buffer_bindings_gles.cc

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// 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.
 
#include "impeller/renderer/backend/gles/buffer_bindings_gles.h"
 
#include <cstdint>
#include <cstring>
#include <vector>
 
#include "impeller/base/validation.h"
#include "impeller/core/buffer_view.h"
#include "impeller/core/device_buffer.h"
#include "impeller/core/shader_types.h"
#include "impeller/renderer/backend/gles/device_buffer_gles.h"
#include "impeller/renderer/backend/gles/formats_gles.h"
#include "impeller/renderer/backend/gles/sampler_gles.h"
#include "impeller/renderer/backend/gles/texture_gles.h"
#include "impeller/renderer/command.h"
 
namespace impeller {
 
// This prefix is used in the names of inputs generated by ANGLE's framebuffer
// fetch emulation.
static constexpr std::string_view kAngleInputAttachmentPrefix =
    "ANGLEInputAttachment";
 
BufferBindingsGLES::BufferBindingsGLES() = default;
 
BufferBindingsGLES::~BufferBindingsGLES() = default;
 
bool BufferBindingsGLES::RegisterVertexStageInput(
    const ProcTableGLES& gl,
    const std::vector<ShaderStageIOSlot>& p_inputs,
    const std::vector<ShaderStageBufferLayout>& layouts) {
  std::vector<std::vector<VertexAttribPointer>> vertex_attrib_arrays(
      layouts.size());
  // Every layout corresponds to a vertex binding.
  // As we record, separate the attributes into buckets for each layout in
  // ascending order. We do this because later on, we'll need to associate each
  // of the attributes with bound buffers corresponding to the binding.
  for (auto layout_i = 0u; layout_i < layouts.size(); layout_i++) {
    const auto& layout = layouts[layout_i];
    for (const auto& input : p_inputs) {
      if (input.binding != layout_i) {
        continue;
      }
      VertexAttribPointer attrib;
      attrib.index = input.location;
      // Component counts must be 1, 2, 3 or 4. Do that validation now.
      if (input.vec_size < 1u || input.vec_size > 4u) {
        return false;
      }
      attrib.size = input.vec_size;
      auto type = ToVertexAttribType(input.type);
      if (!type.has_value()) {
        return false;
      }
      attrib.type = type.value();
      attrib.normalized = GL_FALSE;
      attrib.offset = input.offset;
      attrib.stride = layout.stride;
      attrib.vertex_attrib_divisor =
          layout.input_rate == VertexInputRate::kInstance ? 1u : 0u;
      vertex_attrib_arrays[layout_i].push_back(attrib);
    }
  }
  vertex_attrib_arrays_ = std::move(vertex_attrib_arrays);
  return true;
}
 
static std::string NormalizeUniformKey(const std::string& key) {
  std::string result;
  result.reserve(key.length());
  for (char ch : key) {
    if (ch != '_') {
      result.push_back(toupper(ch));
    }
  }
  return result;
}
 
static std::string CreateUniformMemberKey(const std::string& struct_name,
                                          const std::string& member,
                                          bool is_array) {
  std::string result;
  result.reserve(struct_name.length() + member.length() + (is_array ? 4 : 1));
  result += struct_name;
  if (!member.empty()) {
    result += '.';
    result += member;
  }
  if (is_array) {
    result += "[0]";
  }
  return NormalizeUniformKey(result);
}
 
static std::string CreateUniformMemberKey(
    const std::string& non_struct_member) {
  return NormalizeUniformKey(non_struct_member);
}
 
bool BufferBindingsGLES::ReadUniformsBindings(const ProcTableGLES& gl,
                                              GLuint program) {
  if (!gl.IsProgram(program)) {
    return false;
  }
  program_handle_ = program;
  if (gl.GetDescription()->GetGlVersion().IsAtLeast(Version{3, 0, 0})) {
    return ReadUniformsBindingsV3(gl, program);
  }
  return ReadUniformsBindingsV2(gl, program);
}
 
bool BufferBindingsGLES::ReadUniformsBindingsV3(const ProcTableGLES& gl,
                                                GLuint program) {
  program_handle_ = program;
  GLint uniform_blocks = 0;
  gl.GetProgramiv(program, GL_ACTIVE_UNIFORM_BLOCKS, &uniform_blocks);
  for (GLint i = 0; i < uniform_blocks; i++) {
    GLint name_length = 0;
    gl.GetActiveUniformBlockiv(program, i, GL_UNIFORM_BLOCK_NAME_LENGTH,
                               &name_length);
 
    std::vector<GLchar> name;
    name.resize(name_length);
    GLint length = 0;
    gl.GetActiveUniformBlockName(program, i, name_length, &length, name.data());
 
