// ```c
#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <SDL2/SDL.h>
#include <SDL2/SDL_ttf.h>

const char* font_family = "helvetica";

int font_size_to_fit(const char *s, int w, int h);
void handle_events(bool *running);

int main(int argc, char **argv) {
	if (argc < 2) {
		printf("usage: %s string [colour]\n", argv[0]);
		return 1;
	}

	const char *s = argv[1];
	const char *c = argc > 2 ? argv[2] : NULL;

	if (SDL_Init(SDL_INIT_VIDEO) != 0) {
		printf("SDL_Init Error: %s\n", SDL_GetError());
		return 1;
	}

	TTF_Init();

	SDL_DisplayMode DM;
	SDL_GetCurrentDisplayMode(0, &DM);
	int w = DM.w;
	int h = DM.h;

	SDL_Window *win = SDL_CreateWindow("Banner Message", 0, 0, w, h, SDL_WINDOW_FULLSCREEN_DESKTOP);
	if (win == NULL) {
		printf("SDL_CreateWindow Error: %s\n", SDL_GetError());
		return 1;
	}

	SDL_Renderer *ren = SDL_CreateRenderer(win, -1, SDL_RENDERER_ACCELERATED | SDL_RENDERER_PRESENTVSYNC);
	if (ren == NULL) {
		printf("SDL_CreateRenderer Error: %s\n", SDL_GetError());
		return 1;
	}

	int font_size = font_size_to_fit(s, w, h);
	TTF_Font *font = TTF_OpenFont("path/to/your/font", font_size);

	SDL_Surface *surface = TTF_RenderText_Solid(font, s, c == NULL ? (SDL_Color) {255, 255, 255} : (SDL_Color) {c[0], c[1], c[2]});
	SDL_Texture *texture = SDL_CreateTextureFromSurface(ren, surface);

	SDL_Rect dest_rect;
	dest_rect.x = (w - surface->w) / 2;
	dest_rect.y = (h - surface->h) / 2;
	dest_rect.w = surface->w;
	dest_rect.h = surface->h;

	bool running = true;
	while (running) {
		SDL_RenderCopy(ren, texture, NULL, &dest_rect);
		SDL_RenderPresent(ren);

		handle_events(&running);
	}

	SDL_DestroyTexture(texture);
	SDL_FreeSurface(surface);
	TTF_CloseFont(font);
	SDL_DestroyRenderer(ren);
	SDL_DestroyWindow(win);
	TTF_Quit();
	SDL_Quit();

	return 0;
}

int font_size_to_fit(const char *s, int w, int h) {
	int font_size = 200;

	// Initialize a dummy font to get text size
	TTF_Font *font = TTF_OpenFont("path/to/your/font", font_size);

	int tw, th;
	TTF_SizeText(font, s, &tw, &th);

	int fsw = (int) (font_size * w / tw * 0.90);
	int fsh = (int) (font_size * h / th * 0.90);

	int fs = fsw < fsh ? fsw : fsh;

	TTF_CloseFont(font);

	return fs;
}

void handle_events(bool *running) {
	SDL_Event e;
	while (SDL_PollEvent(&e)) {
		if (e.type == SDL_QUIT) {
			*running = false;
		} else if (e.type == SDL_KEYDOWN) {
			if (e.key.keysym.sym == SDLK_q) {
				*running = false;
			}
		}
	}
}
// ```
// 
// Replace "path/to/your/font" with the path to a font file (for example a .ttf file) corresponding to the font family you want to use. In this example, I used "helvetica" as specified in the original script, but you can use any font file that's available on your system.
// 
// You will also need to install SDL2 and SDL2_ttf libraries to compile and run this code.