text: // dear imgui: Renderer for OpenGL3 / OpenGL ES2 / OpenGL ES3 (modern OpenGL with shaders / programmatic pipeline)
  // This needs to be used along with a Platform Binding (e.g. GLFW, SDL, Win32, custom..)
  // (Note: We are using GL3W as a helper library to access OpenGL functions since there is no standard header to access modern OpenGL functions easily. Alternatives are GLEW, Glad, etc..)
  
  // Implemented features:
  //  [X] Renderer: User texture binding. Use 'GLuint' OpenGL texture identifier as void*/ImTextureID. Read the FAQ about ImTextureID in imgui.cpp.
  
  // 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)
  //  2018-11-30: Misc: Setting up io.BackendRendererName so it can be displayed in the About Window.
  //  2018-11-13: OpenGL: Support for GL 4.5's glClipControl(GL_UPPER_LEFT).
  //  2018-08-29: OpenGL: Added support for more OpenGL loaders: glew and glad, with comments indicative that any loader can be used.
  //  2018-08-09: OpenGL: Default to OpenGL ES 3 on iOS and Android. GLSL version default to "#version 300 ES".
  //  2018-07-30: OpenGL: Support for GLSL 300 ES and 410 core. Fixes for Emscripten compilation.
  //  2018-07-10: OpenGL: Support for more GLSL versions (based on the GLSL version string). Added error output when shaders fail to compile/link.
  //  2018-06-08: Misc: Extracted imgui_impl_opengl3.cpp/.h away from the old combined GLFW/SDL+OpenGL3 examples.
  //  2018-06-08: OpenGL: Use draw_data->DisplayPos and draw_data->DisplaySize to setup projection matrix and clipping rectangle.
  //  2018-05-25: OpenGL: Removed unnecessary backup/restore of GL_ELEMENT_ARRAY_BUFFER_BINDING since this is part of the VAO state.
  //  2018-05-14: OpenGL: Making the call to glBindSampler() optional so 3.2 context won't fail if the function is a NULL pointer.
  //  2018-03-06: OpenGL: Added const char* glsl_version parameter to ImGui_ImplOpenGL3_Init() so user can override the GLSL version e.g. "#version 150".
  //  2018-02-23: OpenGL: Create the VAO in the render function so the setup can more easily be used with multiple shared GL context.
  //  2018-02-16: Misc: Obsoleted the io.RenderDrawListsFn callback and exposed ImGui_ImplSdlGL3_RenderDrawData() in the .h file so you can call it yourself.
  //  2018-01-07: OpenGL: Changed GLSL shader version from 330 to 150.
  //  2017-09-01: OpenGL: Save and restore current bound sampler. Save and restore current polygon mode.
  //  2017-05-01: OpenGL: Fixed save and restore of current blend func state.
  //  2017-05-01: OpenGL: Fixed save and restore of current GL_ACTIVE_TEXTURE.
  //  2016-09-05: OpenGL: Fixed save and restore of current scissor rectangle.
  //  2016-07-29: OpenGL: Explicitly setting GL_UNPACK_ROW_LENGTH to reduce issues because SDL changes it. (#752)
  
  //----------------------------------------
  // OpenGL    GLSL      GLSL
  // version   version   string
  //----------------------------------------
  //  2.0       110       "#version 110"
  //  2.1       120
  //  3.0       130
  //  3.1       140
  //  3.2       150       "#version 150"
  //  3.3       330
  //  4.0       400
  //  4.1       410       "#version 410 core"
  //  4.2       420
  //  4.3       430
  //  ES 2.0    100       "#version 100"
  //  ES 3.0    300       "#version 300 es"
  //----------------------------------------
  
  #if defined(_MSC_VER) && !defined(_CRT_SECURE_NO_WARNINGS)
  #define _CRT_SECURE_NO_WARNINGS
  #endif
  
  #include "hzpch.h"
  #include "imgui.h"
  #include "ImGuiOpenGLRenderer.h"
  #include "glad/glad.h"
  #include <stdio.h>
  #if defined(_MSC_VER) && _MSC_VER <= 1500 // MSVC 2008 or earlier
  #include <stddef.h>     // intptr_t
  #else
  #include <stdint.h>     // intptr_t
  #endif
  #if defined(__APPLE__)
  #include "TargetConditionals.h"
  #endif
  
  // iOS, Android and Emscripten can use GL ES 3
  // Call ImGui_ImplOpenGL3_Init() with "#version 300 es"
  #if (defined(__APPLE__) && TARGET_OS_IOS) || (defined(__ANDROID__)) || (defined(__EMSCRIPTEN__))
  #define USE_GL_ES3
  #endif
  
