Most of the transforms kind of work now need to hook in the new timer.

animate2.cpp

@@ -78,6 +78,7 @@ namespace animate2 {
 
   void Timer::start() {
     clock.start();
+    prev_time = clock.getElapsedTime().asSeconds();
   }
 
   void Timer::reset() {
@@ -86,25 +87,34 @@ namespace animate2 {
 
   void Timer::restart() {
     clock.restart();
+    prev_time = clock.getElapsedTime().asSeconds();
   }
 
   sf::Time Timer::getElapsedTime() {
     return clock.getElapsedTime();
   }
 
-  void Timer::begin() {
-    prev_time = clock.getElapsedTime().asSeconds();
-  }
-
   std::pair<int, double> Timer::commit() {
+    // determine frame duration based on previous time
     current_time = clock.getElapsedTime().asSeconds();
     frame_duration = current_time - prev_time;
+
+    // update prev_time for the next call
+    prev_time = current_time;
+
+    // update accumulator, retaining previous errors
     accumulator += frame_duration;
 
+    // find the tick count based on DELTA
     double tick_count = accumulator / DELTA;
+    // alpha is then the remainder/fractional part
     double alpha = modf(tick_count, &tick_count);
-    accumulator -= tick_count * DELTA;
 
+    // reduce accumulator by the number of DELTAS
+    accumulator -= tick_count * DELTA;
+    // that leaves the remaining errors for next loop
+
+    // return the number of even DELTA ticks and the alpha
     return {int(tick_count), alpha};
   }
 

animate2.hpp

@@ -26,7 +26,6 @@ namespace animate2 {
     double alpha = 0.0;
     sf::Clock clock{};
 
-    void begin();
     std::pair<int, double> commit();
     void start();
     void reset();

ease2.cpp

@@ -15,7 +15,7 @@ namespace ease2 {
     return (std::sin(x) + 1.0) / 2.0;
   }
 
-  double out_circ(double x) {
+  double out_circle(double x) {
     return std::sqrt(1.0f - ((x - 1.0f) * (x - 1.0f)));
   }
 
@@ -46,11 +46,11 @@ namespace ease2 {
       : (std::pow(2.0 * x - 2.0, 2.0) * ((c2 + 1.0) * (x * 2.0 - 2.0) + c2) + 2.0) / 2.0;
   }
 
-  float random(float tick) {
+  double random(double tick) {
     return Random::uniform_real(0.0001f, 1.0f);
   }
 
-  float normal_dist(float tick) {
+  double normal_dist(double tick) {
     return Random::normal(0.5f, 0.1f);
   }
 
@@ -66,7 +66,6 @@ namespace ease2 {
     scale_out.x = std::lerp(tr.min_x, tr.max_x, tick);
     scale_out.y = std::lerp(tr.min_y, tr.max_y, tick);
     pos_out.y = pos_out.y - (pos_out.y * scale_out.y - pos_out.y);
-    fmt::println("RUSH pos={},{}; scale={},{}; tic={}", pos_out.x, pos_out.y, scale_out.x, scale_out.y, tick);
   }
 
   void scale_squeeze(Transform &tr, sf::Vector2f& pos_out, sf::Vector2f& scale_out, float tick) {
@@ -77,7 +76,7 @@ namespace ease2 {
     scale_out.y *= std::lerp(tr.min_y, tr.max_y, tick);
   }
 
-  void scale_strech(Transform &tr, sf::Vector2f& pos_out, sf::Vector2f& scale_out, float tick) {
+  void scale_stretch(Transform &tr, sf::Vector2f& pos_out, sf::Vector2f& scale_out, float tick) {
     scale_out.x = std::lerp(tr.min_x, tr.max_x, tick);
   }
 
@@ -86,8 +85,8 @@ namespace ease2 {
   }
 
   void move_slide(Transform &tr, sf::Vector2f& pos_out, sf::Vector2f& scale_out, float tick) {
-    pos_out.x = std::lerp(tr.min_x, tr.max_x, tick);
+    pos_out.x += std::lerp(tr.min_x, tr.max_x, tick);
-    pos_out.y = std::lerp(tr.min_y, tr.max_y, tick);
+    pos_out.y += std::lerp(tr.min_y, tr.max_y, tick);
   }
 
   void move_none(Transform &tr, sf::Vector2f& pos_out, sf::Vector2f& scale_out, float tick) {

