text: // dear imgui: Renderer for DirectX9
  // This needs to be used along with a Platform Binding (e.g. Win32)
  
  // Implemented features:
  //  [X] Renderer: User texture binding. Use 'LPDIRECT3DTEXTURE9' as ImTextureID. Read the FAQ about ImTextureID!
  //  [X] Renderer: Support for large meshes (64k+ vertices) with 16-bits indices.
  
  // You can copy and use unmodified imgui_impl_* files in your project. See main.cpp for an example of using this.
  // If you are new to dear imgui, read examples/README.txt and read the documentation at the top of imgui.cpp.
  // https://github.com/ocornut/imgui
  
  // CHANGELOG
  // (minor and older changes stripped away, please see git history for details)
  //  2019-05-29: DirectX9: Added support for large mesh (64K+ vertices), enable ImGuiBackendFlags_RendererHasVtxOffset flag.
  //  2019-04-30: DirectX9: Added support for special ImDrawCallback_ResetRenderState callback to reset render state.
  //  2019-03-29: Misc: Fixed erroneous assert in ImGui_ImplDX9_InvalidateDeviceObjects().
  //  2019-01-16: Misc: Disabled fog before drawing UI's. Fixes issue #2288.
  //  2018-11-30: Misc: Setting up io.BackendRendererName so it can be displayed in the About Window.
  //  2018-06-08: Misc: Extracted imgui_impl_dx9.cpp/.h away from the old combined DX9+Win32 example.
  //  2018-06-08: DirectX9: Use draw_data->DisplayPos and draw_data->DisplaySize to setup projection matrix and clipping rectangle.
  //  2018-05-07: Render: Saving/restoring Transform because they don't seem to be included in the StateBlock. Setting shading mode to Gouraud.
  //  2018-02-16: Misc: Obsoleted the io.RenderDrawListsFn callback and exposed ImGui_ImplDX9_RenderDrawData() in the .h file so you can call it yourself.
  //  2018-02-06: Misc: Removed call to ImGui::Shutdown() which is not available from 1.60 WIP, user needs to call CreateContext/DestroyContext themselves.
  
  #include "imgui.h"
  #include "imgui_impl_dx9.h"
  
  // DirectX
  #include <d3d9.h>
  #define DIRECTINPUT_VERSION 0x0800
  #include <dinput.h>
  
  // DirectX data
  static LPDIRECT3DDEVICE9        g_pd3dDevice = NULL;
  static LPDIRECT3DVERTEXBUFFER9  g_pVB = NULL;
  static LPDIRECT3DINDEXBUFFER9   g_pIB = NULL;
  static LPDIRECT3DTEXTURE9       g_FontTexture = NULL;
  static int                      g_VertexBufferSize = 5000, g_IndexBufferSize = 10000;
  
  struct CUSTOMVERTEX
  {
      float    pos[3];
      D3DCOLOR col;
      float    uv[2];
  };
  #define D3DFVF_CUSTOMVERTEX (D3DFVF_XYZ|D3DFVF_DIFFUSE|D3DFVF_TEX1)
  
  static void ImGui_ImplDX9_SetupRenderState(ImDrawData* draw_data)
  {
      // Setup viewport
      D3DVIEWPORT9 vp;
      vp.X = vp.Y = 0;
      vp.Width = (DWORD)draw_data->DisplaySize.x;
      vp.Height = (DWORD)draw_data->DisplaySize.y;
      vp.MinZ = 0.0f;
      vp.MaxZ = 1.0f;
      g_pd3dDevice->SetViewport(&vp);
  
