v0.2.1

This is a bugfix release, intended to backport a number of easy and/or
critical fixes onto v0.2.0, since this is effectively the current 'LTS'
due to its use in VLC 3.0. Despite the included fixes, it's still not
recommended to make use of `pl_renderer` in this release. v0.4.0 is the
first release where that feature could be considered officially
supported.

For a full list of backported changes, see the git log. But aside from
cosmetics, comment fixes, here are the most noteworthy changes:

Fixes:
- Fix some typos in shaders that lead to miscompilation
- Work around the lack of mix(vecN, vecN, bvecN) on GLSL 120
- Avoid the use of platform-dependent locale-invariant printf() calls
  for shader generation. Instead, use a custom implementation
- Work around libshaderc locale dependence (currently only relevant when
  using vulkan)
- Fix various errors with anamorphic content handling
- Fix various errors when using vulkan
- Add some more sanitization to RA calls, and fix some of the existing
  ones

v0.4.0

This release brings with it a major performance change to the renderer's
scaling pipeline, support for vulkan format emulation, improvements to
the HDR peak detection algorithm as well as greatly improved support for
compute shader-based rasterization.

In addition to the above features, this release renames the `RA`
abstraction to `pl_gpu`, and normalizes the `ra_` prefix to `pl_` in
order to match the rest of the API as well as prevent potential future
symbol conflicts with mpv's internal copy of RA.

Additions:
- Add `pl_shader_encode_color`, which is an inversion of
  `pl_shader_decode_color` (NOTE: Some features, such as inverse
  constant luminance or XYZ encoding, are not currently supported)
- Add API for overlay images. This can be used to directly overlay
  arbitrary planes (e.g. subtitles, or menu items) on top of the
  rendered image or the target FBO. Each plane is allowed to have its
  own color space/repr and format. See `struct pl_overlay` for more
  details
- Add various predefined `pl_color_repr` values
- Add scene change detection functionality to the HDR peak detection
  algorithm in `pl_shader_color_map`. The new algorithm is designed to
  allow using larger peak detection buffers without the associated risk
  of eye-adaptation-like effects
- Add support for texel buffers (uniform and storage) in the pl_buf API.
  These can be used to storage raw texels in buffer format, much like 1D
  textures, but with the usual buffer-related functionality
- Add support for vulkan format emulation, which allows users to
  directly upload and download e.g. rgb8 or rgb32f textures, even though
  these are not typically supported by GPUs. The format emulation uses
  compute shaders and texel storage buffers to fix the data
  representation on-GPU, and is significantly faster than doing the same
  with on-CPU software conversion routines
- Add a `pl_dispatch_compute` function, which behaves like
  `pl_dispatch_finish` but without the FBO output, blending and
  rasterization simulation logic. This is useful when dispatching
  pure-compute shaders. (Note: Not currently very useful for API users
  since there are no pure-compute shaders as part of the public API)

Changes:
- Rename the `ra_` series of abstractions to `pl_` for consistency. The
  old `struct ra` was renamed to `struct pl_gpu`
- The dispatch logic for compute shaders will now correctly simulate the
  dispatch rect, by manually translating coordinates in the shader.
- Disallow using compute shader scaling for flipped source rects. API
  users who relied on this behavior are encouraged to instead flip the
  coordinates of the resulting `pl_dispatch_finish` call
- Have the renderer infer `src_rect` and `dst_rect` when not given
- Have the renderer encode colors to the `target.repr` before outputting
  to screen. This includes, for example, conversion to YUV and dithering
  to the target representation's bit depth (where known)
- Add a `pl_blend_params` struct to `pl_dispatch_finish`, which can be
  used to enable blending (including compute shaders)
  including when using compute shaders.
- Subsampled planes must now be an integer multiple (or inverse thereof)
  of the reference size. If this is not the case, the renderer will
  assume the planes are cropped or expanded. This is needed to correctly
  render e.g. 4:2:0 subsampled JPEGs with odd sizes
- Require that all uses of `pl_image` with the same `signature` point to
  the same data, to allow safe cache purging
- Allow dispatching debanding and bicubic shaders at any size
- `pl_plane_find_fmt` may now be called with `out_map=NULL`
- Change the `pl_color_map_default_params` in response to the new scene
  detection feature. The default buffer size has been increased from 21
  to 64, which leads to a much more stable image that flickers less

Fixes and performance improvements:
- Fix typo that lead to incorrect anamorphic rendering
- Fix various rendering issues when using a flipped src_rect
- Fix a double-free that could happen as a result of rendering failing
  in an unexpected way.
- Fix handling of alpha values in `pl_shader_decode_color`
- Correctly set the queue family index for vulkan buffer barriers
- Work around a locale dependence in libshaderc by calling uselocale/XXX
  before calling into shaderc functions
- Remove POSIX dependence in the test suite
- Remove non-portable ffsll call
- Fix demos/sdl2.c building on windows
- Fix an issue where trying to polar sample multiple planes could result
  in a variable conflict
- Fix inverted plane shift offset calculation
- Respect the debanding settings in the renderer
- Sanitize `pl_pass_run_params.scissors` and silently drop no-ops
- Avoid dependence on exact float equality in the renderer's
  upscaling/downscaling checks
- Fix an off-by-one in the HDR peak computation code which lead to
  subtly too-dark output
- Correctly check for and enable required vulkan device features
- Switch to a custom implementation of locale-invariant printf, to avoid
  depending on broken platform-dependent versions
- Overhaul the renderer's scaling pipeline. The new code is
  significantly faster when rendering cropped images, and also fixes an
  issue where src_rect was not applied when FBOs are unavailable
- Minor performance tweaks here and there
- Cap the sizes of various buffer pools and command queues in order to
  avoid OOM scenarios in infinite loops that don't contain enough
  forward dependencies to force command flushing
- Correctly check for and catch buffer access overflow
- Don't segfault when `pl_buf_create` fails
- Don't segfault when running a compute shader without viewport/scissors
- Fix a 32-bit integer overflow that could occurr when using HDR peak
  detection on 4K content with large values of `peak_detect_frames`
- Fix an off-by-one in the generation of literal LUTs such as the type
  used by the dithering code when textures are unavailable, which led to
  these shaders miscompiling
- Various fixes for building on 32-bit systems
- Fix an uninitialized value in the renderer

