placeholder to compute the current pixel

snes-core/src/ppu/interface.rs

@@ -12,7 +12,7 @@ pub struct PPU {
 impl PPU {
     pub fn new() -> Self {
         Self {
-            framebuffer: vec![0; FRAMEBUFFER_SIZE],
+            framebuffer: vec![0xFF; FRAMEBUFFER_SIZE],
             registers: PPURegisters::new(),
             was_vblank_nmi_set: false,
             is_irq_set: false,
@@ -26,6 +26,9 @@ impl PPU {
     }
 
     pub fn dot_cycle(&mut self) {
+        if !self.registers.is_vblanking() && !self.registers.is_hblanking() {
+            self.put_pixel(self.compute_pixel())
+        }
         self.increment_hv_count();
     }
 
@@ -51,6 +54,29 @@ impl PPU {
     pub fn framebuffer(&self) -> &[u8] {
         &self.framebuffer
     }
+
+    fn compute_pixel(&self) -> (u8, u8, u8) {
+        if self.registers.is_hblanking() || self.registers.is_hblanking() {
+            return (0x00, 0x00, 0x00)
+        }
+        (0xFF, 0x00, 0xFF)
+    }
+
+    fn put_pixel(&mut self, pixel: (u8, u8, u8)) {
+        let fb_index = self.get_pixel_index();
+        self.framebuffer[fb_index]     = pixel.0;
+        self.framebuffer[fb_index + 1] = pixel.1;
+        self.framebuffer[fb_index + 2] = pixel.2;
+    }
+
+    fn get_pixel_index(&self) -> usize {
+        let h_count = self.registers.h_count as usize;
+        let v_count = self.registers.v_count as usize;
+        return (
+            (h_count - 22) +
+            ((v_count - 1) * MAX_TV_WIDTH)
+        ) * 4
+    }
 }
 
 impl Default for PPU {
@@ -81,4 +107,38 @@ mod ppu_general_test {
         assert_eq!(ppu.registers.h_count, 0);
         assert_eq!(ppu.registers.v_count, 0);
     }
-}
+
+    #[test]
+    fn test_get_current_pixel_index() {
+        let mut ppu = PPU::new();
+        ppu.registers.v_count = 1;
+        ppu.registers.h_count = 22;
+        assert_eq!(ppu.get_pixel_index(), 0);
+        ppu.registers.v_count = 1;
+        ppu.registers.h_count = 23;
+        assert_eq!(ppu.get_pixel_index(), 4);
+        ppu.registers.v_count = 1;
+        ppu.registers.h_count = 24;
+        assert_eq!(ppu.get_pixel_index(), 8);
+        ppu.registers.v_count = 2;
+        ppu.registers.h_count = 22;
+        assert_eq!(ppu.get_pixel_index(), 2048);
+        ppu.registers.v_count = 2;
+        ppu.registers.h_count = 23;
+        assert_eq!(ppu.get_pixel_index(), 2052);
+        ppu.registers.v_count = 2;
+        ppu.registers.h_count = 24;
+        assert_eq!(ppu.get_pixel_index(), 2056);
+    }
+
+    #[test]
+    fn test_put_pixel() {
+        let mut ppu = PPU::new();
+        ppu.registers.v_count = 2;
+        ppu.registers.h_count = 22;
+        ppu.put_pixel((11, 22, 33));
+        assert_eq!(ppu.framebuffer[2048], 11);
+        assert_eq!(ppu.framebuffer[2049], 22);
+        assert_eq!(ppu.framebuffer[2050], 33);
+    }
+}

snes-core/src/ppu/registers.rs

@@ -375,10 +375,26 @@ impl PPURegisters {
     }
 
     pub fn is_vblanking(&self) -> bool {
-        if self.v_count >= 1 && self.v_count <= 224 {
+        !(self.v_count >= 1 && self.v_count <= 224)
-            return false
+    }
-        }
+
-        true
+    pub fn is_hblanking(&self) -> bool {
+        !(self.h_count >= 22 && self.h_count <= 277)
+    }
+
+    pub fn get_current_res(&self) -> (u16, u16) {
+        let w = if self.is_true_high_res_mode_enabled() {512} else {256};
+        let h = if self.is_interlace_mode_enabled() {448} else {224};
+        (w, h)
+    }
+
+    pub fn is_interlace_mode_enabled(&self) -> bool {
+        self._read(SETINI) & 0x01 == 0b1
+    }
+
+    pub fn is_true_high_res_mode_enabled(&self) -> bool {
+        let current_bg_mode = self._read(BGMODE);
+        current_bg_mode == 5 || current_bg_mode == 6
     }
 }
 
@@ -590,4 +606,70 @@ mod ppu_registers_test {
         registers.v_count = 50;
         assert!(!registers.is_vblanking());
     }
+
+    #[test]
+    fn test_is_hblanking() {
+        let mut registers = PPURegisters::new();
+        registers.h_count = 0;
+        assert!(registers.is_hblanking());
+        registers.h_count = 20;
+        assert!(registers.is_hblanking());
+        registers.h_count = 21;
+        assert!(registers.is_hblanking());
+        registers.h_count = 278;
+        assert!(registers.is_hblanking());
+        registers.h_count = 300;
+        assert!(registers.is_hblanking());
+        registers.h_count = 22;
+        assert!(!registers.is_hblanking());
+        registers.h_count = 100;
+        assert!(!registers.is_hblanking());
+        registers.h_count = 277;
+        assert!(!registers.is_hblanking());
+    }
+
+    #[test]
+    fn test_is_interlace_mode_enabled() {
+        let mut registers = PPURegisters::new();
+        registers._write(SETINI, 0x01);
+        assert!(registers.is_interlace_mode_enabled());
+        registers._write(SETINI, 0x00);
+        assert!(!registers.is_interlace_mode_enabled());
+    }
+
+    #[test]
+    fn test_is_true_high_res_mode_enabled() {
+        let mut registers = PPURegisters::new();
+        registers._write(BGMODE, 1);
+        assert!(!registers.is_true_high_res_mode_enabled());
+        registers._write(BGMODE, 2);
+        assert!(!registers.is_true_high_res_mode_enabled());
+        registers._write(BGMODE, 3);
+        assert!(!registers.is_true_high_res_mode_enabled());
+        registers._write(BGMODE, 4);
+        assert!(!registers.is_true_high_res_mode_enabled());
+        registers._write(BGMODE, 5);
+        assert!(registers.is_true_high_res_mode_enabled());
+        registers._write(BGMODE, 6);
+        assert!(registers.is_true_high_res_mode_enabled());
+        registers._write(BGMODE, 7);
+        assert!(!registers.is_true_high_res_mode_enabled());
+    }
+
+    #[test]
+    fn test_get_current_res() {
+        let mut registers = PPURegisters::new();
+        registers._write(BGMODE, 1);
+        registers._write(SETINI, 0x00);
+        assert_eq!(registers.get_current_res(), (256, 224));
+        registers._write(BGMODE, 1);
+        registers._write(SETINI, 0x01);
+        assert_eq!(registers.get_current_res(), (256, 448));
+        registers._write(BGMODE, 5);
+        registers._write(SETINI, 0x00);
+        assert_eq!(registers.get_current_res(), (512, 224));
+        registers._write(BGMODE, 6);
+        registers._write(SETINI, 0x01);
+        assert_eq!(registers.get_current_res(), (512, 448));
+    }
 }