path: root/src/renderer_m4.c

#include "renderer.h"
#include "text.h"

//
// Parameters.
//

#define SUBPIXEL_LINES 0
#define DEC_BIG_LUT 1

// Front/back buffers for double buffering.
#define BUF_0 ((u32*)(MEM_VRAM))
#define BUF_1 ((u32*)(MEM_VRAM ^ 0x0A000))

// Pointer to the backbuffer.
static u16 *backbuf = BUF_1;

// Boundchecks can be disable at compile time but this will not always improve
// the performance and can in fact make it worse. It is possible that this is
// due to some aliasing optimiztions but not sure at this moment.
#ifdef DISABLE_BOUNDCHECK_SCREEN
#define BOUNDCHECK_SCREEN(X,Y)
#else
#define BOUNDCHECK_SCREEN(X,Y) if ((X) >= SCREEN_WIDTH || (Y) >= SCREEN_HEIGHT) return;
#endif

// Swap A and B values without a tmp variable.
#define SWAP(A, B) (((A) ^= (B)), ((B) ^= (A)), ((A) ^= (B)))

// Swap A and B values to make sure A <= B.
#define MAYBE_SWAP(A,B) if ((A) > (B)) { SWAP(A,B); }

//
// Basic primitives.
//

IWRAM_CODE
void screen_fill(u8 clr)  {
    dma_fill(backbuf, 0x01010101 * clr, KB(75) / 2, 3);
}

IWRAM_CODE
void
draw_pixel(size_t x, size_t y, u8 clr) {
    BOUNDCHECK_SCREEN(x, y);
    u16 *dst = &backbuf[(x + y * SCREEN_WIDTH) / 2];
    if(x & 1) {
        *dst = (*dst &  0xF) | (clr << 8);
    } else {
        *dst = (*dst & ~0xF) | clr;
    }
}

IWRAM_CODE
static inline
void
draw_hline(size_t x0, size_t x1, size_t y0, u8 clr) {
    BOUNDCHECK_SCREEN(x0, y0);
    BOUNDCHECK_SCREEN(x1, y0);
    // Find row positions for the given x/y coordinates.
    size_t tile_x0 = x0 / 8;
    size_t tile_x1 = x1 / 8;
    size_t start_col = x0 % 8;
    size_t end_col = x1 % 8;
    // Horizontal line. There are 3 cases:
    //     1. Lines fit on a single tile.
    //     2. Lines go through 2 tiles, both require partial row updates.
    //     3. Lines go through 3 or more tiles, first and last tiles use
    //        partial row updates, rows in the middle can write the entire
    //        row.
    size_t dx = tile_x1 - tile_x0;
    u64 *dst = &backbuf[(tile_x0 * 8 + y0 * SCREEN_WIDTH) / 2];
    if (dx < 1) {
        u64 row_mask = 0xFFFFFFFFFFFFFFFF;
        row_mask >>= (7 - end_col - dx) * 8;
        row_mask &= 0xFFFFFFFFFFFFFFFF << start_col * 8;
        u64 row = (0x0101010101010101 * clr) & row_mask;
        *dst = (*dst & ~row_mask) | row;
    } else {
        size_t shift_left = start_col * 8;
        size_t shift_right = (7 - end_col) * 8;
        u64 row_mask = 0xFFFFFFFFFFFFFFFF;
        u64 row = 0x0101010101010101 * clr;
        dst[0] = (dst[0] & ~(row_mask << shift_left)) | row << shift_left;
        if (dx != 1) {
            dma_fill(&dst[1], 0x01010101 * clr, (dx - 1) * 8, 3);
        }
        dst[dx] = dst[dx] & ~(row_mask >> shift_right);
        dst[dx] |= row >> shift_right;
    }
}