      // Setup render state: fixed-pipeline, alpha-blending, no face culling, no depth testing, shade mode (for gradient)
      g_pd3dDevice->SetPixelShader(NULL);
      g_pd3dDevice->SetVertexShader(NULL);
      g_pd3dDevice->SetRenderState(D3DRS_CULLMODE, D3DCULL_NONE);
      g_pd3dDevice->SetRenderState(D3DRS_LIGHTING, false);
      g_pd3dDevice->SetRenderState(D3DRS_ZENABLE, false);
      g_pd3dDevice->SetRenderState(D3DRS_ALPHABLENDENABLE, true);
      g_pd3dDevice->SetRenderState(D3DRS_ALPHATESTENABLE, false);
      g_pd3dDevice->SetRenderState(D3DRS_BLENDOP, D3DBLENDOP_ADD);
      g_pd3dDevice->SetRenderState(D3DRS_SRCBLEND, D3DBLEND_SRCALPHA);
      g_pd3dDevice->SetRenderState(D3DRS_DESTBLEND, D3DBLEND_INVSRCALPHA);
      g_pd3dDevice->SetRenderState(D3DRS_SCISSORTESTENABLE, true);
      g_pd3dDevice->SetRenderState(D3DRS_SHADEMODE, D3DSHADE_GOURAUD);
      g_pd3dDevice->SetRenderState(D3DRS_FOGENABLE, false);
      g_pd3dDevice->SetTextureStageState(0, D3DTSS_COLOROP, D3DTOP_MODULATE);
      g_pd3dDevice->SetTextureStageState(0, D3DTSS_COLORARG1, D3DTA_TEXTURE);
      g_pd3dDevice->SetTextureStageState(0, D3DTSS_COLORARG2, D3DTA_DIFFUSE);
      g_pd3dDevice->SetTextureStageState(0, D3DTSS_ALPHAOP, D3DTOP_MODULATE);
      g_pd3dDevice->SetTextureStageState(0, D3DTSS_ALPHAARG1, D3DTA_TEXTURE);
      g_pd3dDevice->SetTextureStageState(0, D3DTSS_ALPHAARG2, D3DTA_DIFFUSE);
      g_pd3dDevice->SetSamplerState(0, D3DSAMP_MINFILTER, D3DTEXF_LINEAR);
      g_pd3dDevice->SetSamplerState(0, D3DSAMP_MAGFILTER, D3DTEXF_LINEAR);
  
      // Setup orthographic projection matrix
      // Our visible imgui space lies from draw_data->DisplayPos (top left) to draw_data->DisplayPos+data_data->DisplaySize (bottom right). DisplayPos is (0,0) for single viewport apps.
      // Being agnostic of whether <d3dx9.h> or <DirectXMath.h> can be used, we aren't relying on D3DXMatrixIdentity()/D3DXMatrixOrthoOffCenterLH() or DirectX::XMMatrixIdentity()/DirectX::XMMatrixOrthographicOffCenterLH()
      {
          float L = draw_data->DisplayPos.x + 0.5f;
          float R = draw_data->DisplayPos.x + draw_data->DisplaySize.x + 0.5f;
          float T = draw_data->DisplayPos.y + 0.5f;
          float B = draw_data->DisplayPos.y + draw_data->DisplaySize.y + 0.5f;
          D3DMATRIX mat_identity = { { { 1.0f, 0.0f, 0.0f, 0.0f,  0.0f, 1.0f, 0.0f, 0.0f,  0.0f, 0.0f, 1.0f, 0.0f,  0.0f, 0.0f, 0.0f, 1.0f } } };
          D3DMATRIX mat_projection =
          { { {
              2.0f/(R-L),   0.0f,         0.0f,  0.0f,
              0.0f,         2.0f/(T-B),   0.0f,  0.0f,
              0.0f,         0.0f,         0.5f,  0.0f,
              (L+R)/(L-R),  (T+B)/(B-T),  0.5f,  1.0f
          } } };
          g_pd3dDevice->SetTransform(D3DTS_WORLD, &mat_identity);
          g_pd3dDevice->SetTransform(D3DTS_VIEW, &mat_identity);
          g_pd3dDevice->SetTransform(D3DTS_PROJECTION, &mat_projection);
      }
  }
  
  // Render function.
  // (this used to be set in io.RenderDrawListsFn and called by ImGui::Render(), but you can now call this directly from your main loop)
  void ImGui_ImplDX9_RenderDrawData(ImDrawData* draw_data)
  {
      // Avoid rendering when minimized
      if (draw_data->DisplaySize.x <= 0.0f || draw_data->DisplaySize.y <= 0.0f)
          return;
  
      // Create and grow buffers if needed
      if (!g_pVB || g_VertexBufferSize < draw_data->TotalVtxCount)
      {
          if (g_pVB) { g_pVB->Release(); g_pVB = NULL; }
          g_VertexBufferSize = draw_data->TotalVtxCount + 5000;
          if (g_pd3dDevice->CreateVertexBuffer(g_VertexBufferSize * sizeof(CUSTOMVERTEX), D3DUSAGE_DYNAMIC | D3DUSAGE_WRITEONLY, D3DFVF_CUSTOMVERTEX, D3DPOOL_DEFAULT, &g_pVB, NULL) < 0)
              return;
      }
      if (!g_pIB || g_IndexBufferSize < draw_data->TotalIdxCount)
      {
          if (g_pIB) { g_pIB->Release(); g_pIB = NULL; }
          g_IndexBufferSize = draw_data->TotalIdxCount + 10000;
          if (g_pd3dDevice->CreateIndexBuffer(g_IndexBufferSize * sizeof(ImDrawIdx), D3DUSAGE_DYNAMIC | D3DUSAGE_WRITEONLY, sizeof(ImDrawIdx) == 2 ? D3DFMT_INDEX16 : D3DFMT_INDEX32, D3DPOOL_DEFAULT, &g_pIB, NULL) < 0)
              return;
      }
  
