fix: small fixes

examples/sdl/src/main.rs

@@ -100,7 +100,13 @@ fn main() {
     //game_boy.load_rom_file("../../res/roms/paradius/cpu/09-op r,r.gb"); // NO FINISH
     //game_boy.load_rom_file("../../res/roms/paradius/cpu/11-op a,(hl).gb"); // NO FINISH
 
+    let mut counter = 0u32;
+
     'main: loop {
+        // increments the counter that will keep track
+        // on the number of visual ticks since beginning
+        counter = counter.wrapping_add(1);
+
         while let Some(event) = graphics.event_pump.poll_event() {
             match event {
                 Event::Quit { .. } => break 'main,

src/cpu.rs

@@ -101,6 +101,13 @@ impl Cpu {
                 self.push_word(pc);
                 self.pc = 0x40;
                 self.mmu.ppu().ack_vblank();
+
+                // in case the CPU is currently halted waiting
+                // for an interrupt, releases it
+                if self.halted {
+                    self.halted = false;
+                }
+
                 return 16;
             }
         }

src/ppu.rs

@@ -77,7 +77,8 @@ pub struct Ppu {
     /// Defines the size in pixels of the object (false=8x8, true=8x16).
     obj_size: bool,
     /// Controls the map that is going to be drawn to screen, the
-    /// offset in VRAM will be adjusted according to this.
+    /// offset in VRAM will be adjusted according to this
+    /// (false=0x9800, true=0x9c000).
     bg_map: bool,
     /// If the background tile set is active meaning that the
     /// negative based indexes are going to be used.