Change so it spins around pointer

inc/App.hpp

@@ -20,4 +20,8 @@ private:
   float rotation = 0.0f;
   Rectangle destB;
   Rectangle destA;
+
+  Vector2 mouseStart;
+  float len;
+  float ofset;
 };

inc/Math.hpp

@@ -1,4 +1,5 @@
 #include "raylib.h"
 
 Color ColorLerp(Color c1, Color c2, float amount);
-Rectangle CalculateRect(Vector2 center, float rotation, float width, float height);
+Vector2 calculateVector(float rotation, float offSet, float len);
+Rectangle calculateRotatedRectangle(Vector2 center, float rotation, float width, float height);

src/App.cpp

@@ -20,20 +20,33 @@ void App::init(int screenWidth, int screenHeight)
 
   center = {(float)screenWidth / 2, (float)screenHeight / 2};
   float rotation = 0.0f;
-  destA = CalculateRect(center, rotation, screenWidth, screenWidth);
-  destB = {destA.x, destA.y, (float)screenWidth, (float)screenWidth};
+  destA = calculateRotatedRectangle(center, rotation, screenWidth, screenWidth);
+  destB = destA;
 }
 
 void App::update()
 {
+  if (IsMouseButtonPressed(MOUSE_BUTTON_LEFT))
+  {
+    mouseStart = GetMousePosition();
+    len = Vector2Distance(mouseStart, center);
+    ofset = std::atan2(center.x - mouseStart.x, center.y - mouseStart.y);
+  }
+
   if (IsMouseButtonDown(MOUSE_BUTTON_LEFT))
   {
-    int mouseX = GetMouseX();
-    center.x = mouseX;
-    center.y = GetMouseY();
-    float l = (float)mouseX / screenWidth;
-    rotation = Lerp(45.0f, -45.0f, l);
-    destA = CalculateRect(center, rotation, screenWidth, screenWidth);
+    Vector2 mousePosition = GetMousePosition();
+
+    float dist = mousePosition.x - mouseStart.x;
+
+    float l = dist / screenWidth;
+    rotation = Lerp(45.0f, -45.0f, (l + 1) / 2);
+
+    Vector2 newCenter = calculateVector(rotation, ofset, len);
+    newCenter.x += mousePosition.x;
+    newCenter.y += mousePosition.y;
+
+    destA = calculateRotatedRectangle(newCenter, rotation, screenWidth, screenWidth);
   }
 
   if (IsMouseButtonReleased(MOUSE_BUTTON_LEFT))
@@ -41,9 +54,7 @@ void App::update()
     canvases[1 - pos].newGen();
     pos = 1 - pos;
     rotation = 0.0f;
-    center.x = screenWidth / 2;
-    center.y = screenHeight / 2;
-    destA = CalculateRect(center, rotation, screenWidth, screenWidth);
+    destA = destB;
   }
 }
 

src/Math.cpp

@@ -12,18 +12,27 @@ Color ColorLerp(Color c1, Color c2, float amount)
   return ret;
 }
 
-Rectangle CalculateRect(Vector2 center, float rotation, float width, float height)
+Vector2 calculateVector(float rotation, float offSet, float len)
+{
+  float angle = ((rotation)*PI) / 180.0f;
+  angle += offSet;
+  return {
+      .x = len * std::sin(angle),
+      .y = len * std::cos(angle)};
+}
+
+Rectangle calculateRotatedRectangle(Vector2 center, float rotation, float width, float height)
 {
   Rectangle ret = {0, 0, width, height};
+
   width /= 2;                                                      // a
   height /= 2;                                                     // b
   float len = std::sqrt(std::pow(width, 2) + std::pow(height, 2)); // c
-  rotation += 180.0f;                                              // add 180 to point 0 up
-  float angle = (rotation * PI) / 180.0f;                          // from degrees to radians
-  angle += std::atan(width / height);                              // add angle alfa
-  float nx = len * std::sin(angle);
-  float ny = len * std::cos(angle);
-  ret.x = center.x + nx;
-  ret.y = center.y + ny;
+  float offSet = std::atan2(width, height);                        // add angle alfa
+
+  Vector2 vec = calculateVector(rotation + 180.0f, offSet, len);
+
+  ret.x = vec.x + center.x;
+  ret.y = vec.y + center.y;
   return ret;
 }