IWRAM_CODE
UNROLL_LOOPS
static inline
void
draw_vline(size_t x0, size_t y0, size_t y1, u8 clr) {
    BOUNDCHECK_SCREEN(x0, y0);
    BOUNDCHECK_SCREEN(x0, y1);
    size_t tile_x0 = x0 / 8;
    size_t start_col = x0 % 8;
    u16 *dst = &backbuf[(start_col + tile_x0 * 8 + y0 * SCREEN_WIDTH) / 2];
    if(x0 & 1) {
        for (size_t i = 0; i <= y1 - y0; i++, dst += SCREEN_WIDTH / 2) {
            *dst = (*dst &  0xF) | (clr << 8);
        }
    } else {
        for (size_t i = 0; i <= y1 - y0; i++, dst += SCREEN_WIDTH / 2) {
            *dst = (*dst & ~0xF) | clr;
        }
    }
}

IWRAM_CODE
UNROLL_LOOPS
void
draw_line(size_t x0, size_t y0, size_t x1, size_t y1, u8 clr) {
    BOUNDCHECK_SCREEN(x0, y0);
    BOUNDCHECK_SCREEN(x1, y1);

    if (y0 == y1) {
        MAYBE_SWAP(x0, x1);
        draw_hline(x0, x1, y0, clr);
    } else if (x0 == x1) {
        MAYBE_SWAP(y0, y1);
        draw_vline(x0, y0, y1, clr);
    } else {
#if SUBPIXEL_LINES == 1
        // Fixed Precision constants.
        const int fp_bit = 6;
        const int fp_one = FP_NUM(1, fp_bit);
        const int fp_half = fp_one >> 1;

        int     dx = x0 > x1 ?       x0 - x1 : x1 - x0;
        int     dy = y0 > y1 ?       y0 - y1 : y1 - y0;
        int dxf = (dx << fp_bit);
        int dyf = (dy << fp_bit);

        if ((dx >= dy && x0 > x1) || (dx < dy && y0 > y1)) {
            SWAP(x0, x1);
            SWAP(y0, y1);
        }

        int frac_x = x0 > x1 ? FP_NUM(x0 - x1, fp_bit) : FP_NUM(x1 - x0, fp_bit);
        int frac_y = y0 > y1 ? FP_NUM(y0 - y1, fp_bit) : FP_NUM(y1 - y0, fp_bit);
        int x_step = x0 > x1 ?            -1 : 1;
        int y_step = y0 > y1 ? -SCREEN_WIDTH : SCREEN_WIDTH;

        u16 *dst = NULL;
        uintptr_t addr = ((uintptr_t)backbuf + y0 * SCREEN_WIDTH + x0);
        u32 mask = x0 & 1 ? ~0xFF : 0xFF;
        u32 color = (clr & 0xFF) | ((clr & 0xFF) << 8);
        if (dx >= dy) {
            int distance = (frac_y - fp_one) * dx - (frac_x - fp_half) * dy;
            int remaining = dx;
            while (distance <= 0  && remaining > 0) {
                dst = (u16*)(addr - (mask >> 31));
                *dst = (*dst & ~mask) | (color & mask);
                distance += 2 * dyf;
                addr += x_step;
                remaining--;
                mask = ~mask;
            }
            distance -= 2 * dxf;
            addr += y_step;

            while (remaining >= 0) {
                dst = (u16*)(addr - (mask >> 31));
                *dst = (*dst & ~mask) | (color & mask);
                if (distance >= 0) {
                    distance -= 2 * dxf;
                    addr += y_step;
                }
                distance += 2 * dyf;
                addr += x_step;
                mask = ~mask;
                remaining--;
            }
        } else {
            int distance = (frac_x - fp_one) * dy - (frac_y - fp_half) * dx;
            int remaining = dy;
            while (distance <= 0  && remaining > 0) {
                dst = (u16*)(addr - (mask >> 31));
                *dst = (*dst & ~mask) | (color & mask);
                distance += 2 * dxf;
                addr += y_step;
                remaining--;
            }
            distance -= 2 * dyf;
            addr += x_step;
            mask = ~mask;

