imgui_impl_impeller.h File Reference

#include <memory>
#include "impeller/core/host_buffer.h"
#include "third_party/imgui/imgui.h"

Go to the source code of this file.

Namespaces
namespace	impeller

Functions
IMGUI_IMPL_API bool	ImGui_ImplImpeller_Init (const std::shared_ptr< impeller::Context > &context)
IMGUI_IMPL_API void	ImGui_ImplImpeller_Shutdown ()
IMGUI_IMPL_API void	ImGui_ImplImpeller_RenderDrawData (ImDrawData *draw_data, impeller::RenderPass &renderpass, impeller::HostBuffer &host_buffer)

Function Documentation

ImGui_ImplImpeller_Init()

IMGUI_IMPL_API bool ImGui_ImplImpeller_Init

(

const std::shared_ptr< impeller::Context > &

context

)

Definition at line 57 of file imgui_impl_impeller.cc.

                                                   {
  ImGuiIO& io = ImGui::GetIO();
  IM_ASSERT(io.BackendRendererUserData == nullptr &&
            "Already initialized a renderer backend!");
 
  // Setup backend capabilities flags
  auto* bd =
      new ImGui_ImplImpeller_Data(context->GetSamplerLibrary()->GetSampler({}));
  io.BackendRendererUserData = reinterpret_cast<void*>(bd);
  io.BackendRendererName = "imgui_impl_impeller";
  io.BackendFlags |=
      ImGuiBackendFlags_RendererHasVtxOffset;  // We can honor the
                                               // ImDrawCmd::VtxOffset field,
                                               // allowing for large meshes.
 
  bd->context = context;
 
  // Generate/upload the font atlas.
  {
    unsigned char* pixels;
    int width, height;
    io.Fonts->GetTexDataAsRGBA32(&pixels, &width, &height);
 
    impeller::TextureDescriptor texture_descriptor;
    texture_descriptor.storage_mode = impeller::StorageMode::kDevicePrivate;
    texture_descriptor.format = impeller::PixelFormat::kR8G8B8A8UNormInt;
    texture_descriptor.size = {width, height};
    texture_descriptor.mip_count = 1u;
 
    bd->font_texture =
        context->GetResourceAllocator()->CreateTexture(texture_descriptor);
    IM_ASSERT(bd->font_texture != nullptr &&
              "Could not allocate ImGui font texture.");
    bd->font_texture->SetLabel("ImGui Font Texture");
 
    auto command_buffer = context->CreateCommandBuffer();
    auto blit_pass = command_buffer->CreateBlitPass();
    auto mapping = std::make_shared<fml::NonOwnedMapping>(
        reinterpret_cast<const uint8_t*>(pixels),
        texture_descriptor.GetByteSizeOfBaseMipLevel());
    auto device_buffer =
        context->GetResourceAllocator()->CreateBufferWithCopy(*mapping);
 
    blit_pass->AddCopy(impeller::DeviceBuffer::AsBufferView(device_buffer),
                       bd->font_texture);
    blit_pass->EncodeCommands();
 
    [[maybe_unused]] bool uploaded =
        context->GetCommandQueue()->Submit({command_buffer}).ok();
    IM_ASSERT(uploaded &&
              "Could not upload ImGui font texture to device memory.");
  }
 
  // Build the raster pipeline.
  {
    auto desc = impeller::PipelineBuilder<impeller::ImguiRasterVertexShader,
                                          impeller::ImguiRasterFragmentShader>::
        MakeDefaultPipelineDescriptor(*context);
    IM_ASSERT(desc.has_value() && "Could not create Impeller pipeline");
    if (desc.has_value()) {  // Needed to silence clang-tidy check
                             // bugprone-unchecked-optional-access.
      desc->ClearStencilAttachments();
      desc->ClearDepthAttachment();
    }
 
    bd->pipeline =
        context->GetPipelineLibrary()->GetPipeline(std::move(desc)).Get();
    IM_ASSERT(bd->pipeline != nullptr && "Could not create ImGui pipeline.");
    IM_ASSERT(bd->pipeline != nullptr && "Could not create ImGui sampler.");
  }
 
  return true;
}

References impeller::DeviceBuffer::AsBufferView(), impeller::TextureDescriptor::format, impeller::TextureDescriptor::GetByteSizeOfBaseMipLevel(), height, impeller::kDevicePrivate, impeller::kR8G8B8A8UNormInt, impeller::TextureDescriptor::mip_count, impeller::TextureDescriptor::size, impeller::TextureDescriptor::storage_mode, and width.

Referenced by impeller::Playground::OpenPlaygroundHere().

