On entering the polyg command, if a polygon is selected, a vertex editing mode is active on all selected polygons. Each vertex of the selected object is marked with a small highlighting box. Clicking on the edge of a selected polygon away from an existing vertex will create a new vertex, which can subsequently be moved.
In order to operate on a vertex, it must be selected. A vertex can be selected by clicking on it, or by dragging over it. Any number of vertices can be selected. After the selection operation, selected vertices are shown marked with a larger box, and unselected vertices are not marked. Additional vertices can be selected, and existing selected vertices unselected, by holding the Shift key while clicking or dragging over vertex locations. Selecting a vertex a second time will deselect it.
Selected vertices can be deleted by pressing the Delete key. This will succeed only if after vertex removal the object does not become degenerate. In particular, one can not delete the object in this manner.
The selected vertices can be moved by dragging or clicking twice. The selected vertices will be translated according to the button-down location and the button up location, or the next button-down location if the pointer did not move. While the translation is in progress, the new borders are ghost-drawn.
All vertex operations can be undone and redone through use of the Undo and Redo commands.
With vertices selected, pressing the Esc or Backspace keys will deselect the vertices and return to the state with all vertices marked.
While in the polyg command, with no object in the process of being created, it is possible to change the selected state of polygon objects, thus displaying the vertices and allowing vertex editing. Pressing the Enter key will cause the next button 1 operation to select (or deselect) polygon objects. This can be repeated arbitrarily. When one of these objects is selected, the vertices are marked, and vertex editing is possible.
If the vertex editor is active, i.e., a selected polygon is shown with the vertices marked, clicking with the Ctrl button pressed will start a new polygon, overriding the vertex editor. This can be used to start a new polygon at a marked vertex location, for example. Without Ctrl pressed, the vertex editor would have precedence and would select the marked vertex instead of starting a new polygon.
While moving vertices, holding the Shift key will enable or disable constraining the translation angle to multiples of 45 degrees. If the Constrain angles to 45 degree multiples check box in the Editing Setup panel from the Edit Menu is checked, Shift will disable the constraint, otherwise the constraint will be enabled. The Shift key must be up when the button-down occurs which starts the translation operation, and can be pressed before the operation is completed to alter the constraint. These operations are similar to operations in the Stretch command.