improve animation panel

src/canvas_layer.cpp

@@ -238,6 +238,12 @@ bool Layer::add_frame()
     return m_frames.back().create(w, h);
 }
 
+void Layer::remove_frame(int frame)
+{
+    m_frames.erase(m_frames.begin() + frame);
+    m_frame_index = glm::clamp(m_frame_index, 0, (int)m_frames.size() - 1);
+}
+
 int Layer::total_duration() const noexcept
 {
     int duration = 0;