            while (remaining >= 0) {
                dst = (u16*)(addr - (mask >> 31));
                *dst = (*dst & ~mask) | (color & mask);
                if (distance >= 0) {
                    distance -= 2 * dyf;
                    addr += x_step;
                    mask = ~mask;
                }
                distance += 2 * dxf;
                addr += y_step;
                remaining--;
            }
        }
#else
        // Diagonal line.
        int     dx = x0 > x1 ?       x0 - x1 : x1 - x0;
        int     dy = y0 > y1 ?       y0 - y1 : y1 - y0;
        int x_step = x0 > x1 ?            -1 : 1;
        int y_step = y0 > y1 ? -SCREEN_WIDTH : SCREEN_WIDTH;

        u16 *dst = NULL;
        uintptr_t addr = ((uintptr_t)backbuf + y0 * SCREEN_WIDTH + x0);
        u32 mask = x0 & 1 ? ~0xFF : 0xFF;
        u32 color = (clr & 0xFF) | ((clr & 0xFF) << 8);
        if (dx >= dy) {
            int diff = 2 * dy - dx;
            for (int i = 0; i < dx + 1; i++) {
                dst = (u16*)(addr - (mask >> 31));
                *dst = (*dst & ~mask) | (color & mask);
                if (diff >= 0) {
                    diff -= 2 * dx;
                    addr += y_step;
                }
                diff += 2 * dy;
                addr += x_step;
                mask = ~mask;
            }
        } else {
            int diff = 2 * dx - dy;
            for (int i = 0; i < dy + 1; i++) {
                dst = (u16*)(addr - (mask >> 31));
                *dst = (*dst & ~mask) | (color & mask);
                if (diff >= 0) {
                    diff -= 2 * dy;
                    addr += x_step;
                    mask = ~mask;
                }
                diff += 2 * dx;
                addr += y_step;
            }
        }
#endif
    }
}

IWRAM_CODE
void
draw_rect(size_t x0, size_t y0, size_t x1, size_t y1, u8 clr) {
    BOUNDCHECK_SCREEN(x0, y0);
    BOUNDCHECK_SCREEN(x1, y1);
    MAYBE_SWAP(x0, x1);
    MAYBE_SWAP(y0, y1);

    draw_hline(x0, x1, y0, clr);
    draw_hline(x0, x1, y1, clr);
    draw_vline(x0, y0, y1, clr);
    draw_vline(x1, y0, y1, clr);
}

IWRAM_CODE
void
draw_filled_rect(size_t x0, size_t y0, size_t x1, size_t y1, u8 clr) {
    BOUNDCHECK_SCREEN(x0, y0);
    BOUNDCHECK_SCREEN(x1, y1);
    MAYBE_SWAP(x0, x1);
    MAYBE_SWAP(y0, y1);

    // Special condition. If the screen is to be completely filled, use the DMA
    // instead.
    if (x0 == 0 && x1 >= (SCREEN_WIDTH - 1) && y0 == 0 && y1 >= (SCREEN_HEIGHT - 1)) {
        screen_fill(clr);
        return;
    }

    // Drawline implementation.
    for (size_t y = y0; y <= y1; y++) {
        draw_hline(x0, x1, y, clr);
    }
}

