SDL2 處理中文輸入

sdl2_text_input_utf8.c

// Use `gcc sdl2_text_input_utf8.c -lSDL2 -lSDL2_ttf -o test_program`.
//
// You must use CJK font for SDL2_ttf and put the same directory with test_program.
// This example use "NotoSansMonoCJKtc-Regular.otf".
#include <stdio.h>
#include <string.h>
#include <stdbool.h>
#include <stdint.h>

#include <SDL2/SDL.h>
#include <SDL2/SDL_ttf.h>

#define GAME_TITLE "輸入文字"
#define WIDTH 800
#define HEIGHT 600

int GRID_LENGTH = 24;


size_t strlen_utf8(char *str) {
  size_t max_counter = strlen(str);
  size_t move_position = 0;
  int64_t len = 0;
  unsigned char check = 0;

  for(size_t index = 0; index < max_counter; index += move_position) {
    check = str[index];
    len++;

    if(check < 0b11000000) {
      move_position = 1;
    }
    else if(check < 0b11100000 && check > 0b11000000) {
      move_position = 2;
    }
    else if(check < 0b11110000 && check > 0b11100000) {
      move_position = 3;
    }
    else if(check > 0b11110000) {
      move_position = 4;
    }
    else if(check == 0) {
      break;
    }
    else {
      printf("bug\n");
      break;
    }
  }
  return len;
}


size_t calculate_grid_width_utf8(char *str) {
  size_t max_counter = strlen(str);
  size_t move_position = 0;
  int64_t len = 0;
  unsigned char check = 0;

  for(size_t index = 0; index < max_counter; index += move_position) {
    check = str[index];
    len += 2;

    if(check < 0b11000000) {
      move_position = 1;
      len--;
    }
    else if(check < 0b11100000 && check > 0b11000000) {
      move_position = 2;
    }
    else if(check < 0b11110000 && check > 0b11100000) {
      move_position = 3;
    }
    else if(check > 0b11110000) {
      move_position = 4;
    }
    else if(check == 0) {
      break;
    }
    else {
      printf("bug\n");
      break;
    }
  }
  return len * (GRID_LENGTH / 2);
}


void remove_last_utf8(char **str) {
  size_t index = strlen(*str);
  unsigned char check = 0;

  for(index; index > 0; index--) {
    check = (unsigned char)((*str)[index - 1]) & 0b11000000;

    if(check == 0b10000000) {
      (*str)[index - 1] = 0;
    }
    else {
      (*str)[index - 1] = 0;
      break;
    }
  }
}


int main(int argc, char *argv[]) {
  SDL_Color white = {255, 255, 255};
  SDL_Window *win;
  SDL_Renderer *render;
  bool running = true;

  char *text = malloc(100);
  size_t target = 0;
  memset(text, 0, 100);

  SDL_Init(SDL_INIT_EVERYTHING);
  if (TTF_Init() != 0) {
    goto INIT_FAILED;
  }
  SDL_StartTextInput();

  win = SDL_CreateWindow(GAME_TITLE, 0, 0, WIDTH, HEIGHT, SDL_WINDOW_OPENGL);
  render = SDL_CreateRenderer(win, -1, SDL_RENDERER_ACCELERATED|SDL_RENDERER_PRESENTVSYNC);

  TTF_Font* font = TTF_OpenFont("./NotoSansMonoCJKtc-Regular.otf", 512);
  SDL_Surface* surfaceMessage = NULL;
  SDL_Texture *access = NULL;
  SDL_Rect rect = {.x = 0, .y = 0, .w = 1 * GRID_LENGTH, .h = GRID_LENGTH};

  while (running) {
    SDL_Event event;

    while (SDL_PollEvent(&event)) {
      SDL_RenderClear(render);

      switch (event.type) {
        case SDL_QUIT:
          running = false;
          break;
        case SDL_TEXTINPUT:
        case SDL_KEYDOWN:
          if(event.key.keysym.sym == SDLK_BACKSPACE && target > 0) {
            if(event.type == SDL_KEYDOWN && event.key.repeat == 0) {
              remove_last_utf8(&text);
            }
          }
          else if(event.type == SDL_TEXTINPUT) {
            strcat(text, event.text.text);
          }

          target = strlen_utf8(text);
          rect.w = calculate_grid_width_utf8(text);

          surfaceMessage = TTF_RenderUTF8_Solid(font,
              text,
              white);
          access = SDL_CreateTextureFromSurface(render, surfaceMessage);
          SDL_FreeSurface(surfaceMessage);
          break;
        default:
          break;
      }

      SDL_SetRenderDrawColor(render, 0, 0, 0, SDL_ALPHA_OPAQUE);
      SDL_RenderCopy(render, access, NULL, &(rect));

      SDL_RenderPresent(render);
    }
  }
  TTF_CloseFont(font);

  SDL_DestroyRenderer(render);
  SDL_DestroyWindow(win);

INIT_FAILED:
  SDL_StopTextInput();
  TTF_Quit();
  SDL_Quit();
  free(text);
}