diff -r 68443f5be176 -r 44679e468ba9 src/mainwindow.cpp
--- a/src/mainwindow.cpp	Sat Oct 05 23:47:03 2019 +0300
+++ b/src/mainwindow.cpp	Sun Nov 03 12:17:41 2019 +0200
@@ -7,6 +7,7 @@
 #include "ui_mainwindow.h"
 #include "settingseditor/settingseditor.h"
 #include "version.h"
+#include "document.h"
 
 MainWindow::MainWindow(QWidget *parent) :
 	QMainWindow{parent},
@@ -43,19 +44,21 @@
 		tr("LDraw models (*.ldr *.dat)"));
 	if (not path.isEmpty())
 	{
-		QFile file{path};
-		const bool open_result = file.open(QIODevice::ReadOnly);
-		if (open_result)
+		QString errorString;
+		QTextStream errorStream{&errorString};
+		QString modelName = this->documents.openModel(path, errorStream);
+		if (not modelName.isEmpty())
 		{
-			QMessageBox::critical(this, "Not implemented", "This functionality is not done yet");
+			Document* document = new Document{this->documents.findModelByName(modelName)};
+			this->ui->tabs->addTab(document, modelName);
 		}
 		else
 		{
-			const QString errorString = format(
+			const QString errorMessage = utility::format(
 				tr("Could not open %1: %2"),
 				path,
-				file.errorString());
-			QMessageBox::critical(this, tr("Problem opening file"), errorString);
+				errorString);
+			QMessageBox::critical(this, tr("Problem opening file"), errorMessage);
 		}
 	}
 }