capi: make viewport optional, defaulting to a viewport that is the entire size of the render target

include/librashader.h

@@ -207,20 +207,6 @@ typedef struct libra_source_image_gl_t {
 } libra_source_image_gl_t;
 #endif
 
-/// Defines the output origin for a rendered frame.
-typedef struct libra_viewport_t {
-  /// The x offset in the viewport framebuffer to begin rendering from.
-  float x;
-  /// The y offset in the viewport framebuffer to begin rendering from.
-  float y;
-  /// The width extent of the viewport framebuffer to end rendering, relative to
-  /// the origin specified by x.
-  uint32_t width;
-  /// The height extent of the viewport framebuffer to end rendering, relative to
-  /// the origin specified by y.
-  uint32_t height;
-} libra_viewport_t;
-
 #if defined(LIBRA_RUNTIME_OPENGL)
 /// OpenGL parameters for the output framebuffer.
 typedef struct libra_output_framebuffer_gl_t {
@@ -237,6 +223,20 @@ typedef struct libra_output_framebuffer_gl_t {
 } libra_output_framebuffer_gl_t;
 #endif
 
+/// Defines the output origin for a rendered frame.
+typedef struct libra_viewport_t {
+  /// The x offset in the viewport framebuffer to begin rendering from.
+  float x;
+  /// The y offset in the viewport framebuffer to begin rendering from.
+  float y;
+  /// The width extent of the viewport framebuffer to end rendering, relative to
+  /// the origin specified by x.
+  uint32_t width;
+  /// The height extent of the viewport framebuffer to end rendering, relative to
+  /// the origin specified by y.
+  uint32_t height;
+} libra_viewport_t;
+
 #if defined(LIBRA_RUNTIME_OPENGL)
 /// Options for each OpenGL shader frame.
 typedef struct frame_gl_opt_t {
@@ -298,31 +298,17 @@ typedef struct _filter_chain_vk *libra_vk_filter_chain_t;
 #endif
 
 #if defined(LIBRA_RUNTIME_VULKAN)
-/// Vulkan parameters for the source image.
+/// Vulkan parameters for an image.
-typedef struct libra_source_image_vk_t {
+typedef struct libra_image_vk_t {
-  /// A raw `VkImage` handle to the source image.
+  /// A raw `VkImage` handle.
   VkImage handle;
-  /// The `VkFormat` of the source image.
+  /// The `VkFormat` of the `VkImage`.
   VkFormat format;
-  /// The width of the source image.
+  /// The width of the `VkImage`.
   uint32_t width;
-  /// The height of the source image.
+  /// The height of the `VkImage`.
   uint32_t height;
-} libra_source_image_vk_t;
+} libra_image_vk_t;
-#endif
-
-#if defined(LIBRA_RUNTIME_VULKAN)
-/// Vulkan parameters for the output image.
-typedef struct libra_output_image_vk_t {
-  /// A raw `VkImage` handle to the output image.
-  VkImage handle;
-  /// The `VkFormat` of the output image.
-  VkFormat format;
-  /// The width of the output image.
-  uint32_t width;
-  /// The height of the output image.
-  uint32_t height;
-} libra_output_image_vk_t;
 #endif
 