      // Backup the DX9 state
      IDirect3DStateBlock9* d3d9_state_block = NULL;
      if (g_pd3dDevice->CreateStateBlock(D3DSBT_ALL, &d3d9_state_block) < 0)
          return;
  
      // Backup the DX9 transform (DX9 documentation suggests that it is included in the StateBlock but it doesn't appear to)
      D3DMATRIX last_world, last_view, last_projection;
      g_pd3dDevice->GetTransform(D3DTS_WORLD, &last_world);
      g_pd3dDevice->GetTransform(D3DTS_VIEW, &last_view);
      g_pd3dDevice->GetTransform(D3DTS_PROJECTION, &last_projection);
  
      // Copy and convert all vertices into a single contiguous buffer, convert colors to DX9 default format.
      // FIXME-OPT: This is a waste of resource, the ideal is to use imconfig.h and
      //  1) to avoid repacking colors:   #define IMGUI_USE_BGRA_PACKED_COLOR
      //  2) to avoid repacking vertices: #define IMGUI_OVERRIDE_DRAWVERT_STRUCT_LAYOUT struct ImDrawVert { ImVec2 pos; float z; ImU32 col; ImVec2 uv; }
      CUSTOMVERTEX* vtx_dst;
      ImDrawIdx* idx_dst;
      if (g_pVB->Lock(0, (UINT)(draw_data->TotalVtxCount * sizeof(CUSTOMVERTEX)), (void**)&vtx_dst, D3DLOCK_DISCARD) < 0)
          return;
      if (g_pIB->Lock(0, (UINT)(draw_data->TotalIdxCount * sizeof(ImDrawIdx)), (void**)&idx_dst, D3DLOCK_DISCARD) < 0)
          return;
      for (int n = 0; n < draw_data->CmdListsCount; n++)
      {
          const ImDrawList* cmd_list = draw_data->CmdLists[n];
          const ImDrawVert* vtx_src = cmd_list->VtxBuffer.Data;
          for (int i = 0; i < cmd_list->VtxBuffer.Size; i++)
          {
              vtx_dst->pos[0] = vtx_src->pos.x;
              vtx_dst->pos[1] = vtx_src->pos.y;
              vtx_dst->pos[2] = 0.0f;
              vtx_dst->col = (vtx_src->col & 0xFF00FF00) | ((vtx_src->col & 0xFF0000) >> 16) | ((vtx_src->col & 0xFF) << 16);     // RGBA --> ARGB for DirectX9
              vtx_dst->uv[0] = vtx_src->uv.x;
              vtx_dst->uv[1] = vtx_src->uv.y;
              vtx_dst++;
              vtx_src++;
          }
          memcpy(idx_dst, cmd_list->IdxBuffer.Data, cmd_list->IdxBuffer.Size * sizeof(ImDrawIdx));
          idx_dst += cmd_list->IdxBuffer.Size;
      }
      g_pVB->Unlock();
      g_pIB->Unlock();
      g_pd3dDevice->SetStreamSource(0, g_pVB, 0, sizeof(CUSTOMVERTEX));
      g_pd3dDevice->SetIndices(g_pIB);
      g_pd3dDevice->SetFVF(D3DFVF_CUSTOMVERTEX);
  
      // Setup desired DX state
      ImGui_ImplDX9_SetupRenderState(draw_data);
  
