Poseidon for UML: Users Guide
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# Diagram Pane

The Diagram Pane is the area used to do most of the diagram creation and modification. It is generally the largest pane.

This section covers some of the functions available from the diagram pane, as well as changing the settings of this pane. Chapter 7, 'Working with Diagrams', provides a more extensive look at all of the functions available. Chapter 9, titled 'A Walk Through the Diagrams', contains detailed information about the diagrams themselves.

The graphical editor is embedded in the Diagram pane. This pane, as has been previously mentioned, is used to display and edit the diagrams of your model

## Diagram Pane Toolbar

Across the top of the Diagram pane, there is a toolbar that contains a number of tools you can use to create and modify your UML models. If you have already worked with a UML tool or a drawing tool capable of creating UML diagrams, you are probably familiar with the general idea. Each diagram type has a specialized set of tools in addition to the tools that are common to all diagram types. To display the name of each individual tool, position your mouse over it and wait a second or so, the name will appear in a box underneath.

In general, the Diagram pane toolbar changes according to the type of diagram currently displayed. There are, however, some tools which are available in all or nearly all of the diagrams:

## Remove Tabs

To remove the a tab from the Diagram pane, move the mouse over the tab to be deleted. A 'delete' button with an 'X' will appear. Click the button and the tab will be removed from the pane.

## Change Properties of the Diagram Pane

### Grid Settings

The first thing you may notice about the Diagram Pane is the grid that is drawn over the drawing area. By default, the drawing area displays this grid. The visible grid is only a collection of lines, they have no functions of their own.

A second grid, called the snap grid, is invisible to the user. When this option is enabled, diagram elements align themselves along the intersections of this grid which are closest to the element (in a process called snapping) to aid with element positioning.

To make elements snap to the visible grid, set the visible and snap grids to be the same size. The settings shown in Figure 10–1 will have the visible grid drawn every 20 pixels, and the elements will be able to snap to intermediate positions of the visible grid.

You can change the properties of both grids from the Grid Settings dialog in View-Adjust Grid...

Figure 6-2. Grid Settings dialog

Grid Settings

- Visible - Determines whether the visible grid is drawn at all.

  Spacing and line appearance are also set for the visible grid here.

- Snap - Determines whether the elements placed in the diagram will be forced to align to a snap grid.

  The pixel dropdown sets the spacing of the snap grid.

### Other Settings

The grid is not the only setting that can be changed for the Diagram pane.

- Display/Hide Tabs - Hide or redisplay diagram tabs at the top of the pane with the Appearance Tab in the Settings Dialog.

- Number of Tabs Displayed - Set the maximum number of tabs with the Settings Dialog, Appearance Tab.

- Display/Hide Information About Elements - Hide or redisplay information such as operations or attributes from the Settings Dialog, Diagram Display Tab.

- Resize the Drawing Area - Drag the pane separation bars to the desired size. The arrows on the bars open and close the panes completely.

- Enlarge/Reduce the Diagram - Change the zoom factor in the Properties tab for the diagram or hold the Ctrl key while turning the mouse wheel.

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