src/tint/lang/wgsl/ast/transform/multiplanar_external_texture.h

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#ifndef SRC_TINT_LANG_WGSL_AST_TRANSFORM_MULTIPLANAR_EXTERNAL_TEXTURE_H_
#define SRC_TINT_LANG_WGSL_AST_TRANSFORM_MULTIPLANAR_EXTERNAL_TEXTURE_H_

#include <unordered_map>
#include <utility>

#include "src/tint/api/common/binding_point.h"
#include "src/tint/api/options/external_texture.h"
#include "src/tint/lang/core/builtin_fn.h"
#include "src/tint/lang/wgsl/ast/struct_member.h"
#include "src/tint/lang/wgsl/ast/transform/transform.h"

namespace tint::ast::transform {

/// Within the MultiplanarExternalTexture transform, each instance of a
/// texture_external binding is unpacked into two texture_2d<f32> bindings
/// representing two possible planes of a texture and a uniform buffer binding
/// representing a struct of parameters. Calls to textureLoad or
/// textureSampleLevel that contain a texture_external parameter will be
/// transformed into a newly generated version of the function, which can
/// perform the desired operation on a single RGBA plane or on separate Y and UV
/// planes, and do colorspace conversions including yuv->rgb conversion, gamma
/// decoding, gamut conversion, and gamma encoding steps. Specifically
// for BT.709 to SRGB conversion, it takes the fast path only doing the yuv->rgb
// step and skipping all other steps.
class MultiplanarExternalTexture final : public Castable<MultiplanarExternalTexture, Transform> {
  public:
    /// This struct identifies the binding groups and locations for new bindings to
    /// use when transforming a texture_external instance.
    using BindingPoints = ExternalTextureOptions::BindingPoints;

    /// BindingsMap is a map where the key is the binding location of a
    /// texture_external and the value is a struct containing the desired
    /// locations for new bindings expanded from the texture_external instance.
    using BindingsMap = ExternalTextureOptions::BindingsMap;

    /// NewBindingPoints is consumed by the MultiplanarExternalTexture transform.
    /// Data holds information about location of each texture_external binding and
    /// which binding slots it should expand into.
    struct NewBindingPoints final : public Castable<NewBindingPoints, Data> {
        /// Constructor
        /// @param bm a map to the new binding slots to use.
        /// /// @param may_collide if true, then validation will be disabled for binding point
        /// collisions generated by this transform
        explicit NewBindingPoints(BindingsMap bm, bool may_collide = false);

        /// Destructor
        ~NewBindingPoints() override;

        /// A map of new binding points to use.
        const BindingsMap bindings_map;

        /// If true, then validation will be disabled for bindign poitn collisions generated by this
        /// transform.
        const bool allow_collisions = false;
    };

    /// Constructor
    MultiplanarExternalTexture();
    /// Destructor
    ~MultiplanarExternalTexture() override;

    /// @copydoc Transform::Apply
    ApplyResult Apply(const Program& program,
                      const DataMap& inputs,
                      DataMap& outputs) const override;

  private:
    struct State;
};

}  // namespace tint::ast::transform

#endif  // SRC_TINT_LANG_WGSL_AST_TRANSFORM_MULTIPLANAR_EXTERNAL_TEXTURE_H_