ease2.hpp

@@ -10,7 +10,7 @@ namespace ease2 {
   using MoveFunc = std::function<void(animate2::Transform &tr, sf::Vector2f& pos_out, sf::Vector2f& scale_out, float tick)>;
 
   double sine(double x);
-  double out_circ(double x);
+  double out_circle(double x);
   double out_bounce(double x);
   double in_out_back(double x);
   double random(double tick);
@@ -20,9 +20,10 @@ namespace ease2 {
   void move_rush(animate2::Transform &tr, sf::Vector2f& pos_out, sf::Vector2f& scale_out, float tick);
   void scale_squeeze(animate2::Transform &tr, sf::Vector2f& pos_out, sf::Vector2f& scale_out, float tick);
   void scale_squash(animate2::Transform &tr, sf::Vector2f& pos_out, sf::Vector2f& scale_out, float tick);
-  void scale_strech(animate2::Transform &tr, sf::Vector2f& pos_out, sf::Vector2f& scale_out, float tick);
+  void scale_stretch(animate2::Transform &tr, sf::Vector2f& pos_out, sf::Vector2f& scale_out, float tick);
   void scale_grow(animate2::Transform &tr, sf::Vector2f& pos_out, sf::Vector2f& scale_out, float tick);
   void move_slide(animate2::Transform &tr, sf::Vector2f& pos_out, sf::Vector2f& scale_out, float tick);
   void move_none(animate2::Transform &tr, sf::Vector2f& pos_out, sf::Vector2f& scale_out, float tick);
   void scale_only(animate2::Transform &tr, sf::Vector2f& pos_out, sf::Vector2f& scale_out, float tick);
+  void move_shake(animate2::Transform &tr, sf::Vector2f& pos_out, sf::Vector2f& scale_out, float tick);
 }

tests/animate2.cpp

@@ -196,9 +196,9 @@ TEST_CASE("confirm transition changes work", "[animation-new]") {
 
 TEST_CASE("playing with delta time", "[animation-new]") {
   animate2::Timer timer;
+  timer.start();
 
   for(int i = 0; i < 20; i++) {
-    timer.begin();
     FAKE_RENDER();
     auto [tick_count, alpha] = timer.commit();
     fmt::println("tick: {}, alpha: {}", tick_count, alpha);

tools/animator.cpp

@@ -55,6 +55,11 @@ namespace animator {
     bool mouse(float x, float y, guecs::Modifiers mods) {
       return $ui.mouse(x, y, mods);
     }
+
+    std::shared_ptr<sf::Sprite> get_sprite() {
+      auto viewer = $ui.entity("viewer");
+      return $ui.get<guecs::Sprite>(viewer).sprite;
+    }
   };
 
   enum class State {
@@ -156,10 +161,10 @@ animate2::Sequence sequence{
 };
 
 animate2::Transform transform{
-  .min_x{0.6f},
+  .min_x{-40.0f},
-    .min_y{0.6f},
+    .min_y{-40.0f},
-    .max_x{0.8f},
+    .max_x{40.0f},
-    .max_y{0.8f},
+    .max_y{40.0f},
     .simple{false},
     .flipped{false},
     .ease_rate{0.5f},
@@ -168,8 +173,8 @@ animate2::Transform transform{
     .stationary{true},
     .toggled{false},
     .looped{true},
-    .easing = ease2::in_out_back,
+    .easing = ease2::out_circle,
-    .motion = ease2::move_rush,
+    .motion = ease2::move_bounce,
 };
 
 int main(int argc, char* argv[]) {
@@ -194,13 +199,19 @@ int main(int argc, char* argv[]) {
   timer.start();
   anim.play();
 
-  auto viewer = main.$ui.$ui.entity("viewer");
+  auto sprite = main.$ui.get_sprite();
-  auto& sprite = main.$ui.$ui.get<guecs::Sprite>(viewer).sprite;
+  sf::Vector2f pos = sprite->getPosition();
+  sf::Vector2f scale = sprite->getScale();
 
   while(main.active()) {
-    timer.begin();
-
     anim.apply(*sprite);
+
+    sf::Vector2f new_pos = pos;
+    sf::Vector2f new_scale = scale;
+    anim.motion(new_pos, new_scale);
+    sprite->setPosition(new_pos);
+    sprite->setScale(new_scale);
+
     main.render();
 
     auto [ticks, alpha] = timer.commit();
@@ -211,8 +222,8 @@ int main(int argc, char* argv[]) {
       anim.update();
     }
 
-
     // do something with alpha....
+
     main.handle_keyboard_mouse();
   }