nese/src/sdl_overlay.c

#include "sdl_overlay.h"

#include "charbits.h"


typedef struct {
    const uint8_t* bits;
    uint8_t shift;
} bit_buffer;

void make_bit_buffer(bit_buffer* buf, const uint8_t* bits) {
    buf->bits = bits;
    buf->shift = 0;
}

uint8_t get_bits(bit_buffer* buf) {
    uint8_t val = ((buf->bits[0] >> buf->shift) & 3);
    if (buf->shift == 6) {
        buf->shift = 0;
        buf->bits++;
    } else {
        buf->shift += 2;
    }
    return val;
}

static const SDL_Color pal[2] = {
    {0, 0, 0, 255}, {255, 255, 255, 255}
};

static SDL_Surface* create_char_surface(const uint8_t* bits) {
    int w = *bits++;
    bit_buffer buf = {0};
    make_bit_buffer(&buf, bits);

    SDL_Surface* surface = SDL_CreateRGBSurfaceWithFormat(
            0, w, char_h, 8, SDL_PIXELFORMAT_INDEX8
        );
    SDL_SetPaletteColors(surface->format->palette, pal, 1U, 2U);
    SDL_SetColorKey(surface, SDL_TRUE, 0);

    uint8_t* line = surface->pixels;
    for (int y = char_h; y > 0; --y) {
        uint8_t* dst = line;
        for (int x = w; x > 0; --x) {
            *dst++ = get_bits(&buf);
        }
        for (int x = (char_w - w); x > 0; --x) get_bits(&buf);
        line += surface->pitch;
    }

    return surface;
}

static SDL_Texture* create_char_texture(SDL_Renderer* rend,
                                        const uint8_t* bits) {
    SDL_Surface* surface = create_char_surface(bits);
    SDL_SetSurfaceBlendMode(surface, SDL_BLENDMODE_NONE);
    SDL_Texture* texture = SDL_CreateTextureFromSurface(
            rend, surface
        );
    SDL_FreeSurface(surface);
    return texture;
}

int sdl_overlay_font_init(SDL_Renderer* rend,
                          sdl_overlay_font* font) {
    font->chars = chars;
    font->charbits = charbits;
    font->char_count = char_count;
    font->textures = calloc(char_count, sizeof(SDL_Texture*));
    for (int i = 0; i < font->char_count; ++i) {
        font->textures[i] = create_char_texture(
                rend, &font->charbits[i * charbit_size]
            );
    }
    return 0;
}

void sdl_overlay_font_done(sdl_overlay_font* font) {
    for (int i = 0; i < font->char_count; ++i) {
        SDL_DestroyTexture(font->textures[i]);
    }
}

#define overlay_start_x (char_w / 2)
#define overlay_start_y (char_h / 2)

static inline int char_index(char c) {
    if (c >= 'a' && c <= 'z') c += ('A' - 'a');
    if (c > ' ' && c < 'a') return (c - ' ');
    if (c >= '{' && c <= '~') return (65 + c - '{');
    return 0;
}

static void render_string(SDL_Renderer* rend, int ox, int oy,
                          int sx, int sy,
                          sdl_overlay_font* font,
                          const char* string) {
    for (const char* c = string; *c; ++c) {
        if (*c == ' ') {
            ox += ((char_w / 2) - 1);
        } else {
            int index = char_index(*c);
            int cw = font->charbits[index * charbit_size];
            SDL_Texture* texture = font->textures[index];

            SDL_Rect rect = {
                .x = ox * sx,
                .y = oy * sy,
                .w = cw * sx,
                .h = char_h * sy,
            };

            SDL_RenderCopy(rend, texture, NULL, &rect);

            ox += (cw - 1);
        }
    }
}

int sdl_overlay_frame(Overlay* overlay, sdl_overlay_font* font,
                      SDL_Renderer* rend,
                      int sx, int sy) {
    int y = overlay_start_y;
    overlay_message* last = NULL, *next = NULL;
    for (   overlay_message* message = overlay->messages;
            NULL != message;
            last = message, message = next) {
        next = message->next;

        render_string(rend, overlay_start_x, y, sx, sy,
                      font, message->string);
        y += (char_h + 1);

        if (message->expiry > 0 && --(message->expiry) == 0) {
            if (NULL == last) {
                overlay->messages = message->next;
            } else {
                last->next = message->next;
            }
            free(message->string);
            free(message);
        }
    }

    return 0;
}