Within the spreadsheet area, the pen should default to a pointer. If the application allows in-cell editing, double-tapping the cell should open a writing window in which the user can write or edit the contents of the cell. This window should include a palette of commonly entered symbols such as "*" or formula names that are hard to recognize. This allows the user to enter an unambiguous symbol by tapping an appropriate button.

A formula bar area should behave more like the word-processor application just described. If the area is empty, the application should display the writing window automatically. Naturally, the recognizer should be configured according to the type of input expected, whether text, numerical, or whatever.

Annotation, including quick notes and diagrams, represents an ideal usage of a pen in a spreadsheet application. Often, annotated text can be kept as ink and does not require recognition. Anchoring and targeting annotations on a spreadsheet is somewhat easier than on a word-processing document because cells do not flow in the same manner as text. Annotations should be anchored to the data and not the cell. This ensures that, if the data moves to another cell, the annotation moves with it.

Because spreadsheets contain much data that is not based on words, on-screen keyboards should be easy to display (and automatic in many circumstances). As with word-processing applications, writing in a spreadsheet will most likely be limited to small editing and format changes.

The user will often wish to edit the contents of a single cell to see how it affects the rest of the spreadsheet. To facilitate this operation with a pen, the application should anticipate as much as possible. For example, double-tapping a field containing a numeric value should display a numeric on-screen keypad.

If the spreadsheet offers text entry with recognition, it should provide an appropriate tool accessible from a toolbar or menu. When the user selects text-entry mode, the spreadsheet should enlarge (zoom), allowing the user to write comfortably within a cell. The application can rely on the automatic targeting capabilities provided by the Pen application programming interface (API), described in Chapter 2, to route text appropriately to different cells.

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