exp_circle_test.c

#include <SDL2/SDL.h>
#include <stdbool.h>
#include <stdio.h>

SDL_Window * window;
SDL_Renderer * renderer;


float get_exp_easing(float ticks, int startSize, int endSize, float duration)
{

	printf("%f, ", ticks);
	float y = endSize * pow( 2, 10 * (ticks / duration - 1) ) + startSize;
	printf("%f\n", y);
	return y;
}

void set_pixel(SDL_Renderer *rend, int x, int y, Uint8 r, Uint8 g, Uint8 b, Uint8 a)
{
	SDL_SetRenderDrawColor(rend, r,g,b,a);
	SDL_RenderDrawPoint(rend, x, y);
}

void draw_circle(SDL_Renderer *surface, int n_cx, int n_cy, int radius, Uint8 r, Uint8 g, Uint8 b, Uint8 a)
{
	// if the first pixel in the screen is represented by (0,0) (which is in sdl)
	// remember that the beginning of the circle is not in the middle of the pixel
	// but to the left-top from it:

	double error = (double)-radius;
	double x = (double)radius - 0.5;
	double y = (double)0.5;
	double cx = n_cx - 0.5;
	double cy = n_cy - 0.5;

	while (x >= y)
	{
		set_pixel(surface, (int)(cx + x), (int)(cy + y), r, g, b, a);
		set_pixel(surface, (int)(cx + y), (int)(cy + x), r, g, b, a);

		if (x != 0)
		{
			set_pixel(surface, (int)(cx - x), (int)(cy + y), r, g, b, a);
			set_pixel(surface, (int)(cx + y), (int)(cy - x), r, g, b, a);
		}

		if (y != 0)
		{
			set_pixel(surface, (int)(cx + x), (int)(cy - y), r, g, b, a);
			set_pixel(surface, (int)(cx - y), (int)(cy + x), r, g, b, a);
		}

		if (x != 0 && y != 0)
		{
			set_pixel(surface, (int)(cx - x), (int)(cy - y), r, g, b, a);
			set_pixel(surface, (int)(cx - y), (int)(cy - x), r, g, b, a);
		}

		error += y;
		++y;
		error += y;

		if (error >= 0)
		{
			--x;
			error -= x;
			error -= x;
		}
		/*
		// sleep for debug
		SDL_RenderPresent(gRenderer);
		std::this_thread::sleep_for(std::chrono::milliseconds{ 100 });
		*/
	}
}

int main(int argc, char* argv[])
{
	SDL_CreateWindowAndRenderer(640, 640, 0, &window, &renderer);
	SDL_SetHint(SDL_HINT_RENDER_SCALE_QUALITY, "nearest"); // To get nice 'pixely' upscaling
	SDL_RenderSetLogicalSize(renderer, 64, 64);
	SDL_SetRenderDrawBlendMode(renderer, SDL_BLENDMODE_BLEND);

	int ticks = SDL_GetTicks();
	int maxCircleDuration = 2500; //Length of time it takes for the circle to reach full size
	int maxCircles = 6;	//Number of total circles onscreen at once
	bool running = true;

	while (ticks < 10000 && running)
	{
		//Poll for events to prevent Gnome from thinking we've locked up
		SDL_Event e;
		while (SDL_PollEvent(&e))
		{
			if (e.type == SDL_QUIT)
			{
				running = false;
				break;
			}
		}

		SDL_SetRenderDrawColor(renderer, 0, 0, 0, 255);
		SDL_RenderClear(renderer);

		for (int i = 0; i < maxCircles; ++i)
		{
			int temp = ticks - i * (maxCircleDuration / maxCircles);
			if (temp > maxCircleDuration) //If the circle has reached its maximum size, reset it back to zero
			{
				temp = temp % maxCircleDuration;
			}

			draw_circle(renderer, 32, 32, get_exp_easing(temp, 0, 64, maxCircleDuration), 0, 255, 0, get_exp_easing(temp, 0, 255, maxCircleDuration));
		}
		
		SDL_RenderPresent(renderer);
		ticks = SDL_GetTicks();
	}


	SDL_DestroyRenderer(renderer);
	SDL_DestroyWindow(window);
	SDL_Quit();
	return 0;
}