+    /// Returns whether any pixel was toggled
+    fn draw_sprite_at_location(&mut self, x: usize, y: usize, n: u8)-> bool {
+        let mut frame_buffer = self.frame_buffer.lock().expect("Failed to grab framebuffer for drawing");
+
+        let mut is_pixel_toggled_off = false;
+        for i in 0..n as usize {
+            let index = Self::get_framebuffer_index(x, y + i);
+            let slice_from_memory = self.memory[self.registers.i as usize + i];
+
+            for bit_index in (0..8).rev() {
+                // if i'm going to the next line, stop
+                if Self::get_framebuffer_index(0, y + 1) == index {
+                    break;
+                }
+                let bit_is_true = (slice_from_memory & (1 << bit_index)) == (1<<bit_index) ;
+
+                // if the pixel is going to be toggled false, set this flag bit to true
+                if(frame_buffer[index + (7 - bit_index)] && (bit_is_true)) { is_pixel_toggled_off = true;}
+                frame_buffer[index + (7 - bit_index)] = frame_buffer[index + (7 - bit_index)] ^ (bit_is_true);
+            }
+        }
+        is_pixel_toggled_off
+    }
+    fn set_flag_register(&mut self, x:bool){
+        self.registers.v[0xf] = if x {1} else { 0 }
+    }
 
     pub fn set_default_font(&mut self) {
         log::info!("Loaded default font from memory");
diff --git a/src/main.rs b/src/main.rs
index f488327..b3233b0 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -83,7 +83,7 @@ fn main() {
     compute_handle.join().unwrap();
 }
 
-fn do_device_loop(mut timer: Timer, frame_buffer: Arc<Mutex<Box<[u8; 2048]>>>, receiver: Receiver<()>) {
+fn do_device_loop(mut timer: Timer, frame_buffer: Arc<Mutex<Box<[bool; 2048]>>>, receiver: Receiver<()>) {
     let mut device = Device::new(timer, frame_buffer);
     device.set_default_font();
     {
@@ -105,8 +105,8 @@ fn do_device_loop(mut timer: Timer, frame_buffer: Arc<Mutex<Box<[u8; 2048]>>>, r
 }
 
 
-fn get_frame_buffer() -> Arc<Mutex<Box<[u8; 2048]>>> {
-    Arc::new(Mutex::new(vec![0u8; Device::FRAME_BUFFER_SIZE].into_boxed_slice().try_into().unwrap()))
+fn get_frame_buffer() -> Arc<Mutex<Box<[bool; 2048]>>> {
+    Arc::new(Mutex::new(vec![false; Device::FRAME_BUFFER_SIZE].into_boxed_slice().try_into().unwrap()))
 }
 
 const ROM_SIZE: usize = 4096 - 0x200;
diff --git a/src/sdl_graphics_adapter.rs b/src/sdl_graphics_adapter.rs
index 22fe8c1..c62c897 100644
--- a/src/sdl_graphics_adapter.rs
+++ b/src/sdl_graphics_adapter.rs
@@ -17,11 +17,12 @@ impl SdlGraphicsAdapter {
             rgb_frame_buffer
         }
     }
-    pub fn draw_screen(&mut self, frame_buffer: MutexGuard<Box<[u8; Device::FRAME_BUFFER_SIZE]>>, window_canvas: &mut WindowCanvas) {
+    pub fn draw_screen(&mut self, frame_buffer: MutexGuard<Box<[bool; Device::FRAME_BUFFER_SIZE]>>, window_canvas: &mut WindowCanvas) {
         for (i, pixel) in frame_buffer.iter().enumerate() {
-            self.rgb_frame_buffer[3 * i] = *pixel;
-            self.rgb_frame_buffer[3 * i + 1] = *pixel;
-            self.rgb_frame_buffer[3 * i + 2] = *pixel;
+            let col_component = if *pixel { 0xff } else { 0 };
+            self.rgb_frame_buffer[3 * i] = col_component;
+            self.rgb_frame_buffer[3 * i + 1] = col_component;
+            self.rgb_frame_buffer[3 * i + 2] = col_component;
         }
         drop(frame_buffer);