fix thumbnail generator for iOS and open document when file clicked

src/app.cpp

@@ -31,6 +31,26 @@ void App::create()
     height = 1080/2;
 }
 
+void App::open_document(std::string path)
+{
+    auto start = path.rfind("/") + 1;
+    doc_name = path.substr(start, path.length() - start - strlen(".ppi"));
+    canvas->reset_camera();
+    layers->clear();
+    canvas->m_canvas->project_open(path, [this] {
+        // on complete
+        async_start();
+        title_update();
+        for (auto& i : canvas->m_canvas->m_order)
+        {
+            auto* l = layers->add_layer(canvas->m_canvas->m_layers[i].m_name.c_str());
+            l->m_opacity->m_value.x = canvas->m_canvas->m_layers[i].m_opacity;
+        }
+        async_end();
+    });
+    ActionManager::clear();
+}
+
 bool App::request_close()
 {
     static bool dialog_already_opened = false;