//
// Sprites (chr/icn).
//

#if DEC_BIG_LUT == 1

static u64 dec_byte_flip_x[256] = {
    0x0000000000000000, 0x0000000000000001, 0x0000000000000100, 0x0000000000000101, 0x0000000000010000,
    0x0000000000010001, 0x0000000000010100, 0x0000000000010101, 0x0000000001000000, 0x0000000001000001,
    0x0000000001000100, 0x0000000001000101, 0x0000000001010000, 0x0000000001010001, 0x0000000001010100,
    0x0000000001010101, 0x0000000100000000, 0x0000000100000001, 0x0000000100000100, 0x0000000100000101,
    0x0000000100010000, 0x0000000100010001, 0x0000000100010100, 0x0000000100010101, 0x0000000101000000,
    0x0000000101000001, 0x0000000101000100, 0x0000000101000101, 0x0000000101010000, 0x0000000101010001,
    0x0000000101010100, 0x0000000101010101, 0x0000010000000000, 0x0000010000000001, 0x0000010000000100,
    0x0000010000000101, 0x0000010000010000, 0x0000010000010001, 0x0000010000010100, 0x0000010000010101,
    0x0000010001000000, 0x0000010001000001, 0x0000010001000100, 0x0000010001000101, 0x0000010001010000,
    0x0000010001010001, 0x0000010001010100, 0x0000010001010101, 0x0000010100000000, 0x0000010100000001,
    0x0000010100000100, 0x0000010100000101, 0x0000010100010000, 0x0000010100010001, 0x0000010100010100,
    0x0000010100010101, 0x0000010101000000, 0x0000010101000001, 0x0000010101000100, 0x0000010101000101,
    0x0000010101010000, 0x0000010101010001, 0x0000010101010100, 0x0000010101010101, 0x0001000000000000,
    0x0001000000000001, 0x0001000000000100, 0x0001000000000101, 0x0001000000010000, 0x0001000000010001,
    0x0001000000010100, 0x0001000000010101, 0x0001000001000000, 0x0001000001000001, 0x0001000001000100,
    0x0001000001000101, 0x0001000001010000, 0x0001000001010001, 0x0001000001010100, 0x0001000001010101,
    0x0001000100000000, 0x0001000100000001, 0x0001000100000100, 0x0001000100000101, 0x0001000100010000,
    0x0001000100010001, 0x0001000100010100, 0x0001000100010101, 0x0001000101000000, 0x0001000101000001,
    0x0001000101000100, 0x0001000101000101, 0x0001000101010000, 0x0001000101010001, 0x0001000101010100,
    0x0001000101010101, 0x0001010000000000, 0x0001010000000001, 0x0001010000000100, 0x0001010000000101,
    0x0001010000010000, 0x0001010000010001, 0x0001010000010100, 0x0001010000010101, 0x0001010001000000,
    0x0001010001000001, 0x0001010001000100, 0x0001010001000101, 0x0001010001010000, 0x0001010001010001,
    0x0001010001010100, 0x0001010001010101, 0x0001010100000000, 0x0001010100000001, 0x0001010100000100,
    0x0001010100000101, 0x0001010100010000, 0x0001010100010001, 0x0001010100010100, 0x0001010100010101,
    0x0001010101000000, 0x0001010101000001, 0x0001010101000100, 0x0001010101000101, 0x0001010101010000,
