Menus from the main menu bar are displayed when the left mouse button (button 1) is pressed over a menu bar entry. The drop-down listing of entries will appear. A selection can be made by releasing the mouse button over the item to be selected. Alternatively, clicking the mouse button will also cause the menu to appear, and clicking over the menu will select the item under the pointer, and retire the menu. While the menu is visible, keypresses are ``grabbed'' by the menu, and so will not be sent to other windows or applications. While a menu is visible, the up and down arrow keys will cycle through the menu entries, highlighting each in sequence. Pressing Enter will ``press'' the highlighted entry. The entries in the side menu are mostly toggle buttons, which are activated by clicking with mouse button 1.
Commands can also be executed by typing an accelerator while the mouse pointer is in a drawing window. Commands can be exited by selecting another command in most cases, or by pressing the Esc key. Some commands are switches which remain in effect until selected again.
There are multiple accelerator functions available.
Under Unix/Linux, the menu accelerators can be changed interactively. Click on a menu to open it, then move the pointer over one of the entries (it will be highlighted). Pressing Shift, Ctrl or Alt along with another key will add that accelerator to the menu entry, or change an existing accelerator. With the menu invisible, entering that key combination will ``press'' the assigned button, unless the combination happens to be used elsewhere for another purpose (it must be unique in the menus, at least). Under Windows, the menu accelerators can not be changed.