C H A P T E R 9
User Input
■Graphics. For the purposes of this discussion, a graphic, or picture, is a discrete object that can be selected individually.
The following sections discuss the general methods of selecting and the specific methods that apply to text, arrays, and graphics.
Selection Methods
This section describes various selection techniques.
Figure 9-4 Selection techniques
Clicking B selects B.
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Range selection of A through C selects A, B, and C.
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Selection by Clicking
The most straightforward method of selecting an object is by clicking it once. Icons, for example, are selected in this way.
186Selecting
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C H A P T E R 9
User Input
Selection by Dragging
The user can select a range of some objects by following this procedure:
1.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.
2.Without releasing the mouse button, the user moves the pointer in any direction.
As the pointer moves, 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 selected area. If appropriate, the view should scroll to allow extending the selection beyond a window.
3.When the desired range is selected, 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.
A Shift-click should result in a continuous selection—the selection is extended to include everything between the old anchor point and the new active end. Graphics applications typically support discontinuous selection, in which the user can extend a selection by adding nonadjacent objects to already selected objects, and the objects between the current selection and the new object are not included in the selection. A Command-click should result in a discontinuous selection.
In text, if the user Shift-clicks within an already selected range, the new range is smaller than the old range.
In an array, a Shift-click can extend the selected range or it can move the selection from the current cell to wherever the user Shift-clicks.
Selecting |
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Apple Computer, Inc. June 2002
C H A P T E R 9
User Input
There are two models for extending a continuous selection using Shift-click. In the addition model, new text is added to a current selection. In the fixed-point model, the user can extend the selection on either side of the insertion point. Figure 9-5 illustrates the results of three consecutive steps in both models.
Figure 9-5 Shift-clicking in the addition model and the fixed-point model
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Setting insertion point
Extending selection to the right.
Extending selection to the left.
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When considering which model to use in your application, keep in mind that the addition model provides more flexibility by allowing users to extend a selection in both directions.
Changing a Selection With Command-Click
In arrays and text in which Shift-click extends a continuous selection, the user can make discontinuous selections by holding down the Command key and clicking. Each Command-click adds the new object to the existing selection. If one of the objects selected with Command-click is already within an existing part of the selection, then it is removed from the selection instead of being added.
188Selecting
Apple Computer, Inc. June 2002