Layers, Pens, and Transmission

Each object, e.g. a circle, has its own property set consisting of line width, line type, line color, fill color, and fill mode. These properties determine the appearance of the object on the screen and later on the paper.

In addition, each object contains a reference to a layer and a pen (unless pens are switched to passive mode), i.e. it lies in a certain layer and uses a certain pen. When the application determines how to draw an object, this not only depends on the object's own properties, but also on the properties transmitted by the assigned layer and the properties specified for the assigned pen.

Both the property set of the layer and the one of the pen do not permanently alter the properties of the object itself, but do only overwrite them temporarily. As soon as the layer or pen reference is changed, the object's appearance will change accordingly - without necessarily changing its properties.

Usually, layers do not transmit any properties, so they do not influence an object's appearance. In this case, the object's appearance is only determined by the pen it uses, i.e. by the pen's properties (see Manage > Pens > Edit). Those pen properties may be different for screen display and printer output.

If a layer property is transmitted (see Manage > Layers > Edit), it overwrites the corresponding pen property. It is therefore decisive for the appearance of the object. Layer properties may also be different for screen display and printer output.

Both types of property transmission (from a layer or a pen) can be refused by the object by fixing one or several of its properties. These fixed properties cannot be overwritten by any transmission and will always remain unchanged. Fixing a property will always effect both screen display and printer output.

Layer "*Standard" and pen "*Standard" never transmit any properties. If an object is assigned to the "*Standard" layer and the "*Standard" pen it isn't influenced by changes applied to layers or pens, i.e. the object is completely independent from layer and pen settings. To draw such an object specify "*Standard" as current layer as well as current pen. After drawing the object its properties are then initialized with those currently defined for pen "*Standard".

If you change the properties of pen "*Standard" this hasn't any effect on already existing objects but all objects you draw from then on will be initialized with these new properties. To comfortably edit the properties of pen "*Standard" please select the command Window > Display Command Bar and activate there the button groups Line Type, Line Color, Filling Mode, and Filling Color. If pens are switched to passive mode, they all behave like pen "*Standard".

This graphic illustrates the process used to determine the properties of an object. Each step is shown in the graphic by the relevant number in a circle:

1)	First of all, the application determines which layer the object belongs to.

2)	Next, the application gets the information about which pen is used by the object (not applicable if pens are passive).

3)	Then the application checks whether or not layer 1 transmits a pen. In such a case the transmitted pen would become the current pen replacing the pen determined in step 2 (not applicable if pens are passive).

4)	All pen properties are initially taken from the pen determined in step 2 (not applicable if pens are passive).

5)	All properties transmitted by the layer override the corresponding pen properties, as here the line color and the fill color.

6)	The application checks each of the object's own properties to see if it is fixed. Fixed object properties are always passed on directly to the output / screen properties. In the diagram line width, fill color, and fill mode are replaced by fixed object properties.

7)	Finally the properties determined in step 1 to 6 are used for output to plotter / display on screen.

When drawing an object, it is always assigned to the current layer and the current pen. You can change the current layer by clicking the corresponding button in the Panel or by selecting the command Manage > Layers > Edit. You can also select a new current pen from the Panel or by choosing the command Manage > Pens > Edit.

For some object types, e.g. texts or dimensions, you can optionally specify a default layer (Manage > Layers > Defaults) and a default pen (Manage > Pens > Defaults) which then will be used instead of the current layer or pen respectively when creating such an object.

If you want to assign an object to a different layer or pen later, you can do so by means of the command Modify > Object Properties > Edit.

Layers and pens are not only used to change the appearance of objects by property transmission but also to structure a drawing logically. The "Edit Layers" / "Edit Pens" dialog allows you to show or hide layers / pens, to enable or disable them for snapping or modification, etc. If you create layers / pens with meaningful names and consequently assign all newly created objects to these layers / pens, you will find that this feature will greatly simplify your work.

In addition to the properties described above, each object can be assigned to a page (i.e. to one of the pages defined in the drawing, see Manage > Pages > Edit). Once an object is assigned to a page, it will only be output if this page is being output (or displayed on the screen if this page is the active page).

The current pen and layer settings are part of the drawing and are saved with it. To make the altered settings available when the application is restarted save them using the command Manage > Template > Save as Default. In addition to all pens and layers the current page format, pen and layer defaults, the coordinate systems, and the line types will be stored as well.