    GLuint block_index = gl.GetUniformBlockIndex(program, name.data());
    gl.UniformBlockBinding(program_handle_, block_index, i);
 
    ubo_locations_[std::string{name.data(), static_cast<size_t>(length)}] =
        std::make_pair(block_index, i);
  }
  use_ubo_ = true;
  return ReadUniformsBindingsV2(gl, program);
}
 
bool BufferBindingsGLES::ReadUniformsBindingsV2(const ProcTableGLES& gl,
                                                GLuint program) {
  GLint max_name_size = 0;
  gl.GetProgramiv(program, GL_ACTIVE_UNIFORM_MAX_LENGTH, &max_name_size);
 
  GLint uniform_count = 0;
  gl.GetProgramiv(program, GL_ACTIVE_UNIFORMS, &uniform_count);
 
  // Query the Program for all active uniform locations, and
  // record this via normalized key.
  for (GLint i = 0; i < uniform_count; i++) {
    std::vector<GLchar> name;
    name.resize(max_name_size);
    GLsizei written_count = 0u;
    GLint uniform_var_size = 0u;
    GLenum uniform_type = GL_FLOAT;
    // Note: Active uniforms are defined as uniforms that may have an impact on
    //       the output of the shader. Drivers are allowed to (and often do)
    //       optimize out unused uniforms.
    gl.GetActiveUniform(program,            // program
                        i,                  // index
                        max_name_size,      // buffer_size
                        &written_count,     // length
                        &uniform_var_size,  // size
                        &uniform_type,      // type
                        name.data()         // name
    );
 
    // Skip unrecognized variables generated by ANGLE.
    if (gl.GetCapabilities()->IsANGLE()) {
      if (written_count >=
              static_cast<GLsizei>(kAngleInputAttachmentPrefix.length()) &&
          std::string_view(name.data(), kAngleInputAttachmentPrefix.length()) ==
              kAngleInputAttachmentPrefix) {
        continue;
      }
    }
 
    auto location = gl.GetUniformLocation(program, name.data());
    if (location == -1) {
      if (use_ubo_) {
        continue;
      }
      VALIDATION_LOG << "Could not query the location of an active uniform.";
      return false;
    }
    if (written_count <= 0) {
      VALIDATION_LOG << "Uniform name could not be read for active uniform.";
      return false;
    }
    uniform_locations_[NormalizeUniformKey(std::string{
        name.data(), static_cast<size_t>(written_count)})] = location;
  }
  return true;
}
 
bool BufferBindingsGLES::BindVertexAttributes(const ProcTableGLES& gl,
                                              size_t binding,
                                              size_t vertex_offset,
                                              size_t instance) {
  if (binding >= vertex_attrib_arrays_.size()) {
    return false;
  }
 
  // For an emulated instanced draw (instance > 0), a binding whose attributes
  // are all vertex-rate (divisor 0) does not change across instances, so the
  // state bound for instance 0 still applies. Skip the redundant re-binding.
  if (instance > 0u) {
    bool has_instance_rate = false;
    for (const auto& array : vertex_attrib_arrays_[binding]) {
      if (array.vertex_attrib_divisor != 0u) {
        has_instance_rate = true;
        break;
      }
    }
    if (!has_instance_rate) {
      return true;
    }
  }
 
  if (!gl.GetCapabilities()->IsES()) {
    FML_DCHECK(vertex_array_object_ == 0);
    gl.GenVertexArrays(1, &vertex_array_object_);
    gl.BindVertexArray(vertex_array_object_);
  }
 
