librashader version 0.5.0 introduces an ABI change to the C ABI that is incompatible with prior versions.
If a version of librashader prior to 0.5.0 was linked via `libashader_ld.h`, it should _correctly_ fail to load when attempting
to load an instance of librashader 0.5.0 or later.
This document is only relevant to consumers of the librashader C ABI. Rust users should consult [docs.rs/librashader](https://docs.rs/librashader/latest/librashader/).
## `LIBRASHADER_CURRENT_ABI` change
`LIBRASHADER_CURRENT_ABI` has changed from `1` to `2`. There is no change to `LIBRASHADER_CURRENT_API`, as new features
have not been added. Option structs should continue to pass `LIBRASHADER_CURRENT_API` for the latest available feature set.
## `SONAME` change
On Linux, the canonical `SONAME` of `librashader.so` has changed from `librashader.so.1` to `librashader.so.2`. This will
affect consumers that link via the linkage table with `-lrashader` or equivalent rather than through `libashader_ld.h`.
## `libra_preset` changes
* The `_internal_alloc` field from `libra_preset_param_list_t` has been removed. This change was made to reduce the potential
surface area for undefined behaviour to occur. If librashader was used correctly, there is no code change required.
## `LIBRA_RUNTIME_VULKAN` changes
The following changes are applicable if `LIBRA_RUNTIME_VULKAN` is defined.
* The `libra_output_image_vk_t` and `libra_source_image_vk_t` structs have been replaced with `libra_image_vk_t`.
*`libra_image_vk_t`has the same layout and semantics for `libra_source_image_vk_t`.
* When passed as `out`, you should now pass what was previously `.width` and `.height` of `libra_viewport_t` to the same fields in `libra_image_vk_t`. The `handle` and `format`
fields retain the same semantics as `libra_output_image_vk_t`.
* A field `queue` of type `VkQueue` was added to `libra_device_vk_t`. This field can be `NULL`. If not `NULL`, it is the handle to the `VkQueue` graphics queue
to use for the filter chain. If `NULL`, a suitable queue will be chosen.
* The `image` and `out` parameters of `libra_vk_filter_chain_frame` has changed from `libra_source_image_vk_t` and `libra_output_image_vk_t`, to `libra_image_vk_t`.
* In `libra_vk_filter_chain_frame`, the position of the `viewport` parameter has moved to after the `out` parameter, and its type has changed from `libra_viewport_t` to `libra_viewport_t *`, which is allowed to be `NULL`.
See [`libra_viewport_t` changes](#libra_viewport_t-changes) for more details.
* It is always thread safe to call `libra_vk_filter_chain_set_param` from any thread [^1].
## `LIBRA_RUNTIME_OPENGL` changes
The following changes are applicable if `LIBRA_RUNTIME_METAL` is defined.
* The `libra_gl_init_context` function has been removed.
* The function `libra_gl_filter_chain_create` now accepts a `loader` parameter of type `libra_gl_loader_t`. This will be the OpenGL loader used to create the filter chain, previously passed to `libra_gl_init_context`
The filter chain will be created against the current OpenGL context.
* The `libra_output_framebuffer_gl_t` and `libra_source_image_gl_t` structs have been replaced with `libra_image_gl_t`.
*`libra_image_gl_t`has the same layout and semantics for `libra_source_image_gl_t`.
* When passed as `out`, you should now pass what was previously `.width` and `.height` of `libra_viewport_t` to the same fields in `libra_image_gl_t`. The `handle` and `format`
fields retain the same semantics as `libra_output_image_gl_t`.
* The `fbo` field previously in `libra_output_image_gl_t` is no longer necessary. librashader will now internally manage a framebuffer object to write to the provided texture.
* In `libra_gl_filter_chain_frame`, the position of the `viewport` parameter has moved to after the `out` parameter, and its type has changed from `libra_viewport_t` to `libra_viewport_t *`, which is allowed to be `NULL`.
See [`libra_viewport_t` changes](#libra_viewport_t-changes) for more details.
* It is always thread safe to call `libra_gl_filter_chain_set_param` from any thread [^1].
## `LIBRA_RUNTIME_D3D11` changes
The following changes are applicable if `LIBRA_RUNTIME_D3D11` is defined.
