engine/src/flutter/impeller/renderer/shader_key.h

// Copyright 2013 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef FLUTTER_IMPELLER_RENDERER_SHADER_KEY_H_
#define FLUTTER_IMPELLER_RENDERER_SHADER_KEY_H_

#include <memory>
#include <string>
#include <string_view>
#include <unordered_map>

#include "flutter/fml/hash_combine.h"
#include "impeller/core/shader_types.h"

namespace impeller {

struct ShaderKey {
  std::string name;
  ShaderStage stage = ShaderStage::kUnknown;

  ShaderKey(std::string_view p_name, ShaderStage p_stage)
      : name({p_name.data(), p_name.size()}), stage(p_stage) {}

  struct Hash {
    size_t operator()(const ShaderKey& key) const {
      return fml::HashCombine(key.name, key.stage);
    }
  };

  struct Equal {
    constexpr bool operator()(const ShaderKey& k1, const ShaderKey& k2) const {
      return k1.stage == k2.stage && k1.name == k2.name;
    }
  };

  /// Build a registry name for a user-supplied shader so it cannot collide
  /// with engine-internal names that share the same source-derived
  /// entrypoint.
  ///
  /// `scope` is a short tag identifying the source kind (see kScope*
  /// constants below). `library_id` is an opaque identifier that is stable
  /// across reloads of the same logical user shader (typically the asset
  /// path that loaded the shader). `entrypoint` is the original shader
  /// entrypoint name as produced by impellerc.
  ///
  /// Engine-internal entrypoints generated by impellerc are valid
  /// identifiers and therefore cannot contain ':', so the colon-separated
  /// format makes user-scoped names unspoofable from the engine namespace.
  static std::string MakeUserScopedName(std::string_view scope,
                                        std::string_view library_id,
                                        std::string_view entrypoint);

  /// Scope tag for `RuntimeStage`-backed shaders (FragmentProgram /
  /// RuntimeEffect).
  static constexpr std::string_view kScopeRuntimeEffect = "re";

  /// Scope tag for Flutter GPU user shader bundles.
  static constexpr std::string_view kScopeFlutterGPU = "fg";

  /// Returns a process-unique library id for user shader sources that were
  /// not constructed via an asset-bearing entry point (e.g. tests, future
  /// in-memory APIs). Stable for the lifetime of the source but distinct
  /// across sources, so the user-scoped registry name cannot collide.
  static std::string MakeFallbackLibraryId();
};

class ShaderFunction;

using ShaderFunctionMap =
    std::unordered_map<ShaderKey,
                       std::shared_ptr<const ShaderFunction>,
                       ShaderKey::Hash,
                       ShaderKey::Equal>;

}  // namespace impeller

#endif  // FLUTTER_IMPELLER_RENDERER_SHADER_KEY_H_