Quartz Composer

Quartz programming through Quartz Composer works by implementing and connecting patches.[4] Similar to routines in traditional programming languages, patches are base processing units. They execute and produce a result. For better performance, patch execution follows a lazy evaluation approach, meaning that patches are only executed when their output is needed. There are three types of patches: Consumers, Processors, and External Input patches that can receive and output mouse clicks, scrolls, and movements; MIDI and audio; keyboard; or other movements. A collection of patches can be melded into one, called a macro. Macros can be nested and their subroutines also edited.

To control the order of rendering, each renderer is assigned a layer, indicated in its upper-right corner. Layers are rendered sequentially, lowest to highest. Renderers can be enabled or disabled, essentially turning on or off that particular layer. Turning off unused layers often results in better performance, since fewer upstream patches need to be evaluated.

Some patches can have subpatches, which allows for global parameter changes to just the included subpatches. This is useful for lighting, 3D transformation, and GLSL shaders, among other things. Subpatch support is indicated by square corners on a patch, rather than the typical rounded corners.

With Version 3.0, it became possible to turn compositions into Virtual Patches. These allow the user to reuse functionality without having to store duplicate copies in each composition. The Quartz Composer Editor allows the user to save a "flattened" copy (with the virtual patches fully expanded inside), for easy distribution. Version 4.0 extended this functionality even more, and automatically includes "flattened" copies of virtual patches for use as a fallback if the desired virtual patch isn't installed on the host system. This greatly simplifies composition distribution.

Network functionality was greatly improved with the release of Leopard. It became possible to transmit data and synchronize over a network interface, and it also added support for Open Sound Control transmission and reception.

Plugins

The Quartz Composer 3.0 interface.

Also new in Version 3.0 was the possibility to write custom patch plugins, using an Xcode template, and the notion of a "safe mode", where plugins and other unsafe patches fail to load. This prevents malicious compositions from performing dangerous or insecure operations. Custom patches using Apple's Xcode template are always considered unsafe.

It was possible to develop custom patch plugins for Version 2.0, but the API was undocumented and private, and was never supported by Apple. Eventually, templates were released to simplify this procedure.[5]

In the Quartz Composer editor, holding the option key while selecting "Preferences..." from the menu adds 3 additional tabs of options for the user to configure. These options include System settings, Editor settings, and QuickTime integration settings. Notable options include expanded tooltips, software rendering, and uncapped framerate rendering. Multisample antialiasing (MSAA) was added as a hidden option in version 4.0, allowing for antialiasing inside the QC Editor, though it only works on GPU's that support MSAA.

Data inside QC can be one of the following types:

• Boolean - a boolean value, 0 or 1
• Index - a positive integer between 0 and 2147483647
• Number - a double precision floating point number
• String - a unicode string
• Color - an RGBA or CMYK quartet, or a Grayscale value
• Image - a 2D image of arbitrary (possibly infinite) dimensions
• Structure - a named or ordered collection of objects, including nested structures
• Virtual - any of the above

Two additional types were introduced in version 4.0:

• Mesh - a collection of vertices, and per-vertex normals, texture coordinates, and colors in 3-space
• Interaction - a valueless type used to associate user input with user-interactive elements of the composition

Quartz Composer documents are called Compositions. Compositions are Binary Property Lists (though XML versions are also supported) with a filename extension .qtz, and a com.apple.quartz-composer-composition UTI.[6] Patches, their connections, and their input port states are saved in the composition file. Images can be stored inside a composition as well, making for self-contained compositions with embedded graphics. By dragging a movie file into the Quartz Composer editor, a reference to the movie file is created, providing a changing image that can be connected to a renderer.

Compositions also store metadata such as composition author, copyright, and description. The user can also add arbitrary metadata items, if desired.

Many image formats are supported, including JPEG, JPEG2000, GIF, PNG, TIFF, TGA, OpenEXR, BMP, ICO, PDF, PICT, ICNS, and some raw digital camera types.[7] Images are maintained in their native form for as long as possible before rasterizing for display. This means that Quartz Composer will keep vector images as vectors when cropping, scaling, rotating, or translating which allows it to work with very large logical image dimensions without consuming large amounts of memory or processing time. Such functionality is most apparent when working with text-based images, or PDFs.

Version 3.0 added the ability to add annotations to areas of the composition, called notes. These notes parallel comments in other programming languages. Notes can be yellow, red, green, blue, or gray, and can overlap other notes.

Pierre-Olivier Latour originally developed the predecessor to Quartz Composer under the name PixelShox Studio.[10]