  #ifdef USE_GL_ES3
  // OpenGL ES 3
  #include <GLES3/gl3.h>  // Use GL ES 3
  #endif
  
  // OpenGL Data
  static char         g_GlslVersionString[32] = "";
  static GLuint       g_FontTexture = 0;
  static GLuint       g_ShaderHandle = 0, g_VertHandle = 0, g_FragHandle = 0;
  static int          g_AttribLocationTex = 0, g_AttribLocationProjMtx = 0;
  static int          g_AttribLocationPosition = 0, g_AttribLocationUV = 0, g_AttribLocationColor = 0;
  static unsigned int g_VboHandle = 0, g_ElementsHandle = 0;
  
  // Functions
  bool    ImGui_ImplOpenGL3_Init(const char* glsl_version)
  {
      ImGuiIO& io = ImGui::GetIO();
      io.BackendRendererName = "imgui_impl_opengl3";
  
      // Store GLSL version string so we can refer to it later in case we recreate shaders. Note: GLSL version is NOT the same as GL version. Leave this to NULL if unsure.
  #ifdef USE_GL_ES3
      if (glsl_version == NULL)
          glsl_version = "#version 300 es";
  #else
      if (glsl_version == NULL)
          glsl_version = "#version 130";
  #endif
      IM_ASSERT((int)strlen(glsl_version) + 2 < IM_ARRAYSIZE(g_GlslVersionString));
      strcpy(g_GlslVersionString, glsl_version);
      strcat(g_GlslVersionString, "\n");
  
      return true;
  }
  
  void    ImGui_ImplOpenGL3_Shutdown()
  {
      ImGui_ImplOpenGL3_DestroyDeviceObjects();
  }
  
  void    ImGui_ImplOpenGL3_NewFrame()
  {
      if (!g_FontTexture)
          ImGui_ImplOpenGL3_CreateDeviceObjects();
  }
  
  // OpenGL3 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)
  // Note that this implementation is little overcomplicated because we are saving/setting up/restoring every OpenGL state explicitly, in order to be able to run within any OpenGL engine that doesn't do so.
  void    ImGui_ImplOpenGL3_RenderDrawData(ImDrawData* draw_data)
  {
      // Avoid rendering when minimized, scale coordinates for retina displays (screen coordinates != framebuffer coordinates)
      ImGuiIO& io = ImGui::GetIO();
      int fb_width = (int)(draw_data->DisplaySize.x * io.DisplayFramebufferScale.x);
      int fb_height = (int)(draw_data->DisplaySize.y * io.DisplayFramebufferScale.y);
      if (fb_width <= 0 || fb_height <= 0)
          return;
      draw_data->ScaleClipRects(io.DisplayFramebufferScale);
  
      // Backup GL state
      GLenum last_active_texture; glGetIntegerv(GL_ACTIVE_TEXTURE, (GLint*)&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);
  #ifdef GL_SAMPLER_BINDING
      GLint last_sampler; glGetIntegerv(GL_SAMPLER_BINDING, &last_sampler);
  #endif
      GLint last_array_buffer; glGetIntegerv(GL_ARRAY_BUFFER_BINDING, &last_array_buffer);
      GLint last_vertex_array; glGetIntegerv(GL_VERTEX_ARRAY_BINDING, &last_vertex_array);
  #ifdef GL_POLYGON_MODE
      GLint last_polygon_mode[2]; glGetIntegerv(GL_POLYGON_MODE, last_polygon_mode);
  #endif
      GLint last_viewport[4]; glGetIntegerv(GL_VIEWPORT, last_viewport);
      GLint last_scissor_box[4]; glGetIntegerv(GL_SCISSOR_BOX, last_scissor_box);
      GLenum last_blend_src_rgb; glGetIntegerv(GL_BLEND_SRC_RGB, (GLint*)&last_blend_src_rgb);
      GLenum last_blend_dst_rgb; glGetIntegerv(GL_BLEND_DST_RGB, (GLint*)&last_blend_dst_rgb);
      GLenum last_blend_src_alpha; glGetIntegerv(GL_BLEND_SRC_ALPHA, (GLint*)&last_blend_src_alpha);
      GLenum last_blend_dst_alpha; glGetIntegerv(GL_BLEND_DST_ALPHA, (GLint*)&last_blend_dst_alpha);
      GLenum last_blend_equation_rgb; glGetIntegerv(GL_BLEND_EQUATION_RGB, (GLint*)&last_blend_equation_rgb);
      GLenum last_blend_equation_alpha; glGetIntegerv(GL_BLEND_EQUATION_ALPHA, (GLint*)&last_blend_equation_alpha);
      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);
      bool clip_origin_lower_left = true;
  #ifdef GL_CLIP_ORIGIN
      GLenum last_clip_origin = 0; glGetIntegerv(GL_CLIP_ORIGIN, (GLint*)&last_clip_origin); // Support for GL 4.5's glClipControl(GL_UPPER_LEFT)
      if (last_clip_origin == GL_UPPER_LEFT)
          clip_origin_lower_left = false;
  #endif
  