  for (const auto& array : vertex_attrib_arrays_[binding]) {
    gl.EnableVertexAttribArray(array.index);
    // For an emulated instanced draw, an instance-rate attribute is
    // re-pointed at instance `instance`, since there is no hardware divisor
    // to advance it. A non-instanced or hardware-instanced draw passes
    // instance 0 and lets the divisor (if any) do the stepping.
    size_t attribute_offset = vertex_offset + array.offset;
    if (array.vertex_attrib_divisor != 0u) {
      attribute_offset += instance * static_cast<size_t>(array.stride);
    }
    gl.VertexAttribPointer(array.index,       // index
                           array.size,        // size (must be 1, 2, 3, or 4)
                           array.type,        // type
                           array.normalized,  // normalized
                           array.stride,      // stride
                           reinterpret_cast<const GLvoid*>(
                               static_cast<uintptr_t>(attribute_offset))  // ptr
    );
    // Set the instancing divisor when the driver supports it. It is core
    // on ES 3.0+ and comes from GL_EXT_instanced_arrays on ES 2.0. When
    // unavailable, only per-vertex (divisor 0) bindings are possible,
    // which is the default. Setting it for every attribute (including
    // divisor 0) also clears any stale divisor left by a prior pipeline,
    // which matters on ES, where there is no vertex array object.
    if (gl.VertexAttribDivisor.IsAvailable()) {
      gl.VertexAttribDivisor(array.index, array.vertex_attrib_divisor);
    } else if (gl.VertexAttribDivisorEXT.IsAvailable()) {
      gl.VertexAttribDivisorEXT(array.index, array.vertex_attrib_divisor);
    }
  }
 
  return true;
}
 
bool BufferBindingsGLES::BindUniformData(
    const ProcTableGLES& gl,
    const std::vector<TextureAndSampler>& bound_textures,
    const std::vector<BufferResource>& bound_buffers,
    Range texture_range,
    Range buffer_range) {
  for (auto i = 0u; i < buffer_range.length; i++) {
    if (!BindUniformBuffer(gl, bound_buffers[buffer_range.offset + i])) {
      return false;
    }
  }
  std::optional<size_t> next_unit_index =
      BindTextures(gl, bound_textures, texture_range, ShaderStage::kVertex);
  if (!next_unit_index.has_value()) {
    return false;
  }
  if (!BindTextures(gl, bound_textures, texture_range, ShaderStage::kFragment,
                    *next_unit_index)
           .has_value()) {
    return false;
  }
 
  return true;
}
 
bool BufferBindingsGLES::UnbindVertexAttributes(const ProcTableGLES& gl) {
  for (const auto& array : vertex_attrib_arrays_) {
    for (const auto& attribute : array) {
      gl.DisableVertexAttribArray(attribute.index);
    }
  }
  if (!gl.GetCapabilities()->IsES()) {
    gl.DeleteVertexArrays(1, &vertex_array_object_);
    vertex_array_object_ = 0;
  }
 
  return true;
}
 
GLint BufferBindingsGLES::ComputeTextureLocation(
    const ShaderMetadata* metadata) {
  auto location = binding_map_.find(metadata->name);
  if (location != binding_map_.end()) {
    return location->second[0];
  }
  auto& locations = binding_map_[metadata->name] = {};
  auto computed_location =
      uniform_locations_.find(CreateUniformMemberKey(metadata->name));
  if (computed_location == uniform_locations_.end()) {
    locations.push_back(-1);
  } else {
    locations.push_back(computed_location->second);
  }
  return locations[0];
}
 
const std::vector<GLint>& BufferBindingsGLES::ComputeUniformLocations(
    const ShaderMetadata* metadata) {
  BindingMap::iterator location = binding_map_.find(metadata->name);
  if (location != binding_map_.end()) {
    return location->second;
  }
 