 #if defined(LIBRA_RUNTIME_VULKAN)
@@ -654,8 +640,8 @@ typedef libra_error_t (*PFN_libra_gl_filter_chain_create)(libra_shader_preset_t
 typedef libra_error_t (*PFN_libra_gl_filter_chain_frame)(libra_gl_filter_chain_t *chain,
                                                          size_t frame_count,
                                                          struct libra_source_image_gl_t image,
-                                                         struct libra_viewport_t viewport,
                                                          struct libra_output_framebuffer_gl_t out,
+                                                         const struct libra_viewport_t *viewport,
                                                          const float *mvp,
                                                          const struct frame_gl_opt_t *opt);
 #endif
@@ -721,9 +707,9 @@ typedef libra_error_t (*PFN_libra_vk_filter_chain_create_deferred)(libra_shader_
 typedef libra_error_t (*PFN_libra_vk_filter_chain_frame)(libra_vk_filter_chain_t *chain,
                                                          VkCommandBuffer command_buffer,
                                                          size_t frame_count,
-                                                         struct libra_source_image_vk_t image,
+                                                         struct libra_image_vk_t image,
-                                                         struct libra_viewport_t viewport,
+                                                         struct libra_image_vk_t out,
-                                                         struct libra_output_image_vk_t out,
+                                                         const struct libra_viewport_t *viewport,
                                                          const float *mvp,
                                                          const struct frame_vk_opt_t *opt);
 #endif
@@ -790,8 +776,8 @@ typedef libra_error_t (*PFN_libra_d3d11_filter_chain_frame)(libra_d3d11_filter_c
                                                             ID3D11DeviceContext * device_context,
                                                             size_t frame_count,
                                                             ID3D11ShaderResourceView * image,
-                                                            struct libra_viewport_t viewport,
                                                             ID3D11RenderTargetView * out,
+                                                            const struct libra_viewport_t *viewport,
                                                             const float *mvp,
                                                             const struct frame_d3d11_opt_t *options);
 #endif
@@ -847,8 +833,8 @@ typedef libra_error_t (*PFN_libra_d3d9_filter_chain_create)(libra_shader_preset_
 typedef libra_error_t (*PFN_libra_d3d9_filter_chain_frame)(libra_d3d9_filter_chain_t *chain,
                                                            size_t frame_count,
                                                            IDirect3DTexture9 * image,
-                                                           struct libra_viewport_t viewport,
                                                            IDirect3DSurface9 * out,
+                                                           const struct libra_viewport_t *viewport,
                                                            const float *mvp,
                                                            const struct frame_d3d9_opt_t *options);
 #endif
@@ -915,8 +901,8 @@ typedef libra_error_t (*PFN_libra_d3d12_filter_chain_frame)(libra_d3d12_filter_c
                                                             ID3D12GraphicsCommandList * command_list,
                                                             size_t frame_count,
                                                             struct libra_source_image_d3d12_t image,
-                                                            struct libra_viewport_t viewport,
                                                             struct libra_output_image_d3d12_t out,
+                                                            const struct libra_viewport_t *viewport,
                                                             const float *mvp,
                                                             const struct frame_d3d12_opt_t *options);
 #endif
@@ -983,8 +969,8 @@ typedef libra_error_t (*PFN_libra_mtl_filter_chain_frame)(libra_mtl_filter_chain
                                                           id<MTLCommandBuffer> command_buffer,
                                                           size_t frame_count,
                                                           id<MTLTexture> image,
-                                                          struct libra_viewport_t viewport,
                                                           id<MTLTexture> output,
+                                                          const struct libra_viewport_t *viewport,
                                                           const float *mvp,
                                                           const struct frame_mtl_opt_t *opt);
 #endif
@@ -1207,6 +1193,23 @@ libra_error_t libra_gl_filter_chain_create(libra_shader_preset_t *preset,
 #if defined(LIBRA_RUNTIME_OPENGL)
 /// Draw a frame with the given parameters for the given filter chain.
 ///
+/// ## Parameters
+///
+/// - `chain` is a handle to the filter chain.
+/// - `frame_count` is the number of frames passed to the shader
+/// - `image` is a `libra_source_image_gl_t`, containing the name of a Texture, format, and size information to
+///    to an image that will serve as the source image for the frame.
+/// - `out` is a `libra_output_framebuffer_gl_t`, containing the name of a Framebuffer, the name of a Texture, format,
+///    and size information for the render target of the frame.
+///
+/// - `viewport` is a pointer to a `libra_viewport_t` that specifies the area onto which scissor and viewport
+///    will be applied to the render target. It may be null, in which case a default viewport spanning the
+///    entire render target will be used.
+/// - `mvp` is a pointer to an array of 16 `float` values to specify the model view projection matrix to
+///    be passed to the shader.
+/// - `options` is a pointer to options for the frame. Valid options are dependent on the `LIBRASHADER_API_VERSION`
+///    passed in. It may be null, in which case default options for the filter chain are used.
+///
 /// ## Safety
 /// - `chain` may be null, invalid, but not uninitialized. If `chain` is null or invalid, this
 ///    function will return an error.
@@ -1221,8 +1224,8 @@ libra_error_t libra_gl_filter_chain_create(libra_shader_preset_t *preset,
 libra_error_t libra_gl_filter_chain_frame(libra_gl_filter_chain_t *chain,
                                           size_t frame_count,
                                           struct libra_source_image_gl_t image,
-                                          struct libra_viewport_t viewport,
                                           struct libra_output_framebuffer_gl_t out,
+                                          const struct libra_viewport_t *viewport,
                                           const float *mvp,
                                           const struct frame_gl_opt_t *opt);
 #endif
@@ -1326,13 +1329,31 @@ libra_error_t libra_vk_filter_chain_create_deferred(libra_shader_preset_t *prese
 /// Records rendering commands for a frame with the given parameters for the given filter chain
 /// to the input command buffer.
 ///
-/// * The input image must be in the `VK_SHADER_READ_ONLY_OPTIMAL` layout.
+/// librashader **will not** create a pipeline barrier for the final pass. The output image must be
-/// * The output image must be in `VK_COLOR_ATTACHMENT_OPTIMAL` layout.
+/// in `VK_COLOR_ATTACHMENT_OPTIMAL`, and will remain so after all shader passes. The caller must transition
-///
-/// librashader **will not** create a pipeline barrier for the final pass. The output image will
-/// remain in `VK_COLOR_ATTACHMENT_OPTIMAL` after all shader passes. The caller must transition
 /// the output image to the final layout.
 ///
+/// ## Parameters
+///
+/// - `chain` is a handle to the filter chain.
+/// - `command_buffer` is a `VkCommandBuffer` handle to record draw commands to.
+///    The provided command buffer must be ready for recording and contain no prior commands
+/// - `frame_count` is the number of frames passed to the shader
+/// - `image` is a `libra_image_vk_t`, containing a `VkImage` handle, it's format and size information,
+///    to an image that will serve as the source image for the frame. The input image must be in
+///    the `VK_SHADER_READ_ONLY_OPTIMAL` layout.
+/// - `out` is a `libra_image_vk_t`, containing a `VkImage` handle, it's format and size information,
+///    for the render target of the frame. The output image must be in `VK_COLOR_ATTACHMENT_OPTIMAL` layout.
+///    The output image will remain in `VK_COLOR_ATTACHMENT_OPTIMAL` after all shader passes.
+///
+/// - `viewport` is a pointer to a `libra_viewport_t` that specifies the area onto which scissor and viewport
+///    will be applied to the render target. It may be null, in which case a default viewport spanning the
+///    entire render target will be used.
+/// - `mvp` is a pointer to an array of 16 `float` values to specify the model view projection matrix to
+///    be passed to the shader.
+/// - `options` is a pointer to options for the frame. Valid options are dependent on the `LIBRASHADER_API_VERSION`
+///    passed in. It may be null, in which case default options for the filter chain are used.
+///
 /// ## Safety
 /// - `libra_vk_filter_chain_frame` **must not be called within a RenderPass**.
 /// - `command_buffer` must be a valid handle to a `VkCommandBuffer` that is ready for recording.
@@ -1347,9 +1368,9 @@ libra_error_t libra_vk_filter_chain_create_deferred(libra_shader_preset_t *prese
 libra_error_t libra_vk_filter_chain_frame(libra_vk_filter_chain_t *chain,
                                           VkCommandBuffer command_buffer,
                                           size_t frame_count,
-                                          struct libra_source_image_vk_t image,
+                                          struct libra_image_vk_t image,
-                                          struct libra_viewport_t viewport,
+                                          struct libra_image_vk_t out,
-                                          struct libra_output_image_vk_t out,
