SDL window updates slowly if I don't move my mouse - c++

Question

I recently tried to implement OneLoneCoder's simple 3d Graphics Engine, from his Code-It-Yourself series, on SDL2. So I made some triangles that move on the window, but these triangles would appear to move at a slower framerate when I left my mouse completely still, and then move at their normal framerate if I started to move my mouse.
You see, to animate these triangles I used some while loops, something like this:
while (true) {
// Black Background
SDL_SetRenderDrawColor(renderer, 0, 0, 0, 255);
SDL_RenderClear(renderer);
SDL_SetRenderDrawColor(renderer, 255, 255, 255, 255);
// Custom function that draws a triangle using SDL_RenderDrawLine()
drawTriangle(renderer, triangle);
SDL_RenderPresent(renderer); // updates the pixels on the renderer
while (SDL_PollEvent(&event)) {
if (event.type == SDL_QUIT)
goto Exit;
}
}
Pretty standard, right?
Here is an example of some code that has this exact same issue:
#include<iostream>
#include"SDL.h"
struct vec {
float x, y;
vec ( float x, float y)
: x(x), y(y)
{}
vec () {}
};
struct triangle {
vec p[3];
triangle() {}
};
void drawTriangle(SDL_Renderer* r, const triangle& tri) {
SDL_RenderDrawLine(r, tri.p[0].x, tri.p[0].y, tri.p[1].x, tri.p[1].y);
SDL_RenderDrawLine(r, tri.p[1].x, tri.p[1].y, tri.p[2].x, tri.p[2].y);
SDL_RenderDrawLine(r, tri.p[2].x, tri.p[2].y, tri.p[0].x, tri.p[0].y);
}
int main(int argc, char **argv) {
uint16_t width = 400;
uint16_t height = 300;
if (SDL_Init(SDL_INIT_VIDEO) > 0) { std::cout << "SDL_INIT FAILED\nERROR: " << SDL_GetError() << std::endl; }
SDL_Window* window = NULL;
SDL_Renderer* renderer = NULL;
SDL_Event event;
window = SDL_CreateWindow("SDL Test :)", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, width, height, SDL_WINDOW_SHOWN);
if (window == NULL) { std::cout << "SDL_WINDOW FAILED\nERROR: " << SDL_GetError() << std::endl; }
renderer = SDL_CreateRenderer(window, -1, SDL_RENDERER_SOFTWARE);
triangle myTri;
myTri.p[0] = vec( width * 0.5, 0);
myTri.p[1] = vec( width * 0.333, height * 0.2);
myTri.p[2] = vec( width * 0.666, height * 0.2);
while (true) {
SDL_SetRenderDrawColor(renderer, 0, 0, 0, 255);
SDL_RenderClear(renderer);
myTri.p[0].y += 0.01f;
myTri.p[1].y += 0.01f;
myTri.p[2].y += 0.01f;
SDL_SetRenderDrawColor(renderer, 255, 255, 255, 255);
drawTriangle(renderer, myTri);
SDL_RenderPresent(renderer);
while (SDL_PollEvent(&event)) {
if (event.type == SDL_QUIT)
goto Exit;
}
}
Exit:
SDL_DestroyWindow(window);
SDL_Quit();
return 0;
}