ImGui_ImplImpeller_RenderDrawData()

IMGUI_IMPL_API void ImGui_ImplImpeller_RenderDrawData	(	ImDrawData *	draw_data,
		impeller::RenderPass &	renderpass,
		impeller::HostBuffer &	host_buffer
	)

Definition at line 139 of file imgui_impl_impeller.cc.

                                                                        {
  if (draw_data->CmdListsCount == 0) {
    return;  // Nothing to render.
  }
 
  using VS = impeller::ImguiRasterVertexShader;
  using FS = impeller::ImguiRasterFragmentShader;
 
  auto* bd = ImGui_ImplImpeller_GetBackendData();
  IM_ASSERT(bd != nullptr && "Did you call ImGui_ImplImpeller_Init()?");
 
  size_t total_vtx_bytes = draw_data->TotalVtxCount * sizeof(VS::PerVertexData);
  size_t total_idx_bytes = draw_data->TotalIdxCount * sizeof(ImDrawIdx);
  if (!total_vtx_bytes || !total_idx_bytes) {
    return;  // Nothing to render.
  }
 
  // Allocate buffer for vertices + indices.
  impeller::DeviceBufferDescriptor buffer_desc;
  buffer_desc.size = total_vtx_bytes + total_idx_bytes;
  buffer_desc.storage_mode = impeller::StorageMode::kHostVisible;
 
  auto buffer = bd->context->GetResourceAllocator()->CreateBuffer(buffer_desc);
  buffer->SetLabel("ImGui vertex+index buffer");
 
  auto display_rect = impeller::Rect::MakeXYWH(
      draw_data->DisplayPos.x, draw_data->DisplayPos.y,
      draw_data->DisplaySize.x, draw_data->DisplaySize.y);
 
  auto viewport = impeller::Viewport{
      .rect = display_rect.Scale(draw_data->FramebufferScale.x,
                                 draw_data->FramebufferScale.y)};
 
  // Allocate vertex shader uniform buffer.
  VS::UniformBuffer uniforms;
  uniforms.mvp = impeller::Matrix::MakeOrthographic(display_rect.GetSize())
                     .Translate(-display_rect.GetOrigin());
  auto vtx_uniforms = host_buffer.EmplaceUniform(uniforms);
 
  size_t vertex_buffer_offset = 0;
  size_t index_buffer_offset = total_vtx_bytes;
 
  for (int draw_list_i = 0; draw_list_i < draw_data->CmdListsCount;
       draw_list_i++) {
    const ImDrawList* cmd_list = draw_data->CmdLists[draw_list_i];
 
    // Convert ImGui's per-vertex data (`ImDrawVert`) into the per-vertex data
    // required by the shader (`VS::PerVectexData`). The only difference is that
    // `ImDrawVert` uses an `int` for the color and the impeller shader uses 4
    // floats.
 
    // TODO(102778): Remove the need for this by adding support for attribute
    //               mapping of uint32s host-side to vec4s shader-side in
    //               impellerc.
    std::vector<VS::PerVertexData> vtx_data;
    vtx_data.reserve(cmd_list->VtxBuffer.size());
    for (const auto& v : cmd_list->VtxBuffer) {
      ImVec4 color = ImGui::ColorConvertU32ToFloat4(v.col);
      vtx_data.push_back({{v.pos.x, v.pos.y},  //
                          {v.uv.x, v.uv.y},    //
                          {color.x, color.y, color.z, color.w}});
    }
 
    auto draw_list_vtx_bytes =
        static_cast<size_t>(vtx_data.size() * sizeof(VS::PerVertexData));
    auto draw_list_idx_bytes =
        static_cast<size_t>(cmd_list->IdxBuffer.size_in_bytes());
    if (!buffer->CopyHostBuffer(reinterpret_cast<uint8_t*>(vtx_data.data()),
                                impeller::Range{0, draw_list_vtx_bytes},
                                vertex_buffer_offset)) {
      IM_ASSERT(false && "Could not copy vertices to buffer.");
    }
    if (!buffer->CopyHostBuffer(
            reinterpret_cast<uint8_t*>(cmd_list->IdxBuffer.Data),
            impeller::Range{0, draw_list_idx_bytes}, index_buffer_offset)) {
      IM_ASSERT(false && "Could not copy indices to buffer.");
    }
 
    for (int cmd_i = 0; cmd_i < cmd_list->CmdBuffer.Size; cmd_i++) {
      const ImDrawCmd* pcmd = &cmd_list->CmdBuffer[cmd_i];
 