+                                          const struct libra_viewport_t *viewport,
                                           const float *mvp,
                                           const struct frame_vk_opt_t *opt);
 #endif
@@ -1457,9 +1478,26 @@ libra_error_t libra_d3d11_filter_chain_create_deferred(libra_shader_preset_t *pr
 #if (defined(_WIN32) && defined(LIBRA_RUNTIME_D3D11))
 /// Draw a frame with the given parameters for the given filter chain.
 ///
-/// If `device_context` is null, then commands are recorded onto the immediate context. Otherwise,
+/// ## Parameters
-/// it will record commands onto the provided context. If the context is deferred, librashader
+///
-/// will not finalize command lists. The context must otherwise be associated with the `ID3D11Device`
+/// - `chain` is a handle to the filter chain.
+/// - `device_context` is the ID3D11DeviceContext used to record draw commands to.
+///    If `device_context` is null, then commands are recorded onto the immediate context. Otherwise,
+///    it will record commands onto the provided context. If the context is deferred, librashader
+///    will not finalize command lists. The context must otherwise be associated with the `ID3D11Device`
+///    the filter chain was created with.
+///
+/// - `frame_count` is the number of frames passed to the shader
+/// - `image` is a pointer to a `ID3D11ShaderResourceView` that will serve as the source image for the frame.
+/// - `out` is a pointer to a `ID3D11RenderTargetView` that will serve as the render target for the frame.
+///
+/// - `viewport` is a pointer to a `libra_viewport_t` that specifies the area onto which scissor and viewport
+///    will be applied to the render target. It may be null, in which case a default viewport spanning the
+///    entire render target will be used.
+/// - `mvp` is a pointer to an array of 16 `float` values to specify the model view projection matrix to
+///    be passed to the shader.
+/// - `options` is a pointer to options for the frame. Valid options are dependent on the `LIBRASHADER_API_VERSION`
+///    passed in. It may be null, in which case default options for the filter chain are used.
 ///
 /// ## Safety
 /// - `chain` may be null, invalid, but not uninitialized. If `chain` is null or invalid, this
@@ -1479,8 +1517,8 @@ libra_error_t libra_d3d11_filter_chain_frame(libra_d3d11_filter_chain_t *chain,
                                              ID3D11DeviceContext * device_context,
                                              size_t frame_count,
                                              ID3D11ShaderResourceView * image,
-                                             struct libra_viewport_t viewport,
                                              ID3D11RenderTargetView * out,
+                                             const struct libra_viewport_t *viewport,
                                              const float *mvp,
                                              const struct frame_d3d11_opt_t *options);
 #endif
@@ -1556,10 +1594,24 @@ libra_error_t libra_d3d9_filter_chain_create(libra_shader_preset_t *preset,
 #if (defined(_WIN32) && defined(LIBRA_RUNTIME_D3D9))
 /// Draw a frame with the given parameters for the given filter chain.
 ///
+/// ## Parameters
+/// - `chain` is a handle to the filter chain.
+/// - `frame_count` is the number of frames passed to the shader
+/// - `image` is a pointer to a `IDirect3DTexture9` that will serve as the source image for the frame.
+/// - `out` is a pointer to a `IDirect3DSurface9` that will serve as the render target for the frame.
+///
+/// - `viewport` is a pointer to a `libra_viewport_t` that specifies the area onto which scissor and viewport
+///    will be applied to the render target. It may be null, in which case a default viewport spanning the
+///    entire render target will be used.
+/// - `mvp` is a pointer to an array of 16 `float` values to specify the model view projection matrix to
+///    be passed to the shader.
+/// - `options` is a pointer to options for the frame. Valid options are dependent on the `LIBRASHADER_API_VERSION`
+///    passed in. It may be null, in which case default options for the filter chain are used.
 ///
 /// ## Safety
 /// - `chain` may be null, invalid, but not uninitialized. If `chain` is null or invalid, this
 ///    function will return an error.
+/// - `viewport` may be null, or if it is not null, must be an aligned pointer to an instance of `libra_viewport_t`.
 /// - `mvp` may be null, or if it is not null, must be an aligned pointer to 16 consecutive `float`
 ///    values for the model view projection matrix.
 /// - `opt` may be null, or if it is not null, must be an aligned pointer to a valid `frame_d3d9_opt_t`
@@ -1571,8 +1623,8 @@ libra_error_t libra_d3d9_filter_chain_create(libra_shader_preset_t *preset,
 libra_error_t libra_d3d9_filter_chain_frame(libra_d3d9_filter_chain_t *chain,
                                             size_t frame_count,
                                             IDirect3DTexture9 * image,
-                                            struct libra_viewport_t viewport,
                                             IDirect3DSurface9 * out,
+                                            const struct libra_viewport_t *viewport,
                                             const float *mvp,
                                             const struct frame_d3d9_opt_t *options);
 #endif
@@ -1673,13 +1725,31 @@ libra_error_t libra_d3d12_filter_chain_create_deferred(libra_shader_preset_t *pr
 /// Records rendering commands for a frame with the given parameters for the given filter chain
 /// to the input command list.
 ///
-/// * The input image must be in the `D3D12_RESOURCE_STATE_PIXEL_SHADER_RESOURCE` resource state.
-/// * The output image must be in `D3D12_RESOURCE_STATE_RENDER_TARGET` resource state.
-///
 /// librashader **will not** create a resource barrier for the final pass. The output image will
 /// remain in `D3D12_RESOURCE_STATE_RENDER_TARGET` after all shader passes. The caller must transition
 /// the output image to the final resource state.
 ///
+/// ## Parameters
+///
+/// - `chain` is a handle to the filter chain.
+/// - `command_list` is a `ID3D12GraphicsCommandList` to record draw commands to.
+///    The provided command list must be open and associated with the `ID3D12Device` this filter chain was created with.
+/// - `frame_count` is the number of frames passed to the shader
+/// - `image` is a `libra_source_image_d3d12_t`, containing a `ID3D12Resource` pointer and CPU descriptor
+///    to an image that will serve as the source image for the frame. The input image must be in the
+///    `D3D12_RESOURCE_STATE_PIXEL_SHADER_RESOURCE` resource state or equivalent barrier layout.
+/// - `out` is a `libra_output_image_d3d12_t`, containing a CPU descriptor handle, format, and size information
+///    for the render target of the frame. The output image must be in
+///    `D3D12_RESOURCE_STATE_RENDER_TARGET` resource state or equivalent barrier layout.
+///
+/// - `viewport` is a pointer to a `libra_viewport_t` that specifies the area onto which scissor and viewport
+///    will be applied to the render target. It may be null, in which case a default viewport spanning the
+///    entire render target will be used.
+/// - `mvp` is a pointer to an array of 16 `float` values to specify the model view projection matrix to
+///    be passed to the shader.
+/// - `options` is a pointer to options for the frame. Valid options are dependent on the `LIBRASHADER_API_VERSION`
+///    passed in. It may be null, in which case default options for the filter chain are used.
+///
 /// ## Safety
 /// - `chain` may be null, invalid, but not uninitialized. If `chain` is null or invalid, this
 ///    function will return an error.
@@ -1697,8 +1767,8 @@ libra_error_t libra_d3d12_filter_chain_frame(libra_d3d12_filter_chain_t *chain,
                                              ID3D12GraphicsCommandList * command_list,
                                              size_t frame_count,
                                              struct libra_source_image_d3d12_t image,
-                                             struct libra_viewport_t viewport,
                                              struct libra_output_image_d3d12_t out,
+                                             const struct libra_viewport_t *viewport,
                                              const float *mvp,
                                              const struct frame_d3d12_opt_t *options);
 #endif
@@ -1802,6 +1872,22 @@ libra_error_t libra_mtl_filter_chain_create_deferred(libra_shader_preset_t *pres
 #if (defined(__APPLE__) && defined(LIBRA_RUNTIME_METAL) && defined(__OBJC__))
 /// Records rendering commands for a frame with the given parameters for the given filter chain
 /// to the input command buffer.
+/// ## Parameters
+///
+/// - `chain` is a handle to the filter chain.
+/// - `command_buffer` is a `MTLCommandBuffer` handle to record draw commands to.
+///    The provided command buffer must be ready for encoding and contain no prior commands
+/// - `frame_count` is the number of frames passed to the shader
+/// - `image` is a `id<MTLTexture>` that will serve as the source image for the frame.
+/// - `out` is a `id<MTLTexture>` that is the render target of the frame.
+///
+/// - `viewport` is a pointer to a `libra_viewport_t` that specifies the area onto which scissor and viewport
+///    will be applied to the render target. It may be null, in which case a default viewport spanning the
+///    entire render target will be used.
+/// - `mvp` is a pointer to an array of 16 `float` values to specify the model view projection matrix to
+///    be passed to the shader.
+/// - `options` is a pointer to options for the frame. Valid options are dependent on the `LIBRASHADER_API_VERSION`
+///    passed in. It may be null, in which case default options for the filter chain are used.
 ///
 /// ## Safety
 /// - `command_buffer` must be a valid reference to a `MTLCommandBuffer` that is not already encoding.
@@ -1817,8 +1903,8 @@ libra_error_t libra_mtl_filter_chain_frame(libra_mtl_filter_chain_t *chain,
                                            id<MTLCommandBuffer> command_buffer,
                                            size_t frame_count,
                                            id<MTLTexture> image,
-                                           struct libra_viewport_t viewport,
                                            id<MTLTexture> output,
+                                           const struct libra_viewport_t *viewport,
                                            const float *mvp,
                                            const struct frame_mtl_opt_t *opt);
 #endif

