BeginMainMenuBar() and BeginViewportSideBar() disappears

[thewoz]

Version/Branch of Dear ImGui:

Version 1.90.5, Branch: docking

Back-ends:

ImGui_ImplGlfw ImGui_ImplOpenGL3

Compiler, OS:

macOS

Full config/build information:

No response

Details:

I can't figure out what I'm doing wrong.
As soon as I click on the window the menu and the status bar disappears

This issue is part of issue #7631
And I don't know if it is related to issue #6283

Screenshots/Video:

screen.mov

Minimal, Complete and Verifiable Example code:

#include <cstdio>
#include <cstdlib>

#include <iostream>

#include <glad/glad.h>

#include <GLFW/glfw3.h>

#define IMGUI_DEFINE_MATH_OPERATORS
#include <imgui/imgui.hpp>

static void glfwErrorCallback(int error, const char * description) {
    fprintf(stderr, "GLFW error (%d): %s\n", error, description);
}

int main(int argc, const char * argv[]) {

  if(!glfwInit()) {
    fprintf(stderr, "GLFW init error\n");
    exit(EXIT_FAILURE);
  }

#if __APPLE__
  const char* glsl_version = "#version 100";
  glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
  glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 2);
  glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
  glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
#else
  const char* glsl_version = "#version 130";
  glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
  glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 0);
#endif

  glfwSetErrorCallback(glfwErrorCallback);

  GLFWwindow * window = glfwCreateWindow(640, 480, "ImGui", NULL, NULL);

  if(!window) {
    glfwTerminate();
    abort();
  }

  glfwMakeContextCurrent(window);
  
  glfwSwapInterval(1);

  if(!gladLoadGLLoader((GLADloadproc) glfwGetProcAddress)) abort();

  IMGUI_CHECKVERSION();
  ImGui::CreateContext();

  ImGui_ImplGlfw_InitForOpenGL(window, true);
  ImGui_ImplOpenGL3_Init(glsl_version);
  
  ImGui::StyleColorsDark();

  while(!glfwWindowShouldClose(window)) {
    
    glfwPollEvents();
    
    ImGui_ImplOpenGL3_NewFrame();
    ImGui_ImplGlfw_NewFrame();
    ImGui::NewFrame();

    ImGuiViewport * viewport = ImGui::GetMainViewport();
    ImGui::SetNextWindowPos(viewport->Pos);
    ImGui::SetNextWindowSize(viewport->Size);
    ImGui::SetNextWindowViewport(viewport->ID);
        
     ImGuiWindowFlags windowFlags = ImGuiWindowFlags_MenuBar | ImGuiWindowFlags_NoDocking | ImGuiWindowFlags_NoCollapse | ImGuiWindowFlags_NoTitleBar | ImGuiWindowFlags_NoDecoration | ImGuiWindowFlags_NoResize | ImGuiWindowFlags_NoNavFocus | ImGuiWindowFlags_NoMove;
    
    ImGui::PushStyleVar(ImGuiStyleVar_WindowPadding, ImVec2(0.0f, 0.0f));
    ImGui::Begin("MainWindow", NULL, windowFlags);
    ImGui::PopStyleVar();
    
    if(ImGui::BeginMainMenuBar()) {
      if(ImGui::BeginMenu("File")) {
        ImGui::MenuItem("About", NULL, false, true);
        ImGui::EndMenu();
      }
      ImGui::EndMainMenuBar();
    }

    float heightSideBar = ImGui::GetFrameHeight();

    if(ImGui::BeginViewportSideBar("StatusBar", viewport, ImGuiDir_Down, heightSideBar, ImGuiWindowFlags_NoScrollbar | ImGuiWindowFlags_NoSavedSettings | ImGuiWindowFlags_MenuBar)) {
      if(ImGui::BeginMenuBar()) {
        ImGui::Text("Status Bar:");
        ImGui::EndMenuBar();
      }
      ImGui::End();
    }

    // right part red
    ImGui::PushStyleColor(ImGuiCol_ChildBg, ImColor(255,0,0).Value);
    ImGui::BeginChild("3", ImVec2(0, 0), true);
    ImGui::PopStyleColor();
    ImGui::EndChild();
    
    ImGui::End();
    
    ImGui::Render();
    int displayW, displayH;
    glfwGetFramebufferSize(window, &displayW, &displayH);
    glViewport(0, 0, displayW, displayH);
    static ImVec4 clearColor = ImColor(60, 55, 15);
    glClearColor(clearColor.x, clearColor.y, clearColor.z, clearColor.w);
    glClear(GL_COLOR_BUFFER_BIT);
    ImGui_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData());

    glfwSwapBuffers(window);
    
  }

  ImGui_ImplOpenGL3_Shutdown();
  ImGui_ImplGlfw_Shutdown();
  ImGui::DestroyContext();
  
  glfwDestroyWindow(window);
  glfwTerminate();
  
  return 0;
  
}

[ocornut]

ImGui::SetNextWindowPos(viewport->Pos);
ImGui::SetNextWindowSize(viewport->Size);
ImGui::SetNextWindowViewport(viewport->ID);

Your window is programmed to fill the entire viewport so that’s what it does. Bringing to front makes it appear over those bars.

You should use viewport->WorkPos and viewport->WorkSize to avoid overlapping menu bars and side bars.

[thewoz]

Hi @ocornut ,
thank you very much for the explanation.
I absolutely did not understand that was the problem.
I implemented what you suggested and indeed nothing disappears anymore.
What I don't understand is why the red part doesn't fill all the available space.

