This changes behaviour for sRGB textures, which weren't previously converting to the correct color space.
Also add unit tests for storing to PNMImage.
Closes: #212
This introduces AsyncFuture as a new base class of AsyncTask. It's modelled after asyncio's Future class, except that it is thread-safe and you can use result() to block the current thread waiting for the future to finish (of course this is not necessary for use with coroutines).
AsyncFuture should be used for any operation that finishes in the future, to get the benefit of awaitability within coroutines as well as a standard interface for querying status and results of the operation as well as cancelling it. As such, it's been implemented in various places, including texture.prepare() and win.trigger_copy().
Note that AsyncFuture is intended to be used *once*; it cannot be used more than once. As an example of how this works, tex.prepare() will return the same future as long as the prepare isn't complete, but when it is done, subsequent calls to tex.prepare() will return a new future.
Gets rid of properties defined as both MAKE_SEQ_PROPERTY/MAKE_MAP_PROPERTY, which are just a bad idea. Instead, adds a way for map properties to define a separate "keys" interface.
Fixes: #203
This test just makes sure that created windows match the default
WindowProperties (with a few exceptions).
This also adds the following fixtures:
* graphics_engine - scope='session', GraphicsEngine
* graphics_pipe - scope='session', default GraphicsPipe
* window - scope='test', GraphicsWindow with default framebuffer and window properties
These tests were converted from the tests branch with some changes:
* Convert from unittest to PyTest
* Update code to use new API (LVector3 instead of Vec3, properties, etc.)