    0x0001010101010001, 0x0001010101010100, 0x0001010101010101, 0x0100000000000000, 0x0100000000000001,
    0x0100000000000100, 0x0100000000000101, 0x0100000000010000, 0x0100000000010001, 0x0100000000010100,
    0x0100000000010101, 0x0100000001000000, 0x0100000001000001, 0x0100000001000100, 0x0100000001000101,
    0x0100000001010000, 0x0100000001010001, 0x0100000001010100, 0x0100000001010101, 0x0100000100000000,
    0x0100000100000001, 0x0100000100000100, 0x0100000100000101, 0x0100000100010000, 0x0100000100010001,
    0x0100000100010100, 0x0100000100010101, 0x0100000101000000, 0x0100000101000001, 0x0100000101000100,
    0x0100000101000101, 0x0100000101010000, 0x0100000101010001, 0x0100000101010100, 0x0100000101010101,
    0x0100010000000000, 0x0100010000000001, 0x0100010000000100, 0x0100010000000101, 0x0100010000010000,
    0x0100010000010001, 0x0100010000010100, 0x0100010000010101, 0x0100010001000000, 0x0100010001000001,
    0x0100010001000100, 0x0100010001000101, 0x0100010001010000, 0x0100010001010001, 0x0100010001010100,
    0x0100010001010101, 0x0100010100000000, 0x0100010100000001, 0x0100010100000100, 0x0100010100000101,
    0x0100010100010000, 0x0100010100010001, 0x0100010100010100, 0x0100010100010101, 0x0100010101000000,
    0x0100010101000001, 0x0100010101000100, 0x0100010101000101, 0x0100010101010000, 0x0100010101010001,
    0x0100010101010100, 0x0100010101010101, 0x0101000000000000, 0x0101000000000001, 0x0101000000000100,
    0x0101000000000101, 0x0101000000010000, 0x0101000000010001, 0x0101000000010100, 0x0101000000010101,
    0x0101000001000000, 0x0101000001000001, 0x0101000001000100, 0x0101000001000101, 0x0101000001010000,
    0x0101000001010001, 0x0101000001010100, 0x0101000001010101, 0x0101000100000000, 0x0101000100000001,
    0x0101000100000100, 0x0101000100000101, 0x0101000100010000, 0x0101000100010001, 0x0101000100010100,
    0x0101000100010101, 0x0101000101000000, 0x0101000101000001, 0x0101000101000100, 0x0101000101000101,
    0x0101000101010000, 0x0101000101010001, 0x0101000101010100, 0x0101000101010101, 0x0101010000000000,
    0x0101010000000001, 0x0101010000000100, 0x0101010000000101, 0x0101010000010000, 0x0101010000010001,
    0x0101010000010100, 0x0101010000010101, 0x0101010001000000, 0x0101010001000001, 0x0101010001000100,
    0x0101010001000101, 0x0101010001010000, 0x0101010001010001, 0x0101010001010100, 0x0101010001010101,
    0x0101010100000000, 0x0101010100000001, 0x0101010100000100, 0x0101010100000101, 0x0101010100010000,
    0x0101010100010001, 0x0101010100010100, 0x0101010100010101, 0x0101010101000000, 0x0101010101000001,
    0x0101010101000100, 0x0101010101000101, 0x0101010101010000, 0x0101010101010001, 0x0101010101010100,
    0x0101010101010101
};