include/librashader_ld.h

@@ -204,8 +204,8 @@ libra_error_t __librashader__noop_gl_filter_chain_create(
 
 libra_error_t __librashader__noop_gl_filter_chain_frame(
     libra_gl_filter_chain_t *chain, size_t frame_count,
-    struct libra_source_image_gl_t image, struct libra_viewport_t viewport,
+    struct libra_source_image_gl_t image, struct libra_output_framebuffer_gl_t out,
-    struct libra_output_framebuffer_gl_t out, const float *mvp,
+    const struct libra_viewport_t *viewport, const float *mvp,
     const struct frame_gl_opt_t *opt) {
     return NULL;
 }
@@ -254,9 +254,9 @@ libra_error_t __librashader__noop_vk_filter_chain_create_deferred(
 
 libra_error_t __librashader__noop_vk_filter_chain_frame(
     libra_vk_filter_chain_t *chain, VkCommandBuffer command_buffer,
-    size_t frame_count, struct libra_source_image_vk_t image,
+    size_t frame_count, struct libra_image_vk_t image, struct libra_image_vk_t out,
-    struct libra_viewport_t viewport, struct libra_output_image_vk_t out,
+    const struct libra_viewport_t *viewport, const float *mvp,
-    const float *mvp, const struct frame_vk_opt_t *opt) {
+    const struct frame_vk_opt_t *opt) {
     return NULL;
 }
 
@@ -306,9 +306,9 @@ libra_error_t __librashader__noop_d3d11_filter_chain_create_deferred(
 
 libra_error_t __librashader__noop_d3d11_filter_chain_frame(
     libra_d3d11_filter_chain_t *chain, ID3D11DeviceContext *device_context,
-    size_t frame_count, ID3D11ShaderResourceView *image,
+    size_t frame_count, ID3D11ShaderResourceView *image, ID3D11RenderTargetView *out,
-    struct libra_viewport_t viewport, ID3D11RenderTargetView *out,
+    const struct libra_viewport_t *viewport, const float *mvp,
-    const float *mvp, const struct frame_d3d11_opt_t *opt) {
+    const struct frame_d3d11_opt_t *opt) {
     return NULL;
 }
 
@@ -358,9 +358,9 @@ libra_error_t __librashader__noop_d3d12_filter_chain_create_deferred(
 
 libra_error_t __librashader__noop_d3d12_filter_chain_frame(
     libra_d3d12_filter_chain_t *chain, ID3D12GraphicsCommandList *command_list,
-    size_t frame_count, struct libra_source_image_d3d12_t image,
+    size_t frame_count, struct libra_source_image_d3d12_t image, struct libra_output_image_d3d12_t out,
-    struct libra_viewport_t viewport, struct libra_output_image_d3d12_t out,
+    const struct libra_viewport_t *viewport, const float *mvp,
-    const float *mvp, const struct frame_d3d12_opt_t *opt) {
+    const struct frame_d3d12_opt_t *opt) {
     return NULL;
 }
 
@@ -401,8 +401,8 @@ libra_error_t __librashader__noop_d3d9_filter_chain_create(
 
 libra_error_t __librashader__noop_d3d9_filter_chain_frame(
     libra_d3d9_filter_chain_t *chain, size_t frame_count,
-    IDirect3DTexture9 *image, struct libra_viewport_t viewport,
+    IDirect3DTexture9 *image, IDirect3DSurface9 * out,
-    IDirect3DSurface9 * out, const float *mvp,
+    const struct libra_viewport_t *viewport, const float *mvp,
     const struct frame_d3d9_opt_t *opt) {
     return NULL;
 }
@@ -453,8 +453,8 @@ libra_error_t __librashader__noop_mtl_filter_chain_create_deferred(
 
 libra_error_t __librashader__noop_mtl_filter_chain_frame(
     libra_mtl_filter_chain_t *chain, id<MTLCommandBuffer> command_buffer,
-    size_t frame_count, id<MTLTexture> image, struct libra_viewport_t viewport,
+    size_t frame_count, id<MTLTexture> image, id<MTLTexture> output,
-    id<MTLTexture> output, const float *mvp,
+    const struct libra_viewport_t *viewport, const float *mvp,
     const struct frame_mtl_opt_t *opt) {
     return NULL;
 }

librashader-capi/src/error.rs

@@ -89,6 +89,8 @@ pub enum LibrashaderError {
     #[cfg(all(target_vendor = "apple", feature = "runtime-metal"))]
     #[error("There was an error in the Metal filter chain.")]
     MetalFilterError(#[from] librashader::runtime::mtl::error::FilterChainError),
+    #[error("This error is not reachable")]
+    Infallible(#[from] std::convert::Infallible),
 }
 
 /// Error codes for librashader error types.
@@ -254,6 +256,7 @@ impl LibrashaderError {
             LibrashaderError::VulkanFilterError(_) => LIBRA_ERRNO::RUNTIME_ERROR,
             #[cfg(all(target_vendor = "apple", feature = "runtime-metal"))]
             LibrashaderError::MetalFilterError(_) => LIBRA_ERRNO::RUNTIME_ERROR,
+            LibrashaderError::Infallible(_) => LIBRA_ERRNO::UNKNOWN_ERROR,
         }
     }
     pub(crate) const fn ok() -> libra_error_t {

librashader-capi/src/runtime/d3d11/filter_chain.rs

@@ -15,6 +15,7 @@ use windows::Win32::Graphics::Direct3D11::{
 };
 
 use crate::LIBRASHADER_API_VERSION;
+use librashader::runtime::d3d11::error::FilterChainError;
 use librashader::runtime::{FilterChainParameters, Size, Viewport};
 
