nesemu/ppu/tile_debugger.c

//
// Created by william on 8/13/24.
//

#include "tile_debugger.h"

// Contains the patterns of every hexadecimal digit encoded as pattern data.
// The first dimension of the table represents a row in a tile.
byte hex_pattern_table[5][0x10] = {
        {0b111, 0b001, 0b111, 0b111, 0b101, 0b111, 0b111, 0b111, 0b111, 0b111, 0b010, 0b110, 0b111, 0b110, 0b111, 0b111},
        {0b101, 0b001, 0b001, 0b001, 0b101, 0b100, 0b100, 0b001, 0b101, 0b101, 0b101, 0b101, 0b100, 0b101, 0b100, 0b100},
        {0b101, 0b001, 0b111, 0b111, 0b111, 0b111, 0b111, 0b010, 0b111, 0b111, 0b111, 0b110, 0b100, 0b101, 0b111, 0b110},
        {0b101, 0b001, 0b100, 0b001, 0b001, 0b001, 0b101, 0b010, 0b101, 0b001, 0b101, 0b101, 0b100, 0b101, 0b100, 0b100},
        {0b111, 0b001, 0b111, 0b111, 0b001, 0b111, 0b111, 0b010, 0b111, 0b001, 0b101, 0b110, 0b111, 0b110, 0b111, 0b100},
};

byte tile_debugger_encode_number_as_pattern(byte num, byte tile_fine_y) {
    if (tile_fine_y == 6) {
        return 0x7f;    // On row 6, a full line is drawn to make it easier to separate tiles
    } else if (tile_fine_y == 5 || tile_fine_y == 7) {
        return 0;
    }

    // The first digit of the hex is encoded
    byte remaining = num % 0x10;
    byte encoded = hex_pattern_table[tile_fine_y][remaining];

    if (num > 0xf) {
        // If the number is greater than 0xF, we need a second digit
        // We encode it, then add it 4 pixels to the left of the already encoded digit
        byte tenths = num / 0x10;
        byte tenths_encoded = hex_pattern_table[tile_fine_y][tenths];
        encoded = (tenths_encoded << 4) | encoded;
    }

    return encoded;
}