v0.3.0

This update brings with it some major changes to the renderer, support
for swapchains, separated sampling, sigmoidization and more. It also
includes, for the first time, a graphical demo capable of rendering to
the screen - as well as a benchmark.

Additions:
- Add a new type (ra_swapchain) encapsulating the concept of a
  presentable surface (e.g. graphical window) which can be presented to
  the display, as well as an implementation for vulkan swapchains
- Add a simple benchmark suite
- Add a new helper utils/upload.h for simplifying the process of picking
  a compatible texture format and uploading raw texture data
- Add a helper function to setup a pl_render_target from a swapchain
- Add a graphical demo based on SDL2 (compiled with vulkan support)
- Add support for separated (orthogonal) scaling, and make the renderer
  use it
- Add support for using the optimized GPU-native sampling methods for
  nearest/bilinear/bicubic where possible
- Add support for sigmoidization/unsigmoidization shaders
- Make the renderer use linearization/sigmoidization where appropriate

Changes:
- Require vulkan >= v1.0.24, rather than the old >= 1.0.50
- Split up vulkan instance and device creation into separate helpers.
  This is needed to satisfy the typical VkInstance -> VkSurface -> VkDevice
  dependency dance required to create a renderable swapchain.
- Change the API of pl_dispatch_finish/abort to make it clear that they
  consume and take over ownership of the pl_shader
- Have the renderer also #include most of its API dependencies, to cut
  down the amount of #include spam needed to use it
- Rename pl_sample_polar_params and generalize it to include separated
  (orthogonal) scaling as well
- Various API changes to pl_render_params

Fixes:
- Allow running the build script without `git` installed
- Fix an invalid bounds check on ra_tex_blit causing it to fail for
  1D/2D textures
- Use global #include paths for all public headers, rather than relative
- Fix the src_rect calculation in the renderer, thus fixing an issue
  where anamorphic scaling produced the wrong result
- Fix a typo in the renderer, causing it to skip some planes
- Fix a memory leak caused by implicit deallocation of pl_shader
- Fix a bug in the renderer causing the image to stop updating after the
  first frame after a resize
- Fixes a bug where the color mapping / tone mapping shaders sometimes
  got (accidentally) triggered when the source colorspace is unknown
- Fix a bug where compute shaders were incorrectly dispatched after a
  resize of the dispatch target
- Fix a bug where the polar compute shader read from uninitialized
  memory when performing anamorphic scaling
- Various other bug fixes and performance tweaks

v0.2.0

Additions:
- Add a public "renderer" API. This is currently very WIP, and not ready
  for stable usage yet. Both the API and the implementation are in flux,
  but the general goal is to make it easier to use libplcaebo to just
  render some data in the optimal way.
- Add pl_deband_default_params
- Expand shader system to support shader merging. This is not directly
  publicly useful yet, but it's used internally in the renderer.
- Allow dispatching to sub-rects of the render target
- Expand the scaling API to allow disabling antialiasing
- Add high quality dithering algorithms (blue noise, arbitrary size bayer
  matrix). This uses a new, genearlized shader LUT mechanism which
  allows the LUT to manifest itself either as a texture, a uniform
  float[] or as an in-line constant array depending on
  environment/hardware capabilities. As such, this can be used to enable
  dithering even without the use of a RA.

Changes:
- Minor RA API changes here and there (e.g. signed -> unsigned stride)

Fixes:
- Improved check logic for various shaders
- More descriptive variable names in some of the generated shaders
- Fix overflow when dithering to bit depths greater than 32
- Fix the RA format finding logic in some cases
- Make the scalers correctly support flipped scaling rects
- Fix some incorrect vulkan texture barriers
- Fix some locale issues on BSD
- GLSL 120 compat fix with the dithering algorithm
- Fix vulkan command polling logic to avoid blocking for longer than
  intended

v0.1.2

Fixes:
- Add missing header file
- Cosmetic fixes in the generated shaders

Improvements:
- Log slightly more debugging information for RAs
- Slight improvement of the internal PRNG
- Add travis CI support

Release v0.1.1

This is a minor bug fix release, to solve some issues that arose while
integrating libplacebo into VLC 3.0.

Fixes:
- various fixes under NDEBUG
- removed the LIBPLACEBO_ENABLE_SECURITY_BUGS nag under NDEBUG
- removed the LIBPLACEBO_LEAK_REPORT check under NDEBUG

Release v0.1.0

This represents the initial release, mostly so we can get VLC with basic
libplacebo support out of the way.

As of v0.1, libplacebo only supports vulkan, and only exposes the
low-level interfaces (dispatch, shader, ra). So as of now, libplacebo is
only useful either as a GLSL shader generator (shaders.h), or as an
offline tool for processing images (dispatch.h + vulkan). There is
currently no high-level image/video rendering interface, and no support
for OpenGL whatsoever.

OpenGL support is planned for v0.2, and the addition of a high level
renderer is planend for v0.3.