Introduction to Pencil Stencils


Pencil controls shapes in its document by mean of stencils. Each stencil (Rectangle, for example) is indeed a template to generate shapes. Each template defines:

  • The look: what the generated shape looks like, defined by means of SVG elements.

    For example: the Rectangle stencil defines a shape formed by a single SVG <rect> element.

  • The properties: which properties the shape has plus optional extra constraints on them.

    For example: the Rectangle stencil has a box property of type Dimension, a strokeStyle property of type StrokeStyle and a fillColor property of type Color.

  • The behaviors: how the shape’s look is changed according to changes made to its properties.

    For example: the Rectangle <rect> element has its fill and fill-opacity change to the fillColor property of the shape.

  • The actions: which actions that external objects and users can ask the shape to do.

    For example: the Rectangle stencil defines a Remove border action to allow users to set the strokeStyle width property to 0px and hence makes the <rect> element’s border disappear.

Stencils are organized into collections. Each collection contains a set of related stencils and can be installed into or uninstalled from Pencil using the collection manager.

The Process of Creating Shapes from Stencils

After being installed into Pencil, a stencil can be used to create shapes by dragging it into the drawing pane of a page. When a stencil is dropped into a page, the following actions will be taken by Pencil to create a shape for that stencil:

  1. Creating a shape as an SVG element containing all SVG elements defined in the content section of the stencil definition.
  2. Putting the newly-created shape into the page content.
  3. Setting initial values for all properties in the shape to the default values as defined in the stencil.
  4. Applying all behaviors defined in the stencil to make the shape’s look change according to these initial property values.

Manipulating Shapes in the Drawing Page

After being successfully inserted into a page, a shape begins its life in that page. During its life, a shape may have its properties changed by the user. Depending on the type, a property value can be changed in a specific way that is easiest for the user.


Pencil reserves the use of some special property names for pre-defined purposes. Please refer the Special Property Names document for detailed information on how these property names can be used in your stencil.

An example of this is that the box property of type Dimension should always be used to determined the dimension of the outermost box surrounding the shape.