 /// Options for Direct3D 11 filter chain creation.
@@ -178,10 +179,26 @@ const _: () = assert!(
 extern_fn! {
     /// Draw a frame with the given parameters for the given filter chain.
     ///
-    /// If `device_context` is null, then commands are recorded onto the immediate context. Otherwise,
+    /// ## Parameters
-    /// it will record commands onto the provided context. If the context is deferred, librashader
+    ///
-    /// will not finalize command lists. The context must otherwise be associated with the `ID3D11Device`
+    /// - `chain` is a handle to the filter chain.
-    //  the filter chain was created with.
+    /// - `device_context` is the ID3D11DeviceContext used to record draw commands to.
+    ///    If `device_context` is null, then commands are recorded onto the immediate context. Otherwise,
+    ///    it will record commands onto the provided context. If the context is deferred, librashader
+    ///    will not finalize command lists. The context must otherwise be associated with the `ID3D11Device`
+    ///    the filter chain was created with.
+    ///
+    /// - `frame_count` is the number of frames passed to the shader
+    /// - `image` is a pointer to a `ID3D11ShaderResourceView` that will serve as the source image for the frame.
+    /// - `out` is a pointer to a `ID3D11RenderTargetView` that will serve as the render target for the frame.
+    ///
+    /// - `viewport` is a pointer to a `libra_viewport_t` that specifies the area onto which scissor and viewport
+    ///    will be applied to the render target. It may be null, in which case a default viewport spanning the
+    ///    entire render target will be used.
+    /// - `mvp` is a pointer to an array of 16 `float` values to specify the model view projection matrix to
+    ///    be passed to the shader.
+    /// - `options` is a pointer to options for the frame. Valid options are dependent on the `LIBRASHADER_API_VERSION`
+    ///    passed in. It may be null, in which case default options for the filter chain are used.
     ///
     /// ## Safety
     /// - `chain` may be null, invalid, but not uninitialized. If `chain` is null or invalid, this
@@ -204,8 +221,8 @@ extern_fn! {
         device_context: Option<ManuallyDrop<ID3D11DeviceContext>>,
         frame_count: usize,
         image: ManuallyDrop<ID3D11ShaderResourceView>,
-        viewport: libra_viewport_t,
         out: ManuallyDrop<ID3D11RenderTargetView>,
+        viewport: *const libra_viewport_t,
         mvp: *const f32,
         options: *const MaybeUninit<frame_d3d11_opt_t>
     ) mut |chain| {
@@ -223,15 +240,21 @@ extern_fn! {
             Some(unsafe { options.read() })
         };
 
-        let viewport = Viewport {
+        let viewport = if viewport.is_null() {
-            x: viewport.x,
+            Viewport::new_render_target_sized_origin(ManuallyDrop::into_inner(out.clone()), mvp)
-            y: viewport.y,
+                .map_err(|e| LibrashaderError::D3D11FilterError(FilterChainError::Direct3DError(e)))?
-            output: ManuallyDrop::into_inner(out.clone()),
+        } else {
-            size: Size {
+            let viewport = unsafe { viewport.read() };
-                height: viewport.height,
+            Viewport {
-                width: viewport.width
+                x: viewport.x,
-            },
+                y: viewport.y,
-            mvp,
+                output: ManuallyDrop::into_inner(out.clone()),
+                size: Size {
+                    height: viewport.height,
+                    width: viewport.width
+                },
+                mvp,
+            }
         };
 
         let options = options.map(FromUninit::from_uninit);

librashader-capi/src/runtime/d3d12/filter_chain.rs

@@ -208,13 +208,31 @@ extern_fn! {
     /// Records rendering commands for a frame with the given parameters for the given filter chain
     /// to the input command list.
     ///
-    /// * The input image must be in the `D3D12_RESOURCE_STATE_PIXEL_SHADER_RESOURCE` resource state.
-    /// * The output image must be in `D3D12_RESOURCE_STATE_RENDER_TARGET` resource state.
-    ///
     /// librashader **will not** create a resource barrier for the final pass. The output image will
     /// remain in `D3D12_RESOURCE_STATE_RENDER_TARGET` after all shader passes. The caller must transition
     /// the output image to the final resource state.
     ///
+    /// ## Parameters
+    ///
+    /// - `chain` is a handle to the filter chain.
+    /// - `command_list` is a `ID3D12GraphicsCommandList` to record draw commands to.
+    ///    The provided command list must be open and associated with the `ID3D12Device` this filter chain was created with.
+    /// - `frame_count` is the number of frames passed to the shader
+    /// - `image` is a `libra_source_image_d3d12_t`, containing a `ID3D12Resource` pointer and CPU descriptor
+    ///    to an image that will serve as the source image for the frame. The input image must be in the
+    ///    `D3D12_RESOURCE_STATE_PIXEL_SHADER_RESOURCE` resource state or equivalent barrier layout.
+    /// - `out` is a `libra_output_image_d3d12_t`, containing a CPU descriptor handle, format, and size information
+    ///    for the render target of the frame. The output image must be in
+    ///    `D3D12_RESOURCE_STATE_RENDER_TARGET` resource state or equivalent barrier layout.
+    ///
+    /// - `viewport` is a pointer to a `libra_viewport_t` that specifies the area onto which scissor and viewport
+    ///    will be applied to the render target. It may be null, in which case a default viewport spanning the
+    ///    entire render target will be used.
+    /// - `mvp` is a pointer to an array of 16 `float` values to specify the model view projection matrix to
+    ///    be passed to the shader.
+    /// - `options` is a pointer to options for the frame. Valid options are dependent on the `LIBRASHADER_API_VERSION`
+    ///    passed in. It may be null, in which case default options for the filter chain are used.
+    ///
     /// ## Safety
     /// - `chain` may be null, invalid, but not uninitialized. If `chain` is null or invalid, this
     ///    function will return an error.
@@ -233,8 +251,8 @@ extern_fn! {
         command_list: ManuallyDrop<ID3D12GraphicsCommandList>,
         frame_count: usize,
         image: libra_source_image_d3d12_t,
-        viewport: libra_viewport_t,
         out: libra_output_image_d3d12_t,
+        viewport: *const libra_viewport_t,
         mvp: *const f32,
         options: *const MaybeUninit<frame_d3d12_opt_t>
     ) mut |chain| {
@@ -253,17 +271,28 @@ extern_fn! {
         };
 
         let options = options.map(FromUninit::from_uninit);
-        let viewport = Viewport {
+
-            x: viewport.x,
+        let output = unsafe {
-            y: viewport.y,
+            D3D12OutputView::new_from_raw(
-            size: Size {
+                out.descriptor,
-                height: viewport.height,
+                Size::new(out.width, out.height),
-                width: viewport.width
+                out.format)
-            },
+        };
-            output: unsafe {
+
-                D3D12OutputView::new_from_raw(out.descriptor,
+        let viewport = if viewport.is_null() {
-                    Size::new(out.width, out.height), out.format) },
+            Viewport::new_render_target_sized_origin(output, mvp)?
-            mvp,
+        } else {
+            let viewport = unsafe { viewport.read() };
+            Viewport {
+                x: viewport.x,
+                y: viewport.y,
+                output,
+                size: Size {
+                    height: viewport.height,
+                    width: viewport.width
+                },
+                mvp,
+            }
         };
 
         let image = image.try_into()?;

librashader-capi/src/runtime/d3d9/filter_chain.rs

@@ -12,6 +12,7 @@ use std::slice;
 use windows::Win32::Graphics::Direct3D9::{IDirect3DDevice9, IDirect3DSurface9, IDirect3DTexture9};
 
 use crate::LIBRASHADER_API_VERSION;
+use librashader::runtime::d3d9::error::FilterChainError;
 use librashader::runtime::{FilterChainParameters, Size, Viewport};
 
