save and restore layers image when context is lost in Android

engine/layout.h

@@ -101,6 +101,8 @@ public:
         auto i = m_layouts.find(id);
         return i == m_layouts.end() ? nullptr : i->second.get();
     }
+    void restore_context();
+    void clear_context();
     //Node& operator[](const char* ids) { return m_layouts[const_hash(ids)]; }
 };
 
@@ -222,10 +224,13 @@ public:
     virtual void restore_context()
     {
         for (auto& c : m_children)
-        {
             c->restore_context();
-        }
     };
+    virtual void clear_context()
+    {
+        for (auto& c : m_children)
+            c->clear_context();
+    }
     void update(float width, float height, float zoom);
     void update();
     void update_internal(const glm::vec2& origin, const glm::mat4& proj);
@@ -482,6 +487,7 @@ public:
     {
         if (!m_path.empty() && TextureManager::load(m_path.c_str()))
         {
+            //LOG("load image node %s", m_path.c_str());
             auto tex_sz = TextureManager::get(m_tex_id).size();
             m_off = m_region.xy / tex_sz;
             m_sz = (m_region.zw - m_region.xy) / tex_sz;
@@ -885,6 +891,7 @@ public:
             i += strlen(s) + 1;
         }
         file.close();
+        TextureManager::load("data/spritesheet.png");
     }
     virtual Node* clone_instantiate() const override { return new NodeIcon(); }
     virtual void clone_copy(Node* dest) const override
@@ -1700,7 +1707,13 @@ public:
     {
         NodeBorder::restore_context();
         init_controls();
-        m_rtt.create(m_rtt.getWidth(), m_rtt.getHeight());
+        if (m_size.x > 0 && m_size.y > 0)
+            m_rtt.create(m_size.x, m_size.y);
+    }
+    virtual void clear_context() override
+    {
+        NodeBorder::clear_context();
+        m_rtt.destroy();
     }
     void draw_stroke()
     {
@@ -1856,6 +1869,7 @@ class NodeCanvas : public Node
     float m_zoom_start;
     bool method = true;
 public:
+    std::string data_path;
     std::unique_ptr<ui::Canvas> m_canvas;
     ui::Brush m_brush;
     Sampler m_sampler;
@@ -1876,7 +1890,15 @@ public:
         Node::restore_context();
         m_canvas->create(512, 512);
         m_sampler.create();
+        //m_canvas->clear();
         m_face_plane.create<1>(2, 2);
+        m_canvas->snapshot_restore();
+    }
+    virtual void clear_context() override
+    {
+        Node::clear_context();
+        m_canvas->snapshot_save(data_path);
+        m_canvas->clear_context();
     }
     virtual void draw() override
     {