Merge pull request #2 from nayutalienx/copilot/fix-2d243eb4-254b-4344-8b38-bd0de531936b

Fix cursor trail interpolation gaps when moving cursor quickly

Author: nayutalienx

CursorTrail/Game.cpp

@@ -71,11 +71,7 @@ void Game::Update(GLFWwindow* window)
 
     TrailPart currentTrail = TrailPart(xpos, ypos, g_config.fadeTime);
 
-    // Add the current cursor position to trail
-    this->AddPart(currentTrail);
-
-    // interpolate trail
-
+    // Calculate previous index BEFORE adding current trail
     int prevIndex;
     if (this->currentIndex != 0) {
         prevIndex = this->currentIndex - 1;
@@ -84,6 +80,11 @@ void Game::Update(GLFWwindow* window)
         prevIndex = g_config.maxParticles - 1;
     }
 
+    // Add the current cursor position to trail
+    this->AddPart(currentTrail);
+
+    // interpolate trail
+
     TrailPart previousTrail = this->parts[prevIndex];
 
     glm::vec2 pos1 = glm::vec2(previousTrail.x, previousTrail.y);

CursorTrail/WindowsOverlay.cpp

@@ -164,11 +164,13 @@ void WindowsOverlay::Update()
     if (GetCursorPos(&cursorPos)) {
         TrailPart currentTrail(static_cast<float>(cursorPos.x), static_cast<float>(cursorPos.y), g_config.fadeTime);
 
+        // Calculate previous index BEFORE adding current trail
+        size_t prevIndex = (m_currentIndex == 0) ? m_trailParts.size() - 1 : m_currentIndex - 1;
+        
         // Add the current cursor position to trail (match OpenGL version exactly)
         AddTrailPart(currentTrail);
 
         // Interpolate trail between current and previous position ONLY (like OpenGL Game.cpp)
-        size_t prevIndex = (m_currentIndex == 0) ? m_trailParts.size() - 1 : m_currentIndex - 1;
         const TrailPart& previousTrail = m_trailParts[prevIndex];
 
         float dx = currentTrail.x - previousTrail.x;