Platform/GFX/Moz2D

The Moz2D graphics API, part of the Azure project, is a cross-platform interface onto the various graphics backends that Gecko uses for rendering such as Direct2D (1.0 and 1.1), Skia, Quartz, and NV Path. Adding a new graphics platform to Gecko is accomplished by adding a backend to Moz2D (see #Implementing a new backend).

Some of the notable features of the API are:

• Mostly stateless—better suited to CSS rendering and eliminates overhead
• Floating-point—better suits platform APIs
• API methods line up with HTML canvas

Current status

The Gecko graphics API preceding Moz2D was Thebes which consists of a C++ wrapper around Cairo, some Gecko-specific utility code, and a text API that uses platform text handling. Currently both the Thebes API and Moz2D API are in use. A Thebes wrapper around Moz2D allows code that still uses the Thebes API to run on top of Moz2D. Over time this code will be migrated to using the Moz2D API directly (see Azure Conversion).

Once the Azure project is completed—that is, all the backends have been implemented and all the calling code converted to use the new Moz2D API—the old Thebes API will be removed.

Side note: For historical reasons, there are some classes with “Thebes” in the name which will be surviving this process as they're not actually part of the graphics API. They may get renamed eventually, to reduce the number of magical words you need to know about, but be warned that just because some code has “Thebes” in the name, it does not mean that the code is on its way out!

See also:

• Progress on Moz2D - July 2013 update
• Azure Conversion

Further reading

The following resources describe the motivation for and goals of this API:

• Introducing the Azure Project
• Mozilla 2D graphics (PDF)
• Graphics API Design