Drop-Down and Pop-Up Menus

Many concepts and technologies had to come together to make the GUI possible: the mouse, memory-mapped video, powerful processors, and pop-up windows. A pop-up window is a rectangle on the screen that appears, overlapping and obscuring the main part of the screen, until it has completed its work, whereupon it disappears, leaving the original screen behind, untouched. The pop-up window is the mechanism used to implement drop-down menus (also called pull-down menus) and dialog boxes.

In modern GUIs, menus are visible across the top row of a screen or window in a menu bar. The user points and clicks on a menu title on a menu bar and its immediately subordinate list of options appears in a small window just below it. A variant of the drop-down menu is a menu that "pops up" when you click (or more frequently, right-click) on an object, even though it has no menu title: a pop-up menu.

After the menu is open, the user makes a single choice by clicking once or by dragging and releasing. There's nothing remarkable about that, except that the menus generally go no deeper than this. The selection the user makes on the menu either takes immediate effect or calls up a dialog box. The hierarchy of menus has been flattened down until it is only one level deep. In other words, it has finally become a monocline grouping (discussed in Chapter 11).

Arguably the most significant advance of the GUI menu was this retreat from the hierarchical form into monocline grouping. The dialog box, another use of the pop-up window, was the tool that simplified the menu. The dialog box enabled the software designer to encapsulate all the sub-choices of any menu item within a single, interactive container. With dialogs, menu hierarchies could flatten out considerably, gathering all the niggling details further down the menu tree into a single dialog window. The deeply hierarchical menu was a thing of the past.

With the higher resolution of GUI displays, enough choices could be displayed on the menu bar to organize all the program's functions into about a half-dozen meaningful groups, each group represented by a one-word menu title. The menu for each group was also roomy enough to include all its related functions. The need to go to additional levels of menus was made almost superfluous.

(Of course, Philistines and reprobates are always with us, and they have created methods for turning pull-down menus back into hierarchical menus. They are called cascading menus, and although they are occasionally useful, more often they merely tempt the weaker souls in the development community to gum up their menus for little gain. We discuss this in more detail in Chapter 28.)