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Gaphas

Gaphas is Gaphor’s diagram drawing widget.

Gaphas has been built with some extensibility in mind. It can be used for many drawing purposes, including vector drawing applications, diagram drawing tools and we even have a geographical map demo in our repository.

The basic idea is:

• Items (canvas items) can be added to a Canvas.
• A Canvas can be visualized by one or more Views.
• The canvas maintains the tree structure (parent-child relationships between
  items).
• A constraint solver is used to maintain item constraints and inter-item
  constraints.
• The item (and user) should not be bothered with things like bounding-box
  calculations.
• Very modular: e.g. handle support could be swapped in and swapped out.
• Rendering using [http://cairographics.org Cairo].

Gaphas is released under the terms of the GNU Library General Public License
(LGPL).

Read more about Gaphas in the [wiki:Tech Tech section].

Gaphas has been build using setuptools and can be installed as Python Egg.

• Python Package index (PyPI): http://cheeseshop.python.org/pypi/gaphas

Class diagram

This class diagram describes the basic layout of Gaphas.

Some highlights:

Canvas:: The main canvas class (container for Items) Item:: Objects placed on a Canvas. Items can draw themselves, but not act on user events Solver:: A constraint solver. Nice to have when you want to connect items together in a generic way. View:: Base class that renders content ({{{paint()}}}). The view is responsible for the calculation of bounding boxes. This information is stored in a [wiki:Tech/Quadtree quadtree] data structure for fast access. !GtkView:: A view to be used in GTK+ applications. This view class is interactive. Interaction with users is handled by Tools. Painter:: Painters are the workers when it comes to painting items. Tool:: Tools are used to handle user events (such as mouse movement and button presses).

The original model file can be found in the subversion repository: source:gaphas/trunk/gaphor-canvas.gaphor