Imgui doesnot render in opengl 2.1 even when unbinding all buffers and shaders

[Anuj-Bhattarai]

I am trying to render a simple triangle and a simple imgui Window,but when i try to render it just shows a black window without any triangle or imgui window(sometimes also crashes).I am Unbinding my VertexBuffer but it still doesnot let the traingle and imgui window render(my driver has s deafult white color shader so i am not writing it) and whenever i comment glBindBuffer(GL_ARRAY_BUFFER,VBO); it works.So,its a problem with the VertexBuffer
But how to fix it??.I think i am doing all of the procedures right(I am a beginner so i dont know how to fix it even after trying for many hours).

My Code:

#include "GL/glew.h"
#include "GLFW/glfw3.h"
#include "imgui_impl_opengl2.h"
#include "imgui_impl_glfw.h"
#include "imgui.h"
#include <vector>

std::vector<float> Vertices = {
    -0.5,0.5,
    0.5,0.0,
    0.5,-0.5
};

int main()
{
    glfwInit();
    GLFWwindow* window = glfwCreateWindow(900,500,"WWW",NULL,NULL);
    glfwMakeContextCurrent(window);
    glewInit();
    
    unsigned int VBO;
    glGenBuffers(1,&VBO);
    glBindBuffer(GL_ARRAY_BUFFER,VBO);
    glBufferData(GL_ARRAY_BUFFER,6 * sizeof(float),&Vertices[0],GL_STATIC_DRAW);
    glBindBuffer(GL_ARRAY_BUFFER,0);
    
    IMGUI_CHECKVERSION();
    ImGui::CreateContext();
    ImGuiIO& io = ImGui::GetIO(); (void)io;
    ImGui::StyleColorsDark();
    
    bool show_another_window = true;
    
    ImGui_ImplGlfw_InitForOpenGL(window, true);
    ImGui_ImplOpenGL2_Init();
    
    while (!glfwWindowShouldClose(window))
    {
        glfwPollEvents();

        // Start the Dear ImGui frame
        ImGui_ImplOpenGL2_NewFrame();
        ImGui_ImplGlfw_NewFrame();
        ImGui::NewFrame();
        
        glBindBuffer(GL_ARRAY_BUFFER,VBO);
        glEnableVertexAttribArray(0);
        glVertexAttribPointer(0,2,GL_FLOAT,GL_FALSE,2* sizeof(float),0);

        glDrawArrays(GL_TRIANGLES,0,3);
        glBindBuffer(GL_ARRAY_BUFFER,0);

        if (show_another_window)
        {
            ImGui::Begin("Another Window", &show_another_window);   // Pass a pointer to our bool variable (the window will have a closing button that will clear the bool when clicked)
            ImGui::Text("Hello from another window!");
            if (ImGui::Button("Close Me"))
                show_another_window = false;
            ImGui::End();
        }
    
        // Rendering
        ImGui::Render();
        int display_w, display_h;
        glfwGetFramebufferSize(window, &display_w, &display_h);
        glViewport(0, 0, display_w, display_h);
        glClearColor(0.2f,0.2f,0.2f,1.0f);
        glClear(GL_COLOR_BUFFER_BIT);

        ImGui_ImplOpenGL2_RenderDrawData(ImGui::GetDrawData());

        glfwMakeContextCurrent(window);
        glfwSwapBuffers(window);
    }
    // Cleanup
    ImGui_ImplOpenGL2_Shutdown();
    ImGui_ImplGlfw_Shutdown();
    ImGui::DestroyContext();

    glfwDestroyWindow(window);glfwTerminate();
    return 0;
}

my Compiler Settings:

g++ Test.cpp imgui.cpp imgui_impl_glfw.cpp imgui_impl_opengl2.cpp imgui_draw.cpp imgui_widgets.cpp imgui_tables.cpp        -o Test -lGL -lGLEW -lglfw -lGLU

[ocornut]

You have access to examples/example_glfw_opengl2 you can compare your code to it and see the difference and track your issue from there. If examples/example_glfw_opengl2/ unmodified works and your code doesn't, then your added code is the culprit, however confusing OpenGL states are this becomes an OpenGL problem not a Dear ImGui problem.

I suggest you use the imgui_impl_opengl3 backend which is more in line with your coding style. Its not guaranteed that OpenGL driver handle both old and new style perfectly.