feat: Implement MVP of Mode 0 Sprites
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parent
d54e593276
commit
17455e40d1
240
src/ppu.zig
240
src/ppu.zig
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@ -8,6 +8,7 @@ const Bit = @import("bitfield").Bit;
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const Bitfield = @import("bitfield").Bitfield;
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const Allocator = std.mem.Allocator;
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const log = std.log.scoped(.PPU);
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pub const width = 240;
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pub const height = 160;
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@ -31,6 +32,7 @@ pub const Ppu = struct {
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framebuf: []u8,
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alloc: Allocator,
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scanline_sprites: [128]?Sprite,
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scanline_buf: [width]?u16,
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pub fn init(alloc: Allocator, sched: *Scheduler) !Self {
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@ -55,6 +57,7 @@ pub const Ppu = struct {
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.vcount = .{ .raw = 0x0000 },
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.scanline_buf = [_]?u16{null} ** width,
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.scanline_sprites = [_]?Sprite{null} ** 128,
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};
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}
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@ -74,6 +77,139 @@ pub const Ppu = struct {
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self.bg[n + 1].cnt.raw = @truncate(u16, word >> 16);
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}
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/// Search OAM for Sprites that might be rendered on this scanline
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fn fetchSprites(self: *Self) void {
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const y = self.vcount.scanline.read();
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var i: usize = 0;
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search: while (i < self.oam.buf.len) : (i += 8) {
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// Attributes in OAM are 6 bytes long, with 2 bytes of padding
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// Grab Attributes from OAM
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const attr0 = @bitCast(Attr0, self.oam.get16(i));
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const attr1 = @bitCast(Attr1, self.oam.get16(i + 2));
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const attr2 = @bitCast(Attr2, self.oam.get16(i + 4));
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const sprite = Sprite.init(attr0, attr1, attr2);
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// Only consider enabled sprites
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if (sprite.isDisabled()) continue;
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// Determine sprite bounds
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// We only care about the Y axis since that value remains constant
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const sy = sprite.y();
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const sy_end = sy + sprite.height;
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if ((sy <= y and sy_end > y) or (sy_end < sy and y < sy_end)) {
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for (self.scanline_sprites) |*maybe_sprite| {
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if (maybe_sprite.* == null) {
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maybe_sprite.* = sprite;
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continue :search;
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}
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}
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log.err("Found more than 128 sprites in OAM Search", .{});
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unreachable;
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}
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}
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}
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fn drawSprite(self: *Self, prio: u2) void {
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// Object VRAM 3rd and 4th (0-indexed) charblocks
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const char_base = 0x4000 * 4;
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const scanline = self.vcount.scanline.read();
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var i: u32 = 0;
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while (i < width) : (i += 1) {
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// Exit early if a pixel is already here
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if (self.scanline_buf[i] != null) continue;
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const x = i;
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const y = scanline;
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// Find Relevant Tile
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var maybe_sprite: ?Sprite = null;
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for (self.scanline_sprites) |sprite_opt| {
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if (sprite_opt) |sprite| {
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if (sprite.priority() != prio) continue;
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const sx = sprite.x();
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const sx_end = sx + sprite.width;
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if (sx <= x and sx_end > x) {
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maybe_sprite = sprite;
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break;
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}
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} else break;
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}
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// // TODO: Scanning OAM for every single pixel is insanely expensive
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// // This should be done once per scanline (and then check for X bounds every pixel)
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// var j: u32 = 0;
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// while (j < self.oam.buf.len) : (j += 8) {
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// // Attributes in OAM are 6 bytes long, with 2 bytes of padding
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// // Grab Attributes from OAM
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// const attr0 = @bitCast(Attr0, self.oam.get16(j));
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// const attr1 = @bitCast(Attr1, self.oam.get16(j + 2));
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// const attr2 = @bitCast(Attr2, self.oam.get16(j + 4));
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// // Only consider enabled sprites on the current priority
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// if (attr0.disabled.read() or attr2.rel_prio.read() != prio) continue;
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// // Determine sprite bounds
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// const d = spriteDimensions(attr0.shape.read(), attr1.size.read());
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// const sy = attr0.y.read();
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// const sx = attr1.x.read();
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// const sx_end = sx + d[0];
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// const sy_end = sy + d[1];
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// // If sprite is in range
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// if (sy < y and sy_end > y and sx < x and sx_end > x) {
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// maybe_sprite = Sprite.init(attr0, attr1, attr2);
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// break;
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// }
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// }
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// If we didn't find a sprite, progress to the next pixel
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const sprite: Sprite = if (maybe_sprite) |s| s else continue;
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const is_8bpp = sprite.is_8bpp();
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// Y and X coordinates within the context of a singular 8x8 tile
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const tile_y = y - sprite.y();
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const tile_x = x - sprite.x();
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const tile_id: u32 = sprite.tile_id();
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const tile_row_offset: u32 = if (is_8bpp) 8 else 4;
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const tile_len: u32 = if (is_8bpp) 0x40 else 0x20;
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const row = if (sprite.v_flip()) 7 - (tile_y % 8) else tile_y % 8;
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const col = if (sprite.h_flip()) 7 - (tile_x % 8) else tile_x % 8;
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const tile_base: u32 = char_base + (0x20 * tile_id) + (tile_row_offset * row) + if (is_8bpp) col else col / 2;
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var tile_offset = (tile_x >> 3) * tile_len;
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if (self.dispcnt.obj_mapping.read()) {
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// One Dimensional
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tile_offset += (tile_y / 8) * tile_len * (sprite.width >> 3);
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} else {
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// Two Dimensional
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tile_offset += (@as(u32, tile_y) >> 3) * tile_len * 0x20;
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}
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const tile = self.vram.buf[tile_base + tile_offset];
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const pal_id = if (!is_8bpp) blk: {
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const nybble_tile = if (col & 1 == 1) tile >> 4 else tile & 0xF;
