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https://github.com/LumaPictures/usd-qt

Reusable Qt Components for Pixar's USD
https://github.com/LumaPictures/usd-qt

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Reusable Qt Components for Pixar's USD

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# UsdQt



### Qt components for building custom USD tools



#### Current Branch Compatibility



- master : USD 19.07

     - Should be compatible with the post-19.07 USD dev branch up to and including [b6ccb4e5](https://github.com/PixarAnimationStudios/USD/commit/b6ccb4e543dea2ab4cd41b0fc162c5501ac9b103)

- dev : USD 19.11+



## Project Goals



The UI components that make up `usdview` are good reference for functionality,

but they’re purpose-built for the application, and are implemented in ways that

make them difficult to decouple from it.



This project is meant to provide application components that can provide similar

(as well as new) functionality, to allow for ad-hoc use in custom tools.



Longer-term, we hope this project will grow to the point that it can be used to

build a fully-functional `usdview` application.



## Contents



This project contains a mixture of pure Python and wrapped C++ code. All Qt code

is written in pure Python to avoid the need to link against Qt and get `moc`

involved in the build process. This may change in the future if deemed

beneficial/necessary.



The compiled extension module provides a set of helper classes that interface

with the USD C++ API to accelerate certain USD queries, operations, etc.



#### Installed Python Packages



- `pxr.UsdQt`: Contains various Qt item data models, helper classes for building

UIs, and some other USD and Qt utility code. The `_bindings` module currently

contains all of the wrapped classes from the compiled extension module.

- `pxr.UsdQtEditors`: Contains various Qt UI elements. These range from

purpose-built display/editor widgets to an extensible outliner UI that also

serves as a good usage example for many of the utilities in `pxr.UsdQt`.

- `treemodel`: Contains a generic item tree and a Qt item model mixin that uses

it, which are used by some of the classes in `pxr.UsdQt`.



## Building/Installation



The recommended (and currently only tested) way to build the project is using

CMake. A `setup.py` file is provided as well, but it has not been tested with

the most recent updates.



#### Build Requirements



- Boost Python

- USD

- TBB



#### CMake Options



- `INSTALL_PURE_PYTHON (BOOL)`: Whether to install the pure Python code in

addition to the compiled extension module. This defaults to `ON`.



#### A note about `UsdQt.py` and `UsdQtEditors.py`



You may notice that the source contains `UsdQt.py` and `UsdQtEditors.py` files

alongside the package source directories. These are "shim" modules that we've

found to be very useful during the development of this project, as they enable

us to do more rapid editing and testing on the pure Python code without needing

to run a CMake build and install between each minor edit. They are not installed

with the project.



## Using `UsdQt` with the USD Python bindings



`UsdQt` uses `pkg_resources` (or `pkgutil` if the former is not available) to

declare `pxr` as a "namespace package" at runtime. This allows it to overlay its

sub-packages onto the same `pxr` package used by the USD Python bindings, so

that the two projects can be installed in separate locations and still work

together.



However, the USD Python bindings do not currently declare `pxr` as a namespace

package in a symmetrical way, which unfortunately means that if the USD Python

bindings are listed before `UsdQt` on the module search path, you will not be

able to import `pxr.UsdQt`. Thus, unless/until the USD Python bindings are

updated to declare `pxr` as a namespace package, you will need to make sure

`UsdQt` is listed before the USD Python bindings on the module search path.



More information on namespace packages in Python can be found in the docs for

`pkg_resources` and `pkgutil`:



https://setuptools.readthedocs.io/en/latest/pkg_resources.html#namespace-package-support



https://docs.python.org/2/library/pkgutil.html



## Using an alternate Qt API



`UsdQt` expects its underlying Qt API to adhere to the Qt5 module layout, and

uses the PySide2 API.



By default, it will attempt to import and use `PySide2`. This can be overridden

by setting the `PXR_QT_PYTHON_BINDING` environment variable to the name of the

API package/module you wish to use instead.



This works with the popular [Qt.py](https://github.com/mottosso/Qt.py) project.



## Planned Future Additions



Here are some of the ideas we've had for future additions to the project. We're

happy to consider new suggestions as well.



- UI components for authoring and working with USD variant sets.

- An adaptor class to translate USD notices to Qt signals.

- A `QSyntaxHighlighter` class for `.usda` syntax.

- A Hydra viewport widget.