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// Rendering alignment tests for background and sprite rendering
#[cfg(test)]
mod tests {
use crate::console::{Nes, TimingMode};
use crate::ppu::ppu::Ppu;
use crate::ppu::test_utils::InesRomBuilder;
use std::cell::RefCell;
use std::rc::Rc;
#[test]
fn test_background_rendering_alignment() {
let mut ppu = Ppu::new_for_testing(TimingMode::Ntsc);
// Create CHR ROM with known tiles
let mut chr_rom = vec![0u8; 0x2000];
// Tile 0 (at $0000): Empty tile (all transparent)
// Pattern low and high bytes are all 0
// Tile 1 (at $0010): Solid tile with pattern value 3 (color 3 in palette)
// Each byte represents one row of 8 pixels
// Pattern low = 0xFF (all bits set)
// Pattern high = 0xFF (all bits set)
// This gives pattern value 3 (both bits set) for all pixels
for row in 0..8 {
chr_rom[0x10 + row] = 0xFF; // Pattern low
chr_rom[0x18 + row] = 0xFF; // Pattern high
}
// Tile 2 (at $0020): Tile with pattern value 1 (only low bit set)
for row in 0..8 {
chr_rom[0x20 + row] = 0xFF; // Pattern low
chr_rom[0x28 + row] = 0x00; // Pattern high
}
// Tile 3 (at $0030): Tile with pattern value 2 (only high bit set)
for row in 0..8 {
chr_rom[0x30 + row] = 0x00; // Pattern low
chr_rom[0x38 + row] = 0xFF; // Pattern high
}
// Build ROM using the builder
let cartridge = InesRomBuilder::new()
.prg_rom_size(2) // 2 * 16KB = 32KB
.chr_rom_size(1) // 1 * 8KB
.chr_rom_data(chr_rom)
.build_cartridge();
ppu.set_cartridge(Rc::new(RefCell::new(cartridge)));
// Set up palette - use distinct colors for each palette entry
// Palette 0 will be: backdrop (black), red, green, blue
ppu.write_address(0x3F, false);
ppu.write_address(0x00, false);
ppu.write_data(0x0F); // Universal backdrop (black)
ppu.write_address(0x3F, false);
ppu.write_address(0x01, false);
ppu.write_data(0x16); // Palette 0, color 1 (red)
ppu.write_address(0x3F, false);
ppu.write_address(0x02, false);
ppu.write_data(0x2A); // Palette 0, color 2 (green)
ppu.write_address(0x3F, false);
ppu.write_address(0x03, false);
ppu.write_data(0x12); // Palette 0, color 3 (blue)
// Set up nametable - create a known pattern
// Place tile 1 (solid, pattern 3) at position (0,0) - top-left corner
ppu.write_address(0x20, false);
ppu.write_address(0x00, false);
ppu.write_data(1); // Tile 1 at (0,0)
// Place tile 2 (pattern 1) at position (1,0) - second tile in first row
ppu.write_data(2); // Tile 2 at (1,0)
// Place tile 3 (pattern 2) at position (2,0) - third tile in first row
ppu.write_data(3); // Tile 3 at (2,0)
// Fill rest of first row with tile 0 (empty/transparent)
for _ in 3..32 {
ppu.write_data(0); // Empty tiles
}
// Set up attribute table - palette 0 for all tiles
ppu.write_address(0x23, false);
ppu.write_address(0xC0, false);
for _ in 0..64 {
ppu.write_data(0x00); // Palette 0 for all
}
// Set scroll position to 0,0
// This ensures t register is properly initialized
ppu.write_scroll(0, false); // X scroll = 0
ppu.write_scroll(0, false); // Y scroll = 0
// Enable rendering
ppu.write_control(0b0000_0000); // BG pattern table at $0000, no NMI, nametable $2000
ppu.write_mask(0b0000_1010); // Enable background rendering, no clipping
// Run PPU to render two complete frames
// NTSC: 262 scanlines * 341 dots/scanline
// First frame: renders with empty shift registers (will show offset)
// Second frame: pre-render scanline 261 of first frame loads shift registers,
// so second frame renders correctly with tiles at positions 0-7, 8-15, etc.
