Selection Methods (HI Guide)

Inside Macintosh: Macintosh Human Interface Guidelines / Part 2 - The Interface Elements: Chapter 10 - Behaviors / Selecting

Selection Methods

This section describes various selection techniques: selection by clicking, selection by dragging, extending a selection, and discontinuous selection. Figure 10-15 shows some of the methods.

Figure 10-15 Selection techniques

Selection by Clicking

The most straightforward method of selecting an object is by clicking it once. Icons and most other things that can be selected are selected in this way. The user positions the pointer over the desired object, then presses and releases the mouse button.

Selection by Dragging

The user selects a range of objects by dragging through them. Although the exact meaning of the selection depends on the type of application, the procedure is always the same:

The user positions the pointer at one corner of the range and presses the mouse button. This position is called the anchor point of the range.
Without releasing the mouse button, the user moves the pointer in any direction. As the pointer is moved, visual feedback indicates the objects that would be selected if the mouse button were released. For text and arrays, the selected area is continuously highlighted. For graphics, a dotted rectangle expands or contracts to show the range that will be selected. If appropriate, the view should scroll to allow extending the selection beyond one window.
When visual feedback shows the desired range, the user releases the mouse button. The point at which the button is released is called the active end of the range.

Changing a Selection With Shift-Click

A user can extend a selection by holding down the Shift key and clicking the mouse button. This action is called Shift-clicking. Exactly what happens next depends on the context.

In text or an array, the result of the Shift-click is always the selection of a range. The position where the button is clicked becomes the new endpoint of the range. If the user Shift-clicks within the current range, the new range will be smaller than the old range. Usually, if the user then Shift-clicks in another location, the additional data is included in the selection. In arrays, however, a different paradigm can be implemented in which the selection always moves from the current cell to wherever the user Shift-clicks, changing rather than extending the selection. This model works only in applications such as arrays, where the current cell is highlighted and the user can always see the active cell. In this case, the user always knows the fixed point from which the selection will start.

Extended selections can be made, even across the panes of a split window. Figure 10-16 shows the effect of extending and shrinking a range of text using Shift-click.

Figure 10-16 Expanding and shrinking a text selection

There are two methods for extending a continuous selection using Shift-click: the addition method and the fixed-point method. The addition method
is based on adding new text to a current selection. The fixed-point method establishes a fixed location for the insertion point and allows the user to extend the selection on either side of the fixed point. Figure 10-16 illustrates the results of three consecutive steps in both the addition method and the fixed-point method.

Figure 10-17 Extending text selections using the addition and fixed-point methods

When considering which method to use in your application, keep in mind that the addition method provides more flexibility by allowing users to extend a selection in both directions rather than in only one direction, as in the fixed-point method. The addition method also provides greater consistency in terms of extending a selection; the fixed-point method can actually end up shrinking a selection rather than extending it, as shown in Figure 10-16. In both methods, if the user positions the insertion point within a selection and Shift-clicks, the selection is shortened from the right side of the selection to the location of the insertion point.

In graphics applications, objects aren't usually considered to be in any particular sequence. A selection is extended by adding objects to it, and the added objects do not have to be adjacent to the objects already selected. The user can add either an individual object or a range of objects to the selection by holding down the Shift key before making the additional selection (Shift-click). When the user does this, the objects between the current selection and the new object are not automatically included in the selection. This kind of selection is called discontinuous selection. If the user holds down the
Shift key and selects one or more objects that are already highlighted,
the objects are removed from the selection or are deselected. For more information about discontinuous selections, see Inside Macintosh: Text.

Changing a Selection With Command-Click

In the case of graphics, all selections are discontinuous selections because graphic objects are discrete. This is not the case with arrays and text, in which an extended selection made by a Shift-click always includes everything between the old anchor point and the new active end. In arrays and text, discontinuous selections are made by clicking while holding down the Command key.

To make a discontinuous selection in a text or array application, the user selects the first piece in the usual way and holds down the Command key while selecting the remaining pieces. Each piece is selected in the same way as if it were the whole selection, but because the Command key is held down, the new pieces are added to the existing selection instead of replacing it. If one of the pieces selected with Command-click is already within an existing
part of the selection, then instead of being added to the selection, it's removed from the selection.

Figure 10-18 shows the process of adding cells to and removing cells from a discontinuous selection.

Figure 10-18 Discontinuous selection within an array

Not all applications support discontinuous selections, and those that do might restrict the operations a user can perform on them. For example, a word processor might allow the user to choose a font after making a discontinuous selection, but not allow the user to type replacement characters. In this situation, it wouldn't be apparent to users which part of the selection the characters would replace. Decide what makes sense in the context of your application and test it with users to make sure that their needs are met.