Movement and movement curves

main.c

@@ -6,6 +6,7 @@
 #include <raylib.h>
 
 #include "card.h"
+#include "move.h"
 
 char *text = "こんにちわ、 世界！";
 
@@ -16,7 +17,26 @@ int main(int argc, char** argv) {
     Card *c = malloc(sizeof(Card));
     c->position = (Vector2) { 200, 200 };
 
+    Move *m = malloc(sizeof(Move));
+    m->origin = c->position;
+    m->destination = c->position;
+    m->curve = CURVE_EASE_IN_OUT;
+
+    float delta;
+    Vector2 mouse_position;
+
     while (!WindowShouldClose()) {
+      delta = GetFrameTime();
+      if (IsMouseButtonPressed(0)) {
+	mouse_position = GetMousePosition();
+	m->origin = c->position;
+	m->destination = mouse_position;
+	m->current_time = 0.;
+	m->end_time = 1.;
+      }
+
+      c->position = move_position(m, delta);
+
       BeginDrawing();
       ClearBackground(RAYWHITE);
       draw_card(c);

move.c

@@ -0,0 +1,23 @@
+#include <math.h>
+#include "move.h"
+
+Vector2 move_position(Move *m, float delta) {
+  m->current_time += delta;
+  float percentage = m->current_time / m->end_time;
+  if (percentage < 0.0) percentage = 0.0;
+  else if (percentage > 1.0) percentage = 1.0;
+
+  switch (m->curve) {
+  case CURVE_LINEAR:
+    return (Vector2) {
+      ((m->destination.x - m->origin.x) * percentage) + m->origin.x,
+      ((m->destination.y - m->origin.y) * percentage) + m->origin.y
+    };
+  case CURVE_EASE_IN_OUT:
+    percentage = -(cos(PI * percentage) - 1) / 2;
+    return (Vector2) {
+      ((m->destination.x - m->origin.x) * percentage) + m->origin.x,
+      ((m->destination.y - m->origin.y) * percentage) + m->origin.y
+    };
+  }
+}

move.h

@@ -0,0 +1,23 @@
+#ifndef _HF_MOVE_
+#define _HF_MOVE_
+
+#include <raylib.h>
+
+typedef enum Curve {
+  CURVE_LINEAR,
+  CURVE_EASE_IN_OUT,
+} Curve;
+
+typedef struct Move Move;
+
+struct Move {
+  Vector2 origin;
+  Vector2 destination;
+  Curve curve;
+  float current_time;
+  float end_time;
+};
+
+Vector2 move_position(Move *m, float delta);
+
+#endif