 /// Options for Direct3D 11 filter chain creation.
@@ -108,10 +109,24 @@ extern_fn! {
 extern_fn! {
     /// Draw a frame with the given parameters for the given filter chain.
     ///
+    /// ## Parameters
+    /// - `chain` is a handle to the filter chain.
+    /// - `frame_count` is the number of frames passed to the shader
+    /// - `image` is a pointer to a `IDirect3DTexture9` that will serve as the source image for the frame.
+    /// - `out` is a pointer to a `IDirect3DSurface9` that will serve as the render target for the frame.
+    ///
+    /// - `viewport` is a pointer to a `libra_viewport_t` that specifies the area onto which scissor and viewport
+    ///    will be applied to the render target. It may be null, in which case a default viewport spanning the
+    ///    entire render target will be used.
+    /// - `mvp` is a pointer to an array of 16 `float` values to specify the model view projection matrix to
+    ///    be passed to the shader.
+    /// - `options` is a pointer to options for the frame. Valid options are dependent on the `LIBRASHADER_API_VERSION`
+    ///    passed in. It may be null, in which case default options for the filter chain are used.
     ///
     /// ## Safety
     /// - `chain` may be null, invalid, but not uninitialized. If `chain` is null or invalid, this
     ///    function will return an error.
+    /// - `viewport` may be null, or if it is not null, must be an aligned pointer to an instance of `libra_viewport_t`.
     /// - `mvp` may be null, or if it is not null, must be an aligned pointer to 16 consecutive `float`
     ///    values for the model view projection matrix.
     /// - `opt` may be null, or if it is not null, must be an aligned pointer to a valid `frame_d3d9_opt_t`
@@ -124,8 +139,8 @@ extern_fn! {
         chain: *mut libra_d3d9_filter_chain_t,
         frame_count: usize,
         image: ManuallyDrop<IDirect3DTexture9>,
-        viewport: libra_viewport_t,
         out: ManuallyDrop<IDirect3DSurface9>,
+        viewport: *const libra_viewport_t,
         mvp: *const f32,
         options: *const MaybeUninit<frame_d3d9_opt_t>
     ) mut |chain| {
@@ -143,15 +158,21 @@ extern_fn! {
             Some(unsafe { options.read() })
         };
 
-        let viewport = Viewport {
+        let viewport = if viewport.is_null() {
-            x: viewport.x,
+            Viewport::new_render_target_sized_origin(ManuallyDrop::into_inner(out.clone()), mvp)
-            y: viewport.y,
+                .map_err(|e| LibrashaderError::D3D9FilterError(FilterChainError::Direct3DError(e)))?
-            output: ManuallyDrop::into_inner(out.clone()),
+        } else {
-            size: Size {
+            let viewport = unsafe { viewport.read() };
-                height: viewport.height,
+            Viewport {
-                width: viewport.width
+                x: viewport.x,
-            },
+                y: viewport.y,
-            mvp,
+                output: ManuallyDrop::into_inner(out.clone()),
+                size: Size {
+                    height: viewport.height,
+                    width: viewport.width
+                },
+                mvp,
+            }
         };
 
         let options = options.map(FromUninit::from_uninit);

librashader-capi/src/runtime/gl/filter_chain.rs

@@ -162,6 +162,23 @@ extern_fn! {
 extern_fn! {
     /// Draw a frame with the given parameters for the given filter chain.
     ///
+    /// ## Parameters
+    ///
+    /// - `chain` is a handle to the filter chain.
+    /// - `frame_count` is the number of frames passed to the shader
+    /// - `image` is a `libra_source_image_gl_t`, containing the name of a Texture, format, and size information to
+    ///    to an image that will serve as the source image for the frame.
+    /// - `out` is a `libra_output_framebuffer_gl_t`, containing the name of a Framebuffer, the name of a Texture, format,
+    ///    and size information for the render target of the frame.
+    ///
+    /// - `viewport` is a pointer to a `libra_viewport_t` that specifies the area onto which scissor and viewport
+    ///    will be applied to the render target. It may be null, in which case a default viewport spanning the
+    ///    entire render target will be used.
+    /// - `mvp` is a pointer to an array of 16 `float` values to specify the model view projection matrix to
+    ///    be passed to the shader.
+    /// - `options` is a pointer to options for the frame. Valid options are dependent on the `LIBRASHADER_API_VERSION`
+    ///    passed in. It may be null, in which case default options for the filter chain are used.
+    ///
     /// ## Safety
     /// - `chain` may be null, invalid, but not uninitialized. If `chain` is null or invalid, this
     ///    function will return an error.
@@ -177,8 +194,8 @@ extern_fn! {
         chain: *mut libra_gl_filter_chain_t,
         frame_count: usize,
         image: libra_source_image_gl_t,
-        viewport: libra_viewport_t,
         out: libra_output_framebuffer_gl_t,
+        viewport: *const libra_viewport_t,
         mvp: *const f32,
         opt: *const MaybeUninit<frame_gl_opt_t>,
     ) mut |chain| {
@@ -209,15 +226,20 @@ extern_fn! {
         let framebuffer = GLFramebuffer::new_from_raw(Arc::clone(chain.get_context()),
             texture, fbo, out.format, Size::new(out.width, out.height), 1);
 