      // Setup render state: alpha-blending enabled, no face culling, no depth testing, scissor enabled, polygon fill
      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);
  #ifdef GL_POLYGON_MODE
      glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
  #endif
  
      // Setup viewport, orthographic projection matrix
      // Our visible imgui space lies from draw_data->DisplayPos (top left) to draw_data->DisplayPos+data_data->DisplaySize (bottom right). DisplayMin is typically (0,0) for single viewport apps.
      glViewport(0, 0, (GLsizei)fb_width, (GLsizei)fb_height);
      float L = draw_data->DisplayPos.x;
      float R = draw_data->DisplayPos.x + draw_data->DisplaySize.x;
      float T = draw_data->DisplayPos.y;
      float B = draw_data->DisplayPos.y + draw_data->DisplaySize.y;
      const float ortho_projection[4][4] =
      {
          { 2.0f/(R-L),   0.0f,         0.0f,   0.0f },
          { 0.0f,         2.0f/(T-B),   0.0f,   0.0f },
          { 0.0f,         0.0f,        -1.0f,   0.0f },
          { (R+L)/(L-R),  (T+B)/(B-T),  0.0f,   1.0f },
      };
      glUseProgram(g_ShaderHandle);
      glUniform1i(g_AttribLocationTex, 0);
      glUniformMatrix4fv(g_AttribLocationProjMtx, 1, GL_FALSE, &ortho_projection[0][0]);
  #ifdef GL_SAMPLER_BINDING
      glBindSampler(0, 0); // We use combined texture/sampler state. Applications using GL 3.3 may set that otherwise.
  #endif
      // Recreate the VAO every time
      // (This is to easily allow multiple GL contexts. VAO are not shared among GL contexts, and we don't track creation/deletion of windows so we don't have an obvious key to use to cache them.)
      GLuint vao_handle = 0;
      glGenVertexArrays(1, &vao_handle);
      glBindVertexArray(vao_handle);
      glBindBuffer(GL_ARRAY_BUFFER, g_VboHandle);
      glEnableVertexAttribArray(g_AttribLocationPosition);
      glEnableVertexAttribArray(g_AttribLocationUV);
      glEnableVertexAttribArray(g_AttribLocationColor);
      glVertexAttribPointer(g_AttribLocationPosition, 2, GL_FLOAT, GL_FALSE, sizeof(ImDrawVert), (GLvoid*)IM_OFFSETOF(ImDrawVert, pos));
      glVertexAttribPointer(g_AttribLocationUV, 2, GL_FLOAT, GL_FALSE, sizeof(ImDrawVert), (GLvoid*)IM_OFFSETOF(ImDrawVert, uv));
      glVertexAttribPointer(g_AttribLocationColor, 4, GL_UNSIGNED_BYTE, GL_TRUE, sizeof(ImDrawVert), (GLvoid*)IM_OFFSETOF(ImDrawVert, col));
  
      // Draw
      ImVec2 pos = draw_data->DisplayPos;
      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)
              {
                  // User callback (registered via ImDrawList::AddCallback)
                  pcmd->UserCallback(cmd_list, pcmd);
              }
              else
              {
                  ImVec4 clip_rect = ImVec4(pcmd->ClipRect.x - pos.x, pcmd->ClipRect.y - pos.y, pcmd->ClipRect.z - pos.x, pcmd->ClipRect.w - pos.y);
                  if (clip_rect.x < fb_width && clip_rect.y < fb_height && clip_rect.z >= 0.0f && clip_rect.w >= 0.0f)
                  {
                      // Apply scissor/clipping rectangle
                      if (clip_origin_lower_left)
                          glScissor((int)clip_rect.x, (int)(fb_height - clip_rect.w), (int)(clip_rect.z - clip_rect.x), (int)(clip_rect.w - clip_rect.y));
                      else
                          glScissor((int)clip_rect.x, (int)clip_rect.y, (int)clip_rect.z, (int)clip_rect.w); // Support for GL 4.5's glClipControl(GL_UPPER_LEFT)
  