  // For each metadata member, look up the binding location and record
  // it in the binding map.
  std::vector<GLint>& locations = binding_map_[metadata->name] = {};
  locations.reserve(metadata->members.size());
  for (const ShaderStructMemberMetadata& member : metadata->members) {
    if (member.type == ShaderType::kVoid) {
      // Void types are used for padding. We are obviously not going to find
      // mappings for these. Keep going.
      locations.push_back(-1);
      continue;
    }
 
    const std::string member_key = CreateUniformMemberKey(
        metadata->name, member.name, member.array_elements.has_value());
    const absl::flat_hash_map<std::string, GLint>::iterator computed_location =
        uniform_locations_.find(member_key);
    if (computed_location == uniform_locations_.end()) {
      // Uniform was not active.
      locations.push_back(-1);
      continue;
    }
    locations.push_back(computed_location->second);
  }
  return locations;
}
 
bool BufferBindingsGLES::BindUniformBuffer(const ProcTableGLES& gl,
                                           const BufferResource& buffer) {
  const ShaderMetadata* metadata = buffer.GetMetadata();
  const DeviceBuffer* device_buffer = buffer.resource.GetBuffer();
  if (!device_buffer) {
    VALIDATION_LOG << "Device buffer not found.";
    return false;
  }
  const DeviceBufferGLES& device_buffer_gles =
      DeviceBufferGLES::Cast(*device_buffer);
 
  if (use_ubo_) {
    return BindUniformBufferV3(gl, buffer.resource, metadata,
                               device_buffer_gles);
  }
  return BindUniformBufferV2(gl, buffer.resource, metadata, device_buffer_gles);
}
 
bool BufferBindingsGLES::BindUniformBufferV3(
    const ProcTableGLES& gl,
    const BufferView& buffer,
    const ShaderMetadata* metadata,
    const DeviceBufferGLES& device_buffer_gles) {
  absl::flat_hash_map<std::string, std::pair<GLint, GLuint>>::iterator it =
      ubo_locations_.find(metadata->name);
  if (it == ubo_locations_.end()) {
    // This should only happen if we have GLESv3 but are using v2 shaders,
    // as GLESv3 shaders compiled by impeller always have
    // **named** uniform buffer blocks
    return BindUniformBufferV2(gl, buffer, metadata, device_buffer_gles);
  }
  const auto& [block_index, binding_point] = it->second;
  if (!device_buffer_gles.BindAndUploadDataIfNecessary(
          DeviceBufferGLES::BindingType::kUniformBuffer)) {
    return false;
  }
  auto handle = device_buffer_gles.GetHandle();
  if (!handle.has_value()) {
    return false;
  }
  gl.BindBufferRange(GL_UNIFORM_BUFFER, binding_point, handle.value(),
                     buffer.GetRange().offset, buffer.GetRange().length);
  return true;
}
 
bool BufferBindingsGLES::BindUniformBufferV2(
    const ProcTableGLES& gl,
    const BufferView& buffer,
    const ShaderMetadata* metadata,
    const DeviceBufferGLES& device_buffer_gles) {
  const uint8_t* buffer_ptr =
      device_buffer_gles.GetBufferData() + buffer.GetRange().offset;
 
  if (metadata->members.empty()) {
    VALIDATION_LOG << "Uniform buffer had no members. This is currently "
                      "unsupported in the OpenGL ES backend. Use a uniform "
                      "buffer block.";
    return false;
  }
 
  const std::vector<GLint>& locations = ComputeUniformLocations(metadata);
  for (size_t i = 0u; i < metadata->members.size(); i++) {
    const ShaderStructMemberMetadata& member = metadata->members[i];
    GLint location = locations[i];
    // Void type or inactive uniform.
    if (location == -1 || member.type == ShaderType::kVoid) {
      continue;
    }
 
    size_t element_count = member.array_elements.value_or(1);
    size_t element_stride = member.byte_length / element_count;
    auto* buffer_data =
        reinterpret_cast<const GLfloat*>(buffer_ptr + member.offset);
 