-        let viewport = Viewport {
+         let viewport = if viewport.is_null() {
-            x: viewport.x,
+            Viewport::new_render_target_sized_origin(&framebuffer, mvp)?
-            y: viewport.y,
+        } else {
-            output: &framebuffer,
+            let viewport = unsafe { viewport.read() };
-            size: Size {
+            Viewport {
-                height: viewport.height,
+                x: viewport.x,
-                width: viewport.width
+                y: viewport.y,
-            },
+                output: &framebuffer,
-            mvp,
+                size: Size {
+                    height: viewport.height,
+                    width: viewport.width
+                },
+                mvp,
+            }
         };
 
         unsafe {

librashader-capi/src/runtime/mtl/filter_chain.rs

@@ -173,6 +173,22 @@ extern_fn! {
 extern_fn! {
     /// Records rendering commands for a frame with the given parameters for the given filter chain
     /// to the input command buffer.
+    /// ## Parameters
+    ///
+    /// - `chain` is a handle to the filter chain.
+    /// - `command_buffer` is a `MTLCommandBuffer` handle to record draw commands to.
+    ///    The provided command buffer must be ready for encoding and contain no prior commands
+    /// - `frame_count` is the number of frames passed to the shader
+    /// - `image` is a `id<MTLTexture>` that will serve as the source image for the frame.
+    /// - `out` is a `id<MTLTexture>` that is the render target of the frame.
+    ///
+    /// - `viewport` is a pointer to a `libra_viewport_t` that specifies the area onto which scissor and viewport
+    ///    will be applied to the render target. It may be null, in which case a default viewport spanning the
+    ///    entire render target will be used.
+    /// - `mvp` is a pointer to an array of 16 `float` values to specify the model view projection matrix to
+    ///    be passed to the shader.
+    /// - `options` is a pointer to options for the frame. Valid options are dependent on the `LIBRASHADER_API_VERSION`
+    ///    passed in. It may be null, in which case default options for the filter chain are used.
     ///
     /// ## Safety
     /// - `command_buffer` must be a valid reference to a `MTLCommandBuffer` that is not already encoding.
@@ -189,8 +205,8 @@ extern_fn! {
         command_buffer: PMTLCommandBuffer,
         frame_count: usize,
         image: PMTLTexture,
-        viewport: libra_viewport_t,
         output: PMTLTexture,
+        viewport: *const libra_viewport_t,
         mvp: *const f32,
         opt: *const MaybeUninit<frame_mtl_opt_t>
     ) |command_buffer, image, output|; mut |chain|  {
@@ -207,15 +223,21 @@ extern_fn! {
             Some(unsafe { opt.read() })
         };
         let opt = opt.map(FromUninit::from_uninit);
-        let viewport = Viewport {
+
-            x: viewport.x,
+        let viewport = if viewport.is_null() {
-            y: viewport.y,
+            Viewport::new_render_target_sized_origin(output, mvp)?
-            size: Size {
+        } else {
-                height: viewport.height,
+            let viewport = unsafe { viewport.read() };
-                width: viewport.width
+            Viewport {
-            },
+                x: viewport.x,
-            output,
+                y: viewport.y,
-            mvp,
+                output,
+                size: Size {
+                    height: viewport.height,
+                    width: viewport.width
+                },
+                mvp,
+            }
         };
 
         chain.frame(&image, &viewport, command_buffer, frame_count, opt.as_ref())?;

librashader-capi/src/runtime/vk/filter_chain.rs

@@ -24,29 +24,16 @@ pub use ash::vk::PFN_vkGetInstanceProcAddr;
 pub type libra_PFN_vkGetInstanceProcAddr =
     unsafe extern "system" fn(instance: *mut c_void, p_name: *const c_char);
 
-/// Vulkan parameters for the source image.
+/// Vulkan parameters for an image.
 #[repr(C)]
-pub struct libra_source_image_vk_t {
+pub struct libra_image_vk_t {
-    /// A raw `VkImage` handle to the source image.
+    /// A raw `VkImage` handle.
     pub handle: vk::Image,
-    /// The `VkFormat` of the source image.
+    /// The `VkFormat` of the `VkImage`.
     pub format: vk::Format,
-    /// The width of the source image.
+    /// The width of the `VkImage`.
     pub width: u32,
-    /// The height of the source image.
+    /// The height of the `VkImage`.
-    pub height: u32,
-}
-
-/// Vulkan parameters for the output image.
-#[repr(C)]
-pub struct libra_output_image_vk_t {
-    /// A raw `VkImage` handle to the output image.
-    pub handle: vk::Image,
-    /// The `VkFormat` of the output image.
-    pub format: vk::Format,
-    /// The width of the output image.
-    pub width: u32,
-    /// The height of the output image.
     pub height: u32,
 }
 
@@ -66,8 +53,8 @@ pub struct libra_device_vk_t {
     pub entry: vk::PFN_vkGetInstanceProcAddr,
 }
 
-impl From<libra_source_image_vk_t> for VulkanImage {
+impl From<libra_image_vk_t> for VulkanImage {
-    fn from(value: libra_source_image_vk_t) -> Self {
+    fn from(value: libra_image_vk_t) -> Self {
         VulkanImage {
             size: Size::new(value.width, value.height),
             image: value.handle,
@@ -240,13 +227,31 @@ extern_fn! {
     /// Records rendering commands for a frame with the given parameters for the given filter chain
     /// to the input command buffer.
     ///
-    /// * The input image must be in the `VK_SHADER_READ_ONLY_OPTIMAL` layout.
+    /// librashader **will not** create a pipeline barrier for the final pass. The output image must be
-    /// * The output image must be in `VK_COLOR_ATTACHMENT_OPTIMAL` layout.
+    /// in `VK_COLOR_ATTACHMENT_OPTIMAL`, and will remain so after all shader passes. The caller must transition
-    ///
-    /// librashader **will not** create a pipeline barrier for the final pass. The output image will
-    /// remain in `VK_COLOR_ATTACHMENT_OPTIMAL` after all shader passes. The caller must transition
     /// the output image to the final layout.
     ///
+    /// ## Parameters
+    ///
+    /// - `chain` is a handle to the filter chain.
+    /// - `command_buffer` is a `VkCommandBuffer` handle to record draw commands to.
+    ///    The provided command buffer must be ready for recording and contain no prior commands
+    /// - `frame_count` is the number of frames passed to the shader
+    /// - `image` is a `libra_image_vk_t`, containing a `VkImage` handle, it's format and size information,
+    ///    to an image that will serve as the source image for the frame. The input image must be in
+    ///    the `VK_SHADER_READ_ONLY_OPTIMAL` layout.
+    /// - `out` is a `libra_image_vk_t`, containing a `VkImage` handle, it's format and size information,
+    ///    for the render target of the frame. The output image must be in `VK_COLOR_ATTACHMENT_OPTIMAL` layout.
+    ///    The output image will remain in `VK_COLOR_ATTACHMENT_OPTIMAL` after all shader passes.
+    ///
+    /// - `viewport` is a pointer to a `libra_viewport_t` that specifies the area onto which scissor and viewport
+    ///    will be applied to the render target. It may be null, in which case a default viewport spanning the
+    ///    entire render target will be used.
+    /// - `mvp` is a pointer to an array of 16 `float` values to specify the model view projection matrix to
+    ///    be passed to the shader.
+    /// - `options` is a pointer to options for the frame. Valid options are dependent on the `LIBRASHADER_API_VERSION`
+    ///    passed in. It may be null, in which case default options for the filter chain are used.
+    ///
     /// ## Safety
     /// - `libra_vk_filter_chain_frame` **must not be called within a RenderPass**.
     /// - `command_buffer` must be a valid handle to a `VkCommandBuffer` that is ready for recording.
@@ -262,9 +267,9 @@ extern_fn! {
         chain: *mut libra_vk_filter_chain_t,
         command_buffer: vk::CommandBuffer,
         frame_count: usize,
-        image: libra_source_image_vk_t,
+        image: libra_image_vk_t,
-        viewport: libra_viewport_t,
+        out: libra_image_vk_t,
-        out: libra_output_image_vk_t,
+        viewport: *const libra_viewport_t,
         mvp: *const f32,
         opt: *const MaybeUninit<frame_vk_opt_t>
     ) mut |chain| {
@@ -286,15 +291,21 @@ extern_fn! {
             Some(unsafe { opt.read() })
         };
         let opt = opt.map(FromUninit::from_uninit);
-        let viewport = Viewport {
+
-            x: viewport.x,
+        let viewport = if viewport.is_null() {
-            y: viewport.y,
+            Viewport::new_render_target_sized_origin(output, mvp)?
-            size: Size {
+        } else {
-                height: viewport.height,
+            let viewport = unsafe { viewport.read() };
-                width: viewport.width
+            Viewport {
-            },
+                x: viewport.x,
-            output,
+                y: viewport.y,
-            mvp,
+                output,
+                size: Size {
+                    height: viewport.height,
+                    width: viewport.width
+                },
+                mvp,
+            }
         };
 