      // Render command lists
      // (Because we merged all buffers into a single one, we maintain our own offset into them)
      int global_vtx_offset = 0;
      int global_idx_offset = 0;
      ImVec2 clip_off = draw_data->DisplayPos;
      for (int n = 0; n < draw_data->CmdListsCount; n++)
      {
          const ImDrawList* cmd_list = draw_data->CmdLists[n];
          for (int cmd_i = 0; cmd_i < cmd_list->CmdBuffer.Size; cmd_i++)
          {
              const ImDrawCmd* pcmd = &cmd_list->CmdBuffer[cmd_i];
              if (pcmd->UserCallback != NULL)
              {
                  // User callback, registered via ImDrawList::AddCallback()
                  // (ImDrawCallback_ResetRenderState is a special callback value used by the user to request the renderer to reset render state.)
                  if (pcmd->UserCallback == ImDrawCallback_ResetRenderState)
                      ImGui_ImplDX9_SetupRenderState(draw_data);
                  else
                      pcmd->UserCallback(cmd_list, pcmd);
              }
              else
              {
                  const RECT r = { (LONG)(pcmd->ClipRect.x - clip_off.x), (LONG)(pcmd->ClipRect.y - clip_off.y), (LONG)(pcmd->ClipRect.z - clip_off.x), (LONG)(pcmd->ClipRect.w - clip_off.y) };
                  const LPDIRECT3DTEXTURE9 texture = (LPDIRECT3DTEXTURE9)pcmd->TextureId;
                  g_pd3dDevice->SetTexture(0, texture);
                  g_pd3dDevice->SetScissorRect(&r);
                  g_pd3dDevice->DrawIndexedPrimitive(D3DPT_TRIANGLELIST, pcmd->VtxOffset + global_vtx_offset, 0, (UINT)cmd_list->VtxBuffer.Size, pcmd->IdxOffset + global_idx_offset, pcmd->ElemCount/3);
              }
          }
          global_idx_offset += cmd_list->IdxBuffer.Size;
          global_vtx_offset += cmd_list->VtxBuffer.Size;
      }
  
      // Restore the DX9 transform
      g_pd3dDevice->SetTransform(D3DTS_WORLD, &last_world);
      g_pd3dDevice->SetTransform(D3DTS_VIEW, &last_view);
      g_pd3dDevice->SetTransform(D3DTS_PROJECTION, &last_projection);
  
      // Restore the DX9 state
      d3d9_state_block->Apply();
      d3d9_state_block->Release();
  }
  
  bool ImGui_ImplDX9_Init(IDirect3DDevice9* device)
  {
      // Setup back-end capabilities flags
      ImGuiIO& io = ImGui::GetIO();
      io.BackendRendererName = "imgui_impl_dx9";
      io.BackendFlags |= ImGuiBackendFlags_RendererHasVtxOffset;  // We can honor the ImDrawCmd::VtxOffset field, allowing for large meshes.
  
      g_pd3dDevice = device;
      g_pd3dDevice->AddRef();
      return true;
  }
  
  void ImGui_ImplDX9_Shutdown()
  {
      ImGui_ImplDX9_InvalidateDeviceObjects();
      if (g_pd3dDevice) { g_pd3dDevice->Release(); g_pd3dDevice = NULL; }
  }
  
  static bool ImGui_ImplDX9_CreateFontsTexture()
  {
      // Build texture atlas
      ImGuiIO& io = ImGui::GetIO();
      unsigned char* pixels;
      int width, height, bytes_per_pixel;
      io.Fonts->GetTexDataAsRGBA32(&pixels, &width, &height, &bytes_per_pixel);
  
      // Upload texture to graphics system
      g_FontTexture = NULL;
      if (g_pd3dDevice->CreateTexture(width, height, 1, D3DUSAGE_DYNAMIC, D3DFMT_A8R8G8B8, D3DPOOL_DEFAULT, &g_FontTexture, NULL) < 0)
          return false;
      D3DLOCKED_RECT tex_locked_rect;
      if (g_FontTexture->LockRect(0, &tex_locked_rect, NULL, 0) != D3D_OK)
          return false;
      for (int y = 0; y < height; y++)
          memcpy((unsigned char *)tex_locked_rect.pBits + tex_locked_rect.Pitch * y, pixels + (width * bytes_per_pixel) * y, (width * bytes_per_pixel));
      g_FontTexture->UnlockRect(0);
  
      // Store our identifier
      io.Fonts->TexID = (ImTextureID)g_FontTexture;
  
      return true;
  }
  
  bool ImGui_ImplDX9_CreateDeviceObjects()
  {
      if (!g_pd3dDevice)
          return false;
      if (!ImGui_ImplDX9_CreateFontsTexture())
          return false;
      return true;
  }
  
  void ImGui_ImplDX9_InvalidateDeviceObjects()
  {
      if (!g_pd3dDevice)
          return;
      if (g_pVB) { g_pVB->Release(); g_pVB = NULL; }
      if (g_pIB) { g_pIB->Release(); g_pIB = NULL; }
      if (g_FontTexture) { g_FontTexture->Release(); g_FontTexture = NULL; ImGui::GetIO().Fonts->TexID = NULL; } // We copied g_pFontTextureView to io.Fonts->TexID so let's clear that as well.
  }
  
  void ImGui_ImplDX9_NewFrame()
  {
      if (!g_FontTexture)
          ImGui_ImplDX9_CreateDeviceObjects();
  }
  