Draw thumbnails as strip overlay. This works for movie and image strips.
To draw thumbnails, this overlay has to be enabled and strips must be
tall enough.
The thumbnails are loaded from source file using separate thread and
stored in cache.
Drawing code uses only images stored in cache, and if any is missing,
background rendering job is started. If job can not render thumbnail,
to prevent endless loop of creating job for missing image it sets
`SEQ_FLAG_SKIP_THUMBNAILS` bit of `Sequence` flag.
To prevent visual glitches during timeline panning and zooming, `View2D`
flag `V2D_IS_NAVIGATING` is implemented. If bit is set, drawing code
will look for set of evenly distributed thumbnails that should be
guaranteed to exist and also set of previously displayed thumbnails.
Due to volatile nature of cache these thumbnails can be missing anyway,
in which case no new thumbnails will be drawn for particular strip.
Cache capacity is limited to 5000 thumbnails and performs cleanup of
non visible images when limit is reached.
ref T89143
Reviewed By: ISS
Differential Revision: https://developer.blender.org/D12266
- Remove Full Render size from VSE preview size. Use just 100% instead.
- Add Use Proxies checkbox to control whether proxies are used globally
- Move preview size to top so it is most prominent
- Set default to 100% preview size and use proxies
Reviewed By: sergey, fsiddi
Differential Revision: https://developer.blender.org/D10362
