sdl test

gistfile1.txt

#define SDL_MAIN_HANDLED
#include <SDL2/SDL.h>

#include <vector>
#include <array>

SDL_Renderer* renderer;
std::vector<SDL_Point> points;
std::vector<std::pair<SDL_Point, float>> fadingPoints;
SDL_Point mousePos;
Uint32 lastTick = 0;
Uint32 deltaTime = 0;


void draw() {
	deltaTime = SDL_GetTicks() - lastTick;
	lastTick = SDL_GetTicks();
	
	float fdeltaTime = static_cast<float>(deltaTime) / 1000.f;
	
	const Uint8 lineColor[3] = { 255, 255, 255 };

	SDL_SetRenderDrawColor(renderer, lineColor[0], lineColor[1], lineColor[2], 255);
	for(SDL_Point point : points) {
		SDL_RenderDrawLine(renderer, point.x, point.y, mousePos.x, mousePos.y);
	}
	
	for(auto it = fadingPoints.begin(); it != fadingPoints.end(); it++) {
		std::pair<SDL_Point, float>& fadingPoint = *it;
		Uint8 alpha = static_cast<float>(fadingPoint.second);
		SDL_SetRenderDrawColor(renderer, alpha, alpha, alpha, alpha);
		SDL_RenderDrawLine(renderer, fadingPoint.first.x, fadingPoint.first.y, mousePos.x, mousePos.y);
		if(fadingPoint.second > 0) {
			fadingPoint.second -= 255.f * fdeltaTime;
		} else {
			it = fadingPoints.erase(it);
			it--;
			
		}
	}
	
	SDL_RenderPresent(renderer);
	SDL_SetRenderDrawColor(renderer, 0, 0, 0, 255);
	SDL_RenderClear(renderer);
}

int main() {
	
	SDL_Init(SDL_INIT_VIDEO);
	
	SDL_Window* window = SDL_CreateWindow("sdl-test",
		SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED,
		960, 540, SDL_WINDOW_OPENGL | SDL_WINDOW_SHOWN );
		
	renderer = SDL_CreateRenderer(window, -1, SDL_RENDERER_ACCELERATED);
	
	for(;;) {
				
		SDL_Event e;
		
		if(SDL_PollEvent(&e) != 0) {
			switch(e.type) {
				case SDL_QUIT:
					SDL_Quit();
					exit(0);
					break;
				case SDL_KEYDOWN:
					switch(e.key.keysym.sym) {
						case SDLK_ESCAPE:
							SDL_Quit();
							exit(0);
							break;
					}
					break;
				case SDL_MOUSEBUTTONDOWN:
					if(e.button.button == 1) {
						points.push_back({e.button.x, e.button.y});
					} else
					if(e.button.button == 3) {
						if(points.begin() != points.end()) {
							fadingPoints.push_back(std::make_pair<SDL_Point, Uint8>(SDL_Point(*points.begin()), 255.f));
							points.erase(points.begin());
						}
					}
					break;
				case SDL_MOUSEWHEEL:
					if(e.wheel.y > 0) {
						points.push_back({rand() % 960, rand() % 540});
					} else
					if(e.wheel.y < 0) {
						if(points.begin() != points.end()) {
							fadingPoints.push_back(std::make_pair<SDL_Point, Uint8>(SDL_Point(*points.begin()), 255.f));
							points.erase(points.begin());
						}
					}
					break;
				case SDL_MOUSEMOTION:
					mousePos.x = e.motion.x;
					mousePos.y = e.motion.y;
					break;
				
			}
		}
		
		draw();
		
	}
	
	
	return 0;
}