add export depth menu

src/canvas.cpp

@@ -1544,6 +1544,30 @@ void Canvas::inject_xmp(std::string jpg_path)
 
 }
 
+void Canvas::export_depth(std::string file_name, std::function<void()> on_complete)
+{
+    if (App::I.check_license())
+    {
+        std::thread t([=] {
+            BT_SetTerminate();
+            export_depth_thread(file_name);
+            if (on_complete)
+                on_complete();
+        });
+        t.detach();
+    }
+}
+
+void Canvas::export_depth_thread(std::string file_name)
+{
+    App::I.async_start();
+    gl_state gl;
+    gl.save();
+
+    gl.restore();
+    App::I.async_end();
+}
+
 void Canvas::export_layers(std::string file_name, std::function<void()> on_complete)
 {
     if (App::I.check_license())