tview/main.cpp

// Dear ImGui: standalone example application for SDL2 + OpenGL
// (SDL is a cross-platform general purpose library for handling windows,
// inputs, OpenGL/Vulkan/Metal graphics context creation, etc.)

// Learn about Dear ImGui:
// - FAQ                  https://dearimgui.com/faq
// - Getting Started      https://dearimgui.com/getting-started
// - Documentation        https://dearimgui.com/docs (same as your local docs/
// folder).
// - Introduction, links and more at the top of imgui.cpp

#include <cstddef>

#include "lib/backends/imgui_impl_opengl3.h"
#include "lib/backends/imgui_impl_sdl2.h"
#include "lib/imgui.h"
#include "lib/imgui_internal.h"
#include <iostream>
#include <stdio.h>

#define STB_IMAGE_IMPLEMENTATION
#include "lib/stb_image.h"

#if defined(__APPLE__)
#include <SDL2/SDL.h>
#if defined(IMGUI_IMPL_OPENGL_ES2)
#include <SDL2/SDL_opengles.h>
#else
#include <SDL2/SDL_opengl.h>
#endif
#else
#include <SDL2/SDL.h>
#if defined(IMGUI_IMPL_OPENGL_ES2)
#include <SDL2/SDL_opengles2.h>
#else
#include <SDL2/SDL_opengl.h>
#endif
#endif

#include "lib/imgui_tex_inspect.h"
#include "lib/backends/tex_inspect_opengl.h"

struct Texture
{
    ImTextureID texture;
    ImVec2 size;
};

Texture LoadTexture(const char * path)
{
    const int channelCount = 4;
    int imageFileChannelCount;
    int width, height;
    uint8_t *image = (uint8_t *)stbi_load(path, &width, &height, &imageFileChannelCount, channelCount);
    if (image == NULL)
    {
        fprintf(stderr, "%s\nFailed to open %s\n", stbi_failure_reason(), path);

        return {nullptr,{0,0}};
    }

    GLenum dataFormat = GL_RGBA;
    GLuint textureHandle;
    glGenTextures(1, &textureHandle);
    glBindTexture(GL_TEXTURE_2D, textureHandle);
    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, dataFormat, GL_UNSIGNED_BYTE, image);

    Texture t;
    t.texture = (void*)(uintptr_t)(textureHandle);
    t.size = ImVec2((float)width,(float)height);

    stbi_image_free(image);
    return t;
}


static bool init = true;

// Main code
int main(int, char **) {
  // Setup SDL
  if (SDL_Init(SDL_INIT_VIDEO | SDL_INIT_TIMER | SDL_INIT_GAMECONTROLLER) !=
      0) {
    printf("Error: %s\n", SDL_GetError());
    return -1;
  }

  // Decide GL+GLSL versions
#if defined(IMGUI_IMPL_OPENGL_ES2)
  // GL ES 2.0 + GLSL 100
  const char *glsl_version = "#version 100";
  SDL_GL_SetAttribute(SDL_GL_CONTEXT_FLAGS, 0);
  SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_ES);
  SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 2);
  SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 0);
#elif defined(__APPLE__)
  // GL 3.2 Core + GLSL 150
  const char *glsl_version = "#version 150";
  SDL_GL_SetAttribute(
      SDL_GL_CONTEXT_FLAGS,
      SDL_GL_CONTEXT_FORWARD_COMPATIBLE_FLAG); // Always required on Mac
  SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_CORE);
  SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3);
  SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 2);
#else
  // GL 3.0 + GLSL 130
  const char *glsl_version = "#version 130";
  SDL_GL_SetAttribute(SDL_GL_CONTEXT_FLAGS, 0);
  SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_CORE);
  SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3);
  SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 0);
#endif

  // From 2.0.18: Enable native IME.
#ifdef SDL_HINT_IME_SHOW_UI
  SDL_SetHint(SDL_HINT_IME_SHOW_UI, "1");
#endif

  // Create window with graphics context
  SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
  SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 24);
  SDL_GL_SetAttribute(SDL_GL_STENCIL_SIZE, 8);
  SDL_WindowFlags window_flags =
      (SDL_WindowFlags)(SDL_WINDOW_OPENGL | SDL_WINDOW_RESIZABLE |
                        SDL_WINDOW_ALLOW_HIGHDPI);
  SDL_Window *window =
      SDL_CreateWindow("tview", SDL_WINDOWPOS_CENTERED,
                       SDL_WINDOWPOS_CENTERED, 1280, 720, window_flags);
  if (window == nullptr) {
    printf("Error: SDL_CreateWindow(): %s\n", SDL_GetError());
    return -1;
  }

  SDL_GLContext gl_context = SDL_GL_CreateContext(window);
  SDL_GL_MakeCurrent(window, gl_context);
  SDL_GL_SetSwapInterval(1); // Enable vsync

  // Setup Dear ImGui context
  IMGUI_CHECKVERSION();

  ImGui::CreateContext();
  ImGuiIO &io = ImGui::GetIO();
  (void)io;
  io.ConfigFlags |=
      ImGuiConfigFlags_NavEnableKeyboard;           // Enable Keyboard Controls
  ImGuiTexInspect::ImplOpenGL3_Init(); // Or DirectX 11 equivalent (check your chosen backend header file)
  ImGuiTexInspect::Init();
  ImGuiTexInspect::CreateContext();

  ImGui::StyleColorsDark();

  ImGuiStyle &style = ImGui::GetStyle();

  ImGui_ImplSDL2_InitForOpenGL(window, gl_context);
  ImGui_ImplOpenGL3_Init(glsl_version);

  ImVec4 clear_color = ImVec4(0.45f, 0.55f, 0.60f, 1.00f);

  Texture t;

  // Main loop
  bool done = false;
  while (!done)
  {
    // Poll and handle events (inputs, window resize, etc.)
    SDL_Event event;
    while (SDL_PollEvent(&event)) {
      ImGui_ImplSDL2_ProcessEvent(&event);
      if (event.type == SDL_QUIT)
        done = true;
      if (event.type == SDL_WINDOWEVENT &&
          event.window.event == SDL_WINDOWEVENT_CLOSE &&
          event.window.windowID == SDL_GetWindowID(window))
        done = true;
    }

    // Start the Dear ImGui frame
    ImGui_ImplOpenGL3_NewFrame();
    ImGui_ImplSDL2_NewFrame();
    ImGui::NewFrame();

    if (init) {
      init = false;
      t = LoadTexture("/home/dubey/Pictures/DSC03199.JPG");
    }

    {
#ifdef IMGUI_HAS_VIEWPORT
      ImGuiViewport *viewport = ImGui::GetMainViewport();
      ImGui::SetNextWindowPos(viewport->WorkPos);
      ImGui::SetNextWindowSize(viewport->WorkSize);
      ImGui::SetNextWindowViewport(viewport->ID);
#else
      ImGui::SetNextWindowPos(ImVec2(0.0f, 0.0f));
      ImGui::SetNextWindowSize(ImGui::GetIO().DisplaySize);
#endif


      ImGui::PushStyleVar(ImGuiStyleVar_WindowRounding, 0.0f);
      ImGui::PushStyleVar(ImGuiStyleVar_WindowBorderSize, 0.0f);
      ImGui::SetNextWindowPos(viewport->Pos);
      ImGui::SetNextWindowSize(viewport->Size);
      ImGui::Begin("Main", NULL,
                   ImGuiWindowFlags_NoDecoration | ImGuiWindowFlags_NoResize);
      auto wSize = ImGui::GetContentRegionAvail();
      if (t.texture != 0) {
        ImGuiTexInspect::BeginInspectorPanel(
          "Inspector",
          t.texture,
          t.size,
          ImGuiTexInspect::InspectorFlags_FillVertical | ImGuiTexInspect::InspectorFlags_FillHorizontal,
          ImGuiTexInspect::SizeExcludingBorder(wSize)
        );
        ImGuiTexInspect::EndInspectorPanel();
      }
      ImGui::End();
      ImGui::PopStyleVar();
      ImGui::PopStyleVar();
    }

    // Rendering
    ImGui::Render();
    glViewport(0, 0, (int)io.DisplaySize.x, (int)io.DisplaySize.y);
    glClearColor(clear_color.x * clear_color.w, clear_color.y * clear_color.w,
                 clear_color.z * clear_color.w, clear_color.w);
    glClear(GL_COLOR_BUFFER_BIT);
    ImGui_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData());
    SDL_GL_SwapWindow(window);
  }

  // Cleanup
  ImGui_ImplOpenGL3_Shutdown();
  ImGui_ImplSDL2_Shutdown();
  ImGui::DestroyContext();

  SDL_GL_DeleteContext(gl_context);
  SDL_DestroyWindow(window);
  SDL_Quit();

  return 0;
}