* The `image` parameter of `libra_d3d11_filter_chain_frame` has changed from `libra_source_image_d3d11_t` to `ID3D11ShaderResourceView *`.
* You should now pass what was previously the `.handle` field of `libra_source_image_d3d11_t` field directly as `image` to `libra_d3d11_filter_chain_frame`.
* The `libra_source_image_d3d11_t` struct has been removed.
* In `libra_d3d11_filter_chain_frame`, the position of the `viewport` parameter has moved to after the `out` parameter, and its type has changed from `libra_viewport_t` to `libra_viewport_t *`, which is allowed to be `NULL`.
See [`libra_viewport_t` changes](#libra_viewport_t-changes) for more details.
* It is always thread safe to call `libra_d3d11_filter_chain_set_param` from any thread [^1].
## `LIBRA_RUNTIME_D3D12` changes
The following changes are applicable if `LIBRA_RUNTIME_D3D12` is defined.
* The fields `format`, `width`, and `height` have been removed from `libra_source_image_d3d12_t`.
* The fields `width` and `height` have been added to `libra_output_image_d3d12_t`.
* You should now pass what was previously `.width` and `.height` of `libra_viewport_t` to these new fields in `libra_output_image_d3d12_t`.
* In `libra_d3d12_filter_chain_frame`, the position of the `viewport` parameter has moved to after the `out` parameter, and its type has changed from `libra_viewport_t` to `libra_viewport_t *`, which is allowed to be `NULL`.
See [`libra_viewport_t` changes](#libra_viewport_t-changes) for more details.
* It is always thread safe to call `libra_d3d12_filter_chain_set_param` from any thread [^1].
## `LIBRA_RUNTIME_D3D9` changes
The following changes are applicable if `LIBRA_RUNTIME_D3D9` is defined.
* In `libra_d3d9_filter_chain_frame`, the position of the `viewport` parameter has moved to after the `out` parameter, and its type has changed from `libra_viewport_t` to `libra_viewport_t *`, which is allowed to be `NULL`.
See [`libra_viewport_t` changes](#libra_viewport_t-changes) for more details.
* It is always thread safe to call `libra_d3d9_filter_chain_set_param` from any thread [^1].
## `LIBRA_RUNTIME_METAL` changes
The following changes are applicable if `LIBRA_RUNTIME_METAL` is defined.
* In `libra_mtl_filter_chain_frame`, the position of the `viewport` parameter has moved to after the `out` parameter, and its type has changed from `libra_viewport_t` to `libra_viewport_t *`, which is allowed to be `NULL`.
See [`libra_viewport_t` changes](#libra_viewport_t-changes) for more details.
* It is always thread safe to call `libra_mtl_filter_chain_set_param` from any thread [^1].
## `libra_viewport_t` changes
All `viewport` parameters for `libra_*_filter_chain_frame` now take a *pointer* to a `libra_viewport_t` struct. In ABI 1, the semantics of `libra_viewport_t`
was unspecified (but not undefined behaviour) if `width` and `height` did not match the width and height of the output texture.
This caused confusion as to what the actual purpose of the `width` and `height` fields were. The behaviour differed across runtimes:
In some runtimes, it specified the size of the output texture, in others they were used to set the clipping rect for the render target.
In ABI 2, the semantics of `viewport` as a parameter in `libra_*_filter_chain_frame` are as specified.
* If `viewport` is `NULL`, then this will be the same as the **specified** behaviour in ABI 1—that is, as if the behaviour where `width` and `height` of `libra_viewport_t` were **equal** to that of the output texture.
* In other words, if `viewport` is `NULL`, then it will set the render viewport to be equal to the width and height of the output texture.
* If `viewport` is not `NULL`, then the following occurs.
* The width and height of the viewport rectangle for the output quad will be set to `viewport.width` and `viewport.height` respectively.
* The origin point of the viewport rectangle will be set to (`x`, `y`), **in the native coordinate system of the runtime**.
* This behaviour may change over an _API_ version bump. **API version 1 will always retain the behaviour specified here.**
* The scissor rectangle will be set to the same size and origin as the viewport rectangle.
[^1]: This has been the case since librashader 0.4.0 on ABI 1. ABI 2 codifies this guarantee: any loosening in the thread-safety guarantees of `libra_*_filter_chain_set_param` in the future may only change across an _API_ version bump. **API version 1 will always retain the behaviour specified here.**
