Tools

Tools are command modes that let the user create and modify different types of data. Common tools include the selection tool, the line tool, and the fill tool. To use a tool, the user first clicks on the tool's icon to select it. Then the user applies the tool to the content area of a frame. Typically, the cursor changes shape to indicate that the user is "holding" the selected tool, such as a paintbrush or an eraser.

Common groups of tools are organized into a floating non-modal window called a palette. See Chapter 4 for information on windows.

Cursors, tools, and activation

Cursors and tools are closely related. The cursor graphic changes when the user selects a tool. The graphic should change shape only when and where the tool can be used. For example, if the text tool is selected, the cursor should only become an I-beam when it moves over text in the active frame. It should change to the default cursor, such as the arrow, when it moves outside the text region.

The active frame controls the appearance and behavior of the cursor. When the user mouses down on an inactive frame, the frame becomes active. The frame determines whether to ignore or handle the activation click. After the mouse up, the frame decides which tool is available to the user. Only the active frame shows the current tool, and then only when the cursor is over the content area of the active frame.

When to create a tool

Here are some suggestions for when to create a tool:

When it makes sense for the user to manipulate the data directly, by extending the user's hand to the computer screen. For example, a tool makes drawing objects easy. It is more productive to have the user draw using a shape tool than to enter coordinates for a shape in a panel.
When the result of an action depends on the data type. Tools are sensitive to the type of data being manipulated and adjust accordingly. For example, when the user drags the cursor across text, the text is selected. When the user works with graphic objects, dragging the cursor might create a selection rectangle around multiple objects.
When an action does not require advance setup. For example, a printing tool would be inappropriate because users often want to change settings such as page orientation or page range before printing.
When the user will want to apply a command repeatedly to different selections of data. For example, the user might want to repeatedly boldface the headings in a document.

One rule of thumb is to create a tool when it makes more sense to bring it to the data than to bring the data to the tool. The printing example illustrates this rule; in this case, it is more efficient to bring the data to the printer than to apply a printing tool to the data.

Types of tools

Tools can be loosely grouped into the following three types. Every tool is accessed by the user the same way regardless of its type. This consistency is an important principle of the CommonPoint human interface.

Selector tools select data objects--for example, the arrow, text arrow, and lasso tools.
Creator tools create new data objects--for example, the rectangle and frame tools.
Effector tools modify existing objects--for example, the fill and color tools.

NOTE

A tool can be a combination of types.

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