|4.5 Reference objects and symbols|
A symbol is a single Ipe object (which can of course be a group) that is defined in a document's stylesheet. A reference object is a reference to a symbol, placed at a given position on the page.
Symbols can be parameterized with stroke and fill color, pen width, and symbol size. Whether or not a symbol accepts which parameter is visible from the symbol's name: if it takes any parameter, the name must end in a pair of parentheses containing some of the letters "s", "f", "p", "x" (in this order), for the parameters stroke, fill, pen, and size. References to parameterized symbols allow all the attributes that the symbol accepts.
All references can be translated around the page. Whether or not the symbol can be rotated or stretched depends on the definition of the symbol in the stylesheet.
If a symbol named "Background" exists in your stylesheet, it is automatically displayed on each page, at the very back. To suppress the automatic display, create a layer named "BACKGROUND" on the page. (If such a layer is present, it suppresses the "Background" symbol. It does not matter if the layer itself is visible or not.)
Marks are symbols with special support from the Ipe user interface. They are used to mark points in the drawing, and come in several different looks (little circles, discs, squares, boxes, or crosses). You can define your own mark shapes by defining appropriate symbols in your stylesheet.
Note that marks behave quite different from path objects. In particular, you should not confuse a disc mark with a little disc created as a circle object: