text: #include "ImGuiRenderer.h"
  #include <QDateTime>
  #include <QGuiApplication>
  #include <QMouseEvent>
  #include <QClipboard>
  #include <QCursor>
  #include <QDebug>
  
  #ifdef ANDROID
  #define GL_VERTEX_ARRAY_BINDING           0x85B5 // Missing in android as of May 2020
  #define USE_GLSL_ES
  #endif
  
  #ifdef USE_GLSL_ES
  #define IMGUIRENDERER_GLSL_VERSION "#version 300 es\n"
  #else
  #define IMGUIRENDERER_GLSL_VERSION "#version 330\n"
  #endif
  
  namespace QtImGui {
  
  namespace {
  
  // Keyboard mapping. Dear ImGui use those indices to peek into the io.KeysDown[] array.
  const QHash<int, ImGuiKey> keyMap = {
      { Qt::Key_Tab, ImGuiKey_Tab },
      { Qt::Key_Left, ImGuiKey_LeftArrow },
      { Qt::Key_Right, ImGuiKey_RightArrow },
      { Qt::Key_Up, ImGuiKey_UpArrow },
      { Qt::Key_Down, ImGuiKey_DownArrow },
      { Qt::Key_PageUp, ImGuiKey_PageUp },
      { Qt::Key_PageDown, ImGuiKey_PageDown },
      { Qt::Key_Home, ImGuiKey_Home },
      { Qt::Key_End, ImGuiKey_End },
      { Qt::Key_Insert, ImGuiKey_Insert },
      { Qt::Key_Delete, ImGuiKey_Delete },
      { Qt::Key_Backspace, ImGuiKey_Backspace },
      { Qt::Key_Space, ImGuiKey_Space },
      { Qt::Key_Enter, ImGuiKey_Enter },
      { Qt::Key_Return, ImGuiKey_Enter },
      { Qt::Key_Escape, ImGuiKey_Escape },
      { Qt::Key_A, ImGuiKey_A },
      { Qt::Key_C, ImGuiKey_C },
      { Qt::Key_V, ImGuiKey_V },
      { Qt::Key_X, ImGuiKey_X },
      { Qt::Key_Y, ImGuiKey_Y },
      { Qt::Key_Z, ImGuiKey_Z },
      { Qt::MiddleButton, ImGuiMouseButton_Middle }
  };
  
  #ifndef QT_NO_CURSOR
  const QHash<ImGuiMouseCursor, Qt::CursorShape> cursorMap = {
      { ImGuiMouseCursor_Arrow,      Qt::CursorShape::ArrowCursor },
      { ImGuiMouseCursor_TextInput,  Qt::CursorShape::IBeamCursor },
      { ImGuiMouseCursor_ResizeAll,  Qt::CursorShape::SizeAllCursor },
      { ImGuiMouseCursor_ResizeNS,   Qt::CursorShape::SizeVerCursor },
      { ImGuiMouseCursor_ResizeEW,   Qt::CursorShape::SizeHorCursor },
      { ImGuiMouseCursor_ResizeNESW, Qt::CursorShape::SizeBDiagCursor },
      { ImGuiMouseCursor_ResizeNWSE, Qt::CursorShape::SizeFDiagCursor },
      { ImGuiMouseCursor_Hand,       Qt::CursorShape::PointingHandCursor },
      { ImGuiMouseCursor_NotAllowed, Qt::CursorShape::ForbiddenCursor },
  };
  #endif
  
  QByteArray g_currentClipboardText;
  
  }
  
  void ImGuiRenderer::initialize(WindowWrapper *window) {
      m_window.reset(window);
      initializeOpenGLFunctions();
  
      g_ctx = ImGui::CreateContext();
      ImGui::SetCurrentContext(g_ctx);
  
      // Setup backend capabilities flags
      ImGuiIO &io = ImGui::GetIO();
      #ifndef QT_NO_CURSOR
      io.BackendFlags |= ImGuiBackendFlags_HasMouseCursors; // We can honor GetMouseCursor() values (optional)
      #endif
      io.BackendPlatformName = "qtimgui";
      
      // Setup keyboard mapping
      for (ImGuiKey key : keyMap.values()) {
          io.KeyMap[key] = key;
      }
      
      // io.RenderDrawListsFn = [](ImDrawData *drawData) {
      //    instance()->renderDrawList(drawData);
      // };
      io.SetClipboardTextFn = [](void *user_data, const char *text) {
          Q_UNUSED(user_data);
          QGuiApplication::clipboard()->setText(text);
      };
      io.GetClipboardTextFn = [](void *user_data) {
          Q_UNUSED(user_data);
          g_currentClipboardText = QGuiApplication::clipboard()->text().toUtf8();
          return (const char *)g_currentClipboardText.data();
      };
  
      window->installEventFilter(this);
  }
  
  void ImGuiRenderer::renderDrawList(ImDrawData *draw_data)
  {
      // if (g_pauseRender)return;
  
      // Select current context
      ImGui::SetCurrentContext(g_ctx);
  
      // Avoid rendering when minimized, scale coordinates for retina displays (screen coordinates != framebuffer coordinates)
      ImGuiIO& io = ImGui::GetIO();
      int fb_width = (int)(io.DisplaySize.x * io.DisplayFramebufferScale.x);
      int fb_height = (int)(io.DisplaySize.y * io.DisplayFramebufferScale.y);
      if (fb_width == 0 || fb_height == 0)
          return;
      draw_data->ScaleClipRects(io.DisplayFramebufferScale);
  
      // Backup GL state
      GLint last_active_texture; glGetIntegerv(GL_ACTIVE_TEXTURE, &last_active_texture);
      glActiveTexture(GL_TEXTURE0);
      GLint last_program; glGetIntegerv(GL_CURRENT_PROGRAM, &last_program);
      GLint last_texture; glGetIntegerv(GL_TEXTURE_BINDING_2D, &last_texture);
      GLint last_array_buffer; glGetIntegerv(GL_ARRAY_BUFFER_BINDING, &last_array_buffer);
      GLint last_element_array_buffer; glGetIntegerv(GL_ELEMENT_ARRAY_BUFFER_BINDING, &last_element_array_buffer);
      GLint last_vertex_array; glGetIntegerv(GL_VERTEX_ARRAY_BINDING, &last_vertex_array);
      GLint last_blend_src_rgb; glGetIntegerv(GL_BLEND_SRC_RGB, &last_blend_src_rgb);
      GLint last_blend_dst_rgb; glGetIntegerv(GL_BLEND_DST_RGB, &last_blend_dst_rgb);
      GLint last_blend_src_alpha; glGetIntegerv(GL_BLEND_SRC_ALPHA, &last_blend_src_alpha);
      GLint last_blend_dst_alpha; glGetIntegerv(GL_BLEND_DST_ALPHA, &last_blend_dst_alpha);
      GLint last_blend_equation_rgb; glGetIntegerv(GL_BLEND_EQUATION_RGB, &last_blend_equation_rgb);
      GLint last_blend_equation_alpha; glGetIntegerv(GL_BLEND_EQUATION_ALPHA, &last_blend_equation_alpha);
      GLint last_viewport[4]; glGetIntegerv(GL_VIEWPORT, last_viewport);
      GLint last_scissor_box[4]; glGetIntegerv(GL_SCISSOR_BOX, last_scissor_box);
      GLboolean last_enable_blend = glIsEnabled(GL_BLEND);
      GLboolean last_enable_cull_face = glIsEnabled(GL_CULL_FACE);
      GLboolean last_enable_depth_test = glIsEnabled(GL_DEPTH_TEST);
      GLboolean last_enable_scissor_test = glIsEnabled(GL_SCISSOR_TEST);
  
      // Setup render state: alpha-blending enabled, no face culling, no depth testing, scissor enabled
      glEnable(GL_BLEND);
      glBlendEquation(GL_FUNC_ADD);
      glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
      glDisable(GL_CULL_FACE);
      glDisable(GL_DEPTH_TEST);
      glEnable(GL_SCISSOR_TEST);
  
      // Setup viewport, orthographic projection matrix
      glViewport(0, 0, (GLsizei)fb_width, (GLsizei)fb_height);
      const float ortho_projection[4][4] =
      {
          { 2.0f/io.DisplaySize.x, 0.0f,                   0.0f, 0.0f },
          { 0.0f,                  2.0f/-io.DisplaySize.y, 0.0f, 0.0f },
          { 0.0f,                  0.0f,                  -1.0f, 0.0f },
          {-1.0f,                  1.0f,                   0.0f, 1.0f },
      };
      glUseProgram(g_ShaderHandle);
      glUniform1i(g_AttribLocationTex, 0);
      glUniformMatrix4fv(g_AttribLocationProjMtx, 1, GL_FALSE, &ortho_projection[0][0]);
      glBindVertexArray(g_VaoHandle);
  
      for (int n = 0; n < draw_data->CmdListsCount; n++)
      {
          const ImDrawList* cmd_list = draw_data->CmdLists[n];
          const ImDrawIdx* idx_buffer_offset = 0;
  
          glBindBuffer(GL_ARRAY_BUFFER, g_VboHandle);
          glBufferData(GL_ARRAY_BUFFER, (GLsizeiptr)cmd_list->VtxBuffer.Size * sizeof(ImDrawVert), (const GLvoid*)cmd_list->VtxBuffer.Data, GL_STREAM_DRAW);
  
          glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, g_ElementsHandle);
          glBufferData(GL_ELEMENT_ARRAY_BUFFER, (GLsizeiptr)cmd_list->IdxBuffer.Size * sizeof(ImDrawIdx), (const GLvoid*)cmd_list->IdxBuffer.Data, GL_STREAM_DRAW);
  
          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
              {
                  glBindTexture(GL_TEXTURE_2D, (GLuint)(size_t)pcmd->TextureId);
                  glScissor((int)pcmd->ClipRect.x, (int)(fb_height - pcmd->ClipRect.w), (int)(pcmd->ClipRect.z - pcmd->ClipRect.x), (int)(pcmd->ClipRect.w - pcmd->ClipRect.y));
                  glDrawElements(GL_TRIANGLES, (GLsizei)pcmd->ElemCount, sizeof(ImDrawIdx) == 2 ? GL_UNSIGNED_SHORT : GL_UNSIGNED_INT, idx_buffer_offset);
              }
              idx_buffer_offset += pcmd->ElemCount;
          }
      }
  
      // Restore modified GL state
      glUseProgram(last_program);
      glBindTexture(GL_TEXTURE_2D, last_texture);
      glActiveTexture(last_active_texture);
      glBindVertexArray(last_vertex_array);
      glBindBuffer(GL_ARRAY_BUFFER, last_array_buffer);
      glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, last_element_array_buffer);
      glBlendEquationSeparate(last_blend_equation_rgb, last_blend_equation_alpha);
      glBlendFuncSeparate(last_blend_src_rgb, last_blend_dst_rgb, last_blend_src_alpha, last_blend_dst_alpha);
      if (last_enable_blend) glEnable(GL_BLEND); else glDisable(GL_BLEND);
      if (last_enable_cull_face) glEnable(GL_CULL_FACE); else glDisable(GL_CULL_FACE);
      if (last_enable_depth_test) glEnable(GL_DEPTH_TEST); else glDisable(GL_DEPTH_TEST);
      if (last_enable_scissor_test) glEnable(GL_SCISSOR_TEST); else glDisable(GL_SCISSOR_TEST);
      glViewport(last_viewport[0], last_viewport[1], (GLsizei)last_viewport[2], (GLsizei)last_viewport[3]);
      glScissor(last_scissor_box[0], last_scissor_box[1], (GLsizei)last_scissor_box[2], (GLsizei)last_scissor_box[3]);
  }
  
  bool ImGuiRenderer::createFontsTexture()
  {
      // Select current context
      ImGui::SetCurrentContext(g_ctx);
  
      // Build texture atlas
      ImGuiIO& io = ImGui::GetIO();
      unsigned char* pixels;
      int width, height;
      io.Fonts->GetTexDataAsRGBA32(&pixels, &width, &height);   // Load as RGBA 32-bits (75% of the memory is wasted, but default font is so small) because it is more likely to be compatible with user's existing shaders. If your ImTextureId represent a higher-level concept than just a GL texture id, consider calling GetTexDataAsAlpha8() instead to save on GPU memory.
  
      // Upload texture to graphics system
      GLint last_texture;
      glGetIntegerv(GL_TEXTURE_BINDING_2D, &last_texture);
      glGenTextures(1, &g_FontTexture);
      glBindTexture(GL_TEXTURE_2D, g_FontTexture);
      glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
      glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
      glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, pixels);
  
      // Store our identifier
      io.Fonts->TexID = (void *)(size_t)g_FontTexture;
  
      // Restore state
      glBindTexture(GL_TEXTURE_2D, last_texture);
  
      return true;
  }
  
  bool ImGuiRenderer::createDeviceObjects()
  {
      // Select current context
      ImGui::SetCurrentContext(g_ctx);
  
      // Backup GL state
      GLint last_texture, last_array_buffer, last_vertex_array;
      glGetIntegerv(GL_TEXTURE_BINDING_2D, &last_texture);
      glGetIntegerv(GL_ARRAY_BUFFER_BINDING, &last_array_buffer);
      glGetIntegerv(GL_VERTEX_ARRAY_BINDING, &last_vertex_array);
  
      const GLchar *vertex_shader =
          IMGUIRENDERER_GLSL_VERSION
          "uniform mat4 ProjMtx;\n"
          "in vec2 Position;\n"
          "in vec2 UV;\n"
          "in vec4 Color;\n"
          "out vec2 Frag_UV;\n"
          "out vec4 Frag_Color;\n"
          "void main()\n"
          "{\n"
          "	Frag_UV = UV;\n"
          "	Frag_Color = Color;\n"
          "	gl_Position = ProjMtx * vec4(Position.xy,0,1);\n"
          "}\n";
  
      const GLchar* fragment_shader =
          IMGUIRENDERER_GLSL_VERSION
          "precision mediump float;"
          "uniform sampler2D Texture;\n"
          "in vec2 Frag_UV;\n"
          "in vec4 Frag_Color;\n"
          "out vec4 Out_Color;\n"
          "void main()\n"
          "{\n"
          "	Out_Color = Frag_Color * texture( Texture, Frag_UV.st);\n"
          "}\n";
  
      g_ShaderHandle = glCreateProgram();
      g_VertHandle = glCreateShader(GL_VERTEX_SHADER);
      g_FragHandle = glCreateShader(GL_FRAGMENT_SHADER);
      glShaderSource(g_VertHandle, 1, &vertex_shader, 0);
      glShaderSource(g_FragHandle, 1, &fragment_shader, 0);
      glCompileShader(g_VertHandle);
      glCompileShader(g_FragHandle);
      glAttachShader(g_ShaderHandle, g_VertHandle);
      glAttachShader(g_ShaderHandle, g_FragHandle);
      glLinkProgram(g_ShaderHandle);
  
      g_AttribLocationTex = glGetUniformLocation(g_ShaderHandle, "Texture");
      g_AttribLocationProjMtx = glGetUniformLocation(g_ShaderHandle, "ProjMtx");
      g_AttribLocationPosition = glGetAttribLocation(g_ShaderHandle, "Position");
      g_AttribLocationUV = glGetAttribLocation(g_ShaderHandle, "UV");
      g_AttribLocationColor = glGetAttribLocation(g_ShaderHandle, "Color");
  
      glGenBuffers(1, &g_VboHandle);
      glGenBuffers(1, &g_ElementsHandle);
  
      glGenVertexArrays(1, &g_VaoHandle);
      glBindVertexArray(g_VaoHandle);
      glBindBuffer(GL_ARRAY_BUFFER, g_VboHandle);
      glEnableVertexAttribArray(g_AttribLocationPosition);
      glEnableVertexAttribArray(g_AttribLocationUV);
      glEnableVertexAttribArray(g_AttribLocationColor);
  
  #define OFFSETOF(TYPE, ELEMENT) ((size_t)&(((TYPE *)0)->ELEMENT))
      glVertexAttribPointer(g_AttribLocationPosition, 2, GL_FLOAT, GL_FALSE, sizeof(ImDrawVert), (GLvoid*)OFFSETOF(ImDrawVert, pos));
      glVertexAttribPointer(g_AttribLocationUV, 2, GL_FLOAT, GL_FALSE, sizeof(ImDrawVert), (GLvoid*)OFFSETOF(ImDrawVert, uv));
      glVertexAttribPointer(g_AttribLocationColor, 4, GL_UNSIGNED_BYTE, GL_TRUE, sizeof(ImDrawVert), (GLvoid*)OFFSETOF(ImDrawVert, col));
  #undef OFFSETOF
  
      createFontsTexture();
  
      // Restore modified GL state
      glBindTexture(GL_TEXTURE_2D, last_texture);
      glBindBuffer(GL_ARRAY_BUFFER, last_array_buffer);
      glBindVertexArray(last_vertex_array);
  
      return true;
  }
  
  void ImGuiRenderer::newFrame()
  {
      // Select current context
      ImGui::SetCurrentContext(g_ctx);
  
      if (!g_FontTexture)
          createDeviceObjects();
  
      ImGuiIO& io = ImGui::GetIO();
  
      // Setup display size (every frame to accommodate for window resizing)
      io.DisplaySize = ImVec2(m_window->size().width(), m_window->size().height());
      io.DisplayFramebufferScale = ImVec2(m_window->devicePixelRatio(), m_window->devicePixelRatio());
  
      // Setup time step
      double current_time =  QDateTime::currentMSecsSinceEpoch() / double(1000);
      io.DeltaTime = g_Time > 0.0 ? (float)(current_time - g_Time) : (float)(1.0f/60.0f);
      g_Time = current_time;
  
      // Setup inputs
      // (we already got mouse wheel, keyboard keys & characters from glfw callbacks polled in glfwPollEvents())
      if (m_window->isActive())
      {
          auto pos = m_window->mapFromGlobal(QCursor::pos());
          io.MousePos = ImVec2(pos.x(), pos.y());   // Mouse position in screen coordinates (set to -1,-1 if no mouse / on another screen, etc.)
      }
      else
      {
          io.MousePos = ImVec2(-1,-1);
      }
  
      for (int i = 0; i < 3; i++)
      {
          io.MouseDown[i] = g_MousePressed[i];
      }
  
      io.MouseWheelH = g_MouseWheelH;
      io.MouseWheel = g_MouseWheel;
      g_MouseWheelH = 0;
      g_MouseWheel = 0;
  
      
      updateCursorShape(io);
      
  
      // Start the frame
      ImGui::NewFrame();
  }
  
  void ImGuiRenderer::render()
  {
    // Select current context
    ImGui::SetCurrentContext(g_ctx);
  
    auto drawData = ImGui::GetDrawData();
    renderDrawList(drawData);
  }
  
  ImGuiRenderer::ImGuiRenderer()
    : g_ctx(nullptr)
  {
  }
  
  ImGuiRenderer::~ImGuiRenderer()
  {
    // remove this context
    ImGui::DestroyContext(g_ctx);
  }
  
  void ImGuiRenderer::onMousePressedChange(QMouseEvent *event)
  {
      g_MousePressed[0] = event->buttons() & Qt::LeftButton;
      g_MousePressed[1] = event->buttons() & Qt::RightButton;
      g_MousePressed[2] = event->buttons() & Qt::MiddleButton;
  }
  
  void ImGuiRenderer::onWheel(QWheelEvent *event)
  {
      // Select current context
      ImGui::SetCurrentContext(g_ctx);
  
      // Handle horizontal component
      if(event->pixelDelta().x() != 0)
      {
          g_MouseWheelH += event->pixelDelta().x() / (ImGui::GetTextLineHeight());
      } else {
          // Magic number of 120 comes from Qt doc on QWheelEvent::pixelDelta()
          g_MouseWheelH += event->angleDelta().x() / 120;
      }
  