    // When binding uniform arrays, the elements must be contiguous. Copy
    // the uniforms to a temp buffer to eliminate any padding needed by the
    // other backends if the array elements have padding.
    std::vector<uint8_t> array_element_buffer;
    if (element_count > 1 && element_stride != member.size) {
      array_element_buffer.resize(member.size * element_count);
      for (size_t element_i = 0; element_i < element_count; element_i++) {
        std::memcpy(array_element_buffer.data() + element_i * member.size,
                    reinterpret_cast<const char*>(buffer_data) +
                        element_i * element_stride,
                    member.size);
      }
      buffer_data =
          reinterpret_cast<const GLfloat*>(array_element_buffer.data());
    }
 
    if (member.type != ShaderType::kFloat) {
      VALIDATION_LOG << "Unsupported uniform data type for key: " << member.name
                     << ", has type " << static_cast<int>(member.type)
                     << ". Only float uniforms are supported.";
      return false;
    }
 
    if (!member.float_type.has_value()) {
      VALIDATION_LOG << "Float uniform should have a float type.";
      return false;
    }
 
    switch (member.float_type.value()) {
      case ShaderFloatType::kFloat:
        gl.Uniform1fv(location, element_count, buffer_data);
        break;
      case ShaderFloatType::kVec2:
        gl.Uniform2fv(location, element_count, buffer_data);
        break;
      case ShaderFloatType::kVec3:
        gl.Uniform3fv(location, element_count, buffer_data);
        break;
      case ShaderFloatType::kVec4:
        gl.Uniform4fv(location, element_count, buffer_data);
        break;
      case ShaderFloatType::kMat2:
        gl.UniformMatrix2fv(location, element_count, GL_FALSE, buffer_data);
        break;
      case ShaderFloatType::kMat3:
        gl.UniformMatrix3fv(location, element_count, GL_FALSE, buffer_data);
        break;
      case ShaderFloatType::kMat4:
        gl.UniformMatrix4fv(location, element_count, GL_FALSE, buffer_data);
        break;
    }
  }
  return true;
}
 
std::optional<size_t> BufferBindingsGLES::BindTextures(
    const ProcTableGLES& gl,
    const std::vector<TextureAndSampler>& bound_textures,
    Range texture_range,
    ShaderStage stage,
    size_t unit_start_index) {
  size_t active_index = unit_start_index;
  for (auto i = 0u; i < texture_range.length; i++) {
    const TextureAndSampler& data = bound_textures[texture_range.offset + i];
    if (data.stage != stage) {
      continue;
    }
    const auto& texture_gles = TextureGLES::Cast(*data.texture.resource);
    if (data.texture.GetMetadata() == nullptr) {
      VALIDATION_LOG << "No metadata found for texture binding.";
      return std::nullopt;
    }
 
    auto location = ComputeTextureLocation(data.texture.GetMetadata());
    if (location == -1) {
      // The texture binding was optimized out of the shader. Continue.
      continue;
    }
 
    //--------------------------------------------------------------------------
    /// Set the active texture unit.
    ///
    if (active_index >= gl.GetCapabilities()->GetMaxTextureUnits(stage)) {
      VALIDATION_LOG << "Texture units specified exceed the capabilities for "
                        "this shader stage.";
      return std::nullopt;
    }
    gl.ActiveTexture(GL_TEXTURE0 + active_index);
 
    //--------------------------------------------------------------------------
    /// Bind the texture.
    ///
    // The `texture_gles` reference is bound `const` because it is reached
    // via a const view into the bound texture list, but `Bind()` mutates
    // GLES-specific lazy-init bookkeeping (`slice_mip_initialized_`,
    // `fence_`). The mutation is implementation detail of the GLES backend
    // and is invisible to the higher abstraction; the `const_cast` is
    // confined to this one call site.
    if (!const_cast<TextureGLES&>(texture_gles).Bind()) {
      return std::nullopt;
    }
 
    //--------------------------------------------------------------------------
    /// If there is a sampler for the texture at the same index, configure the
    /// bound texture using that sampler.
    ///
    const auto& sampler_gles = SamplerGLES::Cast(*data.sampler);
    if (!sampler_gles.ConfigureBoundTexture(texture_gles, gl)) {
      return std::nullopt;
    }
 
    //--------------------------------------------------------------------------
    /// Set the texture uniform location.
    ///
    gl.Uniform1i(location, active_index);
 
    //--------------------------------------------------------------------------
    /// Bump up the active index at binding.
    ///
    active_index++;
  }
  return active_index;
}
 
}  // namespace impeller