ppu.run_ppu_cycles(2 * 262 * 341);
// Debug: Check if palette was actually written
// Use direct memory access to check
ppu.write_address(0x3F, false);
ppu.write_address(0x03, false);
let _pal3 = ppu.read_data();
// Now check the screen buffer for expected colors
let screen_buffer = ppu.screen_buffer();
// Get the system palette colors for our palette entries
let (red_r, red_g, red_b) = Nes::lookup_system_palette(0x16);
let (green_r, green_g, green_b) = Nes::lookup_system_palette(0x2A);
let (blue_r, blue_g, blue_b) = Nes::lookup_system_palette(0x12);
let (black_r, black_g, black_b) = Nes::lookup_system_palette(0x0F);
// Verify all pixels in the topmost 16 rows
// After running two complete frames, the pre-render scanline has properly loaded
// the shift registers, so tiles should appear at their correct pixel positions
for row in 0..16 {
for x in 0..256 {
let (r, g, b) = screen_buffer.get_pixel(x, row);
let expected_color = match row {
0..=7 => {
// First tile row - should show tiles at their correct positions:
// Nametable position 0: tile 1 (blue) at pixels 0-7
// Nametable position 1: tile 2 (red) at pixels 8-15
// Nametable position 2: tile 3 (green) at pixels 16-23
// Rest: tile 0 (black/empty)
if x <= 7 {
(blue_r, blue_g, blue_b) // Tile 1 from nametable position 0
} else if (8..=15).contains(&x) {
(red_r, red_g, red_b) // Tile 2 from nametable position 1
} else if (16..=23).contains(&x) {
(green_r, green_g, green_b) // Tile 3 from nametable position 2
} else {
(black_r, black_g, black_b) // Empty tiles (positions 3+)
}
}
_ => (black_r, black_g, black_b), // Second tile row (nametable row 1), all empty
};
assert_eq!(
(r, g, b),
expected_color,
"Pixel ({}, {}) has wrong color",
x,
row
);
}
}
}
#[test]
fn test_sprite_rendering_alignment() {
let mut ppu = Ppu::new_for_testing(TimingMode::Ntsc);
// Create CHR ROM with known sprite tiles
let mut chr_rom = vec![0u8; 0x2000];
// Tile 0 (at $0000): Empty tile (all transparent)
// Pattern low and high bytes are all 0
// Tile 1 (at $0010): Solid tile with pattern value 3 (color 3 in palette)
for row in 0..8 {
chr_rom[0x10 + row] = 0xFF; // Pattern low
chr_rom[0x18 + row] = 0xFF; // Pattern high
}
// Tile 2 (at $0020): Tile with pattern value 1 (only low bit set)
for row in 0..8 {
chr_rom[0x20 + row] = 0xFF; // Pattern low
chr_rom[0x28 + row] = 0x00; // Pattern high
}
// Tile 3 (at $0030): Tile with pattern value 2 (only high bit set)
for row in 0..8 {
chr_rom[0x30 + row] = 0x00; // Pattern low
chr_rom[0x38 + row] = 0xFF; // Pattern high
}
// Build ROM using the builder
let cartridge = InesRomBuilder::new()
.prg_rom_size(2) // 2 * 16KB = 32KB
.chr_rom_size(1) // 1 * 8KB
.chr_rom_data(chr_rom)
.build_cartridge();
ppu.set_cartridge(Rc::new(RefCell::new(cartridge)));
// Set up sprite palette - use distinct colors
// Palette 0 will be: backdrop (black), yellow, cyan, magenta
ppu.write_address(0x3F, false);
ppu.write_address(0x00, false);
ppu.write_data(0x0F); // Universal backdrop (black)
ppu.write_address(0x3F, false);
ppu.write_address(0x11, false);
ppu.write_data(0x28); // Sprite palette 0, color 1 (yellow)
ppu.write_address(0x3F, false);
ppu.write_address(0x12, false);
