There can be more than one current shape at one time. If there is more than one current shape, there cannot be a current vertex. A vertex can only become current when there is only one current shape, and there can only be one current vertex at a time.
Shapes can be selected in several ways: by pressing the up or down arrow buttons of the "Shape ID" text field, by entering a shape id in the "Shape ID" text field, by using the "Select" operation, or by making selections in the image window using the mouse.
The first two methods of selecting a shape are quite simple and need no explanation. For an explanation on how to use the "Select" operation, see the "Vector Editing Operations" help.
When making shape selections within the image window, the mouse cursor must be in the image window. As the mouse is moved around in the image window with the left mouse button depressed, the current shape and current vertex are updated to reflect the current selection(s). The shape and vertex closest to the cursor are the current shape and vertex selections. The selection operation is complete when the mouse button is released.
Holding down the <SHIFT> key while selecting shapes in the image window adds to or removes from the existing set of current shapes. If the shape is already highlighted, reselecting it with the mouse while holding down the <SHIFT> key will remove it from the set of current shapes. If the shape is not highlighted, selecting it with the mouse while holding down the <SHIFT> key will add it to the set of current shapes.
When a single shape is being selected using the mouse in the image window, the vertex is selected simultaneously. The vertex closest to the cursor becomes the selected vertex.
If a shape is selected using the text field methods, then the first vertex in the shape is automatically selected as the current vertex, unless the shape has no vertices. The current vertex can be changed by pressing the arrow buttons on the vertex id text field or by entering the new current vertex in the vertex id text field. There cannot be a current vertex without a current shape.