static u64 dec_byte[256] = {
    0x0000000000000000, 0x0100000000000000, 0x0001000000000000, 0x0101000000000000, 0x0000010000000000,
    0x0100010000000000, 0x0001010000000000, 0x0101010000000000, 0x0000000100000000, 0x0100000100000000,
    0x0001000100000000, 0x0101000100000000, 0x0000010100000000, 0x0100010100000000, 0x0001010100000000,
    0x0101010100000000, 0x0000000001000000, 0x0100000001000000, 0x0001000001000000, 0x0101000001000000,
    0x0000010001000000, 0x0100010001000000, 0x0001010001000000, 0x0101010001000000, 0x0000000101000000,
    0x0100000101000000, 0x0001000101000000, 0x0101000101000000, 0x0000010101000000, 0x0100010101000000,
    0x0001010101000000, 0x0101010101000000, 0x0000000000010000, 0x0100000000010000, 0x0001000000010000,
    0x0101000000010000, 0x0000010000010000, 0x0100010000010000, 0x0001010000010000, 0x0101010000010000,
    0x0000000100010000, 0x0100000100010000, 0x0001000100010000, 0x0101000100010000, 0x0000010100010000,
    0x0100010100010000, 0x0001010100010000, 0x0101010100010000, 0x0000000001010000, 0x0100000001010000,
    0x0001000001010000, 0x0101000001010000, 0x0000010001010000, 0x0100010001010000, 0x0001010001010000,
    0x0101010001010000, 0x0000000101010000, 0x0100000101010000, 0x0001000101010000, 0x0101000101010000,
    0x0000010101010000, 0x0100010101010000, 0x0001010101010000, 0x0101010101010000, 0x0000000000000100,
    0x0100000000000100, 0x0001000000000100, 0x0101000000000100, 0x0000010000000100, 0x0100010000000100,
    0x0001010000000100, 0x0101010000000100, 0x0000000100000100, 0x0100000100000100, 0x0001000100000100,
    0x0101000100000100, 0x0000010100000100, 0x0100010100000100, 0x0001010100000100, 0x0101010100000100,
    0x0000000001000100, 0x0100000001000100, 0x0001000001000100, 0x0101000001000100, 0x0000010001000100,
    0x0100010001000100, 0x0001010001000100, 0x0101010001000100, 0x0000000101000100, 0x0100000101000100,
    0x0001000101000100, 0x0101000101000100, 0x0000010101000100, 0x0100010101000100, 0x0001010101000100,
    0x0101010101000100, 0x0000000000010100, 0x0100000000010100, 0x0001000000010100, 0x0101000000010100,
    0x0000010000010100, 0x0100010000010100, 0x0001010000010100, 0x0101010000010100, 0x0000000100010100,
    0x0100000100010100, 0x0001000100010100, 0x0101000100010100, 0x0000010100010100, 0x0100010100010100,
    0x0001010100010100, 0x0101010100010100, 0x0000000001010100, 0x0100000001010100, 0x0001000001010100,
    0x0101000001010100, 0x0000010001010100, 0x0100010001010100, 0x0001010001010100, 0x0101010001010100,
    0x0000000101010100, 0x0100000101010100, 0x0001000101010100, 0x0101000101010100, 0x0000010101010100,
    0x0100010101010100, 0x0001010101010100, 0x0101010101010100, 0x0000000000000001, 0x0100000000000001,
    0x0001000000000001, 0x0101000000000001, 0x0000010000000001, 0x0100010000000001, 0x0001010000000001,
    0x0101010000000001, 0x0000000100000001, 0x0100000100000001, 0x0001000100000001, 0x0101000100000001,
    0x0000010100000001, 0x0100010100000001, 0x0001010100000001, 0x0101010100000001, 0x0000000001000001,
    0x0100000001000001, 0x0001000001000001, 0x0101000001000001, 0x0000010001000001, 0x0100010001000001,
    0x0001010001000001, 0x0101010001000001, 0x0000000101000001, 0x0100000101000001, 0x0001000101000001,
    0x0101000101000001, 0x0000010101000001, 0x0100010101000001, 0x0001010101000001, 0x0101010101000001,
    0x0000000000010001, 0x0100000000010001, 0x0001000000010001, 0x0101000000010001, 0x0000010000010001,
    0x0100010000010001, 0x0001010000010001, 0x0101010000010001, 0x0000000100010001, 0x0100000100010001,
    0x0001000100010001, 0x0101000100010001, 0x0000010100010001, 0x0100010100010001, 0x0001010100010001,
    0x0101010100010001, 0x0000000001010001, 0x0100000001010001, 0x0001000001010001, 0x0101000001010001,
    0x0000010001010001, 0x0100010001010001, 0x0001010001010001, 0x0101010001010001, 0x0000000101010001,
    0x0100000101010001, 0x0001000101010001, 0x0101000101010001, 0x0000010101010001, 0x0100010101010001,
    0x0001010101010001, 0x0101010101010001, 0x0000000000000101, 0x0100000000000101, 0x0001000000000101,
    0x0101000000000101, 0x0000010000000101, 0x0100010000000101, 0x0001010000000101, 0x0101010000000101,
    0x0000000100000101, 0x0100000100000101, 0x0001000100000101, 0x0101000100000101, 0x0000010100000101,
    0x0100010100000101, 0x0001010100000101, 0x0101010100000101, 0x0000000001000101, 0x0100000001000101,
    0x0001000001000101, 0x0101000001000101, 0x0000010001000101, 0x0100010001000101, 0x0001010001000101,
    0x0101010001000101, 0x0000000101000101, 0x0100000101000101, 0x0001000101000101, 0x0101000101000101,
    0x0000010101000101, 0x0100010101000101, 0x0001010101000101, 0x0101010101000101, 0x0000000000010101,
    0x0100000000010101, 0x0001000000010101, 0x0101000000010101, 0x0000010000010101, 0x0100010000010101,
    0x0001010000010101, 0x0101010000010101, 0x0000000100010101, 0x0100000100010101, 0x0001000100010101,
    0x0101000100010101, 0x0000010100010101, 0x0100010100010101, 0x0001010100010101, 0x0101010100010101,
    0x0000000001010101, 0x0100000001010101, 0x0001000001010101, 0x0101000001010101, 0x0000010001010101,
    0x0100010001010101, 0x0001010001010101, 0x0101010001010101, 0x0000000101010101, 0x0100000101010101,
    0x0001000101010101, 0x0101000101010101, 0x0000010101010101, 0x0100010101010101, 0x0001010101010101,
    0x0101010101010101
};

