save and restore layers image when context is lost in Android

engine/texture.cpp

@@ -27,6 +27,10 @@ Texture2D& TextureManager::get(uint16_t id)
 
 void TextureManager::invalidate()
 {
+    for (auto& t : m_textures)
+    {
+        t.second.destroy();
+    }
     m_textures.clear();
 }
 
@@ -37,6 +41,7 @@ bool Texture2D::create(int width, int height, GLint internal_format, GLint forma
     m_format = format;
     m_iformat = internal_format;
     glGenTextures(1, &m_tex);
+    LOG("genTex %d", m_tex);
     bind();
     glTexImage2D(GL_TEXTURE_2D, 0, internal_format, width, height, 0, format, GL_UNSIGNED_BYTE, data);
     unbind();
@@ -60,6 +65,7 @@ void Texture2D::assign(GLuint tex, int w/* = -1*/, int h/* = -1*/, GLuint intern
 
 bool Texture2D::load(std::string filename)
 {
+    LOG("load texture %s", filename.c_str());
     ui::Image img;
     if (!img.load(filename))
         return false;