Create render mecanism's squeleton

src/peripherals/ppu.rs

@@ -16,8 +16,8 @@ use crate::{
 //--------------------------------------------------------------------------------------------------
 bitflags! {
 	struct PpuCtrl: u8 {
-        const Nl = 0x1 << 0;
-        const Nh = 0x1 << 1;
+		const NL = 0x1 << 0;
+		const NH = 0x1 << 1;
 		const I = 0x1 << 2;
 		const S = 0x1 << 3;
 		const B = 0x1 << 4;
@@ -29,11 +29,11 @@ bitflags! {
 
 bitflags! {
 	struct PpuMask: u8 {
-        const Gr = 0x1 << 0;
-        const m = 0x1 << 1;
+		const GR = 0x1 << 0;
+		const M_ = 0x1 << 1;
 		const M = 0x1 << 2;
-        const b = 0x1 << 3;
-        const s = 0x1 << 4;
+		const B_ = 0x1 << 3;
+		const S_ = 0x1 << 4;
 		const R = 0x1 << 5;
 		const G = 0x1 << 6;
 		const B = 0x1 << 7;
@@ -50,21 +50,29 @@ bitflags! {
 
 #[allow(dead_code)]
 pub struct Ppu<M: Mapper> {
+	//peripherals
 	vbus: Rc<RefCell<M>>,
+
+	//public registers
 	ppu_ctrl: PpuCtrl,
 	ppu_mask: PpuMask,
 	ppu_status: PpuStatus,
+
 	scroll: u8,
 	addr: u8,
 	data: u8,
+
+	//OAM
 	oam_addr: u8,
 	oam_data: u8,
 	oam_dma: u8,
 	oam: Ram<0x100>,
+
 	blanking: bool,
 	line: u16,
 	dot: u16,
 	nmi: bool,
+	odd: bool,
 
 	// outputs
 	screen: Rc<RefCell<DisplayBuffer>>,
@@ -105,6 +113,7 @@ impl<M: Mapper> Ppu<M> {
 				line: 0,
 				dot: 0,
 				nmi: false,
+				odd: false,
 
 				screen,
 				pattern_table,
@@ -122,53 +131,130 @@ impl<M: Mapper> Ppu<M> {
 	pub fn tick(&mut self) {
 		use crate::utils::Pixel;
 
-        self.screen.borrow_mut()
-            .set_pixel(
-                self.dot.into(),
-                self.line.into(),
-                Pixel::rgba(self.data.into(), 0, 0, 255));
-
+//		self.screen.borrow_mut()
+//			.set_pixel(
+//				self.dot.into(),
+//				self.line.into(),
+//				Pixel::rgba(self.data.into(), 0, 0, 255));
+//
 		self.execute();
 	}
 
 	fn execute(&mut self) {
 
 		match self.line {
-            0..=239 => self.render_frame(),
+			0..=239 => self.visible_line(),
 			241 => {
+				//start of vertical blank
+				self.post_render_line();
 				if self.dot == 1 {
-                    self.ppu_status.set(PpuStatus::V, true);
 				}
 			}
 			261 => {
-                if self.dot == 1 {
-                    self.ppu_status.set(PpuStatus::V | PpuStatus::S | PpuStatus::O, false);
-                }
-                self.render_frame();
-
-                //last line, got back to first line
-                self.line = 0;
+				//end of vertical blank
+				self.pre_render_line();
 			}
 			240..=260 => (), //vertical blank
 			_ => panic!("{}: Invalid line number", self.line),
 		}
 
-        self.dot = (self.dot + 1) % 256;
-        if self.dot == 0 {
-            self.line = (self.line + 1) % 240;
-            if self.line == 0 {
-                self.screen.borrow_mut().is_ready = true;
-                self.data = (self.data + 1) % 255;
+		//increment current dot and line
+		self.dot += 1;
+		if self.dot > 340 {
+			self.dot = 0;
+			self.line += 1;
+			if self.line > 261 {
+				self.line = 0;
 			}
 		}
 	}
 
-    fn render_frame(&mut self) {
+	fn visible_line(&mut self) {
+		match self.dot {
+			0 => (), //nothing done on first cycle
 
+			1..=256 | 321..=336 => {
+				//background
+				match self.dot % 8 {
+					0 => (), //render inc hori v, BG msbit
+					2 => (), //load NT
+					4 => (), //load AT
+					6 => (), //BG lsbit
+					_ => (), //idle clock cycle
+				}
+				//OAM
+				match self.dot {
+					1..=64 => (), //secondary OAM clear
+					65..=256 => (), //sprite evalutation for next scanline
+					_ => (), //idle clock cycle
+				}
+			},
+			257 => (), // hori(v) = hori(t)
+
+			//sprites
+			258..=320 => {
+				//sprites
+				match self.dot % 8 {
+					0 => (), //sprite msbit
+					2 => (), //garbage NT
+					4 => (), //garbageAT
+					6 => (), //sprite lsbit
+					_ => (), //idle clock cycle
+				}
+			},
+
+			_ => (), //idle or unused clock cycles
+		}
+	}
+
+	fn pre_render_line(&mut self) {
 		match self.dot {
 			0 => (),
-            33..=40 => (),
-            _ => (),
+
+			//background
+			1 => {
+				//clear vblank, sprite 0, overflow
+				self.ppu_status.set(PpuStatus::V | PpuStatus::S | PpuStatus::O, false);
+			},
+			2..=248 | 321..=336 => match self.dot % 8 {
+				0 => (), //render inc hori v, BG msbit
+				2 => (), //load NT
+				4 => (), //load AT
+				6 => (), //BG lsbit
+				_ => (), //idle clock cycle
+			}
+			257 => (), // hori(v) = hori(t)
+
+			258..=320 => {
+				//sprites
+				match self.dot % 8 {
+					0 => (), //sprite msbit
+					2 => (), //garbage NT
+					4 => (), //garbageAT
+					6 => (), //sprite lsbit
+					_ => (), //idle clock cycle
+				}
+				//miscelaneous
+				match self.dot {
+					280..=304 => (), //vert(v) = vert(t)
+					_ => (), //idle clock cycle
+				}
+			},
+
+			339 => if self.odd { self.dot = 340 }, //skip on clock cycle every 2 frames
+
+			_ => (), //idle or unused clock cycles
 		}
 	}
+
+	fn post_render_line(&mut self) {
+		match self.dot {
+			1 => {
+				self.ppu_status.set(PpuStatus::V, true);
+				self.screen.borrow_mut().is_ready = true; //screen can be displayed
+			},
+			_ => (), //idle or unused clock cycles
+		}
+	}
+
 }