                      // Bind texture, Draw
                      glBindTexture(GL_TEXTURE_2D, (GLuint)(intptr_t)pcmd->TextureId);
                      glDrawElements(GL_TRIANGLES, (GLsizei)pcmd->ElemCount, sizeof(ImDrawIdx) == 2 ? GL_UNSIGNED_SHORT : GL_UNSIGNED_INT, idx_buffer_offset);
                  }
              }
              idx_buffer_offset += pcmd->ElemCount;
          }
      }
      glDeleteVertexArrays(1, &vao_handle);
  
      // Restore modified GL state
      glUseProgram(last_program);
      glBindTexture(GL_TEXTURE_2D, last_texture);
  #ifdef GL_SAMPLER_BINDING
      glBindSampler(0, last_sampler);
  #endif
      glActiveTexture(last_active_texture);
      glBindVertexArray(last_vertex_array);
      glBindBuffer(GL_ARRAY_BUFFER, last_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);
  #ifdef GL_POLYGON_MODE
      glPolygonMode(GL_FRONT_AND_BACK, (GLenum)last_polygon_mode[0]);
  #endif
      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 ImGui_ImplOpenGL3_CreateFontsTexture()
  {
      // 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);
      glPixelStorei(GL_UNPACK_ROW_LENGTH, 0);
      glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, pixels);
  
      // Store our identifier
      io.Fonts->TexID = (ImTextureID)(intptr_t)g_FontTexture;
  
      // Restore state
      glBindTexture(GL_TEXTURE_2D, last_texture);
  
      return true;
  }
  
  void ImGui_ImplOpenGL3_DestroyFontsTexture()
  {
      if (g_FontTexture)
      {
          ImGuiIO& io = ImGui::GetIO();
          glDeleteTextures(1, &g_FontTexture);
          io.Fonts->TexID = 0;
          g_FontTexture = 0;
      }
  }
  
  // If you get an error please report on github. You may try different GL context version or GLSL version. See GL<>GLSL version table at the top of this file.
  static bool CheckShader(GLuint handle, const char* desc)
  {
      GLint status = 0, log_length = 0;
      glGetShaderiv(handle, GL_COMPILE_STATUS, &status);
      glGetShaderiv(handle, GL_INFO_LOG_LENGTH, &log_length);
      if ((GLboolean)status == GL_FALSE)
          fprintf(stderr, "ERROR: ImGui_ImplOpenGL3_CreateDeviceObjects: failed to compile %s!\n", desc);
      if (log_length > 0)
      {
          ImVector<char> buf;
          buf.resize((int)(log_length + 1));
          glGetShaderInfoLog(handle, log_length, NULL, (GLchar*)buf.begin());
          fprintf(stderr, "%s\n", buf.begin());
      }
      return (GLboolean)status == GL_TRUE;
  }
  
  // If you get an error please report on GitHub. You may try different GL context version or GLSL version.
  static bool CheckProgram(GLuint handle, const char* desc)
  {
      GLint status = 0, log_length = 0;
      glGetProgramiv(handle, GL_LINK_STATUS, &status);
      glGetProgramiv(handle, GL_INFO_LOG_LENGTH, &log_length);
      if ((GLboolean)status == GL_FALSE)
          fprintf(stderr, "ERROR: ImGui_ImplOpenGL3_CreateDeviceObjects: failed to link %s! (with GLSL '%s')\n", desc, g_GlslVersionString);
      if (log_length > 0)
      {
          ImVector<char> buf;
          buf.resize((int)(log_length + 1));
          glGetProgramInfoLog(handle, log_length, NULL, (GLchar*)buf.begin());
          fprintf(stderr, "%s\n", buf.begin());
      }
      return (GLboolean)status == GL_TRUE;
  }
  
  bool    ImGui_ImplOpenGL3_CreateDeviceObjects()
  {
      // 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);
  
      // Parse GLSL version string
      int glsl_version = 130;
      sscanf(g_GlslVersionString, "#version %d", &glsl_version);
  
      const GLchar* vertex_shader_glsl_120 =
          "uniform mat4 ProjMtx;\n"
          "attribute vec2 Position;\n"
          "attribute vec2 UV;\n"
          "attribute vec4 Color;\n"
          "varying vec2 Frag_UV;\n"
          "varying 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* vertex_shader_glsl_130 =
          "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* vertex_shader_glsl_300_es =
          "precision mediump float;\n"
          "layout (location = 0) in vec2 Position;\n"
          "layout (location = 1) in vec2 UV;\n"
          "layout (location = 2) in vec4 Color;\n"
          "uniform mat4 ProjMtx;\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* vertex_shader_glsl_410_core =
          "layout (location = 0) in vec2 Position;\n"
          "layout (location = 1) in vec2 UV;\n"
          "layout (location = 2) in vec4 Color;\n"
          "uniform mat4 ProjMtx;\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_glsl_120 =
          "#ifdef GL_ES\n"
          "    precision mediump float;\n"
          "#endif\n"
          "uniform sampler2D Texture;\n"
          "varying vec2 Frag_UV;\n"
          "varying vec4 Frag_Color;\n"
          "void main()\n"
          "{\n"
          "    gl_FragColor = Frag_Color * texture2D(Texture, Frag_UV.st);\n"
          "}\n";
  