[ocornut]

Because your red window also has a Menubar as you passed ImGuiWindowFlags_MenuBar to it.

[thewoz]

I'm so sorry.
I understand what you mean.
Every time there is some thing I miss.
It's just that I still don't fully understand what the internal architecture of ImGui is.

So I by doing this:

    if(ImGui::BeginMainMenuBar()) {
      if(ImGui::BeginMenu("File")) {
        ImGui::MenuItem("About", NULL, false, true);
        ImGui::EndMenu();
      }
      ImGui::EndMainMenuBar();
    }

I was already defining a menu in the "main" window.

So actually by putting this flag ImGuiWindowFlags_MenuBar I was adding another menu in the window that I was creating below

I was sure that putting ImGuiWindowFlags_MenuBar was to put the menu in the window I was creating here:

ImGui::Begin("MainWindow", NULL, windowFlags);

And that this was the code that was needed to make it work.

    if(ImGui::BeginMainMenuBar()) {
      if(ImGui::BeginMenu("File")) {
        ImGui::MenuItem("About", NULL, false, true);
        ImGui::EndMenu();
      }
      ImGui::EndMainMenuBar();
    }

Anyway here is the complete corrected code.
thank you very much again.

#include <cstdio>
#include <cstdlib>

#include <iostream>

#include <glad/glad.h>

#include <GLFW/glfw3.h>

#define IMGUI_DEFINE_MATH_OPERATORS
#include <imgui/imgui.hpp>

static void glfwErrorCallback(int error, const char * description) {
    fprintf(stderr, "GLFW error (%d): %s\n", error, description);
}

int main(int argc, const char * argv[]) {

  if(!glfwInit()) {
    fprintf(stderr, "GLFW init error\n");
    exit(EXIT_FAILURE);
  }

#if __APPLE__
  const char* glsl_version = "#version 100";
  glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
  glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 2);
  glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
  glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
#else
  const char* glsl_version = "#version 130";
  glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
  glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 0);
#endif

  glfwSetErrorCallback(glfwErrorCallback);

  GLFWwindow * window = glfwCreateWindow(640, 480, "ImGui", NULL, NULL);

  if(!window) {
    glfwTerminate();
    abort();
  }

  glfwMakeContextCurrent(window);
  
  glfwSwapInterval(1);

  if(!gladLoadGLLoader((GLADloadproc) glfwGetProcAddress)) abort();

  IMGUI_CHECKVERSION();
  ImGui::CreateContext();

  ImGui_ImplGlfw_InitForOpenGL(window, true);
  ImGui_ImplOpenGL3_Init(glsl_version);
  
  ImGui::StyleColorsDark();

  while(!glfwWindowShouldClose(window)) {
    
    glfwPollEvents();
    
    ImGui_ImplOpenGL3_NewFrame();
    ImGui_ImplGlfw_NewFrame();
    ImGui::NewFrame();

    ImGuiViewport * viewport = ImGui::GetMainViewport();
    ImGui::SetNextWindowPos(viewport->WorkPos);
    ImGui::SetNextWindowSize(viewport->WorkSize);
    ImGui::SetNextWindowViewport(viewport->ID);
        
    ImGuiWindowFlags windowFlags = ImGuiWindowFlags_NoDocking | ImGuiWindowFlags_NoCollapse | ImGuiWindowFlags_NoTitleBar | ImGuiWindowFlags_NoDecoration | ImGuiWindowFlags_NoResize | ImGuiWindowFlags_NoNavFocus | ImGuiWindowFlags_NoMove;
    
    ImGui::PushStyleVar(ImGuiStyleVar_WindowPadding, ImVec2(0.0f, 0.0f));
    ImGui::Begin("MainWindow", NULL, windowFlags);
    ImGui::PopStyleVar();
    
    if(ImGui::BeginMainMenuBar()) {
      if(ImGui::BeginMenu("File")) {
        ImGui::MenuItem("About", NULL, false, true);
        ImGui::EndMenu();
      }
      ImGui::EndMainMenuBar();
    }

    float heightSideBar = ImGui::GetFrameHeight();

    if(ImGui::BeginViewportSideBar("StatusBar", viewport, ImGuiDir_Down, heightSideBar, ImGuiWindowFlags_NoScrollbar | ImGuiWindowFlags_NoSavedSettings | ImGuiWindowFlags_MenuBar)) {
      if(ImGui::BeginMenuBar()) {
        ImGui::Text("Status Bar:");
        ImGui::EndMenuBar();
      }
      ImGui::End();
    }

    // right part red
    ImGui::PushStyleColor(ImGuiCol_ChildBg, ImColor(255,0,0).Value);
    ImGui::BeginChild("3", ImVec2(0, 0), true);
    ImGui::PopStyleColor();
    ImGui::EndChild();
    
    ImGui::End();
    
    ImGui::Render();
    int displayW, displayH;
    glfwGetFramebufferSize(window, &displayW, &displayH);
    glViewport(0, 0, displayW, displayH);
    static ImVec4 clearColor = ImColor(60, 55, 15);
    glClearColor(clearColor.x, clearColor.y, clearColor.z, clearColor.w);
    glClear(GL_COLOR_BUFFER_BIT);
    ImGui_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData());

    glfwSwapBuffers(window);
    
  }

  ImGui_ImplOpenGL3_Shutdown();
  ImGui_ImplGlfw_Shutdown();
  ImGui::DestroyContext();
  
  glfwDestroyWindow(window);
  glfwTerminate();
  
  return 0;
  
}

[ocornut]

Happy to help!