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if (nybble_tile == 0) break :blk 0;
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const pal_bank: u16 = @as(u8, sprite.pal_bank()) << 4;
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break :blk pal_bank | nybble_tile;
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} else tile;
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// Sprite Palette starts at 0x0500_0200
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if (pal_id != 0) self.scanline_buf[i] = self.palette.get16(0x200 + pal_id * 2);
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}
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}
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fn drawBackround(self: *Self, comptime n: u3) void {
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// A Tile in a charblock is a byte, while a Screen Entry is a halfword
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const charblock_len: u32 = 0x4000;
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@ -139,15 +275,19 @@ pub const Ppu = struct {
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pub fn drawScanline(self: *Self) void {
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const bg_mode = self.dispcnt.bg_mode.read();
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const bg_enable = self.dispcnt.bg_enable.read();
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const obj_enable = self.dispcnt.obj_enable.read();
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const scanline = self.vcount.scanline.read();
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switch (bg_mode) {
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0x0 => {
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const start = framebuf_pitch * @as(usize, scanline);
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self.fetchSprites();
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var i: usize = 0;
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while (i < 4) : (i += 1) {
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// Draw Sprites Here
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if (obj_enable) self.drawSprite(@truncate(u2, i));
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if (i == self.bg[0].cnt.priority.read() and bg_enable & 1 == 1) self.drawBackround(0);
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if (i == self.bg[1].cnt.priority.read() and bg_enable >> 1 & 1 == 1) self.drawBackround(1);
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if (i == self.bg[2].cnt.priority.read() and bg_enable >> 2 & 1 == 1) self.drawBackround(2);
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@ -165,6 +305,8 @@ pub const Ppu = struct {
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// Reset Scanline Buffer
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std.mem.set(?u16, &self.scanline_buf, null);
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// Reset List of Sprites
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std.mem.set(?Sprite, &self.scanline_sprites, null);
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},
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0x3 => {
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const start = framebuf_pitch * @as(usize, scanline);
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@ -377,6 +519,73 @@ const ScreenEntry = extern union {
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raw: u16,
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};
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const Sprite = struct {
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const Self = @This();
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attr0: Attr0,
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attr1: Attr1,
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attr2: Attr2,
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width: u16,
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height: u16,
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fn init(attr0: Attr0, attr1: Attr1, attr2: Attr2) Self {
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const d = spriteDimensions(attr0.shape.read(), attr1.size.read());
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return .{
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.attr0 = attr0,
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.attr1 = attr1,
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.attr2 = attr2,
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.width = d[0],
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.height = d[1],
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};
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}
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fn x(self: *const Self) u16 {
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return self.attr1.x.read();
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}
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fn y(self: *const Self) u8 {
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return self.attr0.y.read();
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}
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fn is_8bpp(self: *const Self) bool {
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return self.attr0.is_8bpp.read();
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}
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fn shape(self: *const Self) u2 {
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return self.attr0.shape.read();
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}
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fn size(self: *const Self) u2 {
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return self.attr1.size.read();
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}
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fn tile_id(self: *const Self) u10 {
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return self.attr2.tile_id.read();
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}
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fn pal_bank(self: *const Self) u4 {
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return self.attr2.pal_bank.read();
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}
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fn h_flip(self: *const Self) bool {
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return self.attr1.h_flip.read();
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}
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fn v_flip(self: *const Self) bool {
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return self.attr1.v_flip.read();
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}
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fn priority(self: *const Self) u2 {
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return self.attr2.rel_prio.read();
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}
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fn isDisabled(self: *const Self) bool {
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return self.attr0.disabled.read();
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}
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};
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const Attr0 = extern union {
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y: Bitfield(u16, 0, 8),
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rot_scaling: Bit(u16, 8), // This SBZ
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@ -384,7 +593,7 @@ const Attr0 = extern union {
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mode: Bitfield(u16, 10, 2),
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mosaic: Bit(u16, 12),
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is_8bpp: Bit(u16, 13),
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shape: Bit(u16, 14, 2),
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shape: Bitfield(u16, 14, 2),
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raw: u16,
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};
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@ -399,5 +608,32 @@ const Attr1 = extern union {
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const Attr2 = extern union {
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tile_id: Bitfield(u16, 0, 10),
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rel_prio: Bitfield(u16, 10, 2),
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pal_id: Bitfield(u16, 12, 3),
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pal_bank: Bitfield(u16, 12, 4),
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};
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fn spriteDimensions(shape: u2, size: u2) [2]u16 {
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@setRuntimeSafety(false);
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return switch (shape) {
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0b00 => switch (size) {
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// Square
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0b00 => [_]u16{ 8, 8 },
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0b01 => [_]u16{ 16, 16 },
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0b10 => [_]u16{ 32, 32 },
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0b11 => [_]u16{ 64, 64 },
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},
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0b01 => switch (size) {
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0b00 => [_]u16{ 16, 8 },
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0b01 => [_]u16{ 32, 8 },
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0b10 => [_]u16{ 32, 16 },
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0b11 => [_]u16{ 64, 32 },
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},
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0b10 => switch (size) {
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0b00 => [_]u16{ 8, 16 },
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0b01 => [_]u16{ 8, 32 },
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0b10 => [_]u16{ 16, 32 },
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0b11 => [_]u16{ 32, 64 },
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},
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else => std.debug.panic("{} is an invalid sprite shape", .{shape}),
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};
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}
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