feat: better drawing of line

src/mmu.rs

@@ -111,7 +111,6 @@ impl Mmu {
             }
             // Graphics: VRAM (8k)
             0x8000 | 0x9000 => {
-                println!("WRITING TO VRAM");
                 self.ppu.vram[(addr & 0x1fff) as usize] = value;
                 if addr < 0x9800 {
                     self.ppu.update_tile(addr, value);

src/ppu.rs

@@ -214,16 +214,18 @@ impl Ppu {
         let y = ((self.scy + self.line) & 0x07) as usize;
         let mut x = (self.scx & 0x07) as usize;
 
-        let mut frame_offset = self.line as usize * SCREEN_WIDTH * RGBA_SIZE;
-
+        // calculates the index of the initial tile in drawing,
+        // if the tile data set in use is #1, the indices are
+        // signed, then calculates a real tile offset
         let mut tile_index = self.vram[map_offset + line_offset] as usize;
-
-        // if the tile data set in use is #1, the
-        // indices are signed, calculates a real tile offset
         if self.bg_tile && tile_index < 128 {
             tile_index += 256;
         }
 
+        // calculates the frame buffer offset position assuming the proper
+        // Game Boy screen width and RGBA pixel (4 bytes) size
+        let mut frame_offset = self.line as usize * SCREEN_WIDTH * RGBA_SIZE;
+
         for _index in 0..SCREEN_WIDTH {
             // in case the end of tile width has been reached then
             // a new tile must be retrieved for plotting