IWRAM_CODE
static inline
u64
decode_1bpp(u8 row, u8 flip_x) {
    if (flip_x) {
        return dec_byte_flip_x[row];
    }
    return dec_byte[row];
}

#else

static u32 dec_nibble[] = {
    0x00000000, 0x01000000, 0x00010000, 0x01010000,
    0x00000100, 0x01000100, 0x00010100, 0x01010100,
    0x00000001, 0x01000001, 0x00010001, 0x01010001,
    0x00000101, 0x01000101, 0x00010101, 0x01010101,
};

static u32 dec_nibble_flip_x[] = {
    0x00000000, 0x00000001, 0x00000100, 0x00000101,
    0x00010000, 0x00010001, 0x00010100, 0x00010101,
    0x01000000, 0x01000001, 0x01000100, 0x01000101,
    0x01010000, 0x01010001, 0x01010100, 0x01010101,
};

IWRAM_CODE
static inline
u64
decode_1bpp(u8 row, u8 flip_x) {
    if (flip_x) {
        u32 *lut = dec_nibble_flip_x;
        return (u64)lut[(row >> 4) & 0xF] << 32 | (u64)lut[(row >> 0) & 0xF];
    }
    u32 *lut = dec_nibble;
    return (u64)lut[(row >> 0) & 0xF] << 32 | (u64)lut[(row >> 4) & 0xF];
}

#endif

IWRAM_CODE
static inline
void
draw_2bpp_row(size_t x, size_t y, u8 a, u8 b, u8 clr, u8 flip_x) {
    BOUNDCHECK_SCREEN(x, y);

    size_t tile_x = x / 8;
    size_t start_col = x % 8;
    size_t shift_left = start_col * 8;
    size_t shift_right = (8 - start_col) * 8;

    u64 *dst = &backbuf[(y * 30 + tile_x) * 8 / 2];
#if DEC_BIG_LUT
    u64 *lut = flip_x ? dec_byte_flip_x : dec_byte;
    u64 clr_a = lut[a];
    u64 clr_b = lut[b];
#else
    u64 clr_a = decode_1bpp(a, flip_x);
    u64 clr_b = decode_1bpp(b, flip_x);
#endif
    u64 mask_a = (clr_a * 0xF);
    u64 mask_b = (clr_b * 0xF);
    u64 mask = (mask_a | mask_b);
    u64 color;
    if (clr == 0) {
        color = clr_a + (clr_b << 1);
    } else if (clr == 15) {
        color = 0;
    } else {
        color = (clr_a | clr_b) * clr;
    }
    dst[0] = (dst[0] & ~(mask << shift_left))  | (color << shift_left);
    dst[1] = (dst[1] & ~(mask >> shift_right)) | (color >> shift_right);
}

IWRAM_CODE
static inline
void
draw_1bpp_row(size_t x, size_t y, u8 a, u8 clr, u8 flip_x) {
    BOUNDCHECK_SCREEN(x, y);

    size_t tile_x = x / 8;
    size_t start_col = x % 8;
    size_t shift_left = start_col * 8;
    size_t shift_right = (8 - start_col) * 8;

    u64 *dst = &backbuf[(y * 30 + tile_x) * 8 / 2];
    u64 color = decode_1bpp(a, flip_x);
    u64 mask = (color * 0xF);
    color *= clr;
    dst[0] = (dst[0] & ~(mask << shift_left))  | (color << shift_left);
    dst[1] = (dst[1] & ~(mask >> shift_right)) | (color >> shift_right);
}

