|3.7 Symbolic and absolute attributes|
Attributes such as color, line width, pen, mark size, or text size, can be either absolute (a number, or a set of numbers specifying a color) or symbolic (a name). Symbolic attributes must be translated to absolute values by a stylesheet for rendering.
One purpose of stylesheets is to be able to reuse figures from articles in presentations. Obviously, the figure has to use much larger fonts, markers, arrows, and fatter lines in the presentation. If the original figure used symbolic attributes, this can be achieved by simply swapping the stylesheet for another one.
The Ipe user interface is tuned for using symbolic attribute values. You can use absolute colors, pen width, text size, and mark size by clicking the button to the left of the selector for the symbolic names.
When creating an object, it takes its attributes from the current user interface settings, so if you have selected an absolute value, it will get an absolute attribute. Absolute attributes have the advantage that you are free to choose any value you wish, including picking arbitrary colors using a color chooser. In symbolic mode, you can only use the choices provided by the current stylesheet.
The choices for symbolic attributes provided in the Ipe user interface are taken from your stylesheet.