Custom Scroll Animations in SDL

1#include <SDL.h>
2
3#include <chrono>
4#include <iostream>
5
6int main(int argc, char* argv[]) {
7  using namespace std::chrono;
8  SDL_Init(SDL_INIT_VIDEO);
9  SDL_Window* window = SDL_CreateWindow(
10    "Custom Scroll Animations Example",
11    SDL_WINDOWPOS_UNDEFINED,
12    SDL_WINDOWPOS_UNDEFINED,
13    800, 600, SDL_WINDOW_SHOWN
14  );
15  SDL_Renderer* renderer =
16    SDL_CreateRenderer(window, -1, 0);
17
18  SDL_Event event;
19  bool running = true;
20  float scrollPosition = 0.0f;
21  float targetPosition = 0.0f;
22  float animationSpeed = 0.1f;  
23  auto lastTime = high_resolution_clock::now();
24
25  while (running) {
26    auto currentTime = high_resolution_clock::now();
27    duration<float> deltaTime =
28      currentTime - lastTime;
29    lastTime = currentTime;
30
31    while (SDL_PollEvent(&event)) {
32      if (event.type == SDL_MOUSEWHEEL) {
33        targetPosition += event.wheel.y * 20.0f;  
34      }
35      if (event.type == SDL_QUIT) {
36        running = false;
37      }
38    }
39
40    // Smoothly interpolate the scroll position
41    // towards the target position
42    scrollPosition += (
43      targetPosition - scrollPosition
44    ) * animationSpeed;
45
46    SDL_SetRenderDrawColor(renderer, 0, 0, 0, 255);
47    SDL_RenderClear(renderer);
48
49    SDL_SetRenderDrawColor(
50      renderer, 255, 255, 255, 255);
51
52    SDL_Rect rect = {
53      375,
54      static_cast<int>(scrollPosition),
55      50,
56      50
57    };
58    SDL_RenderFillRect(renderer, &rect);
59
60    SDL_RenderPresent(renderer);
61  }
62
63  SDL_DestroyRenderer(renderer);
64  SDL_DestroyWindow(window);
65  SDL_Quit();
66  return 0;
67}

1#include <SDL.h>
2
3#include <chrono>
4#include <cmath>
5#include <iostream>
6
7float EaseOut(float t) {
8  return 1.0f - std::pow(1.0f - t, 3);  
9}
10
11int main(int argc, char* argv[]) {
12  using namespace std::chrono;
13
14  SDL_Init(SDL_INIT_VIDEO);
15  SDL_Window* window = SDL_CreateWindow(
16    "Custom Scroll Animations Example",
17    SDL_WINDOWPOS_UNDEFINED,
18    SDL_WINDOWPOS_UNDEFINED,
19    800, 600, SDL_WINDOW_SHOWN
20  );
21
22  SDL_Renderer* renderer =
23    SDL_CreateRenderer(window, -1, 0);
24
25  SDL_Event event;
26  bool running = true;
27  float scrollPosition = 0.0f;
28  float targetPosition = 0.0f;
29  float animationSpeed = 0.1f;
30  auto lastTime = high_resolution_clock::now();
31
32  while (running) {
33    auto currentTime = high_resolution_clock::now();
34    duration<float> deltaTime = currentTime - lastTime;
35    lastTime = currentTime;
36
37    while (SDL_PollEvent(&event)) {
38      if (event.type == SDL_MOUSEWHEEL) {
39        targetPosition += event.wheel.y * 20.0f;
40      }
41      if (event.type == SDL_QUIT) {
42        running = false;
43      }
44    }
45
46    // Smoothly interpolate the scroll position
47    // towards the target position with easing
48    float t = EaseOut(
49      animationSpeed * deltaTime.count());
50    scrollPosition += (
51      targetPosition - scrollPosition) * t;
52
53    SDL_SetRenderDrawColor(renderer, 0, 0, 0, 255);
54    SDL_RenderClear(renderer);
55
56    SDL_SetRenderDrawColor(
57      renderer, 255, 255, 255, 255);
58
59    SDL_Rect rect = {
60      375,
61      static_cast<int>(scrollPosition),
62      50,
63      50
64    };
65
66    SDL_RenderFillRect(renderer, &rect);
67
68    SDL_RenderPresent(renderer);
69  }
70
71  SDL_DestroyRenderer(renderer);
72  SDL_DestroyWindow(window);
73  SDL_Quit();
74  return 0;
75}