A GeometryItem defines a basic, atomic geometric shape, such as a line, rectangle, ellipse, polygon or label. These items are created in a geometry.xml or similarly named file and customized with attribute parameters. These attributes define specific visual aspects of the geometry item and vary depending on the item's basic type.

Once a GeometryItem has been defined, it can be referenced by any number of composites, which group items into new geometry entities of type GeometryDescriptor. This separation of items and composites allows you to easily attain a consistent look and feel for all of your repository elements by centralizing and reusing one or more GeometryItem definitions.

Every GeometryItem consists of a name, a type and a list of optional attributes. A minimal GeometryItem looks like this:

<!-- A Minimal Item -->
<list name="GeometryItem">
 <attribute name="Name" value="GEOMETRY_ITEM_NAME"/>
 <attribute name="Type" value="GEOMETRY_ITEM_TYPE"/>
</list>

The GEOMETRY_ITEM_NAME text in the example above may be any unique string you wish. The GEOMETRY_ITEM_TYPE text, however, must be one of several predefined values that are described in the Elements chapter inside the Framework Manual, which is distributed separately. Please read that chapter when you are finished reading this section. There you will discover which additional attributes are required for each geometry item type listed.

A GeometryDescriptorItem represents the first level of GeometryItem (aka “basic item”) reuse. It exists because basic items will be referenced by one or more composites (which we will discuss next). Additionally, basic items do not specify any coordinate data for the objects that draw them. This makes perfect sense. A composite will need to position basic items relative to one another. In most cases, drawing individual items in the context of a composite will not always begin in the upper left-hand corner of a composite's coordinate system.

To make things perfectly clear, a GeometryDescriptorItem represents an association between a single GeometryItem (atomic geometry, basic item) and a single GeometryDescriptor (composite geometry, to be discussed next). A GeometryDescriptorItem element is embedded inside a <DescriptorItem> tag, which you can see in the XML fragment in the previous section.

Every GeometryDescriptorItem, embedded inside a parent GeometryDescriptor element, consists of its unique name, the name of the referenced GeometryItem as well the drawing coordinates within the composite. A minimal GeometryDescriptorItem therefore looks like this:

<!-- A minimal geometry descriptor item -->
<list name="DescriptorItem">
 <attribute name="Name" value="GEOMETRY_DESCRIPTOR_ITEM_NAME"/>
 <attribute name="GeometryItemName" 
            value="REFERENCED_GEOMETRY_ITEM_NAME"/>
            
 <list name="Coordinates">
  <attribute name="Coordinate" value="X_COMPONENT, Y_COMPONENT" />
  <attribute name="Coordinate" value="X_COMPONENT, Y_COMPONENT" /> 
  [...]
 </list>
 
</list>

The Coordinate attributes listed above define two points for the GeometryItem being referenced. Depending on the item type, you may require more data than this. Please refer to the Elements chapter inside the Framework Manual for more detailed information about specifying coordinate attributes for the various geometry types available in our framework.

A GeometryDescriptor represents a grouping of one or more basic items of type GeometryItem. Each item referenced the GeometryDescriptor file definition is represented as a uniquely named GeometryDescriptorItem.

Each GeometryDescriptor definition consists of a name, a type, a coordinate system and, of course, a list of GeometryDescriptorItem elements. In its minimal form it looks like the following:

<!-- a minimal geometry descritptor -->
<list name="GeometryDescriptor">
  <attribute name="Name" value="GEOMETRY_DESCRIPTOR_NAME"/>
  <attribute name="Type" value="GEOMETRY_DESCRITPOR_TYPE"/>
  <list name="CoordinateSystem">
    <attribute name="ScaleX" value="MINIMUM_VALUE, MAXIMUM_VALUE" />
    <attribute name="ScaleY" value="MINIMUM_VALUE, MAXIMUM_VALUE" />
  </list>
  <!-- optional attributes of the geometry descriptor -->
  <set name="Attributes">
    <attribute name="ATTRIBUTENAME" 
      type="ATTRIBUTETYPE" value="ATTRIBUTEVALUE" />
    [...]
  </set>
  <list name="DescriptorItems">
    <list name="DescriptorItem">
      [...]
    </list>
  </list>
</list>

A GeometryDescriptor has a Type attribute that can be one of the following string enumerations: Composite, CompositeLine or CompositeGroup. Descriptor types are described in more detail in the Elements chapter inside the Framework Manual, which is distributed separately. We recommend that you browse this chapter now to acquire a better understanding of the attributes required for a more complex GeometryDescriptor.