ppu.write_data(0x2C); // Sprite palette 0, color 2 (cyan)
ppu.write_address(0x3F, false);
ppu.write_address(0x13, false);
ppu.write_data(0x14); // Sprite palette 0, color 3 (magenta)
// Set up sprites in OAM
// Sprite 0: tile 1 (pattern 3 = magenta) at position (16, 16)
ppu.write_oam_address(0x00);
ppu.write_oam_data(16); // Y position
ppu.write_oam_data(1); // Tile index 1
ppu.write_oam_data(0x00); // Attributes: palette 0, no flip
ppu.write_oam_data(16); // X position
// Sprite 1: tile 2 (pattern 1 = yellow) at position (32, 16)
ppu.write_oam_data(16); // Y position
ppu.write_oam_data(2); // Tile index 2
ppu.write_oam_data(0x00); // Attributes: palette 0, no flip
ppu.write_oam_data(32); // X position
// Sprite 2: tile 3 (pattern 2 = cyan) at position (48, 16)
ppu.write_oam_data(16); // Y position
ppu.write_oam_data(3); // Tile index 3
ppu.write_oam_data(0x00); // Attributes: palette 0, no flip
ppu.write_oam_data(48); // X position
// Fill rest of OAM with off-screen sprites (Y = 0xFF)
for _ in 3..64 {
ppu.write_oam_data(0xFF); // Y position (off-screen)
ppu.write_oam_data(0); // Tile index
ppu.write_oam_data(0); // Attributes
ppu.write_oam_data(0); // X position
}
// Set scroll position to 0,0
ppu.write_scroll(0, false);
ppu.write_scroll(0, false);
// Enable rendering - sprites only, use sprite pattern table at $0000
ppu.write_control(0b0000_0000); // Sprite pattern table at $0000, no NMI
ppu.write_mask(0b0001_0100); // Enable sprite rendering, no clipping
// Run PPU to render two complete frames
ppu.run_ppu_cycles(2 * 262 * 341);
let screen_buffer = ppu.screen_buffer();
// Get the system palette colors for our sprite palette entries
let (yellow_r, yellow_g, yellow_b) = Nes::lookup_system_palette(0x28);
let (cyan_r, cyan_g, cyan_b) = Nes::lookup_system_palette(0x2C);
let (magenta_r, magenta_g, magenta_b) = Nes::lookup_system_palette(0x14);
let (black_r, black_g, black_b) = Nes::lookup_system_palette(0x0F);
// Verify sprite rendering according to NES hardware specification:
// - X coordinate: Direct mapping, screen_x = OAM.X (no offset)
// - Y coordinate: +1 offset, screen_y = OAM.Y + 1
//
// Sprites with Y=N are rendered on scanlines N+1 to N+8
//
// Expected correct behavior:
// Sprite 0 (magenta) at OAM (X=16, Y=16) should render at pixels (16-23, 17-24)
// Sprite 1 (yellow) at OAM (X=32, Y=16) should render at pixels (32-39, 17-24)
// Sprite 2 (cyan) at OAM (X=48, Y=16) should render at pixels (48-55, 17-24)
for y in 0..240 {
for x in 0..256 {
let (r, g, b) = screen_buffer.get_pixel(x, y);
let expected_color = if (17..=24).contains(&y) {
// Scanlines where sprites are visible (Y position 16 + 1, for 8 rows)
// Using CORRECT X coordinates per hardware specification
if (16..=23).contains(&x) {
(magenta_r, magenta_g, magenta_b) // Sprite 0 (correct position)
} else if (32..=39).contains(&x) {
(yellow_r, yellow_g, yellow_b) // Sprite 1 (correct position)
} else if (48..=55).contains(&x) {
(cyan_r, cyan_g, cyan_b) // Sprite 2 (correct position)
} else {
(black_r, black_g, black_b) // Backdrop
}
} else {
(black_r, black_g, black_b) // Backdrop
};
assert_eq!(
(r, g, b),
expected_color,
"Sprite pixel ({}, {}) has wrong color",
x,
y
);
}
}
}
}