Rendering a basic window with pixels

src/ppu.rs

@@ -3,7 +3,8 @@ use crate::utils::{
     get_bit,
     set_bit,
 };
-use crate::bus::{Bus, BANK_ZERO};
+use crate::bus::{Bus, BANK_ZERO, VIDEO_RAM};
+use rand::Rng;
 
 struct ColorPalette(u8, u8, u8, u8);
 
@@ -42,6 +43,10 @@ pub enum LCDStatus {
     ModeFlag(LCDStatusModeFlag),
 }
 
+pub const WIDTH: u32 = 160;
+pub const HEIGHT: u32 = 144;
+pub const FRAME_BUFFER_LENGTH: u32 = WIDTH * HEIGHT;
+
 const LCD_CONTROL_ADDRESS: u16 = 0xFF40;
 const LCD_STATUS_ADDRESS: u16 = 0xFF41;
 
@@ -82,11 +87,14 @@ impl Window {
 
 pub struct PPU {
     window: Window,
+
+    rgba_frame: [[u8; 4]; FRAME_BUFFER_LENGTH as usize],
 }
 
 impl PPU {
     pub fn new() -> Self {
         Self {
+            rgba_frame: [[0, 0, 0xFF, 0]; FRAME_BUFFER_LENGTH as usize],
             window: Window::new(),
         }
     }
@@ -174,4 +182,51 @@ impl PPU {
         };
         bus.write(LCD_STATUS_ADDRESS, byte);
     }
+
+    fn get_rgba_pixel(two_bit_pixel: u8) -> [u8; 4] {
+        match two_bit_pixel {
+            0x00 => [255, 255, 255, 255],
+            0x01 => [192, 192, 192, 0],
+            0x10 => [128, 128, 128, 0],
+            0x11 => [0, 0, 0, 0],
+            _ => [0, 0, 0, 0],
+        }
+    }
+
+    pub fn draw_background(&mut self, bus: &Bus) {
+        let mut pointer = VIDEO_RAM.begin();
+        let mut pixels_drawn: usize = 0;
+        while pixels_drawn < FRAME_BUFFER_LENGTH as usize {
+            let byte1 = bus.read(pointer);
+            let byte2 = bus.read(pointer + 1);
+            let pixels = PPU::get_byte_pixels(byte1, byte2);
+            self.rgba_frame[pixels_drawn]     = PPU::get_rgba_pixel(pixels[0]);
+            self.rgba_frame[pixels_drawn + 1] = PPU::get_rgba_pixel(pixels[1]);
+            self.rgba_frame[pixels_drawn + 2] = PPU::get_rgba_pixel(pixels[2]);
+            self.rgba_frame[pixels_drawn + 3] = PPU::get_rgba_pixel(pixels[3]);
+            self.rgba_frame[pixels_drawn + 4] = PPU::get_rgba_pixel(pixels[4]);
+            self.rgba_frame[pixels_drawn + 5] = PPU::get_rgba_pixel(pixels[5]);
+            self.rgba_frame[pixels_drawn + 6] = PPU::get_rgba_pixel(pixels[6]);
+            self.rgba_frame[pixels_drawn + 7] = PPU::get_rgba_pixel(pixels[7]);
+            pixels_drawn += 8;
+            pointer += 2;
+        }
+    }
+
+    fn get_byte_pixels(byte1: u8, byte2: u8) -> [u8; 8] {
+        let mut pixels: [u8; 8] = [0; 8];
+        pixels[0] = ((get_bit(byte1, BitIndex::I7) as u8) << 1) | (get_bit(byte2, BitIndex::I7) as u8);
+        pixels[1] = ((get_bit(byte1, BitIndex::I6) as u8) << 1) | (get_bit(byte2, BitIndex::I6) as u8);
+        pixels[2] = ((get_bit(byte1, BitIndex::I5) as u8) << 1) | (get_bit(byte2, BitIndex::I5) as u8);
+        pixels[3] = ((get_bit(byte1, BitIndex::I4) as u8) << 1) | (get_bit(byte2, BitIndex::I4) as u8);
+        pixels[4] = ((get_bit(byte1, BitIndex::I3) as u8) << 1) | (get_bit(byte2, BitIndex::I3) as u8);
+        pixels[5] = ((get_bit(byte1, BitIndex::I2) as u8) << 1) | (get_bit(byte2, BitIndex::I2) as u8);
+        pixels[6] = ((get_bit(byte1, BitIndex::I1) as u8) << 1) | (get_bit(byte2, BitIndex::I1) as u8);
+        pixels[7] = ((get_bit(byte1, BitIndex::I0) as u8) << 1) | (get_bit(byte2, BitIndex::I0) as u8);
+        pixels
+    }
+
+    pub fn get_rgba_frame(&self, bus: &Bus) -> &[[u8; 4]; FRAME_BUFFER_LENGTH as usize] {
+        &self.rgba_frame
+    }
 }