      if (pcmd->UserCallback) {
        pcmd->UserCallback(cmd_list, pcmd);
      } else {
        // Make the clip rect relative to the viewport.
        auto clip_rect = impeller::Rect::MakeLTRB(
            (pcmd->ClipRect.x - draw_data->DisplayPos.x) *
                draw_data->FramebufferScale.x,
            (pcmd->ClipRect.y - draw_data->DisplayPos.y) *
                draw_data->FramebufferScale.y,
            (pcmd->ClipRect.z - draw_data->DisplayPos.x) *
                draw_data->FramebufferScale.x,
            (pcmd->ClipRect.w - draw_data->DisplayPos.y) *
                draw_data->FramebufferScale.y);
        {
          // Clamp the clip to the viewport bounds.
          auto visible_clip = clip_rect.Intersection(viewport.rect);
          if (!visible_clip.has_value()) {
            continue;  // Nothing to render.
          }
          clip_rect = visible_clip.value();
        }
        {
          // Clamp the clip to ensure it never goes outside of the render
          // target.
          auto visible_clip = clip_rect.Intersection(
              impeller::Rect::MakeSize(render_pass.GetRenderTargetSize()));
          if (!visible_clip.has_value()) {
            continue;  // Nothing to render.
          }
          clip_rect = visible_clip.value();
        }
 
        render_pass.SetCommandLabel(
            std::format("ImGui draw list {} (command {})", draw_list_i, cmd_i));
        render_pass.SetViewport(viewport);
        render_pass.SetScissor(impeller::IRect32::RoundOut(clip_rect));
        render_pass.SetPipeline(bd->pipeline);
        VS::BindUniformBuffer(render_pass, vtx_uniforms);
        FS::BindTex(render_pass, bd->font_texture, bd->sampler);
 
        size_t vb_start =
            vertex_buffer_offset + pcmd->VtxOffset * sizeof(ImDrawVert);
 
        impeller::VertexBuffer vertex_buffer;
        vertex_buffer.vertex_buffer = impeller::BufferView(
            buffer, impeller::Range(vb_start, draw_list_vtx_bytes - vb_start));
        vertex_buffer.index_buffer = impeller::BufferView(
            buffer, impeller::Range(index_buffer_offset +
                                        pcmd->IdxOffset * sizeof(ImDrawIdx),
                                    pcmd->ElemCount * sizeof(ImDrawIdx)));
        vertex_buffer.vertex_count = pcmd->ElemCount;
        vertex_buffer.index_type = impeller::IndexType::k16bit;
        render_pass.SetVertexBuffer(std::move(vertex_buffer));
        render_pass.SetBaseVertex(pcmd->VtxOffset);
 
        render_pass.Draw().ok();
      }
    }
 
    vertex_buffer_offset += draw_list_vtx_bytes;
    index_buffer_offset += draw_list_idx_bytes;
  }
  host_buffer.Reset();
}

References impeller::RenderPass::Draw(), impeller::HostBuffer::EmplaceUniform(), impeller::RenderPass::GetRenderTargetSize(), ImGui_ImplImpeller_GetBackendData(), impeller::VertexBuffer::index_buffer, impeller::VertexBuffer::index_type, impeller::k16bit, impeller::kHostVisible, impeller::TRect< Scalar >::MakeLTRB(), impeller::Matrix::MakeOrthographic(), impeller::TRect< Scalar >::MakeSize(), impeller::TRect< Scalar >::MakeXYWH(), fml::Status::ok(), impeller::Viewport::rect, impeller::HostBuffer::Reset(), impeller::TRect< T >::RoundOut(), impeller::TRect< T >::Scale(), impeller::RenderPass::SetBaseVertex(), impeller::RenderPass::SetCommandLabel(), impeller::RenderPass::SetPipeline(), impeller::RenderPass::SetScissor(), impeller::RenderPass::SetVertexBuffer(), impeller::RenderPass::SetViewport(), impeller::DeviceBufferDescriptor::size, impeller::DeviceBufferDescriptor::storage_mode, impeller::Matrix::Translate(), impeller::VertexBuffer::vertex_buffer, and impeller::VertexBuffer::vertex_count.

Referenced by impeller::Playground::OpenPlaygroundHere().

ImGui_ImplImpeller_Shutdown()

IMGUI_IMPL_API void ImGui_ImplImpeller_Shutdown

(

)

Definition at line 132 of file imgui_impl_impeller.cc.

                                   {
  auto* bd = ImGui_ImplImpeller_GetBackendData();
  IM_ASSERT(bd != nullptr &&
            "No renderer backend to shutdown, or already shutdown?");
  delete bd;
}

References ImGui_ImplImpeller_GetBackendData().

Referenced by impeller::Playground::OpenPlaygroundHere().