      // Handle vertical component
      if(event->pixelDelta().y() != 0)
      {
          // 5 lines per unit
          g_MouseWheel += event->pixelDelta().y() / (5.0 * ImGui::GetTextLineHeight());
      } else {
          // Magic number of 120 comes from Qt doc on QWheelEvent::pixelDelta()
          g_MouseWheel += event->angleDelta().y() / 120;
      }
  }
  
  void ImGuiRenderer::onKeyPressRelease(QKeyEvent *event)
  {
      // Select current context
      ImGui::SetCurrentContext(g_ctx);
  
      ImGuiIO& io = ImGui::GetIO();
      
      const bool key_pressed = (event->type() == QEvent::KeyPress);
      
      // Translate `Qt::Key` into `ImGuiKey`, and apply 'pressed' state for that key
      const auto key_it = keyMap.constFind( event->key() );
      if (key_it != keyMap.constEnd()) { // Qt's key found in keyMap
          const int imgui_key = *(key_it);
          io.KeysDown[imgui_key] = key_pressed;
      }
  
      if (key_pressed) {
          const QString text = event->text();
          if (text.size() == 1) {
              io.AddInputCharacter( text.at(0).unicode() );
          }
      }
  
  #ifdef Q_OS_MAC
      io.KeyCtrl  = event->modifiers() & Qt::MetaModifier;
      io.KeyShift = event->modifiers() & Qt::ShiftModifier;
      io.KeyAlt   = event->modifiers() & Qt::AltModifier;
      io.KeySuper = event->modifiers() & Qt::ControlModifier; // Comamnd key
  #else
      io.KeyCtrl  = event->modifiers() & Qt::ControlModifier;
      io.KeyShift = event->modifiers() & Qt::ShiftModifier;
      io.KeyAlt   = event->modifiers() & Qt::AltModifier;
      io.KeySuper = event->modifiers() & Qt::MetaModifier;
  #endif
  }
  
  void ImGuiRenderer::updateCursorShape(const ImGuiIO& io)
  {
  #ifndef QT_NO_CURSOR
      if (io.ConfigFlags & ImGuiConfigFlags_NoMouseCursorChange)
          return;
  
      const ImGuiMouseCursor imgui_cursor = ImGui::GetMouseCursor();
      if (io.MouseDrawCursor || (imgui_cursor == ImGuiMouseCursor_None))
      {
          // Hide OS mouse cursor if imgui is drawing it or if it wants no cursor
          m_window->setCursorShape(Qt::CursorShape::BlankCursor);
      }
      else
      {
          // Show OS mouse cursor
          
          // Translate `ImGuiMouseCursor` into `Qt::CursorShape` and show it, if we can
          const auto cursor_it = cursorMap.constFind( imgui_cursor );
          if(cursor_it != cursorMap.constEnd()) // `Qt::CursorShape` found for `ImGuiMouseCursor`
          {
              const Qt::CursorShape qt_cursor_shape = *(cursor_it);
              m_window->setCursorShape(qt_cursor_shape);
          }
          else // shape NOT found - use default
          {
              m_window->setCursorShape(Qt::CursorShape::ArrowCursor);
          }
      }
  #else
      Q_UNUSED(io);
  #endif
  }
  
  bool ImGuiRenderer::eventFilter(QObject *watched, QEvent *event)
  {
    if (watched == m_window->object()) {
      switch (event->type()) {
      case QEvent::MouseButtonPress:
      case QEvent::MouseButtonRelease:
        this->onMousePressedChange(static_cast<QMouseEvent*>(event));
        break;
      case QEvent::Wheel:
        this->onWheel(static_cast<QWheelEvent*>(event));
        break;
      case QEvent::KeyPress:
      case QEvent::KeyRelease:
        this->onKeyPressRelease(static_cast<QKeyEvent*>(event));
        break;
      case QEvent::Resize:
        g_pauseRender = true;
        QObject::eventFilter(watched, event);
        g_pauseRender = false;
      default:
        break;
      }
    }
    return QObject::eventFilter(watched, event);
  }
  
  ImGuiRenderer* ImGuiRenderer::instance() {
      static ImGuiRenderer* instance = nullptr;
      if (!instance) {
          instance = new ImGuiRenderer();
      }
      return instance;
  }
  
  }
  