         unsafe {

librashader-common/src/lib.rs

@@ -201,47 +201,46 @@ impl<T> Size<T> {
     }
 }
 
-impl<T: Sub<Output=T>> Sub for Size<T> {
+impl<T: Sub<Output = T>> Sub for Size<T> {
     type Output = Size<T>;
 
     fn sub(self, rhs: Self) -> Self::Output {
         Self {
             width: self.width - rhs.width,
-            height: self.height - rhs.height
+            height: self.height - rhs.height,
         }
     }
 }
 
-impl<T: Sub<T, Output=T> + Copy> Sub<T> for Size<T> {
+impl<T: Sub<T, Output = T> + Copy> Sub<T> for Size<T> {
     type Output = Size<T>;
 
     fn sub(self, rhs: T) -> Self::Output {
         Self {
             width: self.width - rhs,
-            height: self.height - rhs
+            height: self.height - rhs,
         }
     }
 }
 
-
+impl<T: Add<Output = T>> Add for Size<T> {
-impl<T: Add<Output=T>> Add for Size<T> {
     type Output = Size<T>;
 
     fn add(self, rhs: Self) -> Self::Output {
         Self {
             width: self.width + rhs.width,
-            height: self.height + rhs.height
+            height: self.height + rhs.height,
         }
     }
 }
 
-impl<T: Add<T, Output=T> + Copy> Add<T> for Size<T> {
+impl<T: Add<T, Output = T> + Copy> Add<T> for Size<T> {
     type Output = Size<T>;
 
     fn add(self, rhs: T) -> Self::Output {
         Self {
             width: self.width + rhs,
-            height: self.height + rhs
+            height: self.height + rhs,
         }
     }
 }

librashader-common/src/metal.rs

@@ -107,3 +107,16 @@ impl GetSize<u32> for ProtocolObject<dyn MTLTexture> {
         })
     }
 }
+
+impl GetSize<u32> for &ProtocolObject<dyn MTLTexture> {
+    type Error = std::convert::Infallible;
+
+    fn size(&self) -> Result<Size<u32>, Self::Error> {
+        let height = self.height();
+        let width = self.width();
+        Ok(Size {
+            height: height as u32,
+            width: width as u32,
+        })
+    }
+}

librashader-common/src/viewport.rs

@@ -1,4 +1,4 @@
-use crate::Size;
+use crate::{GetSize, Size};
 
 /// The rendering output of a filter chain.
 ///
@@ -23,3 +23,24 @@ pub struct Viewport<'a, T> {
     /// by x and y.
     pub size: Size<u32>,
 }
+
+impl<'a, T: GetSize<u32>> Viewport<'a, T> {
+    /// Create a new viewport from an output that can be sized.
+    ///
+    /// This will create a viewport that spans the entire output texture,
+    /// which will give correct results in the general case.
+    #[inline(always)]
+    pub fn new_render_target_sized_origin(
+        output: T,
+        mvp: Option<&'a [f32; 16]>,
+    ) -> Result<Viewport<'a, T>, T::Error> {
+        let size = output.size()?;
+        Ok(Self {
+            x: 0.0,
+            y: 0.0,
+            mvp,
+            output,
+            size,
+        })
+    }
+}

librashader-runtime-d3d11/src/filter_pass.rs

@@ -1,7 +1,7 @@
-use windows::Win32::Foundation::RECT;
 use crate::filter_chain::FilterCommon;
 use crate::options::FrameOptionsD3D11;
 use crate::texture::InputTexture;
+use windows::Win32::Foundation::RECT;
 
 use librashader_common::map::FastHashMap;
 use librashader_common::{ImageFormat, Size, Viewport};

librashader-runtime-gl/src/gl/framebuffer.rs

@@ -136,3 +136,11 @@ impl GetSize<u32> for GLFramebuffer {
         Ok(self.size)
     }
 }
+
+impl GetSize<u32> for &GLFramebuffer {
+    type Error = std::convert::Infallible;
+
+    fn size(&self) -> std::result::Result<Size<u32>, Self::Error> {
+        Ok(self.size)
+    }
+}

librashader-runtime-mtl/src/graphics_pipeline.rs

@@ -208,7 +208,7 @@ impl MetalGraphicsPipeline {
                 x: output.x as usize,
                 y: output.y as usize,
                 width: output.size.width as usize,
-                height: output.size.height as usize
+                height: output.size.height as usize,
             });
 
             rpass.setViewport(MTLViewport {

librashader-runtime-vk/src/texture.rs

@@ -7,7 +7,7 @@ use parking_lot::Mutex;
 use std::sync::Arc;
 
 use crate::error::FilterChainError;
-use librashader_common::{FilterMode, ImageFormat, Size, WrapMode};
+use librashader_common::{FilterMode, GetSize, ImageFormat, Size, WrapMode};
 use librashader_presets::Scale2D;
 use librashader_runtime::scaling::{MipmapSize, ScaleFramebuffer, ViewportSize};
 
@@ -535,3 +535,11 @@ impl ScaleFramebuffer for OwnedImage {
         )
     }
 }
+
+impl GetSize<u32> for VulkanImage {
+    type Error = std::convert::Infallible;
+
+    fn size(&self) -> Result<Size<u32>, Self::Error> {
+        Ok(self.size)
+    }
+}