IWRAM_CODE
void
draw_chr(size_t x, size_t y, u8 *sprite, u8 clr, u8 flip_x, u8 flip_y) {
    BOUNDCHECK_SCREEN(x, y);
    if (!flip_y) {
        for(size_t v = 0; v < 8; v++) {
            if ((y + v) >= SCREEN_HEIGHT) break;
            u8 ch1 = sprite[v + 0];
            u8 ch2 = sprite[v + 8];
            draw_2bpp_row(x, y + v, ch1, ch2, clr, flip_x);
        }
    } else {
        for(size_t v = 0; v < 8; v++) {
            if ((y + v) >= SCREEN_HEIGHT) break;
            u8 ch1 = sprite[(7 - v) + 0];
            u8 ch2 = sprite[(7 - v) + 8];
            draw_2bpp_row(x, y + v, ch1, ch2, clr, flip_x);
        }
    }
}

IWRAM_CODE
void
draw_icn(size_t x, size_t y, u8 *sprite, u8 clr, u8 flip_x, u8 flip_y) {
    BOUNDCHECK_SCREEN(x, y);
    if (!flip_y) {
        for(size_t v = 0; v < 8; v++) {
            if ((y + v) >= SCREEN_HEIGHT) break;
            u8 ch1 = sprite[v];
            draw_1bpp_row(x, y + v, ch1, clr, flip_x);
        }
    } else {
        for(size_t v = 0; v < 8; v++) {
            if ((y + v) >= SCREEN_HEIGHT) break;
            u8 ch1 = sprite[(7 - v)];
            draw_1bpp_row(x, y + v, ch1, clr, flip_x);
        }
    }
}

//
// Flipping buffers/copying memory.
//

IWRAM_CODE
void
flip_buffer(void) {
    backbuf = (u16*)((u32)backbuf ^ 0x0A000);
    DISP_CTRL ^= DISP_PAGE;
}

//
// Text rendering.
//

#include "font.h"

// Font rendering function for the text engine.
void
txt_drawc(char c, size_t x, size_t y, u8 clr) {
    u8 *tile = font_icn;
    draw_icn(x, y, tile + 8 * c, clr, 1, 0);
}

void
txt_drawc_small(char c, size_t x, size_t y, u8 clr) {
    u8 *tile = font_icn;
    c = c < 'a' ? c + 16 * 6 : c + 16 * 4;
    draw_icn(x, y, tile + 8 * c, clr, 1, 0);
}

#define txt_drawf_small(msg, x, y, clr, ...) \
	{ \
		char buf[256] = {0}; \
		posprintf(buf, msg, ##__VA_ARGS__); \
		u8 tmp = text_engine.spacing;\
        txt_spacing(4);\
        text_engine.drawc = txt_drawc_small;\
		txt_draws(buf, x, y, clr); \
        txt_spacing(tmp);\
        text_engine.drawc = txt_drawc;\
	}

//
// Initialization.
//

void
renderer_init(void) {
    // Initialize display mode and bg palette.
    DISP_CTRL = DISP_MODE_4 | DISP_BG_2;

    // Clear VRAM.
    dma_fill((u16*)MEM_VRAM, 0, KB(96), 3);

    // Initialize default palette.
    PAL_BUFFER_BG[0] = COLOR_BLACK;
    PAL_BUFFER_BG[1] = COLOR_WHITE;
    PAL_BUFFER_BG[2] = COLOR_RED;
    PAL_BUFFER_BG[3] = COLOR_BLUE;
    PAL_BUFFER_BG[4] = COLOR_CYAN;
    PAL_BUFFER_BG[5] = COLOR_GREY;
    PAL_BUFFER_BG[6] = COLOR_WHITE;
    PAL_BUFFER_BG[7] = COLOR_GREEN;
    PAL_BUFFER_BG[8] = COLOR_PURPLE;

    // Initialize text engine.
    txt_init(txt_drawc);
}