      const GLchar* fragment_shader_glsl_130 =
          "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";
  
      const GLchar* fragment_shader_glsl_300_es =
          "precision mediump float;\n"
          "uniform sampler2D Texture;\n"
          "in vec2 Frag_UV;\n"
          "in vec4 Frag_Color;\n"
          "layout (location = 0) out vec4 Out_Color;\n"
          "void main()\n"
          "{\n"
          "    Out_Color = Frag_Color * texture(Texture, Frag_UV.st);\n"
          "}\n";
  
      const GLchar* fragment_shader_glsl_410_core =
          "in vec2 Frag_UV;\n"
          "in vec4 Frag_Color;\n"
          "uniform sampler2D Texture;\n"
          "layout (location = 0) out vec4 Out_Color;\n"
          "void main()\n"
          "{\n"
          "    Out_Color = Frag_Color * texture(Texture, Frag_UV.st);\n"
          "}\n";
  
      // Select shaders matching our GLSL versions
      const GLchar* vertex_shader = NULL;
      const GLchar* fragment_shader = NULL;
      if (glsl_version < 130)
      {
          vertex_shader = vertex_shader_glsl_120;
          fragment_shader = fragment_shader_glsl_120;
      }
      else if (glsl_version == 410)
      {
          vertex_shader = vertex_shader_glsl_410_core;
          fragment_shader = fragment_shader_glsl_410_core;
      }
      else if (glsl_version == 300)
      {
          vertex_shader = vertex_shader_glsl_300_es;
          fragment_shader = fragment_shader_glsl_300_es;
      }
      else
      {
          vertex_shader = vertex_shader_glsl_130;
          fragment_shader = fragment_shader_glsl_130;
      }
  
      // Create shaders
      const GLchar* vertex_shader_with_version[2] = { g_GlslVersionString, vertex_shader };
      g_VertHandle = glCreateShader(GL_VERTEX_SHADER);
      glShaderSource(g_VertHandle, 2, vertex_shader_with_version, NULL);
      glCompileShader(g_VertHandle);
      CheckShader(g_VertHandle, "vertex shader");
  
      const GLchar* fragment_shader_with_version[2] = { g_GlslVersionString, fragment_shader };
      g_FragHandle = glCreateShader(GL_FRAGMENT_SHADER);
      glShaderSource(g_FragHandle, 2, fragment_shader_with_version, NULL);
      glCompileShader(g_FragHandle);
      CheckShader(g_FragHandle, "fragment shader");
  
      g_ShaderHandle = glCreateProgram();
      glAttachShader(g_ShaderHandle, g_VertHandle);
      glAttachShader(g_ShaderHandle, g_FragHandle);
      glLinkProgram(g_ShaderHandle);
      CheckProgram(g_ShaderHandle, "shader program");
  
      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");
  
      // Create buffers
      glGenBuffers(1, &g_VboHandle);
      glGenBuffers(1, &g_ElementsHandle);
  
      ImGui_ImplOpenGL3_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    ImGui_ImplOpenGL3_DestroyDeviceObjects()
  {
      if (g_VboHandle) glDeleteBuffers(1, &g_VboHandle);
      if (g_ElementsHandle) glDeleteBuffers(1, &g_ElementsHandle);
      g_VboHandle = g_ElementsHandle = 0;
  
      if (g_ShaderHandle && g_VertHandle) glDetachShader(g_ShaderHandle, g_VertHandle);
      if (g_VertHandle) glDeleteShader(g_VertHandle);
      g_VertHandle = 0;
  
      if (g_ShaderHandle && g_FragHandle) glDetachShader(g_ShaderHandle, g_FragHandle);
      if (g_FragHandle) glDeleteShader(g_FragHandle);
      g_FragHandle = 0;
  
      if (g_ShaderHandle) glDeleteProgram(g_ShaderHandle);
      g_ShaderHandle = 0;
  
      ImGui_ImplOpenGL3_DestroyFontsTexture();
  }
  