Openstreetmap object coordinates (latitude, longitude)

Hello everyone, there is a Windows application that displays the map from http://www.openstreetmap.org. It is necessary to implement dragging of the map displayed in the application with the mouse. That is, the user can hover the cursor over the map, click the left mouse button - and drag it (the map) in different directions.

The problem that I have now is that I do not know how to get the actual coordinates of the map relative to the coordinates mouse cursor offsets.

For example, the user displays a piece of the map with the coordinates of the object: 40.0400,-76.4160 (latitude, longitude). Suppose the user took the map and pulled it in a certain direction, as a result, we got the coordinates of the mouse offset 5;4 (x;y).

Actually, the question itself is how to get the new coordinates of the object (latitude and longitude), taking into account the scale (zoom) in which the map is currently displayed in the user's program, plus that the offset that he (the user) made.